TZR Forum

General Category => General Discussion => Topic started by: Bob the B on April 06, 2018, 07:45:11 PM

Title: Mikuni Carb Strip
Post by: Bob the B on April 06, 2018, 07:45:11 PM
Hi
I'm trying to get to the bottom of a poor running problem with my 2MA. I've had the carbs apart a few times but want to go through them thoroughly one more time. Up to now I haven't split the carb body so thought I would do this for completeness.

So, there are six screws fixing the plate on the side of the carb body, one of which has a strange head on it, it looks a bit like a torx head but has a small boss right in the centre which prevents you from putting a socket in there. Can anyone help me locate the correct tool to remove this screw?

Cheers
Bob
Title: Re: Mikuni Carb Strip
Post by: chubba on April 06, 2018, 07:52:45 PM
Look at security bits ( google it or security Torx ) you can get them all over cheaply , if that's what your after
Title: Re: Mikuni Carb Strip
Post by: Bob the B on April 07, 2018, 09:42:19 AM
Just ordered a set of security bits on eBay. thanks a lot.
Title: Re: Mikuni Carb Strip
Post by: f3 on April 09, 2018, 07:53:49 PM
the security bolt is shorter than the other bolts make sure it goes back in the same place or you can damage the carb body with the longer bolt
Title: Re: Mikuni Carb Strip
Post by: Bob the B on April 09, 2018, 09:23:42 PM
Thanks for the tip  (-P)
Title: Re: Mikuni Carb Strip
Post by: saltysealion on April 13, 2018, 02:01:12 AM
I was under the impression that it's best to leave those as they are. I think there are discussions around here somewhere on that.......

You can dunk the whole unit in a ultrasonic cleaner without removing those security bits, at least, thats what I did :)
Title: Re: Mikuni Carb Strip
Post by: yanw on April 13, 2018, 09:19:59 AM
I think you can do it if you replace the gasket but the gasket is not an available part so you have to make one yourself IIRC.
Title: Re: Mikuni Carb Strip
Post by: teezer250 on April 13, 2018, 03:02:26 PM
I think you can do it if you replace the gasket but the gasket is not an available part so you have to make one yourself IIRC.

You are correct that the gasket is not an available part.
I'll be putting my carbs in my ultrasonic cleaner soon as whole units with the jets,etc. removed.
Title: Re: Mikuni Carb Strip
Post by: tzr-v4 on April 13, 2018, 03:23:12 PM
Reproduction TM28ss gasket is available...
MACCAS https://www.gasketguru.co.uk/product/yamaha-tzr-250-2ma-1kt-carb-body-gasket-premium-quality-pair/ (https://www.gasketguru.co.uk/product/yamaha-tzr-250-2ma-1kt-carb-body-gasket-premium-quality-pair/)
Title: Re: Mikuni Carb Strip
Post by: Kev on April 13, 2018, 06:18:26 PM
Bob, I work a lot on TM28ss carburettors and have found most running problems are caused by blocked pilot jets and poor fuel supply when the bike is on the cold start cycle. You will need a very fine wire probe to ease down the brass tube that faces downwards when the float bowl is off. Regards
Title: Re: Mikuni Carb Strip
Post by: Bob the B on April 15, 2018, 12:17:56 PM
Thanks for all the input. I did take the front off the carb and it all looked fine I was prepared to make up another gasket if needed but the existing ones are in remarkably good condition.

Kev - I wondered if the brass tube could be removed but it looks a bit delicate! I did get a plastic brush bristle up through the bottom and through the cross holes.

I have another carb question. The clip position on the needle should be 2/5 according to the manual. Is that counting from the top or the bottom?

Cheers Bob
Title: Re: Mikuni Carb Strip
Post by: Kev on April 15, 2018, 06:22:06 PM
Bob, holding the needle in your hand sharp end downwards clip goes in 2nd last slot, donít leave out any plastic washers if fitted. No the brass tube in the carb body that feeds fuel in on the cold start cycle cannot be removed. Take your time finding the right size wire, sometimes those plastic/wire ties you get when you buy an electronic item can fit when the plastic is stripped off.
Title: Re: Mikuni Carb Strip
Post by: Bob the B on April 15, 2018, 06:27:46 PM
Kev - Maybe I'm being a bit thick but do you mean second from the top?

Bob
Title: Re: Mikuni Carb Strip
Post by: Kev on April 15, 2018, 06:53:01 PM
No Bob other way 2nd slot up from the sharp end, incidentally if you have the carb apart still and you are a bit of a newbie you might want to clean the jets and the emulsion tube to save problems later, get some cheap lemon juice and 50/50 mix of juice and water in an old pan on the hob, drop the bits in and boil them up for a few mins. Also check the 0 ring on the float needle holder if there is no resistance when you push the unit back in the carb body it will cause flooding. More you do now the less grief later. Regards.
Title: Re: Mikuni Carb Strip
Post by: Bob the B on April 15, 2018, 09:23:28 PM
Ah! in that case the needles in my carbs are in the wrong position, they are second from the top at the mo.

What's the emulsion tube? the plastic extension on the pilot jet?

Bob
Title: Re: Mikuni Carb Strip
Post by: Kev on April 16, 2018, 05:03:12 PM
No itís the brass tube the needle slide into, if you turn the carb upside down with the lid off, then remove the main jet and itís washer you can then tap out the tube with a suitable drift, caution watch out for the locating lug when reassembling. Alternative way of cleaning is to put a cotton bud in an electric hand drill and soak the tip in brasso or t-cut and force it in the tube then give it a good spin.
Title: Re: Mikuni Carb Strip
Post by: Bob the B on April 17, 2018, 05:13:15 PM
Where can I get o rings for the choke plunger and needle valve body? 
Title: Re: Mikuni Carb Strip
Post by: Kev on April 17, 2018, 07:49:59 PM
Legend motorcycles do a nice rebuilt kit Bob for not a lot of money, Iíve got 0 rings here if you donít want to buy the kits.
Title: Re: Mikuni Carb Strip
Post by: jcsnook on April 18, 2018, 01:37:45 PM
Where can I get o rings for the choke plunger and needle valve body?

O rings on the choke plunger?  You mean the float valve?  My choke plungers only have a rubber bottom on them, to seal against the carb body...no o ring.
Title: Re: Mikuni Carb Strip
Post by: Kev on April 18, 2018, 04:42:49 PM
My cold start plungers have o rings and rubber ends, maybe two different versions.
Title: Re: Mikuni Carb Strip
Post by: tzr-v4 on April 18, 2018, 05:10:30 PM
From what I understand...
 - bottom rubber is for sealing the fuel
 - o'ring is for sealing the air

But I maybe wrong...

Olivier.

https://yambits.co.uk/tzr250-choke-plunger-kit-p-69075.html (https://yambits.co.uk/tzr250-choke-plunger-kit-p-69075.html)
Title: Re: Mikuni Carb Strip
Post by: teezer250 on April 19, 2018, 02:00:46 PM
Both my 1kt bikes standard carbs choke plungers have "o" rings on them.
I have bought off ebay a 5 pack of Viton "o" rings for my float valves if necessary when i strip both sets of carbs down.
These are 6.5mm I.D. X 1.5mm cross section to fit keyster float valve brass body,the groove is 1.9mm wide.Not tried them yet.
The genuine yamaha float valve brass bodies "o" ring groove is narrower at 1.5mm
Title: Re: Mikuni Carb Strip
Post by: jcsnook on April 19, 2018, 03:33:44 PM
Intersting!  Maybe mine are missing?  Seems to run/work just fine without them tho...

They can't fit very tight in there, or they would prevent the plungers from moving freely and sealing tight against the carb body.

If you find a source for them, please post.  I've got to order some float valves and gaskets for my carbs, so maybe I'll order some new plungers and see if they come with 0 rings on them.
Title: Re: Mikuni Carb Strip
Post by: James P on April 22, 2018, 02:35:43 PM
You are correct that the gasket is not an available part.

Well, partly correct - the gasket isn't available from Yamaha as far as I know. However, Gasket Guru Dan can supply them. They are also available from Japan either separately or as part of a "rebuild" kit.

Regards,
James

Edit: Oops - have just seen that Olivier beat me to it :-[ !
Reproduction TM28ss gasket is available...
MACCAS https://www.gasketguru.co.uk/product/yamaha-tzr-250-2ma-1kt-carb-body-gasket-premium-quality-pair/ (https://www.gasketguru.co.uk/product/yamaha-tzr-250-2ma-1kt-carb-body-gasket-premium-quality-pair/)
Title: Re: Mikuni Carb Strip
Post by: teezer250 on April 22, 2018, 03:51:50 PM
I have just stripped my 1kt carbs down and found small rust particles in the float bowls causing them to leak when the engine was running.I ultrasonically cleaned them and bought and tried to fit the genuine yamaha net filters on the carb fuel intake spigots but the inside diameter of the spigots are too small for the net filters to go inside.

Has anybody else had this problem fitting net filters to 1kt or 2ma carbs?
As far as i know they are fitted to the 3ma and 3xv models.
Title: Re: Mikuni Carb Strip
Post by: Kev on April 22, 2018, 04:24:24 PM
I wonder if you have been given filters for a Dt125r instead as it has a larger brass fuel inlet spigot than the TZR250. Iím fitting extra in-line filters at the moment, as I cannot trust the filter in the fuel tank as the tank is starting to degrade internally.
Title: Re: Mikuni Carb Strip
Post by: teezer250 on April 22, 2018, 04:48:49 PM
I wonder if you have been given filters for a Dt125r instead as it has a larger brass fuel inlet spigot than the TZR250. Iím fitting extra in-line filters at the moment, as I cannot trust the filter in the fuel tank as the tank is starting to degrade internally.

What bike and what type of in-line filters are you fitting them to?
I bought the net filters from Webbs and the part number is: 1KT-14994-00.

The workshop manual does not show or list them in the exploded diagram of the carbs assembly.
Title: Re: Mikuni Carb Strip
Post by: Kev on April 22, 2018, 05:49:26 PM
Same number on Fowlerís website. Iím just fitting some clear in-line cheapies from eBay as extra insurance. Donít understand why yours donít fit.
Title: Re: Mikuni Carb Strip
Post by: Kev on April 22, 2018, 05:51:28 PM
Picture shows size of one fitted to Dt125r which also uses TM28ss
Title: Re: Mikuni Carb Strip
Post by: Kev on April 22, 2018, 05:56:31 PM
In-line filters on my 89 Tzr.
Title: Re: Mikuni Carb Strip
Post by: teezer250 on April 22, 2018, 08:32:19 PM
Pics showing O/D of filter and O/D of brass fuel spigot.Filter will definitely not fit in.
Title: Re: Mikuni Carb Strip
Post by: Kev on April 22, 2018, 08:49:47 PM
Iíve just checked out Fowlerís for Dt125r filter and itís listing the same part number you quoted yet the carbs definitely have different size fuel inlet spigots. Strange one that.
Title: Re: Mikuni Carb Strip
Post by: teezer250 on April 22, 2018, 08:55:04 PM
maybe 2ma carb spigots are larger than 1kt, or a later carb modification.
My carbs are from a 1986 1kt which I bought from an importers before it arrived from Japan to them,so no mix and match.
Title: Re: Mikuni Carb Strip
Post by: teezer250 on April 30, 2018, 07:07:59 PM
Now fitted inline filters.
Title: Re: Mikuni Carb Strip
Post by: tzr-v4 on May 01, 2018, 03:34:55 PM
teezer250 where did you get the inline filter from ? Look metal one ?
Title: Re: Mikuni Carb Strip
Post by: teezer250 on May 02, 2018, 02:44:37 PM
teezer250 where did you get the inline filter from ? Look metal one ?

Off ebay uk,and a uk seller with a fast delivery,definitely recommend:
https://www.ebay.co.uk/itm/Motopart-Silver-Universal-Inline-Alloy-Fuel-Filter-6mm-Bore-Tubing/361896794314?hash=item5442bad8ca:g:Da4AAOSwAO9ZWl-8
Title: Re: Mikuni Carb Strip
Post by: tzr-v4 on May 02, 2018, 03:10:38 PM
Thanks.
The filter element looks like mesh or other thing ?
Title: Re: Mikuni Carb Strip
Post by: teezer250 on May 02, 2018, 03:47:48 PM
It is a bronze filter similar to this:
https://www.ebay.co.uk/itm/APS-Replacement-30-Micron-Bronze-Fuel-Filter-Element-For-Billet-Filters/311433300571?hash=item4882df0a5b:g:uPMAAOSwT6pV3q8o

Title: Re: Mikuni Carb Strip
Post by: teezer250 on May 12, 2018, 09:28:58 PM
Today I stripped my other 1kt bikes carbs which has 2ma carbs that I bought brand new off ebay in 2005 for £80.
These carbs were in my loft for 10 years until I built this bike 3 years ago from bits I had acquired over the years.
These have larger diameter fuel inlet spigots than my other 1kt and also has the tiny net filters fitted which had accumulated a few rust particles.
Also the carbs floats are the oblong/square type which are different to my other 1kt's round ones.
This means there are differences in carb specifications and no wonder I could not fit the net filters on my other 1kt's carbs on my earlier recent posting.
Title: Re: Mikuni Carb Strip
Post by: Kev on May 13, 2018, 01:55:11 PM
Can I ask? Do any of your carbs have a un drilled passageway on the side of the larger opening ( where the Dt125r has an air mix screw fitted) as mine do but I have never seen on others.
Title: Re: Mikuni Carb Strip
Post by: teezer250 on May 13, 2018, 02:16:59 PM
Not sure what you mean so I have taken some pics of the 2ma carbs that I cleaned yesterday.
Title: Re: Mikuni Carb Strip
Post by: Kev on May 13, 2018, 04:59:31 PM
Wow, nice and clean, I take it they have been aqua blasted. The Dt125r has very similar carbs if fact you can interchange them. It has an adjustable air jet on the side close to the pressed in brass plugs, clearly I can see your carbs have not got them, but thanks for replying. Incidentally my Ď89 tzr started up today after 10 years in the back of albeit heated outhouse, Gave the carbs an ultrasonic clean and rebuild and she eventually fired up.
Title: Re: Mikuni Carb Strip
Post by: teezer250 on May 13, 2018, 05:12:14 PM
Wow, nice and clean, I take it they have been aqua blasted.
No they haven't been aquablasted,only done 1700 miles from new in 3 years.
Today I stripped my other 1kt bikes carbs which has 2ma carbs that I bought brand new off ebay in 2005 for £80.
These carbs were in my loft for 10 years until I built this bike 3 years ago from bits I had acquired over the years.