Triumphrat

jm · 07-09-2004

My 97 Trophy 900 has been staying at relatively high engine RPM (around 2500) after I've closed the throttle and hit the clutch when pulling up to stop signs, stoplights, etc. It will sometimes drop to normal idle speed after a couple seconds but other times stays up until I'm ready to leave the intersection again. Once I start to engage the clutch the RPM drops. There's plenty of free play in the throttle cable. What else should I look at to get this sorted?

Thanks.

1bubba · 07-09-2004

It could be lean. Check for air leaks around the carb boots and if possible adjust your idle air mixture. I'm assuming you have already tried adjusting the idle knob. Did this just start or has it always done this?

Bub

jm · 07-12-2004

The bike started doing this some time ago, and it has been slowly getting more frequent. It seems to happen most often when riding on city streets; over the weekend it worked correctly when I was slowing down from highway speeds and for the first few stops afterwards, but after riding for a few minutes on the street (with a few stoplights and stop signs) it started hanging at high RPM again.

I haven't fiddled with the idle adjuster, because I think it's correct. The bike has always idled at right around 1k RPM after warming up but before riding, and often when stopped on the street too. It's just sometimes, when at a stoplight or stopsign while riding on the street, that the problem occurs.

AndyA · 07-12-2004

Does your throttle grip seem a bit loose?
I had a similar occurance with my bike, it was due to the fact that the plastic locating pin inside the throttle grip housing had broken off.
This caused the housing assembly to rotate slightly on the bars and as a result the engine revs weren't dropping as normal.

Regards
Andy

shedds · 07-12-2004

beleave it or not but sometimes when you are riding and you think you are turning the petcock knob to reserve you might be turning the idle knob instead just a hunch because i,ve done it before and my idle was high when i came to a stop . :???:

RacingGreen · 08-03-2004

JM - any resolution yet?

My 95 Sprint 900 has just started doing pretty much the same thing in the same rev range.

I have 'tested' some scenarios and have found:
- when cruising and I pull in the clutch, the revs will hang at 2800
- when slowing to a stop, if I leave the clutch engaged just long enough to get the revs down below 2500, then I get a correct idle.
- it seems to be heat related since it only happens when the engine is godd and hot - and when the air temp is above about 85.

Could the heat be leaning out the mixture - or could their be a problem with an idle circuit?

:???:

jm · 08-04-2004

I haven't seen the problem lately. I'm waiting to decide if I've got it licked. I did try two things.

After reading AndyA's advice I took the throttle grip assembly apart. I didn't find any loose or broken-looking pieces, so I put it together again. After that the bike misbehaved less for a while but the problem was back before long. .

The other thing is additional proof that I'm a doofus. When I was looking at the free play adjuster, I misunderstood the nature of the part. The male component of the adjuster assembly is part of the thing that attaches to the handlebar, and the female portion is free to turn. I didn't realize this, and jammed the jam nut all the way down against the fixed end of the thread, rather than against the free end. So the jam nut wasn't doing anything and the free play tended to become excessive soon after I adjusted it. I realized and corrected this error within a few days of my last comment on this thread. Since then the free play has stayed small but non-zero, and I haven't noticed the high-rev problem. The bike still takes a couple seconds to come down from running speed, especially if the wheels are still turning, but it hasn't stuck at an elevated engine speed and strikes me as normal.

So the short version is, my problem seems to have been caused by excessive throttle cable play. I'll post again if the problem comes back.

RacingGreen · 08-04-2004

JM thanks - that is helpful. No such thing as a doofus on this site.

I increased my throttle play a few weeks ago. Previously I had all the slack removed. I liked that for rolling on the power exiting a slow corner - but also worried that the throttle may stay open a fraction more than it should (not nice when you're trying to slow down for a tight bend).

I'll tighten it up some more (coz that's easy) and I'll let you know how that goes. The heat thing is weird though.

I had interesting feedback on the workshop forum too (same post title).

-Colin.

RacingGreen · 08-09-2004

I'll cautiously declare this 'fixed' now.....

Tweaking the throttle slack made no difference, so next I looked at the idle adjustment knob and lowered the idle speed back about 100rpm (probably to where it should have been). Rode 150 miles the next day with no problems. Every time I shut the throttle the revs dropped nicely - no issues at all.

Although the previous setting was no problem when the engine was cold, I suspect heat caused something like this to happen:
Since in the throttle-off position the butterfly would not be quite closed, and when the engine is hot the mixture is leaner......when shutting the throttle, enough lean mixture was being sucked from the main jet to over-ride the idle circuit......or whatever.

At least it works - and thanks to all for pointers.

jm · 08-09-2004

RacingGreen, I've decided that my problem is still there even when I am careful about throttle cable free play. I had the bike good and hot Friday evening riding in traffic (the overheat warning light came on faintly a couple times) and it became totally consistent. I will try lowering the idle speed slightly to see if that helps. It's cold here today so I may not be able to give it a good test for a while.

Thanks!