2 Brand new engines Seize?

I recently bought a 70cc 2 stroke kit from ebay. I got everything installed and when I went to start it for the first time, the engine cycled a few times then seized up. So that my back tire would not turn, even with the clutch all the way pressed. The person I got the engine from exchanged it for me and when I got the next engine, something similar happen. But the second time the engine tried to turn over twice before seizing again.

I do have experience with 2 stroke engines, so the obvious should be known. Like I did mix the oil with the gas properly. Had the fuel valve switched on and primed the carb, with the choke up.

I have yet to get two of these engines to even turn over for me once. Am I missing something obvious or do I just have bad luck. As far as buying junk off
ebay.

Eric T

Hmmmm.....Could the chain have bunched up under the cover because of it running too loose or having a tight link?....That can cause the rear wheel not to turn with the clutch pulled in also...

Unusual that the engine would seize up so quickly....I mean within just a few cycles (maybe something like a rod or something broke?)I would guess running straight gas (no oil mix) the engine should last longer than a few strokes (I know because a helper of mine once ran straight gas in a 2 stroke Lawn Boy mower.....actually lasted quite awhile considering no oil....) BUT since you said you did put 2 stroke oil in the fuel I would think it has to be something mechanical....

Andrew

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I will take a good look to see if a chain is bunching up. If this is the problem would not changing the angle that the chain enters the motor relive this tangleing? So that the bunching of the chain would be freed up and then continue normal function of the engine. I would love for that to be the problem, but I doubt it.

Thank you for your prompt response,

ET

angle of chain should not cause chain to bunch or hangup. What can do it is if the "c" clip on the master link is on backwards. The rounded end of the "c" clip should be first to ride over the engine sprocket, followed by open end.

Another thing that could cause the chain to bunch up would be the drive sprocket needs to have the sharp edges ground off. The instructions with my kit suggested this to keep the chain from "sticking" to the sprocket...

Don't forget to get the chain aligned properly and don't over tension it- 1/2"-3/4" play.

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If it ain't broke, and you mess with it long enough, it will be.

A locked up engine will not prevent the sprocket from turning.

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If it ain't broke, and you mess with it long enough, it will be.

When you get these kits out of the box, is there anything you need to do to the clutch or the engine before you start it? Could this be a clutch issue. I did not adjust the engine in any way out of the box. Just installed, gas/oil and go.

Thank for your help,



ET

Yes, there are several things you can do to help have a nice, reliable bike....
Bicycle Motor Preperation And Care

Sometimes the sprockets are tight right out of the box, you should turn the sprocket first, or push the bike slowly and let the clutch out until you know it's free.

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If it ain't broke, and you mess with it long enough, it will be.

Agreed..

Pulling in the Clutch will eliminate any motor strain.

It seems your having a problem with the Drive chain and sprocket.

You need to make sure the drive chain and front sprocket are not jammed..

cheers

Bob