honda xr650r backfiring, help needed !!!!!!
hi all , i have a problem that is taxing my fixing skills, well here goes, i have a honda xr650r i got it after it had sat in a shed for 5 years doing very little, it has 1000k,s from new and it,s a 2000 model, when i got it i put new fuel in gave it a oil change and filter checked it over, then gave it a run, my problem is that when warm if i open the throttle and hold itat 1/2 throttle it backfires through the exhaust and pops and bangs , here is a list of things i have checked.
1, new spark plug N.G.K iridium
2,carb taken apart cleaned , jets checked 175 main , 65 pilot, air screw 1 3/4 out, needle 2nd notch from bottom
3,cylinderhead to carb rubber checked
4,decompressor checked and adjusted
5,valve,s checked exhaust 0.20 inlet 0.15
6, all electrical connections checked , all clean
7, coil lead checked, and plug cap ,all good
8,running unleaded supreme
9,air filter clean and in good condition
10, exhaust standard but with unrestricted baffle
the symtons all point to a air leak, and running lean but i can,t seem to find a cause, well chaps theres something to get your teeth into, any thoughts kindly appreciated, thanks alot freddy