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Motorcycle Forum / General / Yamaha / June 2007Want more power from my XT 550
Howdy, i have an 83 XT 550 and love it but id like to squeeze more power out of it. According to bikez.com (maybe not that reliable) it makes 38hp at 8.5:1 compression. So i was thinking of bumping up the compression and changing the cams. Any thoughts on this or other ideas?? Where can i get parts? much appreciation, drew Drew, Have you replaced the stock muffler? I have been looking for 1 that will work on our XT, but no luck. Mike > Howdy, i have an 83 XT 550 and love it but id like to squeeze more > power out of it. According to bikez.com (maybe not that reliable) it [quoted text clipped - 3 lines] > > much appreciation, drew well heres the thing Mike. Id like to keep the bike looking as stock as possible. My baffle is removed from the muffler, maybe that adds some power, but all the work id like to do, id like to do on the inside. Such as a higher compression piston and different camshaft. Id rather keep the stock carbs also. peace, drew > Howdy, i have an 83 XT 550 and love it but id like to squeeze more > power out of it. According to bikez.com (maybe not that reliable) it [quoted text clipped - 3 lines] > > much appreciation, drew Waste of time Use it as is or buy something newer >> Howdy, i have an 83 XT 550 and love it but id like to squeeze more >> power out of it. According to bikez.com (maybe not that reliable) it [quoted text clipped - 6 lines] >Waste of time >Use it as is or buy something newer ignore that, go here. lots of hop-ups for those bikes. http://thumperpage.com/ >Howdy, i have an 83 XT 550 and love it but id like to squeeze more >power out of it. According to bikez.com (maybe not that reliable) it >makes 38hp at 8.5:1 compression. So i was thinking of bumping up the >compression and changing the cams. Any thoughts on this or other >ideas?? Where can i get parts? Blindly bumping up the compression without knowing what you are doing can result in an engine that pulls like a tractor at low speed but won't rev up to redline. The engine with too much compression actually has LESS horsepower than the stock engine. Don't ask how i know that. Experienced tuners increase the compression ratio only enough to work with the cam timing and give the hot rodded engine enough power to get the motorbike moving without slipping the clutch and using a bazillion RPM. The engine only has one camshaft. In order to get more horsepower out of an engine you need to make it turn faster. It's very possible to get 55 horsepower out of a 550 cc engine, if it can stand the extra RPM. You'd have to turn the engine 30% faster, assuming you didn't install a big bore kit to give it more cc's. But that would make the engine peaky and harder to ride, you'd have to keep it "on the boil" to get the power you want out of it. You can find out if you would enjoy riding a motorcycle with such a peaky engine by degreeing the camshaft to close the intake valve 3 or 4 crankshaft degrees later. Google for information about degreeing cams using the "lobe center" method. If you're going to eventually install a re-ground cam, or an aftermarket billet cam, you're going to have to learn to degree cams sooner or later. http://www.bikebandit.com/partsbandit/showschematic.asp?dept_id=653868 Item #3 is one of a pair of bolts that fastens the camshaft sprocket to the camshaft. In degreeing a camshaft, the sprocket is removed and the holes are filed oval. Then the camshaft and sprocket are reinstalled with the bolts almost tight. The camshaft is repositioned so it closes the intake valve later and the bolts are installed with Loctite to keep the sprocket from shifting. The exhaust valve will open later by the same number of degrees and the exhaust system will be able to extract a little more horsepower from the acoustic effects in the hot exhaust system. >>Howdy, i have an 83 XT 550 and love it but id like to squeeze more >>power out of it. According to bikez.com (maybe not that reliable) it [quoted text clipped - 46 lines] >exhaust system will be able to extract a little more horsepower from the >acoustic effects in the hot exhaust system. like the sr's, all the xt's get a real boost just by making them breathe and exhale better, the exhausts are real strangle points and rob at least 5hp. a better carb like a 38 or 40mm flat slide mikuni will gibe you more. there are better cams and pistons galore. go to the thumper page and yell at big ed. he'll tell you the literal truth about what to change. i have 3 sr's. 1 stocker, 29hp, one with a supertrapp and nect size up main jet, 35hp. the last is a hot rod, hot cam, 10 to 1 piston, 40mm mikuni and the bsr exhaust and big header, 46hp. the main thing on the xt is the tranny. it's a dirt bike so it won't ever be a drag racer. but for more power and torque, a compression boost with a cam will help. those motors have been around since 76 and are thoroughly understood. |
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