I just installed a boyesen rad valve on my blaster with new reeds. Runs great except for 3/4 to wide open throttle it falls on ots face and knocks and sputters. Carb main jet is a 240 on a stock carb. Mods are no tors, .40 piston, LRD full exhaust, no airbox lid. I have been reading alittle about the rad valva and I am seeing you need to go down on the main jet. Is this true? Do I need to go up a jet or two or doI need to go down. Or do I just need to put the stock cage back on. Thanks for any help.
Falling on its face 3/4 throttle
- Thread starter DOERR
- Start date
dude, the only way to know for sure is to do a plug test in the full throttle circuit. jetting is largely dependent on altitude and ambient temp as well as barometric pressure.....
ok, put your plug wrench in your pocket and take the wheeler out on a street or trail and wind her out in like 2nd gear or so, FULL throttle. after you've gotten her wound out, keep the throttle pinned WOT and hit the killswitch and pull in the clutch at the same time (don't let the throttle go or let out the clutch lever till you've come to a complete stop). make sure that the last few combustions in the chamber were w/ the carb at WOT.
now pull the plug and check it's condition. white/blistery = lean (either main jet is too small, plug is too hot, or you've got an air leak somewhere, but if you did you'd have erratic revving), black/dusty = rich (main jet is too big), black/oily = oil leak (either the crank seals or the case half seal).
but if you had a crank seal leak, you'd probably notice a lot of smoke in the exhaust.
ok, put your plug wrench in your pocket and take the wheeler out on a street or trail and wind her out in like 2nd gear or so, FULL throttle. after you've gotten her wound out, keep the throttle pinned WOT and hit the killswitch and pull in the clutch at the same time (don't let the throttle go or let out the clutch lever till you've come to a complete stop). make sure that the last few combustions in the chamber were w/ the carb at WOT.
now pull the plug and check it's condition. white/blistery = lean (either main jet is too small, plug is too hot, or you've got an air leak somewhere, but if you did you'd have erratic revving), black/dusty = rich (main jet is too big), black/oily = oil leak (either the crank seals or the case half seal).
but if you had a crank seal leak, you'd probably notice a lot of smoke in the exhaust.
i would think that a 240 main is too small for those mods, but like quam said do a plug ckeck to know for sure
Sounds like your really lean. I used to run a 330 on a stock carb and motor with no lid, LRD pipe and G3 reeds.
