ok, 99 trailblazer 250 after rideing for about 20 minutes it starts to make a pinging noise and starts to loose power and idles way high... i have replaced both crank seals, replaced the piston and rings .40 over, replaced the intake boot and cleaned the carb( taken apart), i believe the oil injection is working, it even does this if i mix my gas 40/1 and still run the oil injection.. i thougfht i had it fixed with the crank seals,, i guess not... PLEASE HELP

 

Sounds like it's running out of fuel, check the vent line on the fuel tank.
Are you using the right spark plug? (heat range might cause this...long shot, but possible)

Hope it helps

 

UPDATE: i took the carb apart and cleaned out every port with brake cleaner, completely dis-assembled. i am puzzled this only has a 130 main and the air screw a 1 3/4 turn out... i bought this in pieces and put a piston in it and it had to be bored.40 over.. i have done EVERYTHING i can think of and cannot fix this running hot issue , my new plug is brown if this helps...PLEASE HELP ME MY WIFE REALY WANTS TO RIDE HER QUAD...

NO THE VENT IS NOT PLUGED , I JUST DRILLED IT OUT ... THANKS

 

it sounds like a lean detenation. check the plug to make sure its not running to white or you'll be putting a .60 over instead. check to see if the float is set right. like BGRD said it sounds like maybe not getting enough fuel if your sure the air issues are taken care of.

 

the plug is brownish / white... how do i adjsut the floats..thnaks stendori i thoughi had this fixed , guess not..

 

yea the stock jetting is pilot #40 and main#130. if the plug is whitish at all its running on the lean side for sure. how cold is it where you are running the t.blazer. i usualy just make sure w/ the carb upside down that the float is fairly level. i dont have the proper fancy gauge your suppose to have to set it. i know you said this, but your 100% sure there is no air leak? the engine going up in idle is a good sign of one.

 

its about 40 degrees today, man is it beautiful out snow finally starting to melt..whats the best way to check for a air leak, i start it up and spray carb clener i listen for a rpm increase , ya got a better way, thanks stendori, what is the the air srew setting?

 

i think about 1 1/2 turns.

 

so it sound like the carb it set up stock..... shoudl i change it due to the .40 over bore job?? it seems to run ok till it gets warm then the dreeded pinging starts..

 

stock setting i would think would be ok but worse case go up one jet size. what are you using for gas grade? shouldnt be more then 87. if you run higher that coukld cause pinning and excess heat as well. just a thought. probably wrong though.