Yamaha G2 Not Starting

[timquagliata]

Originally Posted by crash12888

Easiest way to quick check is removing the air box tube from the carb and putting your hand over the carb opening while trying to start it like you are trying to choke it.
You should get a strong vacuum pulse on your hand and some fuel should be wet on your hand.
If it doesn't start or at least fire by doing that, remove the spark plug and check the condition. If it is wet then you are not getting spark, if it is dry You are not getting fuel to the plug.
Try spraying a little fuel into the carb and try to start it.
Just to eliminate question, install a new plug, very rare but I have had spark plugs fire on the side of the block but not fire under compression.

Removing the rocker cover and rotating the crankshaft two revolutions will show you the up and down movement of both rockers and valves but lets wait on that for now.

Ok, I think we may be zeroing in on the issue. I removed the airbox tube from the carb and put my hand over the opening while trying to start it and I got no suction whatsoever.

TQ

[CP241]

Originally Posted by timquagliata

Ok, I think we may be zeroing in on the issue. I removed the airbox tube from the carb and put my hand over the opening while trying to start it and I got no suction whatsoever.

TQ

Check valve lash and make sure one of the rocker arms didn’t fall out. If it did, put it back and set the valve lash. There’s lots of threads here with pictures to show you how to do it if you’re not sure

[crash12888]

Yes, Getting close and hopefully something simple and not a big expense.
if valves are moving and everything looks good up top try flashlight down the spark plug hole and hand turn the crank to see if piston is moving.

[timquagliata]

Well, I took the cover off and one of the push rods had fallen off the arm. I put it back on and tried to set the valve lash but I was unable to get the nuts to break free from the threads. Instead the nut and threads broke free from the arm. So I went ahead and tightened them back up. I used the screwdriver in the spark plug hole technique to measure my gap. With the screwdriver at the highest point the gap was next to nothing. Maybe .001 or possibly touching. Anyway, I buttoned her back up like that and gave it a shot. It started up ok. I drove it around the block a few times and then the dame rod fell off again. Luckily I had brought my tools and quickly fixed it again. Any thoughts on what would cause the rod to fall off?

[CP241]

Originally Posted by timquagliata

Well, I took the cover off and one of the push rods had fallen off the arm. I put it back on and tried to set the valve lash but I was unable to get the nuts to break free from the threads. Instead the nut and threads broke free from the arm. So I went ahead and tightened them back up. I used the screwdriver in the spark plug hole technique to measure my gap. With the screwdriver at the highest point the gap was next to nothing. Maybe .001 or possibly touching. Anyway, I buttoned her back up like that and gave it a shot. It started up ok. I drove it around the block a few times and then the dame rod fell off again. Luckily I had brought my tools and quickly fixed it again. Any thoughts on what would cause the rod to fall off?

I don’t think you’re setting the valve lash correctly. I’ve never used a screwdriver to set it. Turn the motor by hand by spinning the clutch until it’s TDC and use feeler gauges to set both valves to .004

[CP241]

https://www.buggiesgonewild.com/show...lve+adjustment

[timquagliata]

Sorry for the confusion. I put a screwdriver in the spark plug hole. Rotated the clutch until the screwdriver was all the way up. Then measured my gaps or lack of gaps I should say.

If I can get the nuts to break free from the threads and set the gaps to .004, do you think that will solve my issue of the rod falling off the arm? Or, do I likely have some other issue going on?

[CP241]

Originally Posted by timquagliata

Sorry for the confusion. I put a screwdriver in the spark plug hole. Rotated the clutch until the screwdriver was all the way up. Then measured my gaps or lack of gaps I should say.

If I can get the nuts to break free from the threads and set the gaps to .004, do you think that will solve my issue of the rod falling off the arm? Or, do I likely have some other issue going on?

Watch the valves as you spin the clutch. There are 2 points where the piston is at the tippy top. Only one of them is top dead center. If you set the valves on the wrong tippy top then they’re gonna be wicked loose and the pushrod is gonna fall out rather quickly. You have to watch both valves go DOWN before setting lash. This is the compression stroke.

[raydhd]

Another method is watch say the exhaust valve fully open and then set the lash on the intake. And then watch the intake fully open and set the exhaust valve lash. There is a sticky of this in the clone section. This procedure works fine with stock duration camshafts.

[timquagliata]

I finally carved out some time to look at this again and CP241 was 100% right. I set the one valve at the wrong tippy top and sucker was "wicked loose". I think I got it purring like a kitten now. Thanks all.