Need help with inline 4 issue! Please help.

[tonyjuliano]

Hello all. I'm new to this forum and I'm looking for some assistance with a tech issue.

A friend recently purchased a 1995 Yamaha XJ600S (known as a "Seca II" in the U.S., "Diversion" everywhere else, I think), and it seems to have some small problem.

The bike had been sitting for a while, and when we first picked it up it was running smooth, but lacked acceleration. So much so, that it topped out at about 45mph. It also surged and hesitated under load. The bike was purchased about 150 miles away, and as it was ridden back, this issue improved somewhat (as did some of the surging) as we were able to get it up to about 75 mph.

It seems to run real smooth, no misfires or anything, but there is definitely a feeling of someting "holding it back". We ran a container of carb cleaner through it with some fresh gas, but top speed is still the same.

I suspect that the carbs are dirty or need to be synchronised. Any thoughts or advice on this subject would be greatly appreciated. I'm pretty good at diagnosing problems with my bikes, but don't have much experience with inline four's.

Thanks in advance for any help.

[TechTMW]

Hey Tony welcome aboard -

An engine's an engine ... be it a v-twin, a four or a single - all the basics are still there, so if you've got experience w/ other configurations, just follow your gut instinct.

If you are sure there is no misfire then it sounds like a thorough carb cleaning is in order. Surging is a telltale symptom of a lean condition. Since the bike has been sitting, there's bound to be buildup in the carbs that some in-tank carb cleaner ain't gonna clean.

Once you have the carbs thoroughly clean, I'd also recommend checking the valve clearances. Once you replace the carbs, you will need to synchronize the carbs, and carb synching is useless without properly adjusted valvetrain.