AT WHAT POINT DOES ONE GIVE UP?? CARBS?? 82 GS850GZ

[Anonymous]

1982 GS850 GZ, 12,500 orignal miles. I am the second owner, first owner older gentleman. Bike is all stock. I am mechanically inclined, X BMW motorcycle mechanic for 5 years.
I have totally taken these carbs apart, cleaned, adjusted floats to spec. 22.4 +-1.0MM. Mine range from 22.3 to 22.7. Fuel pilot screws set at 2 1/2 to 2 3/4. Hot idle at 1050. Sync'd. New carb rebuild kits used and complete O ring kit from Robet Barr. Diaphragms checked for tears, no sign of tears or holes.
I have had these dam things off 17 times, to check for crap floating around in bowls and find nothing, not even water, I keep spraying out every passage way each time I'd had them off. By the way, new fuel lines, filter and new petcock, air filter is a year old from new.
Here is how it's pi--ing me off. I ride pretty easy, curise along at 55 to 65 which is 3500 to 4500 Rpm + or -. The dam bike will act like it's running out of fuel on a couple of cylinders and skip along, until I do one of two things. Twist the throttle open and it will clear out and go or I open the choke lever about 1/2 way and she will clear and run great. The closer I get to 4000 rpm, the less it skips. After it clears out and I return to 3500 rpms it will start to skip again. I have been able to go sometimes 30 to 50 miles and it'll run like new, then for no reason,I know of, it'll start this dam skipping rountine. I am mataining 48 to 51 MPG.
I am at the end of my rope with this crap, and it sure does take away from the enjoyment of ridding. Especially, when I know this machine is has the capacity to run like an electric motor all day.
In advance, I wish to thank anyone for some solid advice to correct. Boat ancor is not an option at this time.
Frank Grimes
Keene, NH
fgrimes@webryders.net
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[Jethro]

Dude, have you checked you timing advancer?

[gremlin]

clean the fuel tap, and get new filter and hoses. and that vent in the fill cap.

had a hose onec that looked good on the out side but the inside turned to mush. at speed it would pinch down cutting fuel flow.

[Anonymous]

Danm thing

What are your plugs telling you? my bike did the same exact thing and it turned out that the connector from my dyna S was loose hit 4,000 go like heck turn off the headlite helped, as well as giving it choke, helped, plugs looked rich, so I knew it was elec. put a vacum pump-tester to the petcock vacum hose, with the petcock in the on posistion, then remove a bowl plug to check the fuel flow into a container, while applying vacum, if ok then put back together, with the tank 1/2-3/4 full shake the bike back and forth between your legs, then pop the gas cap and listen for the sound of air escaping, if you hear it then your vent is plugged, also check that the hoses are in good shape but do not rule out a loose elec. conn. some where

[SqDancerLynn1]

Check all of the AIR box seals for leaks If it leaks it could cause it to run lean

[Anonymous]

Looks like you are running lean, fuel miliage on my GSs is in the 30s. Did you check the main jets in the rebuild kits against the factory specs? Lot of people get the wrong jets in those kits and takes them a long time to straighten it out.

[bwringer]

Intake boot o-rings? Surely you've already replaced those, but they weren't in your list.

http://cycleorings.com/intake.html

Also check the condition of the intake boots themselves -- if they haven't been replaced yet, there's a 99% probability they need to be. The boots between the carbs and the airbox must also be in good condition and seated properly in the airbox. Check the condition of all the clamps, too.

It mostly sounds like you have an airbox air leak. The caps on the sides of the airbox must both be well-sealed. I used weatherstripping foam glued on with yellow trim adhesive. You also have to make sure the foam gasket is good on the top of the metal air filter frame. This can also be replaced with weatherstripping.

Also make sure the drain hose at the bottom of the airbox is properly seated.

The only routes for air to get in must be through the snorkel and through the sets of holes at the bottom of the airbox. 850s HATE extra air. They actually LIKE to breathe through that little snorkel.

Let us know what you find!

[Dark Jedi]

I have the same bike.... identical. (Edited, I misread. Mine was the 650GZ)

Had the same problem.... identical.

Went insane... identical.


It turned out to be the intake boots. They had cracked internally, and seperated ever so slightly from the mounts on the head side. I had finally decided to tear down and rebuild the damn thing, and didn't find this till I'd bought $400 in parts for the rebuild and started tearing it down.

Grrr....

[Anonymous]

I had the same exact problem on my 82 gs1100GL. It would not run right in 4th and 5th gear around the 3500 to 4000 rpm mark. It turned out that I had a 1/4" fuel line hose instead of a 5/16" hose. I put the 5/16" hose and fixed all my problems. runs like a champ now. I had no idea that such a small difference in fuel hose diameter could make any difference. I see why it happens though, I went to the suzuki shop to buy some fuel line and all they had in stock was 1/4". So I went to the auto parts store and bought some 5/16". I thought it was my floats or my petcock, because it felt like a fuel starvation problem. I would have never thought 1/16" of a inch would make a difference. So please take the fuel hose diameter seriously. I was about to rip apart my carbs before I decided to change the fuel line diameter. I remembered reading it on a previous post where a fairly seasoned bike mechanic had neglected to check the fuel line diameter and it fixed his problems.

[bwringer]

Just an addendum -- I had bad intake boots plus cracked o-rings on my GS850GD, and had many of the same symptoms. I wasted hundreds of dollars and hours chasing carb problems.

Meanwhile, the engine was running far too lean, far too hot, and ultimately destroyed the #2 and #3 exhaust valves.

I paid a local shop an embarrassing amount of money to fit new valves, guides, and seats. After three months of excuses (I think the idiot actually broke the head trying to pound out the valve guides with a hammer instead of using heat and a press), the owner skipped town to beat drug charges, the shop closed, and my original cylinder head was lost forever. Don't let this happen to you!

So remove those carbs one last time, remove the intake boots, and replace those o-rings! If the boots have any cracks, or if they pull apart, or if they're too stiff to put the carbs on easily, replace them.

While you're at it, do a compression check -- you've apparently been running very lean for a while, so make sure the valves are still sealing.

If the boots and o-rings are OK, then seal that airbox.

Let me know if you need part numbers -- my microfiche covers the GZ and GD models.

[KEITH KRAUSE]

Some good ideas posted. Also check the two floatbowl vent lines for any kinking or blockage. Be sure the floatbowl vent passages are clear.
Poor venting will create fuel starvation most noticable at steady speeds like you described.

[jlmoulto]

When I read this post I thought, someone has my twin 850! Exact same problems as my 850.

Printed this off so I can have it with me while I am in the garage.

Carbs are coming off tonight and new intake boots to be installed.

[Anonymous]

Update on what I've found so far

Thanks all for the tips. Just wanted to update you all on what I've found so far.
To bwringe, yes I did replace the intake boots O rings about 6 months ago. At that time I checked out the boots them selves and they looked real good, no cracks inside out out and were soft.
This afternoon after work I saw 8O that one corner of the snorkel tube was not seated, so I remove the air box. Checked out the top gasket at the top mount and it appears real nice. pulled the end caps off and the sealing foam was all but gone . cleaned the crap off that was left and put in weather srtiping. Could not feel it compress when I put the caps on so I went and bought some thicker stripping. Now I can feel it compress and so I feel that problem area is taken care of. Redseated the snorkel tube and sealed it with the yellow sealent, that's good for gas and oil. The rubber tubes to the air box from carbs are all tight and in good condidtion.
So tomorrw I'll remount the air box and double check everything, fire it up and start spraying every thing, with carb cleaner in hopes the engine does not speed up, and that those dam end caps were my problem. Yes, I am looking for the easy way out at this point . Oh yes, I did replace my fuel line with 5/16. Fuel filter was new anyway.It's no fun chasing the unknow . But hopefully with everones great suggestions, I'll find out what's wrong. Thanks again to all, and will let you fine folks know how I make out. Of course road test will be the final answer. Thanks again.
Frank Grimes
Keene, NH

[bwringer]

Let us know how it comes out, Frank!

Believe me, the bad airbox sealing you found can definitely cause the problems you're describing. GS 850s are really, really weird that way.

Of course, now you have to sync the carbs again.

I chased a problem for weeks once that turned out to be a kinked clamp on the boot between the airbox and the #3 carb. It was almost perfectly hidden from view, but when I tightened the clamp, one edge would get caught and twist just enough to open an air leak. ARRGH!

Sounds like you have hope for the old 850 again...it's nice to see!

[Anonymous]

This is the last mad dash towards the finish line