Triumphrat

RacingGreen · 08-03-2004

This is a follow on from "jm's" post of the same title on the Trophy site - just opening up to a wider audience.
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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 there be a problem with an idle circuit?

:???:

Will · 08-04-2004

This is only a guess, and it is based on SU carbs, so take it for what it's worth. You could have either a sticking float or something that heats up and starts to rub in either the carb or throttle linkage somewhere. I would start by looking for things that are rubbing, just because it is easier, but my guess is that you will find something gummed up inside the carbs.

dhall10 · 08-05-2004

Just had something similar on my Adventurer. It turns out I had incorrectly adjusted the throttle cable when I installed the new one, no slack in the cable(?) they said.

GaryD · 08-07-2004

Common problem with trash in the carbs is running to lean which can cause a slow descent from high revs when the throttle is closed. Cleaning float bowls may be all you need.
Suggest you fix ASAP.

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.