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High idle with various causes, what else do I check?

  • Thread starter Thread starter ddlaz
  • Start date Start date
D

ddlaz

Guest
Hey all. Back again with some issues.
1982 GS650E
Stock everything engine wise

Was running fine a few months ago before I decided to do some maintenance to replace the valve seals.
Replaced valve seals to stop oil leaking into cylinders then had her running again but got the wrong valve cover gasket so I didn't put it back together until today.
Checked and replaced valve clearances, all are set on the low end of around .038 mm. Spec says .03 to .08.
Also changed points cover gasket(for lack of better term right now, i know it doesnt have points).
While it was down and apart I ordered new intake orings and petcock.
Cleaned the intake mounting surfaces and put on the new orings.
Finished putting it back together and the darn thing idles high and the tach reacts very sluggishly.
took the tach cable off the valve cover and spinning it by hand creates pulses on the tach. Taking the cable off the tach end and the cable spins rapidly. Is my tach screwed somehow? I did take it off when changing handlebars.

Second and worst issue.
First starting it, the idle jumped high and realized the idle screw was in too far. A second start, the throttle cable was too tight from changing throttle cables. Fixed.
Still, high idle. For some time, without choke, it idles to 4 or 5k. With choke, it idles around 1500. With the choke on, the throttle response was great, engine speed returned to normal quickly--thinking lean. Checked spark plugs and theyre black with dry soot--thinking rich.
Messed with the mixture screws on top of the carbs, turned them all out 2.5 turns. Now the engine idles high on choke,won't idle at all without. Now I'm thinking it's super lean but I can't find a mixture screw setting to get it in between.


I've checked for intake leaks by putting gas in a spray bottle an spraying around the carbs on both sides. No changes.
Cleaned the carbs 2 times. First was just spraying, second was full disassembly and overnight dip.

My next thought is the contacts under the cover got dirty with grinding dust since I was working with metal in the same 3 car garage. The magnets had some iron filings stuck and I cleaned as much of it off as I could. I don't have a timing light, nor have I ever checked timing before. I'll have to review the manual for this if it could be a cause.

Any ideas?
 
"Still, high idle. For some time, without choke, it idles to 4 or 5k. With choke, it idles around 1500. With the choke on, the throttle response was great, engine speed returned to normal quickly--thinking lean. Checked spark plugs and theyre black with dry soot--thinking rich. "

This description is opposite of how my "choke" behaves on my bike ,so I have to ask.....are you sure that you have choke actuator connected correctly and not reversed ? The "choke" rod pulls out the plungers from carbs to activate system.
My bike has pitiful throttle response if "choke" is left on
 
Yes. As it should be the opposite. It is just odd.
The cable is on correctly, the cable pulls the plungers to the left and out of the carb bodies when choke is on.
 
I'd hate to throw parts at it without a proper diagnosis but it couldn't hurt -- ordered new intake boots. Tested all boots by taping both ends and submerging in hot water. No air bubbles.
 
Can't hurt to have new boots. Hopefully, you'll get normal hot idle and good throttle response with no choke- and no sooty plugs!
 
Bench sync'd when I reassembled the carbs after the last dip.
Haven't had it running right enough to do a carb sync. Before that, probably 4 months ago.
 
next time you do your valves, set them closer to the wider gap, .08mm. the engine will be a lot happier. also, gas in a spray bottle probably isn't the best tester. I would either use carb spray cleaner or starting fluid(ether) with the straw they provide with the can. it will be easier to pin point the problem. are you sure you had your airbox and manifold boot clamps tight?
 
Figured shim for the smaller gap and have more time before the next shim size is needed.

I used carb cleaner at first and didn't notice any idle changes so I figured I'd flood the whole carb boots with spraying gas.
Airbox leaks don't affect the idle as much as the case here. I've run a bike with CV carbs without airbox before and the idle would only go up 1k or so which got dialed down with the mixture screw. In this case, I can't get it to dial down at all.
So even though I'm almost certain that the airbox and boot clamps were tight, the idle shouldn't be up to 5k.
 
You have valve clearances backwards. The clearances get smaller over time and require smaller shims as a result. By going to the large end of the range, you buy a little extra space.
 
I guess I never thought too much about it. I was thinking the clearances got larger due to wear at the cam lobes. Where is the shrinking coming from?
 
Googled it. There are some disagreements out there but the majority consensus is that the valves wear into the head. Guess I'll have to review my shim inventory and order.
 
You put gas in a spray bottle to check for leaks? Did you at least install new carb orings the last rebuild?
 
Last edited:
Yes, gas in a clear spray bottle. I put new carb orings in prior to tearing the bike down for other maintenance items. I tore the carbs apart to clean and put back together to find that it was leaking gas from the disturbed, cracked orings. Removed carbs and disassembled the gang to put new orings in.
 
ddlaz said:
I guess I never thought too much about it. I was thinking the clearances got larger due to wear at the cam lobes. Where is the shrinking coming from?
Click to expand...

I had the same idea when I joined the forum. The guys here straightened me out. As you already found, the wear occurs on the valve seat, making the valve rise closer to the cam lobe.
 
Well, not sure what the actual problem was but I put the new viton orings in the old boots and nothing changed. I then got new intake boots on with the new orings. One oring fell off during assembly(didn't know it at the time) but the idle was still high. Took airbox off altogether and ran it with decent, low idle. I thought it was fixed. While putting airbox on, noticed the oring under the carbs. Took all carbs off, rings in place, no airbox - high idle again!
Cleaned carbs again, checked diaphragms, reinstalled carbs and airbox. Runs great now.

All sorts of weird scenarios. I guess my problem was a bit of everything.
 
Make sure you vacuum sync those carbs. It will cause lots of other problems, as i found out the hard way
 
Will be tearing down the bike again this winter for new exhaust, cleaning and painting the engine and frame. I'll sync after that.
 
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