Getting a GS850 up to speed

[frasermanx]

BLOWN Head gasket?

I have similar problem with a 1980 GS850. Starts and runs ok but will not accelerate past 3k rpm under load. I have riden around the block in all gears but it dies when I turn up the throttle. I don't have the airbox on because the tubes are so stiff so I have suspected that it might run lean. I have cleaned the carbs twice quite thoroughly with small wires in the jets etc. Timing is not a problem, all 4 cylinders run well although #2 is only 90 lbs. compression with the others 100 or better.

#2 cylinder does spit back occasionally with flame. Because the front of the engine is oily I was told that these engines are notorious for blowing the head gasket .. but I found that hard to believe ... now I am not sure...

The previous owner GAVE me this bike he was so frustrated so I happy although I am beginning to understand his frustration !!

Any truth to this tale about BLOWN HEAD GASKET with this year engine model ? Later years don't have this problem ....

[Killer2600]

I have similar problem with a 1980 GS850. Starts and runs ok but will not accelerate past 3k rpm under load. I have riden around the block in all gears but it dies when I turn up the throttle. I don't have the airbox on because the tubes are so stiff so I have suspected that it might run lean. I have cleaned the carbs twice quite thoroughly with small wires in the jets etc. Timing is not a problem, all 4 cylinders run well although #2 is only 90 lbs. compression with the others 100 or better.

#2 cylinder does spit back occasionally with flame. Because the front of the engine is oily I was told that these engines are notorious for blowing the head gasket .. but I found that hard to believe ... now I am not sure...

The previous owner GAVE me this bike he was so frustrated so I happy although I am beginning to understand his frustration !!

Any truth to this tale about BLOWN HEAD GASKET with this year engine model ? Later years don't have this problem ....

With bikes these old and the fact that they are air cooled and often times left to sit for a long while a blown head gasket is quite possible and although I haven't tried it for myself I've been told by numerous wise men that these bikes won't run well without the airbox and that you need the airbox if you wanna run it above 3k rpm.

Really don't understand your logic regarding the airbox, it may leak and make the engine run lean so you take it off and make the engine run much leaner anyway. The carbs were designed to work in conjunction with the airbox so without it they will run like crap.

[49er]

I referring to the boots from the carb to the box. I will order new o-rings and swap those too.

I went to my local Suzuki shop and got some NGK boots. The #2 pipe is still noticeably colder, but the whole bike runs a LOT better due to the sealed airbox/new boots. I was even able to get it to idle with no choke, something that's never happened before. I started to adjust the idle screw, to get it down from 2200rpm to about 1500, when I noticed it start to get really hot, and smoke more than usual.

I haven't tried switching the plugs, to see if I have a wiring issue.

There is a lot of oil build up on the bottom of the engine and the muffler. It smokes when the bike is running, but it's never been that bad until today.

So, either I'm running it too lean (I'm missing the airbox snorkel and guessing as to the size the gap should be. Maybe it's too small?) or I have a leak or blown gasket somewhere.

Still, it's good to have the airbox taken care of. The exhaust doesn't look factory. Most factory ends look like showerheads... a center pipe with 5 or 6 round pipes around it. Mine has a center pipe, and that's it. It's still a 4-2 design. The pipes themselves are pretty clean, but the muffler (the h-shaped thing referred to as the 'body pre-muffler' on bikebandit) is very grimy, and possibly corroded. The front of the engine, above and below the pipes, is pretty oily too. Maybe I have a head gasket problem? Oh god, please....

Any input?

I had a similar problem with my '79 850 before the engine rebuild. I would arrive back from a ride and it would fume around the back of the engine and oil would leak from the cam chain tensioner, and drip from the botom of the airbox. The answer was found to be a completly blocked engine breather track inside the top of the airbox. Rust builds up and closes the breather tract and causes the crankcase and cam cover areas to pressurise. This pressure started oil leaks in all manner of places around the engine.
You can check for a suspected head gasket by doing a compression check on each cylinder.
Check out your airbox breather first.

[frasermanx]

tips

Yes thanks for tips. I clean carbs often for other riders... yes I know about the airbox being needed for bike to run properly. Unfortunately I can't get the airbox to stay on since the rubbers are very old and stiff -- kinda like me !!

So I am looking for 2" hose of some kind to use instead to at least get the engine running at past 3k rpm

Great tip about breather on top of cam box !!! I would not be surprised to find I have the same problem....

Actually my BMW is worth more $$$ .. and I might sell it and keep the GS850 since I really need the $$$ ...unless someone in Toronto area wants the bike

call me at 416 994 7oneonezero cell phone

[Steve]

runs ok but will not accelerate past 3k rpm under load. ... I don't have the airbox on because the tubes are so stiff so I have suspected that it might run lean. ....

Believe it or not, these bike just flat-out will NOT run without the airbox or pods on the front of the carbs. :shock:

For testing purposes ONLY, you can fold a shop rag in half and drape it over the carb intakes. Use tape or zip-ties to hold it to the two outer carbs. This give is just enough restriction to run decently, but do not do this for jetting checks.


.

[frasermanx]

Testing

hey good idea about shoprag to restrict air flow. I will use that to test ... still not certain that all is well with this engine though. I will tell ya soon ...

I bought some 2" heater hose to replace the tubes for at least awhile.

BTW I have worked on all jap bikes and none of them run properly without the airbox, but I thought that the complete refusal to run over 3k was weird indicating other problems. The engine makes a sound like a governor cutting the engine

The filters on the carbs cost about $100 or more for 4 carbs so kinda pricey -- airbox way cheaper.

thx
frz

[Mr. Brown]

Update

So I've been working on this project slowly, but making progress nonetheless.

I'm excited to say I finally took the bike on its maiden voyage... at least with me. It is a little rough, and needs a carb synch, but it was great to get it moving.

The headlight fuse blew a while ago, and since the bike is up and running, I figured it was time to get that fixed. It turns out that the extra load from the headlamp causes the bike to die... dammit!

Looks like I have an electrical issue. I'll be taking the battery to get checked tonight. I've printed the Stator Papers, and I'm looking forward to running through that. I've gotta say that getting around the hood a few times has really motivated me to keep working on this.

Someday...[-o<

[Mr. Brown]

All too often...

[BassCliff]

Update?

Mr. Brown,

Thanks for the picture. What's the latest?


Thank you for your indulgence,

BassCliff

[Mr. Brown]

I bought this bike to ride it. I made a quick purchasing decision based on price and ignorance. I had no idea how much work I was going to have to do on this thing.... ever heard that before?

So far I've overhauled the airbox, inspected but not overhauled the carbs, spec'd the valve shims, and replaced a coil and all the spark plugs. I just replaced the gasket on the clutch cover because it was dribbling.

I still haven't figured out my charging issue. I'm not so sure I did a good job with the gaskets because both the valve cover and the clutch cover still dribble a little.

As I commented on the picture, I've spent too much time with the machine taken apart and unridable. In the last two weeks I've just left it alone with it's quirks and ridden it all over the place. I leave quarter sized oil drips when I park, and I have to plug it in at night, but I'm really enjoying it.

I'm taking it to a local shop with a good rep. with UJMs for some input. I need a compression check to make sure I don't have larger problems, and I'm tired of trying to diagnose the electronics myself.

Here's a question... why do my gaskets dribble? I think I might be getting a little overzealous when cleaning off the old gasket and I'm making the mating edges too flat... any suggestions on how to roughen them up?

I peruse this site and there are piles of pics of great looking restored bikes. I'd love to have one, but I'm just gonna ride this funky, uncalibrated machine for a bit...

[chef1366]

Is your breather hose connected to your air box and free of clogs?

[Mr. Brown]

I read a related post about the breather hose, I think it was yours. When I removed the valve cover, I checked the breather cover, gasket, and hose. I replaced the airbox 2 months ago and cleaned the whole thing really well prior to install. The leaks don't seem pressure related. If I go out now and wipe off the bottom of the bike, there will be a few drops right along the gasket seam in the morning.

[chef1366]

Did you get all the old gasket off?

[Mr. Brown]

Yes... if anything I was overzealous and might have made the mating edge too flat... can this cause a problem? Should I go back and sand it or something?

[chef1366]

No such thing as a "too flat a mating surface". :-D Try a very thin layer of silicone in the area of the leak. Let it cure before installing the gasket.