yamaha G9 air box leak?

grassfarmer · 06-02-2016, 09:36 PM

Is it possible for the air box to have an internal leak and still be sealed on the outside? I know the lid is sealed well, just not sure about the internal grooves that fit together as you put the lid on. They seem a little warped and its hard to know for sure if everything went together correctly as you put the lid on. thanks Bill

TheNewGuy · 06-03-2016, 05:26 AM

Welcome to BGW!

How does the cart run?

grassfarmer · 06-03-2016, 04:55 PM

Runs fairly well with the choke half out. I've checked the air lines, fuel comes to the carb just fine, can't see any cracks in the carb spacer. the carb gaskets look good also. I also checked the crank seals and there is no oil around them and they too look good. I did clean the carb with carb spray, but did not do any reaming out of the jets, just sprayed through them. thanks Bill

TheNewGuy · 06-04-2016, 06:52 AM

Sounds like it may be running too lean. Adjust the carb for a richer mix.

sho305 · 06-05-2016, 07:59 PM

Yes possible with that rubber thing in there, but usually if the outside is all on they are OK. Only the 2 stroke G1 has runnability issue with crank seals as its a 2 stroke. I usually tell people to just jet it richer its not that hard, but first make sure the carb is clean inside, no leaks at the spacer or intake hose or airbox complete. If that don't fix it you still have a leak or you can jet it. If you jet it I recommend removing that intake silencer its the part over the generator. I took my carb off and removed the jet, you have to be careful not to strip it can be in there tight. After that take jet drill or torch cleaner and make it next size larger, put it back in but not very tight, put on cart and try it. If still lean you can get bowl off in the cart with iirc 10mm wrench and get a screwdriver in there and take *carefully and over pavement* the jet out and enlarge a little more, repeat as needed until it takes off full throttle well. Then tighten it in there when done.

I have put bungee cords around the airbox to hold them tight, you can get the rubber pulls fairly cheap from a dealer, and you can put a bolt through the box side to hook the pull on if it breaks.

grassfarmer · 06-06-2016, 08:23 AM

thanks for the info, I'll try reaming out the jet a little. I adjusted the valves to .004 that helped quite a bit, It now runs at low RPM's very good and at higher RPM's on flat ground, but going up an incline I have to back off the pedal to keep it going. I think there are small backfires through the carb when it has to work. any ideas? Bill

sho305 · 06-07-2016, 05:32 PM

Unless you used the stock airbox and muffler (maybe even then) it will be lean stock. It can be lean and run ok on a governor, but it wont work well without it.

Spicyunicorn · 06-08-2016, 07:38 AM

Have you checked compression?

grassfarmer · 06-12-2016, 04:03 PM

I have not checked compression. Around 120 is good?

06-02-2016, 09:36 PM	#1
grassfarmer Not Yet Wild Join Date: May 2016 Posts: 9	yamaha G9 air box leak? Is it possible for the air box to have an internal leak and still be sealed on the outside? I know the lid is sealed well, just not sure about the internal grooves that fit together as you put the lid on. They seem a little warped and its hard to know for sure if everything went together correctly as you put the lid on. thanks Bill
grassfarmer Not Yet Wild Join Date: May 2016 Posts: 9

06-03-2016, 05:26 AM	#2
TheNewGuy Admin/Moderator Join Date: Dec 2006 Location: Ohio Posts: 18,050	Re: yamaha G9 air box leak? Welcome to BGW! How does the cart run?
	Ron PLEASE VISIT Our Sponsors * BGW GEAR The Store The G2 Project * Swing Arm Drop & Repair * Geep1 Project

06-03-2016, 04:55 PM	#3
grassfarmer Not Yet Wild Join Date: May 2016 Posts: 9	Re: yamaha G9 air box leak? Runs fairly well with the choke half out. I've checked the air lines, fuel comes to the carb just fine, can't see any cracks in the carb spacer. the carb gaskets look good also. I also checked the crank seals and there is no oil around them and they too look good. I did clean the carb with carb spray, but did not do any reaming out of the jets, just sprayed through them. thanks Bill
grassfarmer Not Yet Wild Join Date: May 2016 Posts: 9

06-04-2016, 06:52 AM	#4
TheNewGuy Admin/Moderator Join Date: Dec 2006 Location: Ohio Posts: 18,050	Re: yamaha G9 air box leak? Sounds like it may be running too lean. Adjust the carb for a richer mix.
	Ron PLEASE VISIT Our Sponsors * BGW GEAR The Store The G2 Project * Swing Arm Drop & Repair * Geep1 Project

06-05-2016, 07:59 PM	#5
sho305 Vegas modded 420 Join Date: Jun 2009 Location: West MI Posts: 15,443	Re: yamaha G9 air box leak? Yes possible with that rubber thing in there, but usually if the outside is all on they are OK. Only the 2 stroke G1 has runnability issue with crank seals as its a 2 stroke. I usually tell people to just jet it richer its not that hard, but first make sure the carb is clean inside, no leaks at the spacer or intake hose or airbox complete. If that don't fix it you still have a leak or you can jet it. If you jet it I recommend removing that intake silencer its the part over the generator. I took my carb off and removed the jet, you have to be careful not to strip it can be in there tight. After that take jet drill or torch cleaner and make it next size larger, put it back in but not very tight, put on cart and try it. If still lean you can get bowl off in the cart with iirc 10mm wrench and get a screwdriver in there and take carefully and over pavement the jet out and enlarge a little more, repeat as needed until it takes off full throttle well. Then tighten it in there when done. I have put bungee cords around the airbox to hold them tight, you can get the rubber pulls fairly cheap from a dealer, and you can put a bolt through the box side to hook the pull on if it breaks.

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06-06-2016, 08:23 AM	#6
grassfarmer Not Yet Wild Join Date: May 2016 Posts: 9	Re: yamaha G9 air box leak? thanks for the info, I'll try reaming out the jet a little. I adjusted the valves to .004 that helped quite a bit, It now runs at low RPM's very good and at higher RPM's on flat ground, but going up an incline I have to back off the pedal to keep it going. I think there are small backfires through the carb when it has to work. any ideas? Bill
grassfarmer Not Yet Wild Join Date: May 2016 Posts: 9

06-07-2016, 05:32 PM	#7
sho305 Vegas modded 420 Join Date: Jun 2009 Location: West MI Posts: 15,443	Re: yamaha G9 air box leak? Unless you used the stock airbox and muffler (maybe even then) it will be lean stock. It can be lean and run ok on a governor, but it wont work well without it.

06-08-2016, 07:38 AM	#8
Spicyunicorn Gone Wild Join Date: Jun 2015 Location: NW Iowa Posts: 1,669	Re: yamaha G9 air box leak? Have you checked compression?

06-12-2016, 04:03 PM	#9
grassfarmer Not Yet Wild Join Date: May 2016 Posts: 9	Re: yamaha G9 air box leak? I have not checked compression. Around 120 is good?
grassfarmer Not Yet Wild Join Date: May 2016 Posts: 9

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