Tomos A35 Transmission shudder

Rusty Shackleford /

So I got my Tomos running pretty well finally, its a 94 a35 with 2,600 miles on it. Engine side of things is ship shape, hits 38mph gps on flat and shes mostly stock, but no matter what I do, I cant get her to shift smoothly between first and second. She takes off well in first and second works great once I get it to shift, but she shudders like mad if i maintain full throttle through the shift. If I back off the throttle at the perfect time, I can minimize or almost completely stop the shudder, but that doesnt stop me from feeling like I can improve or fix the situation.

I have tried atf type f at 250ml, 300ml, 350ml and 400ml, seems happiest somewhere between 300-350, but the issue is still present, just slightly more manageable.

I have tried the same quantities with dexron 4, also happiest at 300-350ml, honestly cant tell a difference between dexron and type f, probem still present.

Type a is next to try when i can find it.

I have opened up the case covering the transmission, noted the location of shims etc and reinstalled 3 separate times, can't see anything plainly wrong in there.

The shift return spring was broken in the bottom of the case the first time I opened it up, but from what ive read, no one seems to note ill effects by not having one installed.

Both clutches look perfect, I was expecting the second gear clutch to be totally grenaded, but both first and second have a bunch of pad material left and are assembled correctly.

Both the gears on the clutch assembly shaft look great, as do the ;arger 2 gears on the other shaft. No visible signs of wear on the teeth, no metal shavings or anything alarming.

The only thing that seemed out of the ordinary when inspecting inside the transmission was that the chain between the pedal shaft and the middle shaft with the two gears seemed excessively loose to me, though i dont have a properly functioning transmission to compare it with. The chain is very short and I would say mine has an inch of play in it, which seems like a lot. It does not seem to have enough play to cut a link off though, nor do I know if that would even be a good idea.

At this point i'm out of ideas and I was hoping someone else may have encountered this problem and found a solution or at least has a reasonable hunch I could explore. Thanks for any help. I'll just ride around it until I can get it figured out.

Re: Tomos A35 Transmission shudder

No need to mess with the chain inside the tranny. That is just for peddling while your engine is off.

The clip you found broken during first inspection of your tranny dampens the shift force blah blah blah.

There is no detrimental effect to a shift you are experiencing. There are no hills in Florida where we are. Tomos transmissions will eat you alive if you are not careful. I've rebuilt them front to back and back to front. Some had the same problem you have. Some things just can't be explained

Re: Tomos A35 Transmission shudder

BryAn eurism /

Keep your chain tight and be gentle on braking, you can help the gears live a bit longer and happier

Re: Tomos A35 Transmission shudder

so tj ur saying shuddery shifts won't fuck up a tomos tranny? mines been shuddering but I usually blip shift as a workaround. kinda worried I'm gonna crunch the gears. haven't opened up the tran to look around yet but I did get some new leather lined clutches to see if it was my shoes

Re: Tomos A35 Transmission shudder

ephraim zimbalist jr /

could need more shims

Re: Tomos A35 Transmission shudder

Rusty Shackleford /

Thanks for the heads up on the pedal shaft chain, I figured it was a moot point, but it was the only thing out of the ordinary that I discovered in there.

And i'll go ahead and order that return spring just because its so cheap, though I doubt it will make any positive improvement.

Is it possible that my 2nd gear clutch spring is not the correct tension/too loose and is engaging early and in poor fashion? Has anyone ever fixed a 1-2 shudder with a new, higher tension, second gear clutch spring? The change happens around 17/18mph on the tomos speedo, so maybe 15 actual mph? Feels like its too early, even when she was stock only pushing 29mph. First runs to 18 on the speedo and then im in second from 18-45 on the sppeedo, first feels way under utilized haha.

I briefly considered trying to shim out the middle shaft with the 2 gears on it, but seeing how poorly casted and thin the cover is, I was worried I might crack it if the shims protruded too far and I torqued the case down. It also seemed like it may be a fools errand considering it only does it on the gear change between 1-2. I figured if it was a shimming issue,on that shaft, I would likely experience a shudder as first engaged from a stop, but she works smoothly in that regard and everywhere else other than the 1-2 upshift

I have assessed the problem with a loose drive chain as well as when it has the proper amount of slack, or less, and the issue is present with the same severity.

I do not experience the shudder when slowing down and downshifting from 2-1.

Thanks for the input everyone and as TJ said, luckily I live in flat ass florida, so I can ride around the issue.

So a tangentially related question, that may or may not be sacrilegious, but I think i've read somewhere that a few people have variated a tomos? I did some searching but couldn't find any pertinent fabrication info or even pictures of said set ups. Im tired of my friends 50cc vespa clone smoking me off the line and this shitty gear change/transmission is causing most of the issue haha.

Re: Tomos A35 Transmission shudder

I hate the shudders, and really wish I knew how to stop them - as I am on Maui, there are places where it would be nonstop shuddering for miles if I were to run WOT. Last time I let it shudder for any length of time the shoes grenaded and I still haven't fixed all the damage.

Re: Tomos A35 Transmission shudder

Make sure that the pins are in the leading ends of the clutch shoes.

Re: Tomos A35 Transmission shudder

k blum Wrote:

-------------------------------------------------------

> so tj ur saying shuddery shifts won't fuck up a

> tomos tranny? mines been shuddering but I usually

> blip shift as a workaround. kinda worried I'm

> gonna crunch the gears. haven't opened up the tran

> to look around yet but I did get some new leather

> lined clutches to see if it was my shoes

Don't get me wrong. If you make it shudder and shift for a long period of time you WILL break stuff.

Re: Tomos A35 Transmission shudder

If you cut a diagonal slot in the 2nd clutch shoes the clutch will engage much faster, but as a result it will engage at a lower rpm and the engine will lug a bit before the rpm can pick back up again. With a combination of springs and fresh shoes you can get pretty good performance on flat ground, but mountains and offroad is always going to be hell on a two speed automatic.

Re: Tomos A35 Transmission shudder

A stiffer spring in the second gear clutch wouldn't be a bad idea. You may also want to try another clutch bell and see if you have the same issue. Those bells are just cheap pressed steel and are always off centered and off round to varying degrees. It may be that your 2nd gear bell has an odd warp in it that is causing the shoes to grab at different rates.

Re: Tomos A35 Transmission shudder

ephraim zimbalist jr Wrote:

-------------------------------------------------------

> could need more shims

^ This could be the problem. Check for looseness,end play,wobble. don-ohio (:^)

Re: Tomos A35 Transmission shudder

Rusty Shackleford /

Ordered 2 20lb clutch springs from treats yesterday. Would've got a 25 and a 30 as well, but they were out of stock. Hope it helps the shudder, should definitely help me off the line at least.

I know the pins were on the leading edge of 1st, but my memory is hazy on 2nd (thanks beer). Will confirm its correct when I do the springs.

I did check for up/ down and side to side play on all the shafts. The clutch shaft had almost no play, but the shaft with 1st and 2nd gear on it had considerably more play. At the time I didn't think much of it because it seats in the bearing in the side case. How much play should it have?

I guess I'll scoop up some shims of various thickness to play with and see if I can get an improvement. When I opened it up the first time, there were two thin shims of large diameter on the pedal shaft, one thick (1/8"?) shim of smaller diameter on the clutch shaft and no shim at all on the shaft with 1/2 gears. From what I've read, it seems each bike is shimmed differently, but is it normal to be sans shims?

The last few times I rode it I really tried to vary how I modulate the throttle during the shift and found that if I only back the throttle off to 60-70% instead of all the way to 0%, the clutch actually slips some and seems to function correctly. If I don't do it just so, it will either shudder or completely grab second and drop revs significantly. Not really an improvement or repair, but it does give me hope that I can get it to work correctly with enough fiddling.

Thanks again for all the input and patience, ill keep everyone updated once I have anything to report.

Re: Tomos A35 Transmission shudder

Rusty Shackleford Wrote:

-------------------------------------------------------

> I know the pins were on the leading edge of 1st,

> but my memory is hazy on 2nd (thanks beer). Will

> confirm its correct when I do the springs.

Correcting that fixed the same problem for me.

Re: Tomos A35 Transmission shudder

Rusty Shackleford /

Noted. I'll be making sure that's correct next time I'm in there.

Re: Tomos A35 Transmission shudder

can't believe no ones mentioned this yet.... The problem is this...you can pop the side cover off a million times, scratch your head a zillion times and still have a f up tomos. unless...it's balance man.... that's it, your double clutch bell is not balanced (inspect outer rims carefully) your shoes aren't balanced, your body ain't balanced, yes new stiffer springs nice but will produce more wobbles, shakes, shutters unless balanced. i gotta a cheap free way to balance bells too

Re: Tomos A35 Transmission shudder

Rusty Shackleford /

I really doubt it's the bell being out of balance, the vibration should be tied to rpms/speed if so. The vibration/shudder only happens when 2nd starts to engage, I'll agree unbalanced shoes or an out of round bell could produce my symptoms. The bell didn't seem out of round when I was in there, and I spun it with my hands extensively. And when I can get the clutch to slip while engaging second, it does so smoothly.

The shudder, while hard to describe concretely, feels more like a mechanical oscillation bounded by very sharp peaks, basically a ratchety feel. I'm good with a scale and file, so those shoes will get weighed/balanced when I do the clutch springs. Though I hope they're good to begin with. Total weight definitely affects engagement point, but I would have no way to measure their center of gravity which I feel would be equally or more important than their weight given their hinge point and centrifugal operation.

So I have the return spring/sprag coming on Wednesday. Clutch springs arriving on Tuesday and some other goodies unrelated to the transmission en route as well. Think I'm gonna paint the beast today, so I'll be pulling the whole engine and be taking a good look around in the transmission over the next couple days. Ill keep everyone posted on any developments.

Re: Tomos A35 Transmission shudder

sooo I just looked at my tranny that was shuddering. both sets of clutches were completely bare metal lol! put in new leather lined pads from Tim here on the forums. (good luck with the springs they tricky). shifts like butter now and shoots off the line. so if ur trans got the shakes it's probly something to do with the clutches.

Re: Tomos A35 Transmission shudder

Rusty Shackleford /

So it turns out my second gear clutch shoes were not correctly installed. The pin was installed on the trailing edge of the shoe, not the leading like it should be. So major points to dgjessing for calling that one.

I also had a chance to get 20lb springs on both first and second. Definitely helped my acceleration some, but I feel like I need 30 pounders on at least first, maybe second too. All in all though, majorly hyped to solved the shudder.

My stock cork lining on the clutches looks perfect, how quick should I expect that to change with 20/30 lb springs on there?

Re: Tomos A35 Transmission shudder

Rusty Shackleford /

And I ordered some 30 pounders, a #2 slide, a hi comp head and a new reed block. Wednesday should be fun.

Re: Tomos A35 Transmission shudder

Hey Buddy,

Did changing the pin location on the 2nd gear shoes fix the problem? I've been experiencing this exact same issue.

Thanks!!!

Re: Tomos A35 Transmission shudder

Brandon Weiss (Detective brandon to you) /

I would be careful putting too stiff a spring on the first gear....the cork wont last nearly as long if you live in a stop n' go traffic area.

I put a 20lb blue spring on 2nd, now i shift at around 16mph up from 12mph, and it revs much higher too before shifting.

Re: Tomos A35 Transmission shudder

What pins are people talking about. First Tomos and relined the 1 and 2 gears clutches with 3/32 and still have the same issue. Very very hard to get second gear but on a downward hill it goes in fine. Thing runs mint. Any help. Thanks

3E857586-3669-4ED5-9C2E-B6DC01821748.jpeg

Re: Tomos A35 Transmission shudder

Kevin Borcheld /

I think you have Wear out "rollenkooi"

https://wiki.tomosforum.nl/index.php?title=Rollenkooi_repareren

This is the same solution for 2speed

Re: Tomos A35 Transmission shudder

Kevin Borcheld /

I think you have Wear out "rollenkooi"

https://wiki.tomosforum.nl/index.php?title=Rollenkooi_repareren

This is the same solution for 2speed

Where standing "controleren" in picture, there check for wear, sanding on that place helping the metal rolls working right or something. My English is to worst for explaining it good

Re: Tomos A35 Transmission shudder

> Kevin Borcheld Wrote:

> -------------------------------------------------------

> I think you have Wear out "rollenkooi"

>

> https://wiki.tomosforum.nl/index.php?title=Rollenkooi_repareren

>

> This is the same solution for 2speed

>

> Where standing "controleren" in picture, there check for wear, sanding

> on that place helping the metal rolls working right or something. My

> English is to worst for explaining it good

Here is that^ page in English :

https://translate.google.com/translate?hl=en&tab=wT1&sl=auto&tl=en&u=https%3A%2F%2Fwiki.tomosforum.nl%2Findex.php%3Ftitle%3DRollenkooi_repareren

Re: Tomos A35 Transmission shudder

When main bearing on sprocket shaft ( the big one between cases) gets worn it will shudder and shake replace all bearing in the cases it shift like it should

Re: Tomos A35 Transmission shudder

Had an a3 with a shudder, was the spring for the overrunning/ one way clutch was broken.

Re: Tomos A35 Transmission shudder

I have rocked a number of different tomos over the years. They ALL shudder to some capacity it seems, some more than others. I think it's mostly just from the fact that they were crudely made and assembled. +1 for balancing things. Jake balanced all his gears/clutch bell/etc on Toby and it's one of the smoothest running and shifting bikes he claims. The bike I've had the longest has gotten smoother with different modifications. I now have a jammer first, a recorked second with grooves cut in it, and a stiffer 2nd spring. As far as I'm concerned you're just losing sleep over a silly arbitrary issue. It's just mopeds.

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