| Author | Message | ||
     Dantindell |
I just bought a 2002 Blast. The guy put a Vance & Hines pipe on it but didn't jet the carb or change the breather. I've noticed when it's under a little torque it will sputter and sometimes spit out the breather. It will pick up speed and once it smooths out it's fine. It starts good, it idles fine, it runs fine down the expressway up to 80mph, but get in a curve/hill or shift into 5th at less than 60-65 and it loses power and spits once or twice before it picks up speed. With the V&H pipe, does this sound like I need to rejet the carb? If so, can you tell me what size jets I should go with? And do I need to put a K&N on to let it breath better on the intake side? I plan to replace the boot regardless but I'm thinking it seems to be running too good at if it's not under torque to be the entire problem. Thanks, Dan} | ||
| Swampy |
Welcome to the Thumper Forum Dantindell! Yes you should probably make some adjustments. Carb first. If your Blast has not been re-jetted it will improve the way it runs by installing at least a 175 main jet and a 46 to 48 primary jet, also do the idle air adjustment as outlined in the carb section. Also you probably should shim the needle to improve the mid-range on the carb. Also if the exhaust is leaking at the cylinder head to flange gasket that can cause the problem you are describing. That being said, generally, dificulty reaching top speed is an indication of a too tight primary chain adjustment. All you want is for the chain to be as loose as possible without making noise, I usually set mine by "ear" it is the simplist way to do it. If you do not know if your priamary has been adjusted yet you can look at the adjuster screw and see if the thick stop washer has been removed from between the adjuster bolt head and the lock nut. If it is in place it has not been adjusted yet, if it is gone it has probably been adjusted too tight. If it is too tight it will cause your top speed to be lower as there is too much drag on the primary drive and it will cause you to have difficult shifting. So there you go, a couple of directions to start in, do one thing at a time and check to make sure you didn't make the situation worse. Carb jets are available(stocked) everywhere H-D(spit) motorcycle parts are sold, except the H-D(spit) dealers, if you go to the H-D(spit) dealer you usually will have to order them by H-D(spit) part numbers though the service area has a selection for when they install chrome exhausts and air cleaners and and leather fringed goodies. Good luck, let us know how you did! | ||
| Dantindell |
Thanks Swampy! I'll try that and let you know. On the top speed, really about 84 was it. Down a long steep grade hugging the tank it got 89 but had no idea what the bike should top out at. "or so they say"  I'm really just wanting to get something for good gas mileage, and realize re-jetting can lower my mileage slightly... but I also realize if it's not the right configuration for the aftermarket parts you have, it would be lower yet (every time it spits or loses power, that's just gas thrown out the tailpipe. Speaking of tailpipe, funny you should mention the exhaust potentially leaking. I kinda wondered if that may be happening because it almost sounded like a tiny "header" leak at the front of the engine. I'm going to check that as well. I just didn't realize it would cause a performance problem. Thanks again. (Message edited by dantindell on December 18, 2010) | ||
| Swampy |
A header leak will cause the problem you are describing because it causes the engine to run a bit lean. 96 is the top speed of a properly running stock Blast provided you don't weigh 400 lbs riding into the wind. To get to 96 will take a little bit but if all is right you should be able to ride right up there. It sounds like you have a too tight primary chain. Did you look for the spacer on the primary adjustment bolt? The back firing can be anything from a header leak to a failing ignition module. |
