Hi, I purchased a cheap quad and it's now becoming one of those money pits, with many previous bodge jobs from previous owner causing constant issues, it has a new wiring loom, ignition, electrical components and coils with all cut offs inc rear tether now working as it should (perfect spark), new carb as the old was damaged internally (fuel supply is now good), gave it an oil change (10/40 fully synthetic oil) we had it working for about an hour (working very well) then it stopped and hasn't run since!?

I've checked all of the above and it still looks fine, with good spark, fuel going through and what seems like plenty of compression, on further inspection I noticed that the timing was out by 4 teeth but is now in place as it should be, the spark plug hole also needed rethreading and has now been done, with a snug fitting plug in theory it should have started............nope still not starting!

The starter motor is turning, it now has a new battery, loom, carb and yet still won't turn over, out of process of elimination I drained the oil and it partially turned over!?!?
Can the wrong oil stop these things from running?
Please someone help before it gets thrown in the river. Lol.
Thanks
Mark

 

If the starter turns but crankshaft doesn't, there is a problem with the starter mechanism, either gears/chain, or the one way clutch, or the flywheel come loose. Take the cover off the flywheel and see what happens when you press the start button. If the flywheel has come loose, you will need to re-time the valves after fixing the flywheel key, as you will have set them with the T mark not being at TDC.

Really thick oil could cause problems, and the wrong additives can cause trouble with the wet clutches, but 10/40 should be OK as far as being thin enough.

 

Hi, Thank you for your response, that's a very good point about the flywheel/timing, I did think it strange that the timing was out after having it running for an hour!
Could this of most likely have happened if the flywheel has come loose, caused by the keyway/flywheel key on the crank shearing, meaning I've probably just put the timing even further out if place. FML.
Any advice on fixing this issue?
Thanks again.

Mark

 

Hi, so the Starter is turning the flywheel as I believe it should, I can turn the flywheel manually without it moving the chain, how can I tell if the flywheel key isn't working?
Thanks

Mark

 

Normally, on cars, the "key" is nothing more than a notch on the shaft or a metal tab insert that slips into a notch on the shaft. It's job is to make sure the gear on the end of the shaft doesn't move from a certain location. It should be pretty noticable if your "key" isn't working because you will see a notch on the gear and nothing in the notch.

 

The flywheel is keyed to the crankshaft so, if the crank isn't turning but flywheel is, then your key has sheared. I always grind the tapers of crank and flywheel in if this has happened, as the broken key tends to chew them up a bit. You treat it like a valve and smear valve grinding paste on the taper, then the backwards and forwards turning motion to grind the tapers in, until both surfaces are that mat grey when the paste is washed off with solvent.