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On my newly acquired 1998 k1200 RS (98kmiles) the bike starts and runs but if I rev it to 2000rpm and hold there, the engine revs will dip down to 1500 and back up to 2000 again on it's own. I hold the throttle still and the revs fluctuate, which translates into not being able to roll away with low revs, I have to race the engine and slip the clutch to get going.

I was told this is a failed TPS. Does this sound right?

The bike had been sitting for 6 years prior to me getting it running 3 days ago.

thanks
 

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K1200GT 2006
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Although I own a 2006 K1200GT (with the forward leaning engine), I have the same symptoms. With throttle opened up, there's no problems. To me it translates to about 3000 rpm, with the engine being super jerky. Did you fix the problem? Was it the TPS in the end?
 

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Cheap things first. Do the TPS reset and check again. Then if still there check for vacuum leaks at all the usual problem areas. Emissions hoses, throttle body to rubber manifold connections and connections between manifold boots and block.
 

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K1200GT 2006
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Already did the TPS reset. No result. Wanted to change out the TPS with the one on the old throttlebody that I had laying around, but found out the bottom intake grommets are severely dried out. Ordered some new ones to see if it make sure that's not the issue either. It's quite a pain in the ass to get all the way to the intake, so rather safe than sorry.
 

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Get the bodywork off . Check for leaks with some (just a little, use a "straw" on the nozzle) carb cleaner around connections when running. Idle will change if there's a leak. I'd pinch or plug the line to the evap canister while testing.
 

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two K1300S bikes, S1000R & Vespa 150 Primavera clown paint job
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While your checking for air leaks in your throttle body to engine Rubber connectors also the Orings under the metal engine spigots need changing. And these bikes suffer from clogged carbon vapor recovery canisters if they are the USA model. Look up how to route and plug lines and remove the darn thing.
There is a pretty good chance that the crankcase breather tube running on top of the engine block is trash and allowing air to leak in also.
 

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The breather tube/manifold makes a mess and is probably worth replacing if you pull the throttle bodies... But, it shouldn't cause the symptoms you describe since it's ported above the plates in the throttle bodies. The EVAP system (charcoal canister) on the other hand is ported to below the plates (butterflies if you like) and is a possible culprit, especially at very small throttle openings. The EVAP hose to each throttle body is prone to coming off since they don't have any clamps. On my 03 GT two of the 4 had slipped off their spigot. Caused somewhat erratic/roughish idle AND intermittent stall when decelerating to a stop. I left the plumbing in place upstream of the EVAP solenoid valve and just added clamps and plugged it on the downstream side ditching the canister and remaining vacuum tubing downstream. Some remove it all together, I feel like it provides a minor balancing function at idle. You have to reroute the tank vent if removed. If somewhere they inspect for that stuff just leave it all there and plug the line inconspicuously. What is the idle speed warmed up, hand off throttle?
 

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Although I own a 2006 K1200GT (with the forward leaning engine), I have the same symptoms. With throttle opened up, there's no problems. To me it translates to about 3000 rpm, with the engine being super jerky. Did you fix the problem? Was it the TPS in the end?
Hey guys, all your advices are for the classic flying brick engine not for this newest model.

BTW, Dutch_rider, you should post in the appropriate section. You will get advices and help related to your forward leaning engine (K12/1300GT (Next Gen))

Cheers,
 

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I'm leaning towards a bad O2 sensor. It give the sympton os a bad TPS but the TPS is really solid and rarely go bad, and if the issue seems to have come out of nowhere. If your tailpipes are black and sooty I bet that's the issue, especially if the fuel mileage goes to crap. There are ways to check the sonsor on youtube, it own't be specific to motorcycle but automotive and make no difference they all work the same. Just find a test for the wire count which I believe is 4-wires on the RS.
 
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