rough idle

[Glacier_g_rt]

have a rough idle on my RT and would like to know where to start. any posts I could go to that discusses this problem? thanks.

[ShovelStrokeEd]

When was the last complete service done on the bike?

 

By that I mean, valves adjusted, spark plugs replaced, throttle bodies synchronized and probable non-related items like oil change, trans and rear drive serviced, tire pressure checked, alternator belt checked, ets.

 

Given the age of your bike, you might have issues with the throttle body mounting sleeves, the throttle shaft seals and/or vacuum leaks elsewhere in the system as the rubber parts deteriorate with time and ozone.

 

It could also be as simple as a small boulder stuck in the throttle pulleys.

 

What diagnostics have you done so far?

[Glacier_g_rt]

have about 3.5k on the valve adjustment, put new plugs in at that time. Haven't done the tbs yet, over 20k. Regular 6k oil changes with amsoil. should have done the tbs before this but the bike was running good with not a lot of vibration which I heard is an indicator of out of sync. "if it ain't broke don't fix it"

[ShovelStrokeEd]

Well, I would check both the valve adjustment and the spark plugs. Valve adjustment and plugs are kinda a pre-requisite to a proper throttle body synch anyway. If nothing else on the plugs, check that the gaps are even.

 

You can then build a manometer for about $10 and check your throttle body synch. There are any number of threads about building a simple manometer and a good deal more refer to how to check/adjust TBS.

[Glacier_g_rt]

Thanks.

[T__]

have a rough idle on my RT and would like to know where to start. any posts I could go to that discusses this problem? thanks.

 

Dave, a rough engine idle on the oilhead boxer can be caused by variety of reasons.. Such as one cylinder pulling harder than the other,, or low idle RPM’s,, or excess engine load at idle,, or even something loose in the drive train allowing excesses engine/trans/exhaust shake at idle..

 

Knowing when the problem started would help us to help you diagnosis the problem.. Such as; did it happen suddenly after a long high speed run or?, did it appear after a long storage period?, or has it appeared slowly over a long time?, or maybe after a service or adjustment or accessory addition?, or after the last time you fueled the motorcycle?. (the more you can tell us here the better we can help you)

 

The easiest place to start is to advance the choke (actually fast idle) lever a little to see if that helps the idle roughness.. If that helps,, then put a precision tachometer on the engine & set the engine idle to high side of specs.. If raising the engine idle RPM helps then look for coked up BBS (brass idle air screw) screw tips or BBS seats in the TBI’s (a common problem on older oilheads)..

 

Make sure all the engine & trans bolts are tight..

 

Check the R/H spark plug wire for contact with the R/H TBI cam at idle (another somewhat common issue)..

 

Maybe try disconnecting the 02 sensor as a quick test as a poisoned 02 sensor can disrupt the idle air/fuel ratio & cause a rough idle..

 

Otherwise as mentioned in threads above do a TBI balance & valve adjust..

 

Might not hurt to run a hot compression test or even a leakdown test then use a heat sensor gun on the exhaust pipes where they exit the cyl heads (with the engine idling) to see if you are getting somewhat even exhaust exit temps..

 

Lots of possibilities so more info from you can help pin it down to a manageable level..

 

 

Twisty

 

 

[Glacier_g_rt]

Wow, thanks Twisty.

[ianboydsnr]

if its a twinspark, then it could be the coil caps