fast idle on a hot engine.

[PBJ]

two weeks ago I had a problem i know others have had. It was a hot night and the idle on my bike started to go up. I could not get it down so headed home . there i lubed all my throttle cables and choke linkages then finally readjusted my idle getting it down to around 1000 rpms. i latter realized this may have been a vacuum leak problem and have seen that suggested here by others as well.

 

What I'm looking for here is a previous thread from someone that may have had this problem and hunted down the offending vacuum line so i know where to look and how to fix it to prevent it from happening again. oddly this only happens when its hot.

 

So if anyone knows of a thread like this could you point me in that direction?? Thanks a lot.

 

I like the 86 a lot I have headset for the com system and love the whole set up the bike still has a few bugs to work out from sitting for 5 years but She runs great and I'm enjoying every minute. While working on the radio i did find a cozy mouse nest under the cassette player unit. Luckily not residents at the time.

[KIC]

One recent leak was discovered to be the vacuum line on the front left carb to the TCI (?). It is the only line that comes off the lower carb area.

 

Also, you might have a bad diaphragm in one ( or all) carbs. My 87 kept idling up once warm... to the point of ridiculousness. Once I checked my diaphragms, they all had holes/tears etc from age.

 

The other trick is to spray starter fluid around the carbs and lines to check for a leak.

[PBJ]

Thanks Kic I'll start there . Any other ideas guys?

[Yamamike]

Hate to point out the obvious but just because someone had a vacuum leak at a certain spot does not mean your is (if there is) the same. That said, spraying some (not too) flammable liquid can locate a vacuum leak pretty quick. Some say WD40 works...just do a very small area at a time and wait a few seconds. You'll know you found it when your idle speed goes up suddenly.

[Yamamike]

I type too slowLOL

[PBJ]

I just found an old thread with someone talking about the same problem his answer seemed to be to check and or replace the vacuum line to the #2 carb (left front) to the baro sensor. Along with checking to make sure the carb boots were properly in place so that's where I'll start looking for my leak. Hope this helps others too seems to be a regular problem .

 

 

Love this site!!!!!

[Squidley]

Phil,

 

Have you done a carb sync on the bike since you have had it? If you haven't done it already, replace the vac line from #2 Cylinder to the boost sensor, and replace the other 3 caps on the vac ports in the manifold boots. This way your not 2nd guessing those components being good or not.

[raybear71]

Mine was where the carb boots meet the manifold. A little permatex ultra black took care of the problem.

[Snaggletooth]

Hey Phil,

 

I was one of the guys with a similar problem since the weather got hot. Been doing a lil playing around with the odds and ends since I posted on the other thread.

 

So far I've chased down one issue. My vacumn caps on the intake boots have never been the best. I took them off and dip coated them with "Dip It" and let them dry. The next hot day I had only a smaller increase in the idle. Looks like I'll be ordering new caps and clamps as I don't see the Dip It as a long time fix.

 

Most the rubber lines have been replaced over the years but a few still remain. I'm going to pull and spray each one of the lines with "Dip It" to check for changes or replace them as I go.

 

I always figured the rubber lines would be more prone to leak when cold rather than hot but I guess the heat will cause more movement allowing any small crack to expand.

 

My intake boots don't seem to be an issue anymore since the last time I R/R'd the carbs but it is a good place to start.

 

It's supposed to hit the triple digits here again the next few days so I guess that's good "testing" weather.

 

 

 

Mike

[Prairiehammer]

Here's a thread I started a couple years ago about my high hot idle.

http://www.venturerider.org/forum/showthread.php?t=52794