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New Owner '80 GS850G - Missing at steady highway speed

  • Thread starter Thread starter Anonymous
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Anonymous

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It's got only 14.4K miles and had new rings and lower gasket put in within last 400 according to receipts. I put in new synthetic oil, filter, plugs, new Uni filter. The oringinal plugs were not fouled out. The idiot who owned it only drove 200 miles for the whole last year and tells me the gasoline was the same for the entire year. Anyway, I put in new gasoline and carb cleaner. So now after my "tuning" efforts, it idles and accelerates absolutely beautifully, smoothly and quietly, much better than when I picked it up. However, when holding a steady 60-65 mph it continually misses (4000-4300 rpm). Do you think the carbs are messed up somehow? Will continuing to ride it around with cleaner help (seeing as it hasn't been used)? Is there some electrical issue that I should be looking at (coils, electronic ignition?). I love this bike and it looks great. Any advise vastly appreciated!!!!
 
Chances are the jets are varnished up. SO the carbs will need cleaning. I would PUT reg oil in it. IF the rings have just been changed. You need to give them at least 1K miles to seat in, before changing to syn oil
 
I agree with the oil recommendation. You should use a straight 30 wt for breaking in rings.
 
As Lynn said, you probably need to clean the carbs too.
Steady speeds will show a problem you did'nt notice at various/changing throttle positions. You may need to vacuum synch the carbs too. A pinched or blocked floatbowl vent tube will result in fuel starvation most noticable at steady speed. So will a blocked air vent in the gas cap. Also, a failing vacuum line to the petcock or a failing diaphragm can result in your symptoms.
 
dogging & surging at highway speeds.

dogging & surging at highway speeds.

I have an '82 GS850G. After replacing the air filter, the bike went from running great to dogging and surging, especially at sustained highway speeds. I had sprayed WAY too much sticky stuff on the air filter':oops:'. I fouled the spark plugs and replaced them. I figured the sticky stuff had clogged the carburetors. I ran carb cleaner in the gas, which didn't help. A mechanic I talked to checked that the gas cap was venting proprly. I fiddled with the airscrews, all to no avail.

After reading about someone else's experience on the GS Foum, I replaced the petcock. That seemed to help with some of the surging. Then I read a posting that rotted out seals on the airbox let in too much air making the the bike run lean. I checked and sure enough the seals on the "doors" on both sides of the air box were all but gone. I spent $1.79 on some 1/4" weather stripping at Home Depot, scraped the old seals off, put two layers of weather stripping, and put the airbox back together. The bike runs MUCH, MUCH better after fixing the seals on the airbox.

Caleb
 
Thanks all, these are some great suggestions, I will figure this out!!
 
By the way, if you check back on this post, I just had the carburetors synchronizd on my '82 GS850G. The bike runs pretty much perfectly now. Its good to have her back.
 
I can only add that over the years I have been told ceaselessly.. and check the technical links (maybe) on the gs home..

NEVER use synthetic oils as they do BAD things to the clutch as it works being bathed in the engine oil...

I thought so important I saved the posting.....

Here it is....

the friction modifiers are also found in the heavyer weights of oil and they dont hurt the engine or transmission.
the friction modifyer is in automotive oil to make it sliker and reduce internal friction, the problem with using it in motorcycles is that most motorcycle clutches run in the same oil as the engine and the friction modifiers coat the clutch plates causing the clutch to slip, ruining it.
When I bought my gs1000g and returned it to life after a six year slumber I put valvolene 10w40 in it and the clutch started to slip after a couple of weeks, I took the clutch apart and it still had plenty of material and the springs wear still good so I did some reserch on oils and learned about the differances.
_________________
I do what the voices in my head tell me to do.
1980 GS 1000g, 1985 voyager1300, 1989 tt350

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brit7.11
Casual User



Joined: 17 May 2002
Posts: 13
Location: Sussex, England Posted: Sat May 25, 2002 4:51 am Post subject:


The above is correct. Certain car engine oils have friction modifiers added to enable them to become more fuel efficient. They can be identified in some cases by being labelled "JASO MB". "JASO MA" oils are OK in motorcycle engines. Most older type car oils should be ok in bikes and I personally have heard of a GS750 covering 92000 miles using Castrol GTX, a basic 20/50 CAR engine oil.
I have heard oil company chemists advising not to use the latest fully synthetic oils in older aircooled engines, and definitely not when running in new components.
You have to remember that when the GS design was initiated, the oils available were pretty basic, and there was no advice from the manufacturer to avoid car oil.
The best advice I can distill from 20 odd years as a motorcyclist, and training as an aircraft piston engine engineer, is to use a fairly basic oil, preferably one intended for motorcycle engines, and change it regularly. I, like most GS owners I know, change my oil and filter every 2000 miles. The oil I use is Castrol GPS, a semi-synthetic m/c oil.

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earlfor
Familiar User



Joined: 14 May 2002
Posts: 84 Posted: Sat May 25, 2002 7:08 am Post subject:


I've used Castrol GTX20W50 in every bike I've had starting in
1973. I've never had the first problem with it. My GS750 is
motoring happily on it now.

Earl

[quote="brit
You have to remember that when the GS design was initiated, the oils available were pretty basic, and there was no advice from the manufacturer to avoid car oil.
The best advice I can distill from 20 odd years as a motorcyclist, and training as an aircraft piston engine engineer, is to use a fairly basic oil, preferably one intended for motorcycle engines, and change it regularly. I, like most GS owners I know, change my oil and filter every 2000 miles. The oil I use is Castrol GPS, a semi-synthetic m/c oil.[/quote]
 
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