Urgent help needed with Jackshaft / Chain Problems (Predator 212cc)

Ooooooooooooook here we go......

As some of the people here know. I am building or basically finished building my first complete ride. For details and pics, here is the link to the thread:

http://motorbicycling.com/showthread.php?t=43358

Now.. I wanted to use my old china cr*p kit rear sprocket because the only way to install it was by drilling through both walls of the hub because I use 68 spoke rims (also see details in the thread of the bike).

I originally planned to use

12 clutch #35
22 JS in #35
11 JS out #41
44 rear #41

but I ended up with

12
15
10
44

because the JS in sprocket with mount..

http://www.affordablegokarts.com/mm...re_Code=A&Product_Code=0502&Category_Code=PCJ

http://www.affordablegokarts.com/mm...e_Code=A&Product_Code=0520*&Category_Code=PCJ

.. did not fit the mount and neither did it fit the shaft with the key, it had a lot of movement on the shaft so I replaced it with a 15t I had lying around because in the beginning I thought the problem I have could be caused my that. Sadly my ratio got MUCH higher with that exchange.

So here is my actual problem:

When I accelerate from dead stop it pulls away with the killer torque with no problem at all, regardless of the high gearing, but as soon it rolls with 5mph and I keep using a little bit of throttle, the chain vibrates like crazy around the jackshaft and especially after JS out to the rear sprocket between JS out and tire. I deleted one possible cause after the other, including grinding the JS out sprocket because the chain used to jump there and didnt get in correctly so now its grinded like the rear sprocket so a #40 bicycle chain could fit but nothing of what I did changed the problem that as soon its rolling, its "crunching" like the chain doesnt get into the small sprocket from JS out because of the combination of turning speed and vibration. I installed two chain idlers/tensioners today and its slightly better but only if I pull the throttle with almost close to zero throttle. As soon I give it some juice, it sounds and feels horrible all the way through the frame. Very unhealthy sound.

So right now after installing the tensioners I also cut together a BMX chain from my friends store to the right size and its a tiny little bit better, meaning I can go higher speeds if I accelerate extremely carful but I can literally almost not use any throttle or if it slightly goes uphill it crunches like crazy.

So with all that done it MUST BE the small JS out sprocket. I thought it might be too small and because I am using a #41 chain, it might not get around quick enough due the small size of the sprocket and I thought maybe I needed to change my setup to a #35 all the way to the rear too, but then I looked up a conversation with buck0 (David) from whom I bought the engine and I realized that he too was using a bigger chain for the rear:

"I ran a #35 chain to the 22 tooth then the other side was a #415 chain and used a 9 tooth"

Even smaller sprocket than I did. So what in the world could be the problem???

At this point I start to wonder if cutting the tube of the jackshaft (also explained in the thread) could cause that vibration, but then again, when its rolling without throttle it works. The problem only comes up when I use throttle.

I know the high gear ration doesnt help but right now I doubt that if I had a 60t sprocket in the rear, anything would change since I cant even get to a speed where the clutch engaged completely.

I have a million options like getting a 26t JS in sprocket and a larger JS out sprocket, or switching to a #35 chain and sprockets all the way but before I waste another week and 100 bucks for nothing, I would like to have some help because I really am out of ideas. I tried everything I could.

Thank you very much!!!!

Hmmmmm.. I am wondering if it could be also something else now that I read through all that again. Because the shaft sticks out more on the JS out sprocket than at the JS in sprocket. Maybe that causes the extreme vibration. I could try to move it to the other way towards the JS in sprocket as well.........Its not in the middle. I didnt think of that before.

Anytime. I know the gearing is very long, but as I said, from dead stop the power of the engine pulls that thing away like nothing. So it cant be the ratio at all. Let me take some picture with the iphone of how it looks in this moment. I am attempting to move the shaft to the other side because its not centered.

I use a #41 chain and the sprockets would fit also a #40. The JS sprocket I bought for #41 sprocket did NOT work with the #41 sprocket because some links did not get in complete and jumped and cracked instead so I grinded the sprocket and its better.

Here we go:

I moved the shaft more to the JS-in sprocket than the other way around and reinstalled the 22t sprocket at JS in. So now I have

12
22
10
44

If its still the same tomorrow, I am completely clueless.

After trying the 22t sprocket again that gave me problems before because it had too much space moving around freely at the key, I am starting to nail it down to the clutch itself. I cant even get it to run now with the 22t sprocket because of the power when the clutch engages. It ripped the 22t mount wider again and now the whole sprocket (22t JS-in) is moving again as it did before and the vibration makes it impossible to even get it moving.

I read about the thermodynamically designed clutch shoes I have (sadly after ordering) and that they seem to engage pretty violent. So maybe thats the main problem I have, giving way too much vibration on the jackshaft and so on the sprockets there and from there to the chain.

What do you guys think?

Except for the WD40 (which will be burned off in a second because that clutch is on fire in a second) I tried to get it going and then open the throttle slightly or little more. I got it to speed 10-15mph it rolls good without clutch and as soon the clutch engages everything shakes and crushes around the JS-out sprocket and the chain vibrates like crazy and I mean crazy! More than an inch left right and everywhere else. and that is when its super tight as it could be.

I am probably ordering this one tomorrow:

http://www.bmikarts.com/item/Clutch---35-34-400935-3162

Plus a one piece 20t sprocket from the same guys. If David drove it with the same JS-in sprocket/mount (and for me it get damaged just from engaging the clutch) and a 9t sprocket with same chain works and for me a 10t doesnt work, it can only be the clutch.

This is the one I have btw - completely metal.

No its a #35 that one runs perfectly smooth. The problem is the other chain.

I dont know what you see there to say that. But thank you

hey, yes david told me a lot about your builds. no, the stall cant be adjusted. the frame is stiff as it could be. and the engine as well is mounted as hard it could be, so is the jackshaft. i really looked into every possible cause and everything points at the clutch since yesterday.

as for the rear chain tensioner i will order one too, i will need one, but this is not the cause of my problem here, it happens even when the chain is super tight.

the clutch i want to order is just 25 bucks, so i will do that. i also want to try the wd40 thing after i took of the 22t sprocket again because that one was damaged by the vibrations and the mount is junk now.

culver - your the man! i put everything back together, still same sh*t, then i sprayed wd40 on the clutch shoes and voila - works like a charm.... for about 30 seconds until the wd is gone haha. so i will order a different clutch and sell this one. i think this clutch would work good with a smaller engine but not with the 212cc.

I bought hydraulic motorcycle brakes. They work so well that Im worried some car will crash me. Very powerful.

BTW I sell the clutch because I think it works well with any smaller engine. The problem here is the power of the engine with this clutch.

It runs well without clutch, its only when the clutch engages and when Im not standing anymore. Its the combination of the power of the engine and the type of clutch.

Hi KCvale. Thank you for your long answer but I already pointed the problem 100% to the clutch and the way it engages in a combination with the power of the engine already in very low rpm.

I sprayed WD40 on the clutch and the problem was gone completely. So I need to replace the clutch. Everything else you mentioned was checked first and is ok. Thank you!