Motorcycle Repair: carburators, air fuel mixture, intermediate jet

Question
QUESTION: I have a super E shorty on a revtech 88" motor and Im getting alot of backfire  - the intermediate jet is .o31 and the main is .o76 -  do I need to change one or both of these sizes - it seems to start alright but after I run her up into 4th and 5th it all hits the fan sorta speak - thx

ANSWER: Has it always done this or is somthing that just started?
Mike

---------- FOLLOW-UP ----------

QUESTION: Ive had recurring problems with egtting the carb running well - the original intermediate jet was .029 according to everything Ive read the minimum for an 88" is .031 - so I moved to that jet - I also tightened down the throttle screw to almost closed and that helped - but it still back fires and stalls out when I open the throttle all the way especially in 4th and fifth above 3000rpm -

ANSWER: What you did was add fuel by changing jets makeing it run right. Jet sizes that are suggested are just that. A starting point. Cam and exhaust also will affect what jets you use. go to a .028 intermediate jet. Once the bike warms up adjust the air/fuel mixture screw. It should be turned outward until the bike starts to stumble and then back inward about 1/4 of a turn. Now go for a ride for about 5 miles. Do not go over 2500 RPM. Once you get back, check the plugs. If they are black your rich and need to go lower, white you need to go bigger, to lean. You are looking for a tan color.
Once you have the intermediate set, do the main jet the same way. When you go for the test ride, ride over 3000 RPM
Good luck and happy riding
Mike

---------- FOLLOW-UP ----------

QUESTION: ok mike I have that tan color below 3000 with an intermediate of .031 - but when I crack the throttle to go above 3000 she back fires and stalls out dead - is this a main jet issue or something else - itll run all day under 2500 in any gear rev it up in any gear and it dies - as always your help is greatly appreciated - cuurent main jet size is .072

Answer
Make sure you close the pumper when testing the main jet. Go for a ride with it closed. If it is still doing the same theing go smaller with the main jet and test ride. As always, when you make a jet change readjust the air/fuel mixture screw. Once you have the main adjusted open the pumper screw about 1 1/2 turns and test ride. You want it closed as much as possible without the bike bogging between gears
Good luck and happy riding
Mike