Re: '85 Tomos GB engine "scrubbing"...

So my Tomos runs a bit ragged and its throwing oil all over the chain and rear wheel.

When I get up to any decent speed 15+mph, I can feel and hear the engine sorta catching and releasing. It's really hard to describe. So it sounds like waaaaaaa waaaaaaaa waaaaaaaaa waaaaaaaaaaa... instead of

waaaaaaaaaaaaaaaaaaaaaaaaaaaaaahhhhhhhhhhh...

I can feel it too. So I'm riding along and I can literally feel and see my body jerking with the tension (thats a good way to describe it) on the engine/crank.

I replaced and rebuilt the transmission but didn't take the crank case off. I used to think it was in my rear axle b/c I had an interesting situation there as well but fixed that problem and still I get the "scrubbing" (another good way to describe the way it feels). I've pretty much narrowed this thing down to something going wrong with my crankshaft, seal or other related part(s). Any help in that regard is much appreciated.

The black oil on my chain and wheel is leading me to believe that that crank seal/bearing is shot, allowing the oil out and to fix that, I'm going to have to remove that crank case and somehow get the old seal out and a new one in. I don't have the special tools to pull out seals so I'm knowing that this will be a bitch.

I don't have any pictures up because I haven't taken it apart yet. (edited)

Re: '85 Tomos GB engine "scrubbing"...

the crank seals are easy enough to change but,

the oil on your chain and wheel sounds like the tomos "black wheel of death"

at any rate you need to recheck your "tranny rebuild" for errors (edited)

Re: '85 Tomos GB engine "scrubbing"...

"special tools to pull out seals so I'm knowing that this will be a bitch. " I don't use special tools. Stab n dig'em out. Just don't scrape on the case, its aluminum. The crank is nice n hard steel.

Myron's mopeds has a good write up on black wheel of death. Email them for info to fix it.

Now this grinding/scraping/whatever... several things to check:

Chain tension

Tranny fluid level. Needs to topped off periodically since ur loosin it.

Clutch lining

Theres a oneway bearing behind the larger gear on the midele shaft in the tranny. Check it for cracks and ware.

Re: '85 Tomos GB engine "scrubbing"...

Thanks.

-Tuck, yeah the bike seems to run better when the chain is tensioned properly. I just seem to have a problem with it continuing to go from tight to loose but I'm pretty sure thats because I'm not tightening the wheel down good against the swingarm (thats a whole nother story involving seamed bearing upgrade and using PVC as axle spacers! That's getting fixed...).

However, here is something weird: when I do tension the chain and tighten the wheel, if I slowly turn the pedal and watch the chain, there seems to be places in the revolution where the chain is tight and places where it loosens. Does that makes sense? So if I'm turning the pedal, you can see the chain visibly getting tighter and then looser as you turn the pedal.

-I will be changing my tranny fluid soon and will be sure to keep an eye on it.

-the clutch lining is good. brand new and with less than 100 miles on it.

-that one way bearing is good too. when I rebuilt the transmission, the first gear (the larger one) was shot to hell. It was chipped and in bad shape. I replaced it and that bearing seemed fine and undamaged.

I'm reading all of the other resources on the black wheel of death too. I'll get what I need and try to address the leak when I replace the sprocket. I found this nut that comes with a seal on treats. I think I'll give it a try.

http://www.treatland.tv/tomos-UPGRADE-M22-nut-for-front-sprocket-with-seal-p/tomos-m22-nut-n-seal-234388.htm

Thanks

Re: '85 Tomos GB engine "scrubbing"...

That nut works good. Maybe time for new chain and sprockets? Its best to replace all 3 at once.

Re: '85 Tomos GB engine "scrubbing"...

Yep. I plan to get all three in my next order. Some Sava tires as well. Treats has a really nice chain with gold links for my Golden Bullet.

Re: '85 Tomos GB engine "scrubbing"...

Terencio Safford Wrote:

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

> Thanks.

>

> However, here is something weird: when I do

> tension the chain and tighten the wheel, if I

> slowly turn the pedal and watch the chain, there

> seems to be places in the revolution where the

> chain is tight and places where it loosens. Does

> that makes sense? So if I'm turning the pedal, you

> can see the chain visibly getting tighter and then

> looser as you turn the pedal.

The chain has tight spots. Usally it's from a neglected chain that has rusted between the links. From what you have described it has been ridden long enough to cause uneven wear on the chain and both sprockets. Replace all three as a set and inspect tension again. If you still have uneven tension with the new parts then check that the rear sprocket is centering up correctly on wheel.

Re: '85 Tomos GB engine "scrubbing"...

Hmmm...

I think we're getting somewhere now, Pacer. That makes sense to me and what you describe seems like a real possibility with my bike. I will be adding those sprockets and chain to my Treats list for next week. This will give me the opportunity to go ahead and change my gear ratio as well.

Thanks for your input as well as everyone else who is following and commenting.

Re: '85 Tomos GB engine "scrubbing"...

Terencio Safford Wrote:

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

> Hmmm...

> I think we're getting somewhere now, Pacer. That

> makes sense to me and what you describe seems like

> a real possibility with my bike. I will be adding

> those sprockets and chain to my Treats list for

> next week. This will give me the opportunity to go

> ahead and change my gear ratio as well.

> Thanks for your input as well as everyone else who

> is following and commenting.

No problemo...glad to help.

Remove chain from ped and the tight links will show themselves.

Re: '85 Tomos GB engine "scrubbing"...

Alas, I took the case off over the front sprocket and the rear sprocket. The wear on the sprockets is obviously bad! It's terrible actually and my chain...well, it's stretched all to hell and it shows. So the chain was stretched so bad over worn sprockets that at certain points in its revolution it d not sit flush down into the sprocket teeth but instead would ride OVER THE TOP of the teeth!

Also, after taking the case off, i noticed some super serious grinding that went on inside the case. I'm thinking the previous owner must have thrown the chain once or twice and it chewed up the case on the inside. I'm guessing that all of this has everything to do with my rough "scrubbing".

I've ordered 28t front sprocket (26t is stock) and a 20t rear (22t is stock). The front gear change requires grinding down the separator inside the case but oh well and the rear requires some modifications to the wheel and/or the sprocket setup itself but it's worth the extra 8mph or so.

I would post pics but this damn site has like a 1mb limit (which is stupid).

So hopefully this helps anyone who might follow this thread in the future. I'll keep it updated...

Thanks for all the help.

Re: '85 Tomos GB engine "scrubbing"...FIXED

Just thought I'd come in here and wrap this up for anyone who might find themselves in a similar situation.

I changed both sprockets in front and rear and the chain. This completely fixed my problem. Chain was stretched to hell and the sprockets were so worn thin that they looked like little vampire teeth!

If you have this problem, inspect your sprockets and chain!!

Want to post in this forum? We'd love to have you join the discussion, but first:

Login or Create Account