Missing at low RPM

966 Views 11 Replies 8 Participants Last post by rb7632, Sep 21, 2009

EMiT

Discussion Starter · Sep 17, 2009

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Hello everyone,
I've got a little problem I'm hoping you can help with.
I recently got a 1983 GL 1100.
It was one of those made opportunities sort of thing.
I kept seeing this bike sitting in front of a costumers house, same spot all the time.
I found out that it had been sitting there for at least two years.
When I first went there to look at it closely and maybe buy it, I had to hear it run.
It ran fine. A little miss every once in a while. Once about every thirty seconds at idle.
A few weeks later when I did in fact buy the bike, the miss was constant at idle/low rpm.
It smooths out very nicely at about 1500rpm, sounds strong, very smooth.
Smooths out at about 1000rpm when it's warmed up.

What I've tried so far,
New plugs and wires, cleaned the snot out of the carbs,cleaned the air filter, changed the timing belts,re-set the timing and tested the coils the best I could.
I replaced two of the plug boots, because the bike shop only had two in stock.
I'm picking up the other two today.
When I replaced the two boots, it did sound better, but the miss was still there.

This is driving me nuts.
I need to fix a little wiring and install new brake pads, and she's ready to go, but I'm not taking an unfamiliar bike out on the road if it's missing.
I haven't ridden it about 20 years, I'd like to give myself every chance of nit getting killed the first time out in all that time.

:action:

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Bagmaster

· #2 · Sep 17, 2009

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Go grab some Seafoam and run it in the gas for at least 2 tanks full.

Also in the list of things done, I didn't see valve adjustments in the list.

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k1w1t1m

· #3 · Sep 17, 2009

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A compression test might be beneficial too.

Don't take too much notice of the actual numbers as it's been sitting a while but if you see a really low pot you'll know where to start looking.

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EMiT

Discussion Starter · #4 · Sep 17, 2009

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Cool, thanks.
I'll see if I can borrow a compression tester from a buddy at work.
And I haven't adjusted the valves.
I thought that they'd be ok, since it ran fine when I first looked at it.
I should know better than to assume.
Here's a cool symptom that I just found.
If I hold my hand at the left side exhaust, it feels warm/hottish.
The right side however feels cool.
Hmmmmmm.....
That leads me to believe the the problem is on the right side.
I put the new plug boots on, now all 4 cylinders have new wires and boots.
No further improvement I'm afraid.
I'll try the seafoam, but I have to get brake pads and a tag first.

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EMiT

Discussion Starter · #5 · Sep 19, 2009

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A little update on the bike.
I mentioned earlier that I had replaced the timing belts.
I followed the tutorial I found on this forum.
(Superb write up BTW)
So this morning I pulled the timing covers back off, thinking that the belt may have jumped a notch.
It did.
I got that straightened out, nice tension on the belts, bolts nice and tight, everything looks good.
I went to fire her up, all happy, thinking that I fixed the problem.
Turn the key, choke on, push the button. Sounds great for about a second and a half, the the evil miss begins.
ARRRRRG!
Well, as along she's running, I'll check the spark.
Good spark on all 4, but I did determine that the right side isn't firing at all.
Turn the bike off and decided to check the valves.
Lined up the timing marks and checked as well as I could.
Everything seemed fine, but honestly, I'm not sure what I'm looking for here.
It's not just like a car engine.
Anyway, thinking about it, it seems to me that since she was sitting for so long, the gas that was in there turned into shellac.
That had to leave some crap in there.
For whatever reason, it didn't clog the left side carbs, just the right.
Going into town later, and I'll pick up some sea foam and or 2+2 gum cutter.
I'm thinking of pulling tank and cleaning that out real well.
I don't want to loosen crap in the tank, just to pump it into the carbs.

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Cal-D

· #6 · Sep 19, 2009

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If the miss is only there at low RPM and runs smooth and strong once the revs are up, I would guess you have blockage in the carbs low speed circut. Since you said it did sit for two years, that is where I would start. Pull the carbs and have them properly cleaned and adjusted.

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EMiT

Discussion Starter · #7 · Sep 20, 2009

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'Pull the carbs and have them properly cleaned and adjusted.'

That's good advice Cal-D.
At the moment I've spent most of my motor cycle allowance.
What I did do this afternoon, I got myself a can of sea foam and 4 gallons of high test gas.

Love that high test.
Anyway, I put some sea foam in the tank, and by some I really mean about 1/3 of a can, followed by about three and half gallons of gas.
It took a little cranking, but she started.
Still missing, POP.....POP......BANG...POP...,After about a minuet of this, she smoothed out quite a bit.
Still misses, but not as much.
An occasional pop every now and again, but iit was slowley getting better.
After about 45 minuets I decided that I had annoyed the neighbors enough for one evening.
I plan on going out there tomorrow and letting it run while I do my weekend yard stuff.
When I get some more funds in the bike account I may just take Cal-D's advice.
Hopefully, this will improve things enough that I'd be confident taking her out on the road.

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Cody in MN

· #8 · Sep 20, 2009

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Glad to hear you're getting an 1100 on the road... :action:we want pictures ...

I think it will get better as you run it... If it has good brakes, just get her out and run

her , rev it up all through the RPM's, will not hurt to get her close to redline, may

help actually... keep her above 3000 RPM's... that is were they like it...

Good Luck & Ride safe Welcome to the Forum :waving:

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EMiT

Discussion Starter · #9 · Sep 20, 2009

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Thanks Cody,

I was just out there running it.
It seems a bit better.
If I pull the plug wires on the right, it makes no difference.
If I pull one on the left, she stalls.
I'm going to try to find out how to adjust the valves and look at that again.
After I mow the lawn, trim the sidewalk, ect.....

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sfruechte

· #10 · Sep 20, 2009

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Adjusting the valves is pretty easy but critical and can cause a miss or weak or non-idle. Make sure you have the engine in the correct position according to the manual. Too little clearance and the valves do not close all the way and they will rapidly burn. Then the miss will never go away.

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superhawk1022

· #11 · Sep 21, 2009

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I'm betting on the carbs. #1 since you said it had sat for 2 years and #2 pulling right side plug wires makes no difference. Have you had the carbs off and disassemled? Thats the only way to clean them. Know anyone who's familiar with wings that could listen to it for you? If you've been away for 20 years it may be missing worse than you think. When you first start it feel the pipes at the heads. If one stays cold it's most likely the carbs.

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rb7632

· #12 · Sep 21, 2009

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The SeaFoam seems to have helped. I usually dump a full can to a tank of gas. I do this about every 3-4 months. You might try a heavier dose for even better results. It does sound like the low idle side of the carbs that is causing the problem.

If the SeaFoam doesn't clear it up then the slow idle jets ares probably your culprit and they can be a bugger to clean. Someone said they used a piano wire but a guitar string might work also.

Hang in there. The 1100 engine is a fine piece of work and extremely dependable once you get it right.

:action:

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