So where to go from here with the GS850 carbs.

[jlmoulto]

OK...advice please....I may have bad mouthed an honest mechanic (My first mechanic still sucks but just maybe I misunderstood this second guy.)

Tell me if what he is saying makes sense to you.

I went to have a chat with the guy out of frustration from the bike problems and to find out more information to share with you. He explained that in my carbs, the diaphrams won't seat. The rubber appears to be stretched. They are not smooth when they are inserted, but have "ribs" and creases in the rubber. He showed me a carb on his bench with the same problem and then showed me one that was seated "correctly". In looking at them, my diaphrams in all four carbs look like the ones he considered bad. He claimed that this would cause air leaks. His words of unservicable he said was because it would cost more to fix these then to buy a good used set. He also offered to sync and install another set for me for free if I get another set.

Does this make sense? Would the bad diaphrams cause this problem?

[UTgws]

I had the same problem with a pilot screw. I _CAREFULLY_ drilled a small hole in the _center_ of the pilot screw (1/8" bit i think) about half way through the threaded portion of the screw, then tapped a TORX bit into the hole in the pilot screw, and turned that sucker right out

[Anonymous]

I would not have suspected the carbs for a bad running condition after an engine rebuild, unless it took two years and I left them sitting around with the old gas in them. If you get a set of used carbs, they will probably need cleaning also. Try to get the best ones you can. Some or all the jets will be the wrong size. An often overlooked jet is the needle jet (your mains screw into it). They simply push up out after the mains are removed. Compare everything to the manual, not the old carbs, you probably didn't buy the bike new and they may not be the stock carbs.
The diaphrams always look bad, they have a very rough life, in a vacuum on one side with tornadic fuel and air storms on the other side. I can't really vision what they look like from your discription but the only way I see them not working is if they have a hole in them. The tops have a ridge and pretty much have to seat. The body is constantly stretched and colasped. Diaphrams are very expensive, think four of them would cost more than used carbs, so the guy was telling the truth there. Don't really know what the mechanic is saying about diaphrams, maybe Keith does if he's around? He's probably the best carb person on this site. You can purchase o-ring lube and try to straighten them out with that?

[opiewontaylor]

Diaphrams usually only become unusable when there is a hole or rip in them. They can usually be "cajoled" into seating with a little patience, even when old. I do agree that your best bet is to just get a used set of carbs off e-bay. After having these 2 "mechanics" work on them, it's entirely possible your carbs are now unservicable.

[KEITH KRAUSE]

The diaphragms should be fairly supple. No pin holes or larger cracks. We're talking possibly original parts here. A good shot of silicone spray can help.
Most often if a diaphragm is bad, the carb won't accept throttle above idle. With any cracks/holes, the compromised vacuum can't lift the piston and the throttle valves (plates) won't open.
You do have to make sure the spring/piston assembly is installed just right and the diaphragm "tab" is in the right spot.
Your problem could be a poor carb synch. Too little vacuum at that cylinder will cause your problem. At idle/slower speeds, the low vacuum is creating a very lean mixture compared to the others. Once the throttle opens up a little more there's enough fuel being drawn up to fire the cylinder correctly.
It could also be a clogged pilot circuit. If it's jetting related, it depends on what throttle position you're at when the bike acts up, not rpm's.

[jlmoulto]

So, I guess I'm left at this point to decide where to go. I'm past my level of expertise. I can't seem to get anyone who can fix this carb issue, and I'm reluctant to spend more money on a set to have the same problem occur.

I think I may have mentioned this before, but is there an "expert" who would be willing to have a go at these carbs for me? I don't mind paying someone reasonable compensation. Even if it is just to tell me they are garbage and to get rid of them. At least I'd have some confidence that if I spend more money I might see the bike run right.

If you are, drop me an email and let me know what you can or can't do!

jlmoulto@hotmail.com

[KEITH KRAUSE]

yeah, there are no gaurantees with used carbs. It's always a risk buying used carbs that have sat dry for who knows how long. The rubber parts take the worst of it. You could get lucky but there's the rest of the carbs too. Mixture screws, floats, etc. It's 50/50. :roll:
The diaphragms are expensive and you say the rest of the carbs are questionable if you did go ahead and buy them.
Just going by the mechanics words, he sounded like he wasn't trying to rip you, but I would still like to see the diaphragms he compared yours to. His offer to do free work seems honest. By your description, I'd say he was being honest. Could you actually see how the diaphragms seated?
I would attempt a carb synch and see what happens. If the diaphragms are bad, you won't be able to synch, period. You would have to pay of course, that's if he would even try.
Normally, if a diaphragm is bad, that carb will not accept any throttle above idle. It only takes one bad carb to cause the problem.
Maybe "wiredgeorge" would look at your carbs? He says he rebuilds them for a living. He posts his charges up front.

[Anonymous]

carbs

Get an exchange set from wiredgeorge he puts them on a bike and tunes them, so there very close when you get them and his prices are very fair