Author Topic: 2ma conversion  (Read 18155 times)

xracer

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Re: 2ma conversion
« Reply #30 on: February 24, 2014, 09:31:53 PM »
Hi Jim
This could go on forever , My 3ma4 front forks are full adjustable , unlike earlier models ,my rear shock is a cbr600rr Honda , again fully adjustable . The front forks are as you have suggested 50mm shorter ( see photo ) however the standard 2ma forks protrudes above the top yokes to allow the clip on's and spacer to be fitted ( total of 52mm ) .Many racers drop there yokes even further . The weight of each fork leg can be seen in the photo's , slightly heavier I agree, but now controlled by a more advanced compression and rebound system .I have yet to disassemble the front forks but it would be interesting to see where exactly the extra 1lb or so was gained , is it sprung or unsprung . I am at present slightly restricted in my tyre selection and will be running Bridgestone's  cross-ply's. When I am able to find a suitable 17" rear wheel I will change both tyres to radials , enjoying the benefits of superior grip and the reduction of sprung weight. Incidentally the standard 2ma swing arm, with bearings ( No linkages ) is 7lbs and the 3ma swing arm with bearings ( again no linkage ) 9.2lbs .The longer swing arm of the 3ma will allow the rear suspension to react more progressively and has been a trend in modern bikes both on the road and race track for many years.
« Last Edit: February 24, 2014, 10:05:17 PM by xracer »

Bngt

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Re: 2ma conversion
« Reply #31 on: February 24, 2014, 11:18:57 PM »
Very interesting! I am reading and learning while waiting for my three boxes of parts on a boat from Japan.

I admit I have bought it blindfolded but with some reasoning about their suitability. I was thinking that a 3XV-SP front end would likely be an upgrade with both better damping systems, adjustability, better brakes and a 17" wheel with options for modern radials.

I have recently put together and for the first time tested a stock 2MA and agree that better brakes is probably not needed, I am very impressed. The Kawasaki 636 brakes with 4 individual pads that I now use on my Yamasaki is slightly better in feel but that could be pad material as well.

For the rear I am also going for the 3MA swingarm. It is just so great looking with the bracing under the arm instead of above. I don't know if the bracing is needed but I think a slightly longer and stronger arm with such a low weight penalty must be better.

On my Yamasaki I have the 120/17 & 180/17 combination from the ZX636 and it works surprisingly well. It turns really fast compared to stock and it seems like the wider wheels contribute to this since the contact patch moves sideways as you lean. The wheels are lighter than stock YPVS wheels in spite of their increased width but I expect the 3XV wheels to be even lighter and probably not much heavier than the 2MA.

My 2MA that has been raced weigh 117kg without fuel otherwise wet. I want a light bike but am not that concerned about unsprung weight unless the road is very bad.

I have no clue about how to fit the parts yet but increasing swingarm axle hole size in the frame seems like one alternative?
2x2MA+2xF2

xracer

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Re: 2ma conversion
« Reply #32 on: February 24, 2014, 11:38:14 PM »
Hi Bgnt
 Don't rush to bore the swing arm spindle point just yet , my earlier photo's may offer an alternative solution .When I get the swing arm machined to fit I post some more photo's ,can't really see why it won't work but who knows !!

Jim Lyon

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Re: 2ma conversion
« Reply #33 on: February 26, 2014, 08:35:07 PM »
PART 1 - UNSPRUNG WEIGHT CONTINUED

   While I'm generally in favour of cast type wheels as they're stiffer & the run out is more accurate ( & maintained ), I sometimes despair @ what Yamaha have chosen to produce. Granted that the state of deterioration of UK roads is deplorable,but  I still feel lighter is better,
especially considering that a stock/O.E. 2.75 x17" minus tyre & discs weighs almost 12 lbs & a 3.50x17" with cush drive, but minus tyre, disc & sprocket comes in @ a chunky 15 lbs. it almost makes me want to go back to wire wheels & alloy rims,  & even if it means increasing unsprung weight slightly, sod it, fit an inner tube inside a radial tyre !
  With present technology clearly carbon fibre is best, but companies like BST seem only interested in doing them for superbikes! While I've mentioned before a possible alternative source on one of my earlier threads

                                     http://pure2strokespirit.net/forums/index.php?topic=77.msg1613#msg1613         


  All I got was moans about the expense - well, due to medical problems as the result of an accident I've been on low income for what seems like forever, so just do what I do, scrimp & scrape on the small stuff in order to be able to afford the things that make life worth living - it's called saving up !
  While the Aprilia RS250 forum(s) had got organised in order to get BST to do a small run ( but I was suggesting a alternative small independent source as a possibility, but getting organised in order to get better deals from manufacturers seems beyond this forum [ see also my thread on H.E.I.S. - High Energy Ignition systems here

                                       http://pure2strokespirit.net/forums/index.php?topic=554.0


where, behind the comments, it seems that some people didn't want to give up on their small  improvement for something MUCH better ] ), a lot of comments were getting off the point e.g. suggesting we use RS250 rims sizes on our Yams. I just see that as lacking focus, as to me
the Aprilia RS250 chassis is BIG for a 250 c.c. To me, there's a chassis badly in need of a bigger engine, & as I prefer something more on the lines of a "pocket rocket", why on earth would I be interested in rims that are too wide?? - No, if I could get carbon fibre wheels, I wouldn't then undermine the whole point by trying to ADD unsprung weight, I'd continue trying to pare it down e.g. single drilled discs front & rear, alloy rear sprocket, optimum tyre sizes of 110/70 front & 150/60 rear, both radials & the OPTIMUM rim widths for that are 3:00" front & 4.00" which also gives the best tyre profile, etc.
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Jim Lyon

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Re: 2ma conversion
« Reply #34 on: February 26, 2014, 08:42:36 PM »
PART 2 - USD FORK CONVERSIONS CONTINUED

 Seems like xracer's 3MA4 forks are SPS? So, regardless of whether they're R/RS or SP, both 3MA & 3XV forks appear to be the 'same' leg lengths ( & 2" short for our needs? ), which is our main consideration @ this point. Certainly, my concern is avoiding the "extra hinge in the frame" syndrome that I experienced when dropping the yokes down on myLC350. So, whether we find out if this syndrome is a problem on 2MAs or not would seem to depend on if  somebody tries 3MA/3XV short USD forks on a 2MA? If it doesn't work, then we're going to have start looking for other sources with longer fork legs ( min. of 740 m.m. from top yoke to middle of front wheel spindle & probably a bit longer to allow for tuning out any OVERsteer problems ).  If we have to go down that road, personally, I'd prefer to use a Yamaha set ( as in keep the bike all O.E. Yamaha if possible, with the lightness of a R/RS USD fork, with the diameter of the lower chromed part @ the bottom of the leg being 39 m.m.)
   I'm not only aware that the 2MA forks have an extra 2" that I've ignored, but that was deliberate. The reason for that being while the factories probably have expensive instruments to measure rake & trail etc., but as that level isn't available to us "garden shed mechanics", we need something easier. So what I'm trying to obtain is a quick easy measurement that ( assuming the bike being measured gives reasonably neutral steering ) can be used to give a direct comparison to other similar bikes, or in this situation, comparing lengths of fork legs in situ, so as to see if there is a reasonable chance  ( in this case ) of seeing what alternative USD forks can be used for 2MAs. whether a particular bike's ride height is horizontal or not, they all have their own "stance", which seems to be, basically, how high the steering head is above the ground ( @ the moment I'm  ignoring the rear whilst we're concentrating on front forks ) ride height . Clearly you need to know wheel & tyre sizes, & I'd suggest that most of the time your not that bothered if you have some spare fork leg stuck above the top yoke (unless, as I mentioned you have an OVERsteer condition, then sliding the yokes UP the fork leg seems to be the easiest way to correct that condition ). I also did the
measuring with the legs UNcompressed not only because it was easiest for me, but it eliminates other variables.
 P.S. I'm aware that xracer has brought up another topic ( swinging arm length ), but as this thread has enough separate topics being discussed, I'd prefer to cover that separately, in PART 3, so that we can discuss these topics in separate & distinct groups, so that it's easier to locate & extract specific info.
YAMAHA RIDERS GO IN DEEPER AND COME OUT HARDER

xracer

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Re: 2ma conversion
« Reply #35 on: February 27, 2014, 01:24:50 PM »
 Unfortunately due to work commitment I've not been able to make much physical progress on my bike . Where possible I've tried to find any information regarding handling issues with guys in the 3ma section of this forum including posts from the old archives section. Very little if any can be found  regarding this issue. Certain ideas were discussed ,mainly replacement rear wheels , ( we'd all like a 17" if the right one could be found ) and even the possibility of raising the fork legs above the top yoke to enhance steering. One article even suggested the swing arm adjuster slots be extended to allow the wheelbase to be shortened . It would appear that most owners of the 3ma are more than happy with their current suspension components , allowing for the odd change of rear shock which is understandable given the age of most bikes . I am convinced that with both front and rear end of a 3ma fitted to my 2ma I will have a bike that will handle and stop equally as good if not better that the original set up , obviously time will tell. Finally regarding over brakes motorcycles , this is something  I have never experienced. I've used many brakes in various condition and have had to adapt accordingly. Could this sensation be as a result of a mismatch between the master cylinder piston and those found in the caliper. One has to remember the effect ,applying the front brake has on a bike , the movement of mass can be clearly felt and measured. The forces acting on the suspension can easily overload  it and cause the front to temporarily lock. The line between late braking and locking the front is in it's self a skill ,as can be witnessed every racing weekend at the Motogp's !!!!!!
« Last Edit: February 27, 2014, 01:51:54 PM by xracer »

Bngt

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Re: 2ma conversion
« Reply #36 on: February 27, 2014, 08:25:25 PM »
Is your plan to use clip ons below the top yoke and if so do you intend to use such ones that raise them above the yokes?

That was my plan.
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mboddy

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Re: 2ma conversion
« Reply #37 on: February 27, 2014, 10:03:24 PM »
I am convinced that with both front and rear end of a 3ma fitted to my 2ma I will have a bike that will handle and stop equally as good if not better that the original set up ...
What makes you think that? I am not convinced that it will be better.
Increased wheel base will slow the steering.
Wider wheels will slow the steering and require higher lean angle to maintain the same corner speed.
Higher lean angle will make the ground clearance problems worse. Even if you fix the ground clearance issue then your corner speed may still be reduced.
Heavier wheels and swing arm and brakes will increase unsprung weight.
Are the new suspension components sufficiently better to deal with this weight increase and provide an improvement?
 
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Crank

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Re: 2ma conversion
« Reply #38 on: February 28, 2014, 07:47:53 AM »
Wayne (ZoomZoom on this forum) has a 1kt with 3MA front end and rear fitted.

Edit: 3MA1
« Last Edit: February 28, 2014, 02:59:49 PM by Crank »

mboddy

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Re: 2ma conversion
« Reply #39 on: February 28, 2014, 12:32:14 PM »
Sorry about my last post. I can get a bit carried away when I am in the middle of a pretty full on week.
I shouldn't assume that my opinions on what is better for me will be better for everyone.

Your fully adjustable 3MA4 forks should be an improvement over the stock 2MA forks.
They may be more cost effective than modding the stock 2MA forks with Emulator Valves and better springs and larger axle.
And they will modernise the look too.

I happen to like the way my bike handles. As Jools says our 2MAs with 125GP slicks are almost telepathic in their handling.
But others may like a more planted feel. Longer wheelbase and wider tyres will assist stability.

I too always liked the deep braced look of the 3MA arm. But to my way of looking at things the 3LN delta box is the ultimate for these light bikes.

ps. Just received my copy of the latest suspension book: Motorbike Suspensions Modern Design and Optimisation
Have only browsed it but so far it looks good.
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xracer

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Re: 2ma conversion
« Reply #40 on: February 28, 2014, 03:22:39 PM »
Thanks guys for your interest and advice. I have had to wait many years to finally get back to owning a 2 stroke,  regularly filling the gap in my life by watching and reading anything that involved 2 strokes. Modern 4 stroke racing does hold my interest as much, I appreciate their talents but still believe that 250cc class was the breeding ground for some best riders in the world. Mark is right in many of the things he says and is very passionate about his beliefs. If I was a team manager Id want him in my team. I get back to the build process .Keep you all updated as it goes along

Jim Lyon

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Re: 2ma conversion
« Reply #41 on: February 28, 2014, 04:34:29 PM »
PART 3 - ENGINES & SWINGING ARMS, etc.

 As Mark implied, trying to understand motorcycle engineering trends can be a bit like "peering through a glass darkly"; nevertheless, here's what I THINK I understand. While there may be more than I can see, we can see that, from the 350YPVS, while such moves as changing from cylinder to crankcase reed induction should lead to longer piston life, a 2MA engine further benefits by being  aproximately 14 lbs lighter than the 350, & slightly shorter. If we look @ the 3MA & 3XV, while their side loading gearbox does make it easier to access, & thus is more beneficial for racing applicatins rather than road, the potential benefit to us is that, @ the same time, Yamaha chose to change the traditional horizontal alignment of the gearbox input & output shafts to a more vertical
alignment, thus making the engine significantly shorter. This effectively puts more weight to the front of the chassis, & with more weight on the front tyre, & with this increased front end stability, riders can push it harder.
  While a long wheelbase tends to create stability @ the cost of slow steering  that can be compensated for, to a degree by a steeper steering head. But clearly getting that right is a balancing act. And while I admit I don't  really understand why, clearly Yamaha see some benefit from changing the proportions within  a given wheel base i.e. a shorter engine can lead to a longer swinging & that apparently can lead to more progressive rear suspension action?. Before this new combination, of longer swinging arms used with a shorter engines, from time to time longer swinging arms had been used, but either they made the steering too slow, or because it wasn't stiff enough, on occasions, when cornering hard, sufficient force would build up in the swinging arm that, when the rear tyre lost traction, it would do so viciously,like a coiled spring suddenly let loose?
  My own experiences of this are quite limited, but when I first made enquiries about buying a Metmachex alloy swinging arm, I was asked whether I wanted standard length, or the quite popular version of 20 m.m. longer. So, I said that I'd come back on that. What I did do with the stock swinging arm is make use of the fact that the rear axle sits in a slot that allows it to be moved to accomodate chain wear. I fitted a longer worn chaim with an extra section added to move the axle as far back in the slot as possible, & tried that. After I'd tried it for a while, I fitted a brand new chain of stock length, which put the rear axle close to the front of the slot. I have to admit there wasn't a huge difference, & probably a careless, insensitive rider wouldn't notice any difference, but what I found was that with the axle to the rear, the bike turned a little more slowly in corners, & I was tending to push the front end more, trying to get the back end to come round.
With the axle to the front of the slot, I felt the bike was more willing to turn into corners, feeling more eager to turn, yet felt more sure footed. Granted  I was more used to it, but unlike with the longer wheelbase, I didn't have to consciously think what I was doing, the bike just went where I pointed it, without me having to think about it, thus leaving me more attention to focus on the road & traffic. For me it just felt more comfortable & natural to be able to automatically point the bike & it would follow the line I'd chosen without using any conscious effort.
  So, it sems we have two groups-

1) The 1KT/2MA/2XT series which still retain the horizontal gearbox shaft latout, thus have a slightly longer engine, with a shorter swinging arm, & slightly less steep steering head angle & 2" longer RWU forks ( measured from top yoke to mid front axle, being 740 m.m UNcompressed. ( but that probably is intended to compliment the shorter swinging arm.

2) The 3MA/3XV series has a more vertically aligned cassette geabox layout, longer swinging arm & steeper steering head angle with 2" shorter USD forks ( measured  from top yoke to mid axle, being 690 m.m. UNcompressed )

 Whether that makes a significant difference on the street, not having ridden any of the latter ones, I don't know.
  However, with these two combinations I tend to doubt if you can "mix & match" &  while it might work to a degree, I suspect that it'll no longer be the optimum, e.g.a longer 3MA swinging arm on a 2MA is just likely to make it turn more slowly. And while I quite like the reverse cylinders & pipes of the 3MA, though I've only seen photos, I tend to suspect it's another of those bikes with a big chassis that I don't care for. And while I've heard it's a bit slow steering., how much  of
that may be the rear 18" wheel increasing the polar moment of inertia? -  I don't know. Clearly some guys want to go for a a 17"rear wheel  to get better rubber, but it's likey they might have to play around with tyre size &/or ride height to obtain neutral steering.
  Obviously, with either set of bikes you can play around with ride height to fine tune how quick you want the steering to be. My experience with a 1980 LC350 showed there wasn't much room to manoeuvre before it developed the "extra hinge in the middle" syndrome", I don't know how much other bikes may be prone to that? But clearly you can only go so far with this adjustment before you run out of ground clearance! The advantage of this is it's quick & easy ( but I do
recommend that if you do it, you make your adjustments in small increnents. ). And if you adjust the ride height @ the rear, then the first obvious place is the shock preload ( which while it may give a softer action does NOT alter the spring strength - to do that, oddly enough, you need to fit a different strength spring ), as that's free.  After that ride height adjusters &  different length
"dog bones" start costing money. - HTH?

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Jim Lyon

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Re: 2ma conversion
« Reply #42 on: February 28, 2014, 04:38:00 PM »
Sorry about my last post. I can get a bit carried away when I am in the middle of a pretty full on week.
I shouldn't assume that my opinions on what is better for me will be better for everyone.


Nothing wrong with being passionate - especially as you're right ( as in the theory correctly predicts your experiences - & it also works for me ) - Keep it coming !   :)
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Bngt

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Re: 2ma conversion
« Reply #43 on: February 28, 2014, 06:07:11 PM »
Theory is good, it helps you understand directions but experience help you understand magnitude. Some effects are very small others much bigger and certain only in combinatioon with others. Often you do not get at all what you predict.

The biggest difference I think on a small bike is if you weigh 60 or 110kg. You can't expect that a bike which is optimal for the small rider will be set up well for the big rider. I also believe that there is a dramatic difference in different tyres and the grip and flex etc will require different set ups to work well.

Let's test and see what works.
2x2MA+2xF2

xracer

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Re: 2ma conversion
« Reply #44 on: February 28, 2014, 11:23:26 PM »
Hi Bngt
Meant to reply earlier : Think I'll run the bike with the clip on's below the top yoke , it's what I'm use to and it's as Yamaha intended. Never seen the ones in your attachment before, but if I'm struggling to overcome the aches and pains of too many racing crashes then I might consider getting a set .
FYI : Originally thought as the headstock bearing were the same sizes and the stems the same length it would be a simple matter of swapping  yokes etc. , Unfortunately other issues mean that further work will be required to make the swap work . Both bottom yokes, plus stems, are off to the engineers tomorrow to have them pressed out and swapped . Another problem solved ( I hope )