Yay, I got a new toy!

[Linksep]

I stumbled upon a mini bike on craigslist today; $60 needs throttle hooked up. I was thinking weekend project, I'll fix it this weekend and ride it next weekend. Well when I got out to look at the bike he tells me it doesn't idle but it will run wide open. On top of that when you roll the bike around the chain goes tight-slack-tight-slack. The chain actually gets so tight that the tire locks up.

So it's got problems, but I figure what the hell... $60 is cheaper than a Northern Tool frame kit.

Anyone experience that same phenomenon with a chain that loosens and tightens? I'm thinking it has to be a bent axle, something wrong with the clutch, or someone bought the wrong bolt pattern sprocket and drilled their own holes in it off center.

Argh, I have to do my homework and then clean off the old work-bench so I can tear into this thing!

Pictures and/or build thread to follow...

 

[mrfreyguy]

For the throttle look at the gov. linkage and the factory throttle linkage if it has one. As for the chain I'm guessing the sprockets offcenter. Both of these things happed to me but it was a pretty easy fix. Good luck

 

[EagleTalons]

Also low quality, gritty chain can cause the chain popping.

 

[Walter Keller]

the chain

Look at the chain closley - had a similar problem - chain was bent.

 

[Linksep]

Well I got the bike up on the bench and removed the wheel & chain. The chain seems straight and in fine condition, but in need of a serious clean and lube. The wheel bearing on the chain side feels like it might have shelled, I think that's my starting point.

Soooo, it's been about 17 years since I dealt with this stuff... Would you guys clean and re-lube the chain or just replace it? I'm thinking a can of gas for cleaning and some chain lube after. Would you replace that wheel bearing or the entire wheel? If just the bearing can I tap the new one in or do I need to invest in a 8" C-clamp to "press" it in?

Maybe later I'll rip the carby off and start checking that out to make sure it's in proper working condition.

 

[SpyGuy]

Might as well just go ahead and clean and re-lube .... doing things right the first time is less tedious than doing them over ....

 

[mike75925]

i have a mini, but i've worked more with bicycles. your presumption on an over eager jockey sounds good. on bikes, it is normally the crank sprocket has moved due to too much clearence between the crank and crank sprocket. remove the bolts that hold the sprocket to the wheel to see if they are bent. otherwise it may be a fried link.

 

[Linksep]

Upon further digging (removing the sprocket) I figured out the chain tension problem. Someone decided to enlarge the holes in the sprocket to use whatever bolts they had on hand. It's actually a pretty cheesy setup as the bike has Manco wheels like the one pictured below:

Those 6 holes are not actually holes but dimples to locate your drill-bit should you decide to drill them through to mount a sprocket. One of the many bolt patterns on NEW sprockets at Northern is a 4-bolt pattern that lines up with 4 of the 6 dimples pictured.

So at this point I see two options:
1) Buy a new sprocket for $26 and try my luck at drilling the front wheel (using the NEW sprocket and dimples in the wheel as a guide). Then put the FUBARed wheel on the front, or:

2) Spend $30+ (more than half what I paid for the bike) on a new Tri-star rim and reuse my old sprocket (the 3 on 3-3/4" bolt pattern on my sprocket appears to be unmolested).

Either way the cost of the bike has gone from $60 to $90+ and I haven't even tried to start the engine yet... They guy said it ran...

 

[Linksep]

Well at least the engine runs...pretty good too considering there was as much exhaust coming out of the head gasket as there was coming out of the muffler...

 

[KartRacer695]

i would buy a single wheel drive for northern tool, and they are about $50 or cheaper, depending on what size you need.