82 g1 gas sputters & backfires wont turn over

[Bigblock460]

I have fire to the plug, gas pulses from pump although sometimes it doesn't seem to pulsate that strong. Don't know if that's because I've disrupted the vacuum trying to check if I have good flow. After cranking for a bit I will get a pop and some backfire from the exhaust. This cart was sitting when I got it, here's what I've done so far. New gas, New fuel filter, new plug and cleaned carb. There is one needle valve that screws in from the top outside of the carb that I don't understand how it works? Sometimes when it does hit it's like the starter spins faster"cranks faster" and that's the closest I've got to the engine running. If I hold my hand over carb while cranking it feels to have good suction. What do I need to try to hear this cart run? Thanks

[Lochlin]

Being that you have spark and gas really narrows things down. It's critical that you check compression. It should be 120 or higher. If that's ok then crank seals are another sore spot. A couple of notes: If you have no compression then nothing that you do will make the engine run. If the crank seals are bad you may get a couple of burps on starting fluid or some fuel manually injected into the cylinder. Compression is critical, though.

[mikeasis]

Originally Posted by Bigblock460

I have fire to the plug, gas pulses from pump although sometimes it doesn't seem to pulsate that strong. Don't know if that's because I've disrupted the vacuum trying to check if I have good flow. After cranking for a bit I will get a pop and some backfire from the exhaust. This cart was sitting when I got it, here's what I've done so far. New gas, New fuel filter, new plug and cleaned carb. There is one needle valve that screws in from the top outside of the carb that I don't understand how it works? Sometimes when it does hit it's like the starter spins faster"cranks faster" and that's the closest I've got to the engine running. If I hold my hand over carb while cranking it feels to have good suction. What do I need to try to hear this cart run? Thanks

IF it is an 82 then its the J17 engine 80-90 psi is good for them

[Lochlin]

Originally Posted by mikeasis

IF it is an 82 then its the J17 engine 80-90 psi is good for them

Good call. Those dastardly 82s are the like the proverbial red-headed step children.

[Bigblock460]

Ok thanks, I'll check compression. It is a J17 unfortunately. I'll check crank seals too, after looking I did notice an oil under the fan side of the motor on the concrete.

[mikeasis]

Originally Posted by Bigblock460

Ok thanks, I'll check compression. It is a J17 unfortunately. I'll check crank seals too, after looking I did notice an oil under the fan side of the motor on the concrete.

The J17 while an odd ball is still a good little motor. Crank seals are very common and relatively cheap

[Bigblock460]

If I end up needing to do the clutch side where do I find a puller? Will i need a puller for the fan side? Also prolly a silly question but why are these crank seals such an issue to this engines performance?

[mikeasis]

Originally Posted by Bigblock460

If I end up needing to do the clutch side where do I find a puller? Will i need a puller for the fan side? Also prolly a silly question but why are these crank seals such an issue to this engines performance?

They are an issue because they are over 30 years old. The crank seals seal the crank case where vacuum is present for proper operation of the vacuum fuel pump. Bad crank seals equal low or no vacuum which creates no fuel or not enough. The clutch puller is around 25 bucks on ebay / amazon. Make sure you get the correct puller for the clutch you have. The comet clutch takes a different puller than the stock Yamaha clutch.

Fan side you can use a harmonic balancer remover tool you can rent at autozone.

[Bigblock460]

I would say this seal is bad lol. Is there a good spot to hold the crank so this nut will break loose?

[mikeasis]

Originally Posted by Bigblock460

I would say this seal is bad lol. Is there a good spot to hold the crank so this nut will break loose?

I use a piston stop tool. Ive heard of people using rope in the plug hole as a piston stop.