runs on choke, dies on throttle...

[snowbeard]

hey guys, back to the old 850 again. got the "new" brain in it and it seems to run more smoothly, no random intermittent stalls, but it has a long way to go I know...

so I can get it started and running on choke, it comes and goes as I lower the choke, and I can rev it pretty high with just the choke, but it won't let me shut the choke all the way, and it just kinda bogs if I give it any throttle (course that's what happens when you break the choke circuit, eh?)

so what should that tell me? lean? rich?

there's a good chance of a leak in the airbox system, but I did run it once last season where it ran spot on (or so it seemed comparatively...) would it maybe just be gunked jets from sitting overwinter? I added some techron to try to clean it up a little, I plan to just keep starting it and running it often as I can to see what happens as it works thru things

one other thing, which way from the back of the bike would turn up the idle, clockwise or counter?

[rphillips]

Would think idle adjustment or pilots stopped up. Turn idle knob clockwise to idle up. Sounds rare for either to happen, just sitting over the winter.

[Jethro]

Choking the bike creates a richer condition than the carbs normally allow, so my feeling is that your cylinders are not getting enough fuel without choke. This could be any one of a hundred problems, but assuming it is a carb related problem here is how I would start (in this order):

1. Make sure the petcock is flowing fuel (don't forget the gas cap vent can get blocked)
2. Make sure you have 5/16" fuel line and if you have a filter is it blocked
3. Open the bowl drains and see if the bowls are filling with fuel
4. Clean/inspect the float needles and seats
5. Make sure your jets are not blocked

From there it can go anywhere, but it sounds as if the pilot circuit isn't getting fuel. The choke basically draws fuel to the top of the carb, bypassing the jets entirely and dumps it directly into the intake manifold.

[Mr. Jiggles]

If it had been sitting all winter with fuel in the carbs I'd pull the carbs, take off the bowls and spray out the main and pilot jets with carb cleaner. Also spray out the air jets and make sure the slides are not bound. The best solution is probably a complete carb rebuild however. I know it sounds like a big job but it will probably make for a more enjoyable riding season.

[nabrams]

What you're describing could be air leaks.
Too much air getting in = too lean.
The bottom line: With these CV carbureted bikes, the pressure situation at any point before (airbox), after (exhaust) or in between (boots connecting carb-to-engine and airbox-to-carb) can and will affect the bike's performance. Obviously, the air fillter element itself must be OK as well.
I had leaks at all of the above places that took me weeks to find and seal. I was surprised at what a huge difference they made.
The point where the pipes join the head will appear to be just fine when in fact it is leaking slightly - make sure you have brand new exhaust gaskets and that you've torqued those bolts properly.
Very minor leaks at the boots may not be detected with the "mist spray" test.

[Guest]

Sounds like you just need to clean your carbs...

[mark]

Its the same old story with these 850's. Could be what other folks say, but if you have a leak in your airbox that could be the whole story right there. You're airbox needs a perfect seal for the bike to run well....

[bwringer]

Don't forget the intake boots and o-rings...

http://bwringer.com/gs/intakeorings.html

[snowbeard]

thanks guys, it probably is the needles & jets I will start w/ the bowls and clean them first. just wanted that second opinion!

[snowbeard]

after further idling on choke, etc. I have identified the problem as the airboots from the carbs. I hereby declare I will buy brand new rubbers for the old girl. !! :-)

thank you, thank you.