Yamaha g8 low engine rpm till warms up

[Drew4u]

Everything seems ok with the cart but it has low power at first then after 3 min or so you can notice the rpm speed up and the cart runs fine. I have cleaned the carb, changed the plug 2 times and ensured the air box is tight. Any ideas?

[slonomo]

Low speed circuit mixture might be off. If there's a screw on the side of the carb that's the idle air jet. Spin it all the way in (gently) and count how many turns it takes to bottom out. Be careful not to apply force when it bottoms out or you might damage the jet, just "finger tight" as they say.

[crash12888]

Yup, usually 1 1/2 turns out to start.

[Drew4u]

I did adjust that and it back fired some so I adjusted it and the throttle. Seemed to stop the back fire. Still having issues with it running well. It has low rpm like it is missing and then it just comes out of it. Then you can hear the rpms are increased and the cart runs great. It does smell a lot like fuel. Maybe it’s a spark issue but I have changed plug and held the plug up against the muffler and it showed spark. Maybe it is week not sure. I should also mention I did put a cheap China carb on but went back to the oem one once I cleaned it. Same results with both carbs.

[crash12888]

If the carb needle and seat are leaking fuel while sitting the engine might be loaded up when you first start up but three minutes is kinda excessive.
I would lean toward a engine warm up situation verses a fuel clear up change.
I would check valve adjustment and compression.
As far as the backfire, make sure your carb throttle plate is closing completely in the carb throat and not just against the idle stop screw.
Was the OEM soaked in carb cleaner and then washed/blown out or just blown out?
Very important to get all varnish out of it.

[Drew4u]

It was just blown out with carb cleaner. I will need to get a feeler gauge today and check the clearance. .004 right? I will let you know what I find out. Thanks!

[Drew4u]

I did adjust the valves. Both off a little but good now. I noticed that once I adjusted them I rotated it by hand then check and they was both way loose. Readjusted and seem fine now. Compression is at 15. Still missing once I adjusted every and then a couple minutes later takes off and runs great. I ohmed out the cool and it bounces around from 3.2 - 5.7 not sure if it should do that or not. I am looking for my nicer multimeter to ensure it is reading right. Any other ideas?

[smallblock450sl]

Now remember I have forgotten more then I remember. Spark witch normally fails when it runs for a while. Fuel normally works or it doesn't. A "Dynamic spark tester" that you plug onto the the spark plug and coil wire will show if bad spark at start up, like 8 bucks at the auto part store. Fuel, take the line off the carb and crank the engine over. It's not high pressure, but should have a constant output. Compression good/ valves adjusted/ cab cleaned 2 thoughts... unscrew the spark plug cap (counterclockwise), cut off a small section of the coil wire and screw the cap back on and test. You are using a NGK-BBR2ES spark plug right ? Now, the negative battery cable is attatched to the starter generator, if it is like G2/G9's it would have a small 18 gauge wire pigtailed onto the the connector. Cut back the electrical tape, cut off the 18 gauge wire at the eye let, install a new eye let and install it with the negative battery cable on the starter generator post. It is the main ground and is what the ignition system runs off. Sorry for the long post...I can not post as fast I think. Good luck

[Drew4u]

I will check to see if I can get a tester at the parts store when I take back the compression gauge. I checked the primary coil with a known good meter and it has 4.6 ohms that seems ok with what the manual says for the g9 but I am working on a g8 but can’t find the exact manual for it. It also shows to test the secondary coil by going from the red white wire to the spark plus cap. I don’t get continuity at all there. Maybe that’s the difference in the j38 and jf2 coil? I have never used a spark tester do I just compare the light strength from when it’s running rough to when it’s running good? The small ground cable is spliced to ensure a good ground to the starter generator. Thanks for the help so far. Hope you guys keep helping with this issue! When I disconnect the fuel line it pulses fuel out not with a lot of pressure but I would think enough. I could pull the carb off and ensure the bowl is full when it’s running rough if you think that would show it’s getting low fuel.

[Drew4u]

I got a tester and hooked it it ran great. I will try again tomorrow to see if it starts missing.