[stsuperbike]

I have a bike that Im not sure on the mileage or service. but the bastard is backfiring alot, more & more every week. When I let of the gas, and especially when I downshift it really backfires alot. I dont have any exhaust leaks, so Im thinking about a tuneup or valvejob. has anyone done it themselves? How hard is it or what do I need to know as first-timer?

Thanx Guys............

 

[dharhay]

There is a device called a leak down tester. It is available at AutoZone, Summit Racing, and SnapOn. It will tell you the condition of the rings and valves. That will give you a number of which you can make a determination of your issue.

Dave Harhay

 

[mcd]

The leak down test is definitely one of the best ways of determining the fundamental health of an engine and the suggestion to conduct the test is a good one. There are also a bunch of other issues that may be causing your problems other than valve spec issues (TPI misalignment, improper amount of air getting into the fueling process, lack of proper fuel pressure, timing problems, electrical issue... etc.) all of which can be determined through a series of specific tests. As a first, no cost step... pull the plugs and take a look at them. They will likely show you a rich, lean or normal condition (in your case, I suspect lean) and then go from there. Also, knowing what bike we are dealing with here (??) is also helpful information.

 

[stsuperbike]

sorry, its 98 st2 944cc

 

[mcd]

Pull the plugs and have a look at them. You'll need to remove them to do the leak down test anyway. Just curious... is the fuel pump in the tank giving you a pretty good whine when you turn on the ignition? If the motor compression checks out OK and you don't have any history on the bike, I'd put a TPI check and the fuel filter on the consideration list next.

 

[stsuperbike]

fuel filter replaced over the winter, and fuel pump sound....seems fine. Sounds like my monster used to. But Ill check that leak down test. Thanx for the tips.

 

[ward]

Are the pipes / exhaust standard? Airbox modded? Any other mods that might influence fueling. Has it just started to do this, or just got worse over time...