Yamaha g8 low engine rpm till warms up

Drew4u · 10-05-2021, 04:44 PM

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 · 10-05-2021, 10:44 PM

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 · 10-06-2021, 06:26 AM

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

Drew4u · 10-13-2021, 03:01 AM

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 · 10-13-2021, 06:17 AM

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 · 10-13-2021, 07:25 AM

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!

Dannyb1171 · 10-09-2023, 11:28 AM

Drew4u, what was the end result? I have the same issue and cannot find any answers. I had also tested everything that was mentioned as well. Please let me know. Thanks

10-05-2021, 04:44 PM	#1
Drew4u Not Yet Wild Join Date: Sep 2021 Posts: 12	Yamaha g8 low engine rpm till warms up 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?
Drew4u Not Yet Wild Join Date: Sep 2021 Posts: 12

10-05-2021, 10:44 PM	#2
slonomo Searching for The Way Join Date: Oct 2009 Location: Medina, Ohio (NEOHIO) Posts: 11,436	Re: Yamaha g8 low engine rpm till warms up 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.

10-06-2021, 06:26 AM	#3
crash12888 Gone Crazy Join Date: Jan 2007 Location: Chesterfield, Va Posts: 6,021	Re: Yamaha g8 low engine rpm till warms up Yup, usually 1 1/2 turns out to start.

10-13-2021, 03:01 AM	#4
Drew4u Not Yet Wild Join Date: Sep 2021 Posts: 12	Re: Yamaha g8 low engine rpm till warms up 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.
Drew4u Not Yet Wild Join Date: Sep 2021 Posts: 12

10-13-2021, 06:17 AM	#5
crash12888 Gone Crazy Join Date: Jan 2007 Location: Chesterfield, Va Posts: 6,021	Re: Yamaha g8 low engine rpm till warms up 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.

10-13-2021, 07:25 AM	#6
Drew4u Not Yet Wild Join Date: Sep 2021 Posts: 12	Re: Yamaha g8 low engine rpm till warms up 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 Not Yet Wild Join Date: Sep 2021 Posts: 12

10-09-2023, 11:28 AM	#7
Dannyb1171 Not Yet Wild Join Date: Oct 2023 Posts: 1	Re: Yamaha g8 low engine rpm till warms up Drew4u, what was the end result? I have the same issue and cannot find any answers. I had also tested everything that was mentioned as well. Please let me know. Thanks
Dannyb1171 Not Yet Wild Join Date: Oct 2023 Posts: 1

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