Racing Idle after riding 20 mins or so?

I'm having trouble with my bike after riding for several minutes.It idles at 1000 rpms when started,but after bit the engine will race when I come to stop jumps up to bout 5000 rpms.The only way I can knock it down is to let out of the clutch or hit the choke that usully knocks it down.I have checked the outer boots for air leaks and applied some silicone sealant.I hvae used seafom several times.I have never taken the carbs out and cleaned them.I don't know if the throttle is sticking haven't really checked the cable.I tried to do search and read several links this one seems to be about the best any suggestions.http://xjbikes.com/Forums/viewtopic/t=5 ... =idle.html

 

Have you tuned it recently? It sounds like your engine warms up and at that point, the mixture isn't correct. Dunno though.

 

I have a similar problem that I have yet to have addressed. High idle after a brief period. Seems I have my idle set too high, indicating my initial idle adjustment was not when the engine was warmed up. Clean your cables, run some SeaFoam through the fuel system, tune it up and set your idle. That should clear out the problem.

 

what do you suggest for cleaning throtle cable

 

I've always had good results from just about any brake cleaner but WD-40 will work. The manufacturer suggests lubing the cables with motor oil. The way I see it, WD ought to do both cleaning and lubing duty rather nicely. I used it exclusively for years but have been lazy as of late.

 

High idle after prolonged warm up is a Common/classic symptom on these bikes when they get old/worn (out?) Dicking with the idle screw masks the obvious symptom, but opens up other problems.
Usually caused by an Air leak..which can have seriously harmfull consequences. Start by looking at the Manifold Boots, then the Carb butterfly shaft seals... assuming of course that the carbs were setup passably well to start with.
G'luck

 

Mine just started doing the same thing, and this after having balanced the carbs with the vacuum gauges. I'll throw some Seafoam in the tank and see what happens. Failing that, I've got the restrictors made up, so maybe I can take another swipe with the gauges.

I'm hoping it's not butterfly shaft seals... I really don't want to have to pull the carbs for the 8th or 9th time.

 

You can do a spot check of the outer two shaft seals without pulling the carbs. Just remove the "E" clip and washer, then you can get an idea what condition they are in.

 

Hi Guys, Had this same problem it was was two loose clamps on air box side of carb boots. Tightened clamps and all is well...


-chris

 

i found that mine was idleing on 2 cylinders when cold, pretty roughly then when warmed up the mixture was so lean it was able to fire on all 4 causeing the idle to spike as you describe. I cleaned up my pilot jets and pilot screws plus all the passageways and it helped out alot

 

Did that this morning. They don't appear to be rotten, and they came out fairly easily. The clamps for the airbox boots are on as tight as they can go. I'll double check the midget condoms... er, vacuum caps and see if there's anything not as it should be.

 

I've been having the same issue with my '81 Seca. I took it to a trusted shop earlier this week and he said that it was because it starts out with 2 or 3 cylinders firing, and then, after it warms up, all 4 start firing. I've adjusted the idle after it was warm quite a few times, but doesn't consistently seem to fix the problem. The mechanic told me that the rubber manifolds going between the carbs and the engine were cracked and air may be leaking in there. I bought two of four new manifold pieces, both outer pieces, because they were charging $15 each piece and I didn't have enough to shell out $60.

It sounds like we're experiencing the same problem, so check for air leaks, they should be pretty noticeable.

A few questions pertaining to some suggestions: What is seafoam and where can I get it? Where is the "e" clip on the shaft seals? I haven't received my repair manual in the mail yet (got the bike 6 days ago) so I'm a little blind when it comes to specific parts. And, does anyone know where I can get those rubber manifolds for a good price?

 

Seafoam is a fuel/oil additive and can be found in most automotive suppliers in the US from what I understand. A bit harder to find in my neck of the woods!

The two outer "e" clips can be found on either end of the rack of carbs. Look just in the center of the carb pretty much where they connect to the rubber manifolds (engine side). If you have a look they should be very noticable.

$15 each for the engine side manifolds, are they new? that's pretty darn cheap in my opinion!

 

Quick update on mine:

Last week, I think it was, when I came home from a warmup ride it shot up to 2k, and I remember throwing two of the vacuum gauges at it (on #1 and #3) and tweaked it a bit. Also, not too long ago, I had noticed fuel dribblng from the petcock, so I swapped the stock spring with one I had jury-rigged using a spring I bought at Ace Hardware.

Today, I decided to top up the tank (I had been on reserve) and go for another warmup ride, and maybe throw all four vacuum gauges at it again. Let it warm up a couple of extra minutes, went to the nearby Chevron (instead of the Costco I had been using), and went riding. Really opened up the throttle when I hit the onramp. Put about 15 or 20 miles on it and went home. End result?

Bike idled perfectly.

I don't get it. I'm not complaining, mind, but I don't get it. Because it's impossible to graph a curve on one data point, I'll ride it into work tomorrow (40 minute run) and see what happens then.

 

Load-up something that will squirt a stream spray with Marvel Mystery Oil.

Shoot the Butteryfly Shaft Seals and Exercise the Throttles as you work it in.

That situation you guy's keep referring to as High Idle ...

Above 1,200 rpm's isn't Idle anymore. You need a touch of Main Jet Fuel.
If you "Lube the Hinges" on them Fly's ... and the Bearing Points ... and spray the Linkage Return Springs Clean with some Carb Cleaner followed by a shot of Marvel ... at least once every 20-years or so ...

The Carbs will work better!

 

this has to be done THAT often!? man i CANT STAND maint that is required so much.... :wink:

d