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-   -   Irregular idle (http://www.horizonsunlimited.com/hubb/yamaha-tech/irregular-idle-27235)

vainoman 22 May 2007 10:50

Irregular idle
Got a -87 XT600 (2KF/NF) which runs strong and smooth most of the time but occasionally I get this idle problem: when the engine is warm the idle sometimes drops from the usual 1300-1500 rpm to 1000 and lower and the engine dies when I try to rev it up. This happens only intermittently. Any ideas who's the culprit?

In the winter I removed, emptied and flushed the tank so there should be no garbage coming from there. The bike is garaged overnight so no water condensation is possible.

If this is some gunk in the carb is there a low tech way of dissolving it with some fuel additive (i.e. avoiding disassembling the carb)? TIA

aukeboss 22 May 2007 11:04

Rocket science
Instead of the chemical solution, advise the technical approach:

From your symptoms, I think you have either one, or both of the following issues:
- Sticking throttle cables - lubricate and reinstall
- Setting of idle mix incorrect (see earlier posts)

Advise to correct both and then see what happens


*Touring Ted* 22 May 2007 11:42

There are soo many things that can cause irregular idle.

This only seems to happen when warm which leads me to think that maybe the pilot mixture could be a little rich or the choke isnt closing propery and possibly sticking.

Sure this only happens when warm ?? Does the bike run ok at full throttle ?

tomwest 22 May 2007 20:02

high revs?

Your idel revs are a bit high, my bike idels at 900-1000rpm depending on temperature. have a look at your cabels and choke as mentioned above.
If the bike is running good normaly and just does this once in a while I donĀ“t think the mixture is off.
You might allso want to take a look at the ignition cable, sometimes a change to a new and "fresh" one can do wounders on a old bike.


vainoman 25 May 2007 08:43

My Clymer says idle should around 1300 and based on this I raised the rpms a bit - the idle used to be (last riding season when I didn't have this problem) just a tad above 1000 according to bike's tacho.

The gas cables I lubricated some months ago and now checked again. They slide fine.

The bike runs strong at full throttle, no problem there. At cold start full choke brings the rpm's in a minute or two to 3000 and then I take it down. So no cold problem with the choke.

In Clymer they say that gas may go bad during the off-months and recommend some operation to flush the carbs. I'm a bit hesitant to do this not to screw up the set-up. My car which has fuel injection (presumably more sensitive to gas quality) and even after months of unuse never has gas problems. Is this chemical thing real or not?

Thanks guys for ideas. Have to keep checking, ignition cable and else.


oldbaldrick 26 May 2007 00:27

With the bike running, spray some WD40 or similar on the rubbers between the carbs & cylinder head. If there's no change then all is well there. But more likely, the bike will either stall or rev up due to the rubber separating from the metal on the inlet manifolds. Known fault - get 'em changed.

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