98 GTS major Backfiring PLEASE HELP

[Ride4dathrill]

I have a 98 GTS rebuilt carb, cleaned out crankcase and put it all back together and now we have major backfire through the carb at high rpm's. We noticed the accelerator pump on the carb is missing. Would this cause it? Or what else might it be? HELP

 

[timmyboy76]

Did you remove the RV plate?, if so, I'd recheck the timing of it, 147* opening...so when installed, with mag piston at TDC, the plate should be installed with the PTO side port hole covered...

 

[Ride4dathrill]

update

We are buying a pressure tester to test the carb and I will recheck that timing. According to the dealer, they say it is getting to much fuel causing the backfire. I really need help with this one. It is kicking my butt.:ack::banghead:
I am willing to try anything at this point. Thank you for the help. If you have any more ideas feel free to spill your guts.

 

[salmonkiller01]

When you cleaned out the crankcase did you remove the rotary valve because it sounds like your timing is off. If so do a search of roatry timing to get a step by step.
Does it backfire at an idle also?

 

[kustomkarl]

If the engine was getting too much fuel it wouldn't back fire. It will back fire if the rotary valve timing is off, as it fires at the wrong time as related to the intake timing.

Karl

 

[Ride4dathrill]

It only backfires at high rpm's. about 3/4 to full throttle. I will check the timing, yes we did have the rotary off. So that will definetly be a must. Would you be able to walk me thru a step by step process as to the timing process. Thank you

 

[Ride4dathrill]

Does the fact that it doesnt have the accelerator pump on the carb be related to the issue. We do not know if they changed any of the pins in the carb to allow for not having the accelerator pump.

 

[kustomkarl]

There is a lot of information to re-type in the forum to check the rotary valve timing. If you join the "premium membership" you can download a manual and see how to do it properly and quicker than me trying to type it here.

Karl

 

[timmyboy76]

Hey stud...from looks, that carb, most likely, WAY off, why...?
the 98GTS carb setting w/ xlatr pump should be 36-40psi(n/s) along with lsa=1.25,hsa=0
If he blocked off the eccelorator, (correctly), then goin off 97GTS specs(same motor and carb, minus the xlrator pump) carb should be jetted at main=175(98=167.5) and pilot=70(98=67.5) with the n/s(needle and seat) psi=23-43psi. So, i'd double check the "guts" of the carb and most likely, purchase n/s assy(1.5) and install the 80gram spring(black spring) which will put around 38psi...:cheers:along with the lsa(low speed adj)=1, hsa=1.5...98setting is lsa=1.25,hsa=0