New to the forum, have backfire issue
 

Hello all, my problem is as follows, with a rundown of what Iv done thus far. My bike is a 2004 GZ250 with a little over 6k miles. When I went to start it this spring, it sprayed raw fuel out of the head gasket. I replaced the gasket torqued everything down per the manual, and it ran great. Then a wiring issue popped up, bad terminal on coil. Fixed that. Ran great for a while. Carb started acting funny, took it apart and cleaned it (was like new anyways) put it back on. Now the reason I did that is because the bike started backfiring on me. Now the backfire is even worse, to the point that the bike kills and will not restart for a little while. Last night I changed the oil bc like a dumbass I left the Petcock on prime and it dumped a cpl quarts of gas into the crankcase. I also put a new plug in it while I was @ it. Just got back from a test ride, roughly 3 miles, ran great till I got back home, backfired and killed as I pulled into the driveway. I'm at a loss, any ideas? I'm a car mechanic, bikes are a different animal to me.

Did you change the oil? You didn't mention that if you did.

Sorry, oil has been changed as well as filter. Second time this year. First was bc I had the block open

OK. You hydraulic'd gasoline. Just wow.
So:
1) you have an issue with your petcock
2) you have an issue with the carb. (even if it looks clean)

You caught the wiring problem. Good job

Carb acting funny and backfiring.....

I suggest you replace needle and seat in carb and reset float level.
I suggest you replace the exhaust gaskets.
Read up the service manual on torque settings and recheck the torque after
some use.

Also recheck the torque on all bolts involved in your new head gasket.
As if bike is new.

I'm thinking your carb is letting to much gas in and I'm thinking air is seeping in
your exhaust header at the head.
These ingredients lead to BANG!!!!!]

One last thing. Check valve adjustments.

Should i just order a carb kit n rebuild it, as well as the petcock? I'll go ahead and order new exhaust gaskets too. I'm going to be selling the bike here soon, but want it reliable first, so I can enjoy it some more. Used it as a beginner bike, and it's time to go bigger and more comfortable on the highway.

Also stands to mention that last year I was getting 65mpg, and I haven't gotten more than 45mpg this year.

heading to work. Will respond later. Sorry XD

No biggie, I'm doing the same, but appointments and class. Starting school today for truck driving. Thanks for your help!!

Petcock can be rebuilt. Just a couple/few rubber parts.
I replaced mine with a non vacuum model and capped the tap on the carb but
do that repair however you want.
Complete carb rebuild probably isn't necessary if it looks clean.
Just figure how that much gas got past the petcock and needle seat.
Blowing a head gasket by hydraulicing gasoline is quite something.

And 45 mpg is screaming problems. Your 65 number is definitely in the healthy range.
How does the spark plug read?
perhaps post a picture of it.

oooOOOooo... I should post a picture of mine. We could start another spam thread guys.
Just all post pictures of our spark plug electrodes :lmao:

Plug reads rich. It's black. I'm wondering if the floats are set wrong? Also, cleaned the petcock and filters when did head gasket, thinking preventative maint. Also, what should the fuel bleed screw be set @?

Has someone messed with the carb settings while the bike was put away?

Yes. An improperly set float could be your problem on the rich condition. And part of your
backfire problem. and part of the cylinder full of gas blown gasket problem.