1988 yamaha g2 backfires

gerald grove

Up to half throttle runs fairly well Past that up to full throttle acts like not getting enough gas. It's like when you quickly giving it gas then letting off it then jerking and backfires through carb . Here is what I have done
adjust valves , clean gas tank , new inline filter , electric fuel pump, new air filter and resealled the air box . New plug (burning white) rebuilt primary clutch (broken weight) removed govener , generater out put is 13.5 \ 13.7
compression 110, cleaned and rejetted carb 112/115 new spacer and gaskets .
Any help would be appreciated Thanks in advance
Gerald

BGW

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cgtech

Stock airbox? What reason for re jetting? Compression 110 is crap.

gerald grove

stock box but I do not have insides box only
jetting it did not seem to be getting enough gas very lean
as far as compression I thought any thing above 100 was fare
Thanks

Spicyunicorn

On a two stroke g1 above 100 is good not so much for your four stroke should be around 150 area

gerald grove

after checking compession with repaired tester reading is 148

cgtech

If the inside of the box is gutted, that's a good reason to need a re jet. Might just not have the jetting correct yet.

G1-G9

If you have removed the governor and you are tuning a lot more rpm's it will always cut out because G2's igniters have a rev-limiter in them. How many rpm's are you turning?

gerald grove

no way to tell do not have a tach. but is only half throtle at best when it starts cutting:help out

G1-G9

If you by passed the governor then half throttle may be full throttle now.

sho305

At top speed it should start cutting out due to the rev limit in the ignitor, assuming you have no governor or disabled governor. If the airbox is gutted it will need the jet hogged out. If you drive along with the choke on part way (you can find a spot where it runs good) and it stops missing then the jet needs to be enlarged more to get it right. You can use a torch tip cleaner to file it out or get a $10 jet drill set on amazon. If you take the carb off and get the jet out, then put it in not real tight, you can get the bowl off and jet out while in the cart to jet it and keep driving around testing it. Make it larger little at a time until it goes WOT with no missing and takes off good with no choke (have warm engine when you test). Only need a 10mm wrench to get bowl off and screwdriver to get jet out. Watch the e tube does not fall out the carb from above the jet when you do it. When it runs good get the jet in tighter and check carb mounting/etc. Never over tighten the carb mount it can break the spacer.

If you can't get it to run better with the choke on part way, then it may be some other problem like bad ignition component or something.