Ask the Editors: Mysterious Misfires

We’d begin looking here for answers.

First the good news- you diagnosed and replaced all of the components we would recommend checking. Now the bad. Symptoms such as these are usually indicative of a more serious issue when the simple things make no difference in correcting the problem.

From the sounds of it, we would guess your machine’s timing chain is falling out of time slightly. This suspicion makes more sense when you couple the mysterious symptoms to the fact that they occur when the engine gets hot as metal expands in higher temps. The timing spec may be close enough to be unnoticeable when cool but becomes exaggerated as the engine internals heat up.

We’re assuming you haven’t recently had the engine torn apart? If so there’s a very good possibility the timing was set incorrectly upon rebuild. If not, it may simply have worn with time to the point of slipping. Are you experiencing any ticking sounds when the engine is running? Before investing in any other parts or diagnostics, this is where we would begin our investigation.

There is also the very slim possibility that the quad’s head gasket is going but would consider this only if the timing chain investigation yields no results.

Got questions for us? Ask them here!