Carb fix on a Yamaha G1

Johnnyo · 12-15-2013, 10:20 AM

I have an older G1, I think it's a G1.. The carb goes into a rubber intake & is secured with a hose clamp. It runs but I have to keep the choke out a bit. If I try to speed up it will hesitate & I have to pull the choke out and then it responds. If I'm driving along & take my foot off the gas pedal & step on it again, more often than not it will backfire.
I have had the carb off several times, & cleaned every jet I could see. When I try to adjust the jet on the side, it doesn't make a difference where I turn it to, I even turned it in all the way & nothing happens.. I'm at a loss..
It starts real easy, even after sitting a long time..
John

smallblock450sl · 12-15-2013, 11:01 AM

When a 2 stroke runs better with the choke pulled out and you've already cleaned/checked the carb, useually means low compresion or crank seals leaking.

1989Marathon · 12-15-2013, 11:36 AM

It sounds like you have two issues. If it backfires when you hit the throttle, after coasting for a bit, the throttle plate is likely not closing all the way when you let off the throttle. That is adjustable with the linkages.

The issue with having to choke it... if it starts real easy, it isn't likely that the crank seals are bad or you have low compression. It sounds more like you have a problem in the carb main circuit. When you cleaned the jets, did you remove them and spray through the hole in the jets. Also, did you spray through all the holes in the carb and make sure that it came out another hole in the carb?

Johnnyo · 12-15-2013, 01:34 PM

Thanks for your replies.. I had another good look, & under the body (clutch Side), there is a black streak supposedly from oil .. From all appearances it looks like the seal on that side may be leaking.. I will replace it..
No I didn't spray anything through the carb, I only took all the jets out, cleaned them, & blew air through them.. I will pick up some carb cleaner & spray cleaner through all holes..
thanks much..
John

slonomo · 12-16-2013, 10:22 PM

Probably should replace both seals. The other side is likely in similar condition. Also, I've heard that the "Yamaha" brand seals are much better than the aftermarket ones. Just a thought.

Johnnyo · 12-17-2013, 12:22 AM

Thanks. I went to the Yamaha dealer today & bought 2 seals.. Took me most of the day to get the inner sheave off.. I never saw anything frozen on that tapered shaft like this one was.. I had the bolt puller in there, & used the impact wrench, but no go.. squirted penetrating oil inside & in behind to no avail, even used a hammer on the end of the bolt thinking that might help... Finally went in to get a drink, & went out to give it one last try before hauling it to the dealer & see what they can do. I put the impact on it, & pop, it came off. So the rest of the job will come tomorrow..

slonomo · 12-17-2013, 05:02 PM

Sounds like the penetrating oil just needed time to work it's way in there....either that or "YOU WEREN'T HOLDING YOUR MOUTH RIGHT" as gramps would say....LOL

Johnnyo · 12-17-2013, 05:20 PM

Yup, & maybe a shot of that rum helped me, & my determination.. But now I got me anudder problem.. See my other post..

12-15-2013, 10:20 AM	#1
Johnnyo Not Yet Wild Join Date: Nov 2011 Location: Prince Albert Sask. & winters in Donna Texas. Posts: 49	Carb fix on a Yamaha G1 I have an older G1, I think it's a G1.. The carb goes into a rubber intake & is secured with a hose clamp. It runs but I have to keep the choke out a bit. If I try to speed up it will hesitate & I have to pull the choke out and then it responds. If I'm driving along & take my foot off the gas pedal & step on it again, more often than not it will backfire. I have had the carb off several times, & cleaned every jet I could see. When I try to adjust the jet on the side, it doesn't make a difference where I turn it to, I even turned it in all the way & nothing happens.. I'm at a loss.. It starts real easy, even after sitting a long time.. John

12-15-2013, 11:01 AM	#2
smallblock450sl Sometime's............ Join Date: Oct 2007 Location: Tacoma Washington Posts: 11,874	Re: Carb fix on a Yamaha G1 When a 2 stroke runs better with the choke pulled out and you've already cleaned/checked the carb, useually means low compresion or crank seals leaking.

12-15-2013, 11:36 AM	#3
1989Marathon Gone Wild Join Date: Oct 2010 Posts: 6,730	Re: Carb fix on a Yamaha G1 It sounds like you have two issues. If it backfires when you hit the throttle, after coasting for a bit, the throttle plate is likely not closing all the way when you let off the throttle. That is adjustable with the linkages. The issue with having to choke it... if it starts real easy, it isn't likely that the crank seals are bad or you have low compression. It sounds more like you have a problem in the carb main circuit. When you cleaned the jets, did you remove them and spray through the hole in the jets. Also, did you spray through all the holes in the carb and make sure that it came out another hole in the carb?
1989Marathon Gone Wild Join Date: Oct 2010 Posts: 6,730

12-15-2013, 01:34 PM	#4
Johnnyo Not Yet Wild Join Date: Nov 2011 Location: Prince Albert Sask. & winters in Donna Texas. Posts: 49	Re: Carb fix on a Yamaha G1 Thanks for your replies.. I had another good look, & under the body (clutch Side), there is a black streak supposedly from oil .. From all appearances it looks like the seal on that side may be leaking.. I will replace it.. No I didn't spray anything through the carb, I only took all the jets out, cleaned them, & blew air through them.. I will pick up some carb cleaner & spray cleaner through all holes.. thanks much.. John

12-16-2013, 10:22 PM	#5
slonomo Searching for The Way Join Date: Oct 2009 Location: Medina, Ohio (NEOHIO) Posts: 11,436	Re: Carb fix on a Yamaha G1 Probably should replace both seals. The other side is likely in similar condition. Also, I've heard that the "Yamaha" brand seals are much better than the aftermarket ones. Just a thought.

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12-17-2013, 12:22 AM	#6
Johnnyo Not Yet Wild Join Date: Nov 2011 Location: Prince Albert Sask. & winters in Donna Texas. Posts: 49	Re: Carb fix on a Yamaha G1 Thanks. I went to the Yamaha dealer today & bought 2 seals.. Took me most of the day to get the inner sheave off.. I never saw anything frozen on that tapered shaft like this one was.. I had the bolt puller in there, & used the impact wrench, but no go.. squirted penetrating oil inside & in behind to no avail, even used a hammer on the end of the bolt thinking that might help... Finally went in to get a drink, & went out to give it one last try before hauling it to the dealer & see what they can do. I put the impact on it, & pop, it came off. So the rest of the job will come tomorrow..

12-17-2013, 05:02 PM	#7
slonomo Searching for The Way Join Date: Oct 2009 Location: Medina, Ohio (NEOHIO) Posts: 11,436	Re: Carb fix on a Yamaha G1 Sounds like the penetrating oil just needed time to work it's way in there....either that or "YOU WEREN'T HOLDING YOUR MOUTH RIGHT" as gramps would say....LOL

12-17-2013, 05:20 PM	#8
Johnnyo Not Yet Wild Join Date: Nov 2011 Location: Prince Albert Sask. & winters in Donna Texas. Posts: 49	Re: Carb fix on a Yamaha G1 Yup, & maybe a shot of that rum helped me, & my determination.. But now I got me anudder problem.. See my other post..

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