Need some trouble shooting help

I have a problem with my 99 R1100RT (62500miles) that seems to be temperature related. In the morning when it's cool I depart on a 2 hr or so ride the bike runs smooth & strong at all rpms. I stop,have lunch & hang out a bit & then get back on the bike and whenever I increase the RPM above 3500-4000 in any gear it gets very buzzy. The mirrors are a blurr. & the vibes in the bars is very noticable & the bike seems to be down a little on throttle response.
The bike has had the 0/0 TPS adj. & Autolite 3923 plugs
Things that I have checked:
Valve adj. a couple of times. Changed plugs a couple of times. Rechecked TPS adj.
Checked plug wires & coil with an Ohm meter (Readings verified by the guy at Beemer Boneyard. Checked TB sync several times/ Did off idle sync at 4000RPM
I checked the Outside Air Temp sensor with an ohmmeter & it seemed to be within the specs that that I found on another Forum. I also checked the computer for fault codes with an analog voltmeter / counting the blips & had an OAT sensor fault. Which has cleared & hasn't reoccured. I have ordered another OAT sensor and am awaiting its arrival.
I just finished replacing all of the throttle cables (4ea.) No pebbles in bellcranks.
Any help diagnosing this problem would be greatly appreciated.

stab in the dark- but i just replaced the alternator belt on my bike, and found that afterwards it began running significantly smoother. possibility?

Thanks. I changed mine a year ago. But I can take a look at it again

Could it be a coil starting to go south?

Any thoughts on how to check a coil out other than the standard ohm meter check? Would it do any good to heat it up with a heat gun & then check the resistance????????

LCampbell said:

Would it do any good to heat it up with a heat gun & then check the resistance????????

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I've always understood that coils need to be checked when they're hot (Though I've never needed to check one - so I am NOT the voice of experience).

It does seem reasonable though to check the resistance with it cold, and then warm it up by degrees, rechecking at intervals to look for a rise in resistance.

Could a heat gun potentially get it too hot - I mean, hotter than its usual operating temperature?

Your diagnostic thinking seems to be on track. The only other thing that comes to mind would be a possible air leak, either at the intake or exhaust end, resulting from a poor seal that malfunctions after things really heat up, causing the effected cylinder to run lean.

The coil sounds like a likely culprit. Keep us posted.

alien_hitchhiker said:

I've always understood that coils need to be checked when they're hot (Though I've never needed to check one - so I am NOT the voice of experience).

It does seem reasonable though to check the resistance with it cold, and then warm it up by degrees, rechecking at intervals to look for a rise in resistance.

Could a heat gun potentially get it too hot - I mean, hotter than its usual operating temperature?

Your diagnostic thinking seems to be on track. The only other thing that comes to mind would be a possible air leak, either at the intake or exhaust end, resulting from a poor seal that malfunctions after things really heat up, causing the effected cylinder to run lean.

The coil sounds like a likely culprit. Keep us posted.

Click to expand...

Thanks for the imput. I'll ck for intake/ exh. leaks and maybe try heating up the coil a bit & check the resistance as I go.

I have a 2004 R1150RT and it is the basis of my knowledge. It is my 1st oilhead. Could it be your bike could be going thru another phase of wear in?? My suggestion is to sync your throttle bodies where the vibration is its worst and see what happens. I've found on mine I have to use two high velocity fans on the engine to get a good sync at running temperature. It really makes a difference. My bike at 56K miles is just about as smooth as glass from 3.5k up to 4.8k rpm.

Dave Faria
Austin, Tx

Dave_Faria said:

I have a 2004 R1150RT and it is the basis of my knowledge. It is my 1st oilhead. Could it be your bike could be going thru another phase of wear in?? My suggestion is to sync your throttle bodies where the vibration is its worst and see what happens. I've found on mine I have to use two high velocity fans on the engine to get a good sync at running temperature. It really makes a difference. My bike at 56K miles is just about as smooth as glass from 3.5k up to 4.8k rpm.

Dave Faria
Austin, Tx

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Thanks Dave. I have mine bike synched at approx 4000 RPM which is in the range of the buzzing. To me it seems to be a heat issue. It will run smooth as glass & strong in the morning but be buzzy/not quite as peppy in the afternoon

temp related performance issues can also be the HES on its way out; you might want to look at that as a possiblity.