Roar Posted May 19, 2020 Share Posted May 19, 2020 My bike start normal then it revs up to about 3/4 k when getting warm... What could be the problem? Its a 99 efi btw Quote Link to comment Share on other sites More sharing options...
XXitanium Posted May 19, 2020 Share Posted May 19, 2020 Vacuum leak? Quote Link to comment Share on other sites More sharing options...
jon haney Posted May 19, 2020 Share Posted May 19, 2020 (edited) Sounds like the fast idle mechanism isn't releasing once the coolant starts to get warm. There is a plunger, filled with wax, I believe that disengages the fast idle. The wax expands with heat and moves the plunger. I believe it's on the left side of the throttle bodies. Edited May 19, 2020 by jon haney Quote Link to comment Share on other sites More sharing options...
SwampNut Posted May 19, 2020 Share Posted May 19, 2020 +1 on what Jon said. Mine is failing in the other direction, idle drops really low (doesn't stall). It's a shit design like the CCT. Vacuum leak can cause some erratic idle, but I don't think it can send it up that high on this vehicle. Quote Link to comment Share on other sites More sharing options...
tomek Posted May 19, 2020 Share Posted May 19, 2020 Vacuum leak can cause erratic idle only on engines with feedback idle control speed, so it doesn't apply here. Going back to OP, I think there are couple compounding issues here. I don't think wax stuck wide open would send idle speed that high. Most likely idle speed is set too high as well. I would disconnect fast idle speed apparatus first and check idle speed after the engine is up to normal operating temps. There could be vacuum leaks as well. Quote Link to comment Share on other sites More sharing options...
Roar Posted May 20, 2020 Author Share Posted May 20, 2020 It was like this last year as well It went away eventually but back now.. The idle is set right. I never tuched that knob.. Quote Link to comment Share on other sites More sharing options...
SwampNut Posted May 20, 2020 Share Posted May 20, 2020 1 hour ago, Roar said: It was like this last year as well It went away eventually but back now.. The idle is set right. I never tuched that knob.. You didn't quite catch what we were saying. There is a wax-filled capsule that automatically opens the throttle when cold. As the engine warms up, it slowly allows the throttle to close. Cold engines need more throttle and a richer mixture. When it's working well, you don't notice this because it works at the same rate as the change in temp-based idle speed. My idle starts normal when cold, then drops a lot as the throttle closes too soon. Yours seems to be doing the opposite. I don't recall what it takes to remove that part, but if not hard, I'd start by doing that and see if the problem stops. Quote Link to comment Share on other sites More sharing options...
jon haney Posted May 20, 2020 Share Posted May 20, 2020 Keep in mind that "fast idle" is the default position for that mechanism. If you could remove the wax, it would idle fast all the time. I agree with Carlos that it's not a great design. Quote Link to comment Share on other sites More sharing options...
superhawk996 Posted May 21, 2020 Share Posted May 21, 2020 On 5/19/2020 at 8:23 AM, Roar said: My bike start normal then it revs up to about 3/4 k when getting warm... What could be the problem? Its a 99 efi btw What's the RPM at initial cold start and does it slowly steadily climb as the engine warms up, or suddenly go up to 3-4K? The fast idle device is probably the answer, but could be other stuff. Quote Link to comment Share on other sites More sharing options...
ironmike Posted May 21, 2020 Share Posted May 21, 2020 Just to eliminate one possibility (cable binding), trace your throttle cables and then rotate the forks lock-to-lock; there should be no change in the idle rpms. If there is, look for something binding/pinching/etc. the cables, or miss-adjusted cable slack. If there's no fork movement when your idle fluctuates, it's more likely not a cable problem (but double check to be certain). Otherwise, the fast idle circuit and potential intake air leaks would merit close scrutiny. 1 Quote Link to comment Share on other sites More sharing options...
Roar Posted May 21, 2020 Author Share Posted May 21, 2020 16 hours ago, superhawk996 said: What's the RPM at initial cold start and does it slowly steadily climb as the engine warms up, or suddenly go up to 3-4K? The fast idle device is probably the answer, but could be other stuff. It slowly goes up.. Quote Link to comment Share on other sites More sharing options...
jon haney Posted May 26, 2020 Share Posted May 26, 2020 On 5/21/2020 at 3:17 PM, Roar said: It slowly goes up.. I stand by my original diagnosis. Keep in mind that lack of coolant flow to that mechanism can also cause the same symptoms. Quote Link to comment Share on other sites More sharing options...
SwampNut Posted May 26, 2020 Share Posted May 26, 2020 Agreed. Quote Link to comment Share on other sites More sharing options...
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