Intermittent bog at full throttle...strange vin what year is this thing?

badbrad63 · 07-15-2019, 09:42 PM

Hello everyone . I have a yamaha which I believe to be a G2. The vin is j38-082977. The vin decoder doesnt show this so does anyone know what year it is? Now to the problem. When you cruise at half throttle it runs good but at full throttle it runs good, cuts out for a second runs good, cuts out over and over. It just falls flat on its face, goes, falls, goes. I have put an aftermarket filter and tube on it but have been increasing jet size looking for sweet spot. It did this with the stock airbox too. It has 160 cranking compression. I replaced the plastic intake carb is clean. I'm not sure what I'm missing here. The gasis new, spark plug, fuel lines etc. Its done this since I bought it and I'm stumped. Gov is unhooked also with cable rerouted to carb. I'm going to change fuel filter in bottom of tank and replace the belts but I doubt this will fix the cutting out at heavy throttle. Thanks in advance for your insight into this.

CP241 · 07-15-2019, 11:19 PM

You are hitting the rev limiter. That's what you're experiencing. The rev limiter is built into the ignitor and cant be bypassed without replacing the ignitor with something else (like HEI conversion).

I would get a tach, see what RPM its cutting at, and just be sure to keep it below that limit. These are low revving engines, spin them too fast and you'll drop a valve, drop a pushrod, or worse.

cgtech · 07-16-2019, 04:01 AM

J38-0xxxxx should be first year G2A.

badbrad63 · 07-16-2019, 05:34 AM

Ok thank you maybe I can put taller tires on it to get a little more speed out of her!

badbrad63 · 07-16-2019, 05:35 AM

Ok thank you very much your guys knowledge on these things is much appreciated!

badbrad63 · 07-16-2019, 07:51 PM

If it's the rev limiter why is it hitting it so early? Even with all stock including airbox it did this. I'm going to change drive belt that's the only thing I can think of that would make it hit rev limiter so quick like a lower gear ratio with the belt being pretty worn?

CP241 · 07-16-2019, 08:04 PM

A clutch/belt problem can contribute to hitting the rev limiter early. Running the throttle pedal straight to the carb can also cause it. Instead of an easy smooth acceleration up to speed, it can rev out early before it gets to speed.

I guess the big question would be, how fast are you going when it starts cutting out? And is it lifted, if so how big are your tires?

CP241 · 07-16-2019, 08:07 PM

Also as for the filter in the bottom of the tank, just rip it out and throw it in the trash. Use a regular in-line filter on the fuel line instead. Serves the same purpose but lots easier to replace

badbrad63 · 07-16-2019, 10:00 PM

It's going about 8 mph when it does it. Thanks alot I'll do that with the fuel filter! I will go over clutch real good and I ordered a new yamaha belt no cheapo. Should I just hook up the dang governor again? I'm not looking for a hot rod but 8mph ain't cutting it! Thanks alot for all your help!

badbrad63 · 07-16-2019, 10:01 PM

Also not lifted but I will if you think taller tires will be beneficial!

07-15-2019, 09:42 PM	#1
badbrad63 Not Yet Wild Join Date: Jul 2019 Posts: 6	Intermittent bog at full throttle...strange vin what year is this thing? Hello everyone . I have a yamaha which I believe to be a G2. The vin is j38-082977. The vin decoder doesnt show this so does anyone know what year it is? Now to the problem. When you cruise at half throttle it runs good but at full throttle it runs good, cuts out for a second runs good, cuts out over and over. It just falls flat on its face, goes, falls, goes. I have put an aftermarket filter and tube on it but have been increasing jet size looking for sweet spot. It did this with the stock airbox too. It has 160 cranking compression. I replaced the plastic intake carb is clean. I'm not sure what I'm missing here. The gasis new, spark plug, fuel lines etc. Its done this since I bought it and I'm stumped. Gov is unhooked also with cable rerouted to carb. I'm going to change fuel filter in bottom of tank and replace the belts but I doubt this will fix the cutting out at heavy throttle. Thanks in advance for your insight into this.
badbrad63 Not Yet Wild Join Date: Jul 2019 Posts: 6

07-15-2019, 11:19 PM	#2
CP241 Nincompoop village idiot Join Date: Apr 2018 Location: Michigan Posts: 9,683	Re: Intermittent bog at full throttle...strange vin what year is this thing? You are hitting the rev limiter. That's what you're experiencing. The rev limiter is built into the ignitor and cant be bypassed without replacing the ignitor with something else (like HEI conversion). I would get a tach, see what RPM its cutting at, and just be sure to keep it below that limit. These are low revving engines, spin them too fast and you'll drop a valve, drop a pushrod, or worse.

07-16-2019, 04:01 AM	#3
cgtech Over This Interview Is... Join Date: Jun 2012 Location: AZ Posts: 17,449	Re: Intermittent bog at full throttle...strange vin what year is this thing? J38-0xxxxx should be first year G2A.

07-16-2019, 05:34 AM	#4
badbrad63 Not Yet Wild Join Date: Jul 2019 Posts: 6	Re: Intermittent bog at full throttle...strange vin what year is this thing? Ok thank you maybe I can put taller tires on it to get a little more speed out of her!
badbrad63 Not Yet Wild Join Date: Jul 2019 Posts: 6

07-16-2019, 05:35 AM	#5
badbrad63 Not Yet Wild Join Date: Jul 2019 Posts: 6	Re: Intermittent bog at full throttle...strange vin what year is this thing? Ok thank you very much your guys knowledge on these things is much appreciated!
badbrad63 Not Yet Wild Join Date: Jul 2019 Posts: 6

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07-16-2019, 07:51 PM	#6
badbrad63 Not Yet Wild Join Date: Jul 2019 Posts: 6	Re: Intermittent bog at full throttle...strange vin what year is this thing? If it's the rev limiter why is it hitting it so early? Even with all stock including airbox it did this. I'm going to change drive belt that's the only thing I can think of that would make it hit rev limiter so quick like a lower gear ratio with the belt being pretty worn?
badbrad63 Not Yet Wild Join Date: Jul 2019 Posts: 6

07-16-2019, 08:04 PM	#7
CP241 Nincompoop village idiot Join Date: Apr 2018 Location: Michigan Posts: 9,683	Re: Intermittent bog at full throttle...strange vin what year is this thing? A clutch/belt problem can contribute to hitting the rev limiter early. Running the throttle pedal straight to the carb can also cause it. Instead of an easy smooth acceleration up to speed, it can rev out early before it gets to speed. I guess the big question would be, how fast are you going when it starts cutting out? And is it lifted, if so how big are your tires?

07-16-2019, 08:07 PM	#8
CP241 Nincompoop village idiot Join Date: Apr 2018 Location: Michigan Posts: 9,683	Re: Intermittent bog at full throttle...strange vin what year is this thing? Also as for the filter in the bottom of the tank, just rip it out and throw it in the trash. Use a regular in-line filter on the fuel line instead. Serves the same purpose but lots easier to replace

07-16-2019, 10:00 PM	#9
badbrad63 Not Yet Wild Join Date: Jul 2019 Posts: 6	Re: Intermittent bog at full throttle...strange vin what year is this thing? It's going about 8 mph when it does it. Thanks alot I'll do that with the fuel filter! I will go over clutch real good and I ordered a new yamaha belt no cheapo. Should I just hook up the dang governor again? I'm not looking for a hot rod but 8mph ain't cutting it! Thanks alot for all your help!
badbrad63 Not Yet Wild Join Date: Jul 2019 Posts: 6

07-16-2019, 10:01 PM	#10
badbrad63 Not Yet Wild Join Date: Jul 2019 Posts: 6	Re: Intermittent bog at full throttle...strange vin what year is this thing? Also not lifted but I will if you think taller tires will be beneficial!
badbrad63 Not Yet Wild Join Date: Jul 2019 Posts: 6

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