neil.nu.archive :: TZR The TZR forum

TZR » Tech » 3XV » Backfiring when starting up

Pages: (2) < [1] 2 > [ Track this topic :: Email this topic :: Print this topic ]

Gavsp Group: Members Posts: 76 Joined: April 2006 Posted: Aug. 24 2006,20:01 I go to kick start my bike from cold it backfiring, Is there any suggestions what the cause my be, is it time to rebuild the top end?     Mr stinkwheels what Exhaust Gasket Have you got and what do’s it look like, Are they same as the RD?   Thanks Gav Back to top

Warwickb Group: Members Posts: 1911 Joined: Sep. 2003 Posted: Aug. 24 2006,21:26 Are you kicking it over several times before it starts, Gav? If so then it's unburnt fuel igniting in the exhaust. However. A happy 3XV will usually start first or second kick, so you may have a problem elsewhere. Plugs? Correct carb settings? Poor ignition wiring connections? If all these are fine, it might be wise to do a compression check or do a quick visual inspection of the rings through the ehaust port to see if there's anything obvious before pulling the cylinders off - no point wasting base gaskets unnecessarily   Hows it running at the top end? Will it rev to 11.5k in top gear? If not then I'd think maybe a nicked ring or something similar Rgds Wb -------------- A garage overflowing with old stinkers... Back to top

Gavsp Group: Members Posts: 76 Joined: April 2006 Posted: Aug. 24 2006,21:55 The bike starts on the Second kick all the time and Revs out to 11.5K fine in top gear. I think that the power band is sticking around 9K I will have to check to make shore.   I’ve recently replaced the spark plugs BR9 ECM. Back to top

Warwickb Group: Members Posts: 1911 Joined: Sep. 2003 Posted: Aug. 24 2006,22:16 Hmmm. If the powervalves were sticking I doubt it'd rev to 11.5 in top. Are you able to identify if it's consistently backfiring on just one cylinder? if so that would make it easier to track down the fault. Maybe try standing behind the bike while someone else starts it up a few times? Have you altered any carb settings recently? Rgds Wb -------------- A garage overflowing with old stinkers... Back to top

Gavsp Group: Members Posts: 76 Joined: April 2006 Posted: Aug. 24 2006,23:43 A spark plug has blown as I was going down the road, the spark plug has been in there since Monday. Its jet black is that the 2stroke oil pump needs adjusting? Back to top

Warwickb Group: Members Posts: 1911 Joined: Sep. 2003 Posted: Aug. 25 2006,00:05 Gav, spark plugs don't really 'blow'. The insulation can 'break down' over time but that plug looks far too new for that. More commonly they get 'fouled' if the air/fuel/oil mix isn't right. that's what yours looks like, so the problem will be with the carburation/motor, not the plug I'd think. I can't tell from the pic' what yours is really like though. Is it wet black or dry sooty black? Does the bike run properly with a new plug in? What size main jets are you running - did you jet up for the Lomas's? Could a main jet have fallen out completely (it happens).  Answers to those questions should help narrow the possible causes down a bit. Rgds Wb -------------- A garage overflowing with old stinkers... Back to top

Gavsp Group: Members Posts: 76 Joined: April 2006 Posted: Aug. 25 2006,00:11 Its is a wet black, Does the bike run properly with a new plug in? Yep What size main jets are you running - did you jet up for the Lomas's? no I did not as Mr stinkwheels said that his bike run fine with standard. Thanks Warwickb Back to top

jools Group: Members Posts: 1221 Joined: Oct. 2005 Posted: Aug. 25 2006,00:18 Air filters maybe ?? dirty or disintegrating.... -------------- "The only thing worse than being talked about is not being talked about...." oscar Wilde Back to top

Gavsp Group: Members Posts: 76 Joined: April 2006 Posted: Aug. 25 2006,00:20 fine just cleaned them and oiled them. Back to top

Gavsp Group: Members Posts: 76 Joined: April 2006 Posted: Aug. 25 2006,00:22 What do you mean disintegrating? And how do you know that has happened? Back to top

jools Group: Members Posts: 1221 Joined: Oct. 2005 Posted: Aug. 25 2006,01:27 My old filters basically came apart in my hands, like a powdery foam. probably as they had not been used or looked after in a while. -------------- "The only thing worse than being talked about is not being talked about...." oscar Wilde Back to top

Warwickb Group: Members Posts: 1911 Joined: Sep. 2003 Posted: Aug. 25 2006,12:46 Quote (Gavsp @ Aug. 24 2006,23:11) Its is a wet black, Does the bike run properly with a new plug in? Yep What size main jets are you running - did you jet up for the Lomas's? no I did not as Mr stinkwheels said that his bike run fine with standard. Thanks Warwickb OK, shouldn't be running too rich then. Did you squeeze the oil out of the filters after cleaning and re-oiling them? If too oily they will be too restrictive and lead to rich running even on the stock jetting. I run my filters virtually dry. You may have an electronic misfire on that side though? try taking the plug out of the opposite cylinder and running it only on the 'poorly' one. Can you get a steady tickover? Does it rev cleanly? If it's popping and banging at all? If so then you need to check all of the ignition circuit closely. Check the orange Low tension wire where it conncts to the coil. The little right angle spde connectors can de-grade over time. Clean up the contacts and consider fitting a new one if it looks at all suspect. also check and clean up the other (black) coil wire that fits to the coil mounting bolt. Clean it up to ensure a good connection with the bolt that goes through the eye of the connector and the coil bracket - basically just work through the ignition system to ensure everything is tight, free from rust and well connected to ensure a good, strong spark. check the HT lead is firmly connected to the coil and the HT cap too. Anything I've missed on the ignition, side, sparkytypes? Let us know how you get on, OK? Which cylinder is it that's casuing the problems anyway? Cheers Wb -------------- A garage overflowing with old stinkers... Back to top

Gavsp Group: Members Posts: 76 Joined: April 2006 Posted: Aug. 25 2006,14:20 I think I have found the problem, I pulled off the both Exhaust systems and looked through the exhaust port and seen the piston and rings, I put my finger to touch the to of the piston’s and noticed that there was a lot of carbon build up on both pistons, I then check both piston rings as well I will presumed that  the piston rings are nicked as you can see from the picture below. I’ve been on this websites below and it mentioned that if the spark plugs are Oil Fouled (Wet black)   1, Excessive Choking 2, Trouble within the ignition system 3, Oil pumping past worn piston rings and valve guides http://www.dansmc.com/Spark_Plugs/Spark_Plugs_catalog.html My Pistons and rings need replacing, I’ve been given a price off £202 for both pitons and rings, Base Gasket £19.06 and top Gasket £36.34, Is there any over gaskets I need for the top end, will I need the YPVS outer and inner seal, And do’s anyone now where I can get both pistons and rings cheaper elsewhere with in the UK? Do I need to have the barrels checked out? And Warwickb yes I did squeeze the oil out of the filters after I cleaned them, I will have to make a point of running over my electronics to make a 100% that this will not happen in the future. And what is the best way of cleaning your power valves and Exhaust ports? Thanks for the Help. Back to top

Warwickb Group: Members Posts: 1911 Joined: Sep. 2003 Posted: Aug. 25 2006,17:01 Hi Gav. The carbon build up would suggest rich mixture or poor quality oil. While there is a fair bit of blow past on the piston, suggesting that the pistons and/or rings could do with replacing soon, I'm not sure this is really your problem - unless one of the rings is clearly damaged of course. The info from dansmc.com refers to 4 strokes in particular - hence the mention of valve guides. If it were me, I'd be checking the ignition system before rebuilding the top end (especially if you could do without spending the money just now). The choke is a possibility too. It'd certainly be worth removing the plungers to check they haven't seized in the 'choke on' position. This sometimes happens - especially on the lower carb as water seems to run down the cable and rust the spring which can then break - especially if the little rubber boot where it connects to the carb is missing. I had one like that once. It'd be worth popping them out, cleaning and lubing in any case as it's only a quick job. If you do rebuild it, you don't really need the head gaskets as you can lift the barrels off from the base without disturbing the heads. You may want to clean the heads up though and this is easier with them removed from the barrels. It can be done without removing them, but it's a little more 'faffy'. Depends how much you want to save the cost of the head gaskets, really. You don't need to do the YPVS seals, but you might want to if they are leaking at all - this usually only affects the powervalve shaft seals. You should also replace the little end bearings - and ideally the gudgeon/wrist pins and very importantly make sure you use new Gudgeon pin clips when you put it back together. But bear in mind that this may not solve your problem. Or at least I've never had a stroker misfire simply due to worn rings in any case. That said, if you do rebuild it, you'll know that you have a good top end, and know the exact milegae of the pistons, which, in view of the tendency of the pistons to ride the top ring pin if left too long between rebuilds could be a good thing. If it were me, though, I'd be making sure that all the obvious stuff was OK first and then maybe do the top end in any case as a security measure. You might not be very happy if you shell out the time and money to rebuild the top end and find that the bike is no better than before. Gotta be worth a couple of hours checking the electrics and carburation before ripping the motor apart, I'd think Hope this is of some help. You never did say which cylinder, and whether the problem was sproradic or constant? Cheers Wb -------------- A garage overflowing with old stinkers... Back to top

Gavsp Group: Members Posts: 76 Joined: April 2006 Posted: Aug. 25 2006,17:55 I’ am going to rebuilt the top end whilst I’ve got some time off work, As you maybe able to see from the picture above, It looks like one off the pistons rings have gone(I think) What is a gudgeon? I’ am running Morrison 2 stroke oil, And what kind of lube should I use on the Coke and how will I know if the choke has seized in the on position? Thanks Back to top

Mr stinkwheels Group: Members Posts: 206 Joined: May 2006 Posted: Aug. 25 2006,18:02 Hi Gav. I use the standard copper type exhaust gaskets, I think they are the same as the YPVS 350 etc. I had a slight problem with my spark plug on the lower pot, the insulation leaked and I was getting miss-fire and single pot running, the plug was very black and wet, it turned out my lower carb needle was set wrong causing a rich mixture, I have adjusted it and had no problem since. If you take the power valves out of the cylinder to clean excessive carbon build up off them, use a 2p piece to scrape the carbon off but gently does it, dont for god sake use things like sand paper. Hope this helps Martin Back to top

Gavsp Group: Members Posts: 76 Joined: April 2006 Posted: Aug. 25 2006,18:42 Is the 2 stroke pump setup right? Mr stinkwheels How did you adjusted the lower carb needle? Thanks HAHA, Just looked at the topic on 2 stroke oil pump, what is the setup method? Well my 2 stroke pump is well off. Back to top

gbowie Two stroke spirit Group: Members Posts: 264 Joined: May 2006 Posted: Aug. 25 2006,19:26 I'd say that motor is seriously oiled up, you say you are getting 11.5k out of the motor, how much smoke is it making at those revs ? By the looks of the ex. port you should be choking all the traffic behind !!! -------------- You'll live a lot longer if you give up the things that make life worth living ! Back to top

Gavsp Group: Members Posts: 76 Joined: April 2006 Posted: Aug. 25 2006,19:38 There’s only a little bit of smoke when I open it up, It’s only when I start him up from cold he's a bit Smokey. Back to top

gbowie Two stroke spirit Group: Members Posts: 264 Joined: May 2006 Posted: Aug. 25 2006,19:54 I think I'm getting it now ! That pic of the port is upside down... Yes ..No ? If so it looks like a single ring piston which is certainly damaged . Single ring piston with domed crown ?? Call on Warwick.!! -------------- You'll live a lot longer if you give up the things that make life worth living ! Back to top

Gavsp Group: Members Posts: 76 Joined: April 2006 Posted: Aug. 25 2006,20:01 It has two piston rings and the picture is upside down and it’s the lower barrel.   And I will correct the picture so there’s no confusion. Back to top

Warwickb Group: Members Posts: 1911 Joined: Sep. 2003 Posted: Aug. 25 2006,20:03 Quote (Gavsp @ Aug. 25 2006,16:55) I’ am going to rebuilt the top end whilst I’ve got some time off work, As you maybe able to see from the picture above, It looks like one off the pistons rings have gone(I think) What is a gudgeon? I’ am running Morrison 2 stroke oil, And what kind of lube should I use on the Coke and how will I know if the choke has seized in the on position? Thanks It's hard to tell from the pic, Gav - are you saying the upper ring is AWOL? I'd assumed both were in situ and you were just concerned by the piston discolouration caused by blow-by If the ring has gone walkies, it will have almost certainly totalled your barrel plating and damaged the head too, so you will need the barrel replating (about 100 to 120 quid) and the head repairing too - or a new one, sop you will need to factor these into your costs. The gudgeon or 'wrist' pin is the large hollow pin that goes through the piston to attach it to the rod. If this is your first top end rebuild take it slow and check with someone who has done it before (most of us 2-stroke freaks on here will have done a few top ends in ouir time, i'd think or better still ask someone experienced to oversee your work and advise as you go). It's not particularly difficult, but you really don't want to do it wrong or you will be throwing a sizeable chunk of hard-earned down the shi**er. If you are using Morris semi or fully synthetic 2 stroke oil for injector (not pre-mix) systems, then the oil should be fine. Just use any multi-purpose oil to lube the choke plungers - it's really just to stave off corrosion, they don't really need real lubrication in the normal sense. It'll be obvious when you take the choke plunger out if there is any problem with one of them. Just undo the 14mm retaining nut and lift the plunger out leaving the cable attached - operate the choke lever to check they both move with the lever and that the return springs are sound. If they are, just rub a bit of light oil on with a finger and re-fit. 10 minute job with the fairing sides, tank and airboxes off If the bike has only recently started misfiring, it's unlikely to be needle position unless you have changed it yourself. Happy fettling. Wb -------------- A garage overflowing with old stinkers... Back to top

Gavsp Group: Members Posts: 76 Joined: April 2006 Posted: Aug. 25 2006,20:10 I did not clock that the picture was upside down. I've only used fully synthetic 2 stroke oil for injector. I will have to take a new picture, both piston and rings are more or less the same condition Back to top

gbowie Two stroke spirit Group: Members Posts: 264 Joined: May 2006 Posted: Aug. 25 2006,20:22 Ok, just saved it and turned it around , can see it clearly .. the pic is only showing the bottom ring, the top ring is above the port opening. Pull the barrel off and pray that Warwick is wrong. -------------- You'll live a lot longer if you give up the things that make life worth living ! Back to top

Gavsp Group: Members Posts: 76 Joined: April 2006 Posted: Aug. 25 2006,20:36 The piston rings has not gone walkies yet there still in the original place.   This is the lower barrel, one piston ring you can’t see. Back to top

Warwickb Group: Members Posts: 1911 Joined: Sep. 2003 Posted: Aug. 25 2006,21:17 That's good news, Gav. You had me looking for the number for the re-platers for you for a minute there . As I said though, if the rings are undamaged (and if they are it's usually on the exhaust side, so you would normally see the damage through the 'ex port) I really dont think that the misfire will have been caused by simple ring wear. Remember that the info you were looking at related to 4 stroke bikes. 2 stroke motors are inherently 'messier' than 4 strokes. I could be wrong of course, but it is not something I have ever really heard of on a stroker. Has anyone reading ever experienced a misfire due to ring wear before? I honestly think it would be well worth trying to sort the misfire problem  before refreshing the top end, as you really want it to be running well when you are running the new parts in. If it's mis-firing and over oiling etc. it will be much harder to run the new parts in effectively I'd think. Incidentally, when you do rebuild it, you are probably better off using a mineral or at best a semi synth' oil to run it in, as the fully synthitic stuff is often just too good to allow the rings and barrel to wear to a nice seal. It's always best to check the simple stuff first Gav'. I fully learned this when I was about to strip a motor to find the duff crank seal that I was convinced was 'causing' lean running and power loss at high revs. I thought I'd checked all the obvious stuff - turned out to be a clogged fuel filter - took 2 minutes to fix it.   -------------- A garage overflowing with old stinkers... Back to top

Gavsp Group: Members Posts: 76 Joined: April 2006 Posted: Aug. 25 2006,21:34 Warwickb or anyone else go back a page and tell me what you think of the oil pump, is it set to high? Back to top

Mr stinkwheels Group: Members Posts: 206 Joined: May 2006 Posted: Aug. 25 2006,21:49 Quote (Gavsp @ Aug. 25 2006,20:34) Warwickb or anyone else go back a page and tell me what you think of the oil pump, is it set to high? 1) Turn ignition on. 2) Let power valve do thier sequence. 3) Twist throttle fully open. You should hear 4 clicks from the air solenoids, 2 each. 4) The line on the pump pully should line up with the line on the pump body. This is assuming you have the standard throttle cable linkages and they are all in working order. Back to top

Gavsp Group: Members Posts: 76 Joined: April 2006 Posted: Aug. 25 2006,21:56 No it's out a bit, And thinking about it I never mentioned when the bike was backfiring, It was when I was starting the bike up it’s only done this twice, It happened when I first kick the bike over. Back to top

Warwickb Group: Members Posts: 1911 Joined: Sep. 2003 Posted: Aug. 25 2006,22:14 Gotta be either an ignition circuit fault - meaning that the cylinder is only catching once there is a fair amount of unburnt fuel already in the motor and exhaust - that'll give you a backfire alright. Or a fuel system fault - meaning that there is simply too much fuel going in in the first place, again leading to a backfire on starting. That's the best I can come up with in any case. Rgds Wb -------------- A garage overflowing with old stinkers... Back to top

Warwickb Group: Members Posts: 1911 Joined: Sep. 2003 Posted: Aug. 25 2006,22:17 Quote (Gavsp @ Aug. 25 2006,20:34) Warwickb or anyone else go back a page and tell me what you think of the oil pump, is it set to high? You need to follow the set up procedure as Mr Stinkwheels suggests, Gav. Can't tell you anything from viewing it in the 'resting' position - apart from that it needs a clean . Wb -------------- A garage overflowing with old stinkers... Back to top

jools Group: Members Posts: 1221 Joined: Oct. 2005 Posted: Aug. 26 2006,01:48 Just a point - is it backfiring through the exhaust or the carb ? If it runs fine its unlikely to be an ignition fault I would have thought, perhaps idle circuit & pilots need cleaning out. -------------- "The only thing worse than being talked about is not being talked about...." oscar Wilde Back to top

Gavsp Group: Members Posts: 76 Joined: April 2006 Posted: Aug. 26 2006,13:03 I’ve just noticed that there was no exhaust Gasket installed on both pipes, Will this play a big part in the carbon build up in the exhaust port? And Jools the sound came from the exhaust system. Back to top

Warwickb Group: Members Posts: 1911 Joined: Sep. 2003 Posted: Aug. 26 2006,13:42 A degree of carbon build up is normal in 2 stroke ex ports - good oil and a well set up motor will minimise build-ups though and I get virtually none on my 3XV. Unless there is more than a 1mm thick build up I wouldn't worry too much about it for the time being - a good caning will also help remove some . The lack of gaskets shouldn't really cause backfiring on it's own, Gav, but the bike will probably run better with properly sealed flanges as leaks here will stop the expansion chambers working effectively to optimise engine performance. The gaskets are the same as used on the 350YPVS so you should be able to source them easily. A couple of ebay sellers list them. Rgds Wb -------------- A garage overflowing with old stinkers... Back to top

gbowie Two stroke spirit Group: Members Posts: 264 Joined: May 2006 Posted: Aug. 26 2006,18:24 Warwick, going back to the pic looking up the ex. port, what do you make of the mark/damage directly below the ring in the middle of the pic ? No one has mentioned it !! -------------- You'll live a lot longer if you give up the things that make life worth living ! Back to top

Warwickb Group: Members Posts: 1911 Joined: Sep. 2003 Posted: Aug. 26 2006,18:50 I had just assumed that was simply glare/reflection in the oil from the camera flash, Geoff. Can you confirm, Gav'? It's always hard to go from pic's. Rgds Wb -------------- A garage overflowing with old stinkers... Back to top

Gavsp Group: Members Posts: 76 Joined: April 2006 Posted: Aug. 26 2006,22:58 Yes that’s a bit of 2 stroke oil running down the side of the Piston, The piston has no damage at all, When checking the barrel what should I be look for? I’ve compared both barrels to a new one, the only thing I am concerned about is a very light brown mark around the top of both barrels, Will this be ok? Thanks Back to top

jools Group: Members Posts: 1221 Joined: Oct. 2005 Posted: Aug. 27 2006,01:18 Thats normal as the rings don't go right up to the cylinder deck. Not sure about those black vertical lines from the ports though........ put a new ring in the bore and push it down about 1" with a piston to keep it square then measure the end gap. SHould be between 0.35 and 0.45mm indicating bore wear is ok. I'd give it a complete decoke and clean up and see how you go with new pistons and rings gaskets etc. -------------- "The only thing worse than being talked about is not being talked about...." oscar Wilde Back to top

Warwickb Group: Members Posts: 1911 Joined: Sep. 2003 Posted: Aug. 27 2006,20:55 Ditto what Jools said. When you've rebuilt it tho' you might want to run some radiator/cooling system cleaner through it? Looks to be quite a bit of corrosion on that cylinder stud (good idea to clean them up before putting it back together). If the rad and coolant galleries are corroded inside it wont be cooling as efficiently as it should. Won't make any difference to the misfire issue, but it will help prevent overheating and/or pump damage from bits of rust in the system in the future Rgds Wb -------------- A garage overflowing with old stinkers... Back to top

gbowie Two stroke spirit Group: Members Posts: 264 Joined: May 2006 Posted: Aug. 27 2006,21:57 In my opinion, that bore looks fine, hone marks are still there and only a few mild scratches. -------------- You'll live a lot longer if you give up the things that make life worth living ! Back to top

Warwickb Group: Members Posts: 1911 Joined: Sep. 2003 Posted: Aug. 27 2006,23:21 Yup. I'd have no problem running that barrel, Gav. It'd probably be wise to measure up the end gap of a new ring as Jools notes (the old worn ones would give a misleading reading as the rings themselves will have worn too) just to check it's within the wear limit, but I'd be surprised if the plating is too worn as you can still so clearly see the cylinder honing marks. Cheers Wb -------------- A garage overflowing with old stinkers... Back to top

ybk Group: Super Administrators Posts: 214 Joined: Mar. 2006 Posted: Aug. 28 2006,01:02 I'll just chip in and say that the bore looks fine to me as well. Back to top

Gavsp Group: Members Posts: 76 Joined: April 2006 Posted: Aug. 29 2006,21:31 Can anyone tell me the correct jetting for a 95 TZR 250 R? Back to top

Warwickb Group: Members Posts: 1911 Joined: Sep. 2003 Posted: Aug. 29 2006,22:03 I doubt very much that it's really a '95, Gav. - importers sometimes gave them later plates so they could charge more for them. The most reliable way to tell is by the frame number and cylinder casting markings. Most of the ones in the UK seem to be 91 models with the odd 92 or 93. The base R model was no longer being made by 95 - only the RS and SP/R models. I have a useful cross ref' chart but as it's not an image file I can't seem to host it and paste it in here. If you give us the id No's from the cylinders (eg 3XV-40 - you'll find it at the base of each cylinder) and the first 5 numbers from the frame Number that should be enough to identify it with accuracy and give you the factory jetting settings. Cheers Wb -------------- A garage overflowing with old stinkers... Back to top

Gavsp Group: Members Posts: 76 Joined: April 2006 Posted: Aug. 30 2006,11:03 I believe that my jet settings are wrong .   3xv-00 cylinders Thanks Back to top

Warwickb Group: Members Posts: 1911 Joined: Sep. 2003 Posted: Aug. 30 2006,11:15 Those are 91/92 R & RS model cylinders, Gav, Stock Main Jet size for the '91 is 190 in the upper carb and 260 in the lower. I think 92 R jetting is slightly different, but I haven't got the specs to hand. Check the frame number so that we can identify if the motor is likely to be 91 or 92, OK? What mains are in it? Rgds Wb -------------- A garage overflowing with old stinkers... Back to top

Gavsp Group: Members Posts: 76 Joined: April 2006 Posted: Aug. 30 2006,11:18 230 upper and lower. Back to top

Gavsp Group: Members Posts: 76 Joined: April 2006 Posted: Aug. 30 2006,15:02 What way do’s the piston go in, do’s the arrow point to the exhaust port? I’m just making shore as I can,t remember what way the arrow points. What is the torque settings for the Base and cylinder head. Thanks Back to top

Mr stinkwheels Group: Members Posts: 206 Joined: May 2006 Posted: Aug. 30 2006,16:46 Have a look on the outside of the carb bodies, on the side part, where the slide is located, and see if you can see anything printed in small letters or digits, there should be 3XV and a number, though it my be faint. If you cant see anything take some  pictures of the carbs and post them up to see if we can id them, tell us which one is the upper and the lower. 230 for the lower carb is 3 sizes smaller than std. but your plug was wet and black if i remeber correctly. Just wondering if some one has fitted 1KT/2MA carbs, i think they are 230 main jets, and slightly different outside parts. The arrow on the piston crown points to the exhaust. Back to top

Gavsp Group: Members Posts: 76 Joined: April 2006 Posted: Aug. 30 2006,17:04 The number on the side of the carb's is 3XV00 T143. And I’ve only just found out that my bike is a 3XV1. Thanks Back to top

Warwickb Group: Members Posts: 1911 Joined: Sep. 2003 Posted: Aug. 30 2006,18:55 If it's definitely a 3XV-1 then the frame No should be between 000101-045000 and the (stock) Main Jets should be 190 upper and 260 in the lower. Getting the jetting back to stock would be a good idea I'd think, but then you may want to do a plug chop or get it on a dyno with a gas analyser to check the jetting is suitable. Have the airboxes been modded at all? What's the number on the upper airbox lid? Rgds Wb -------------- A garage overflowing with old stinkers... Back to top

jools Group: Members Posts: 1221 Joined: Oct. 2005 Posted: Aug. 30 2006,21:10 Aslo make sure your float heights are set correctly and blow all the pilot drillings and breather airways out in the floatbowl. -------------- "The only thing worse than being talked about is not being talked about...." oscar Wilde Back to top

Gavsp Group: Members Posts: 76 Joined: April 2006 Posted: Aug. 30 2006,21:28 What are the torque settings for the Base and cylinder head is it the same as the TZR125 4FL and the 4DL? I’ve cleaned both carb’s out once but I am going to clean them again. Warwickb my upper airbox lid is 3XV 1, Thanks Back to top

Warwickb Group: Members Posts: 1911 Joined: Sep. 2003 Posted: Aug. 30 2006,22:01 The cleaner the better for carb's I always think. Torque settings are 14ft/lb for the cylinders & 8 ft/lb for the head. The upper airbox is the R type, then. Just wondered if someone had fitted an SP one (marked 3XV-2) as it was jetted up on that cylinder - Gawd knows why it was jetted down on the lower one though? - and the carb numbers suggest that they are re-jetted pukka 3XV carbs as Martin identified, rather than 2MA/1KT carbs, so that's one variable cleaned up It'll probably run better with the stock jets in though, as it will have been running lean on the lower cylinder and rich on the upper with the 230s. None of this really clears up why your lower plug was fouling though? I still think you should go over the ignition set up for that cylinder as I can only really think that it wasn't firing effectively or consistently on that pot and allowing unburnt fule and oil to accumulate til it fouled the plug? - check the connections to the coil particularly as they are not particularly robust - especially the angled one on the orange wire. I had a spradic misfire for a while on one of mine caused by a cracked one of those.   As you are not running the stock pipes, you should keep an eye on the mixture (on the upper cylinder definitely) when you go back to stock jetting too. A plug chop will give you an idea if it's too lean, tho I think Martin runs stock jetting with the Lomas's, so maybe it'll be fine. Happy fettling Wb -------------- A garage overflowing with old stinkers... Back to top

Gavsp Group: Members Posts: 76 Joined: April 2006 Posted: Aug. 30 2006,22:08 Warwickb I’m not to shore what you mean by a plug chop? Thanks Back to top

Warwickb Group: Members Posts: 1911 Joined: Sep. 2003 Posted: Aug. 30 2006,22:58 OK. Sorry, Gav. A 'plug chop' is a quick and reasonably accurate way to get an idea of whether your main jet size is somewhere near the mark. Basically you run the engine under a fair load - a good straight with a slight uphill end to it is ideal. Cane it through the gears - ideally to 5th or 6th. When the bike is at top revs in top (or fifth if you can't find a long enough straight), whip the clutch in, hit the kill switch, bring it to a halt and then whip a plug out to get an idea of the fuel/air mix on that cylinder. You are looking for a nice biscuity-tan colour around the electrode. This indicates a good fuel/air mix. Paler and you are weak (need to go up on the main), darker = rich, and you need to jet down. This is perhaps too simplistic an explanation, but if you do a google search for plug chop you should get some nice images to illustrate. It's not foolproof, and it takes some experience to develop a 'feel' for reading plugs, but you've got to start siomewhere and the 3XV seems to be pretty forgiving on jetting, so it's a good bike to start your experiments with I'd say.   Do a few practice runs to 'clean' the plugs so that you get a consistent reading (abort if the electrodes are very pale after the first run as this would suggest it's dangerously lean - not good) and don't forget to check both cylinders. Also, don't forget this will only give you a guide to the jetting, but I've always set my bikes up this way in the past and I find the 3XV fairly easy to 'read' Obviously you should not do this til the motor is run in . It's a pretty pleasant way to spend an afetrnoon, but obviously you need to select your spot - an old airfield is ideal. Be careful if doing it on the road. And dont' forget yer plug spanner Cheers Wb -------------- A garage overflowing with old stinkers... Back to top

jools Group: Members Posts: 1221 Joined: Oct. 2005 Posted: Aug. 31 2006,01:52 And don't forget to hold the clutch in till you come to a halt. Warning ! Don't be tempted to changed down as you coast with the clutch in as you could fry your clutch up or bugger up a gearbox!!   -------------- "The only thing worse than being talked about is not being talked about...." oscar Wilde Back to top

Gavsp Group: Members Posts: 76 Joined: April 2006 Posted: Aug. 31 2006,17:51 Can anyone tell me what this is, It came from where the red arrow points Is it a Thermostat switch? Thanks Back to top

Warwickb Group: Members Posts: 1911 Joined: Sep. 2003 Posted: Aug. 31 2006,18:56 That's your temperature sender, Gav' (the thermostat is simply heat controlled - no external switch or wiring. It simply opens when the water around it get's up to temp). The sender is missing it's connector 'spade' (they break off pretty easily), so I'm guessing your temp guage doesn't work? If you take it to a breakers they will probably have a similar compatible unit you could put in and connect up. there should be an unconected wire in the vicinity? Hopefully you'll then know how hot your motor is running. A happy 3XV usually sits around 60-65 under normal conditions. Rgds Wb -------------- A garage overflowing with old stinkers... Back to top

Gavsp Group: Members Posts: 76 Joined: April 2006 Posted: Sep. 03 2006,16:40 I’m still having problems with my bike, the lower cylinders is not firing again I’ve gone over the ignition system with no result the ignition coil is ok is there any thing you guys can suggest? Can it be the Magneto on the way out? Thanks Back to top

[ Track this topic :: Email this topic :: Print this topic ] Pages: (2) < [1] 2 >

TZR » Tech » 3XV » Backfiring when starting up

© nobody in particular Powered by Ikonboard 3.1.2a © 2003 Ikonboard