1982 GS 650 revival - carb trouble

[rick1234567]

Hello everyone - a new guy to the gsresources - but I have to say this site is helping me out a ton - have a few questions:

Have a 1982 gs650g "project bike" I believe mikuni bs32ss carbs (gleaned from this site.) - sat for a long time before I bought it and for about 2 years in my hands - cleaned the carbs as per the great pdf here - got it all back together and not starting - seems to be fuel starved -

So i am a carb idiot - things i am not sure about - for the fuel/air screw on top - do you tighten this as tight as it will go and then turn back. Also - for the float height - is this the distance it should contact or fully depress the needle valve from where the gasket sits? (i.e. where is this height measured from) LAst - should the throttle plates be fully closed at the idle setting or open somewhat and if so how much.

So here is the main problem - bike will not start, however the good news is that it runs for about 3 seconds if I spray starer fluid in the airbox (so not spark - etc...) I am pretty sure the fuel petcock is trashed - but I tried hooking up a gas tank (Honda CX500) with a normal on/off petcock - still no luck. So what are the things I should be looking at / suspecting next - currently have the carbs back out and didn't see anything too horrible in there (recently cleaned the tank worried there may have been residual grit/rust etcc...) , also all the bowls seemed to have gas. Any help would be greatly appreciated.

thanks

Rick

[tconroy]

Is the vacum line hooked up properly? Do you have the airbox on?Have you tried it on choke? Did you make sure you set your petcock to prime so the bowls will fill up.If it runs with start fluid it should be just the carbs at fault.the float bowl height is 21.4 to 23.4 mm without the float chamber gasket.If the gasket is still in place reduce this measurement by 1mm., measure from the gasket to where the bend in the tang starts.

[rick1234567]

Thanks - the vaccuum line was from the up facing fitting on the 2 or 3 carb to the little fitting on the petcock - The petcock was a mess and I pulled it apart to try and fix - the little metal thing inside was all twisted et...so as this was suspect I put on that other tank - it should run as long as the fuel is heading in right? Also the choke was full on and air box installed - no filter yet though.

[brveagle]

If you messed with the airfuel mixture on the top of the carbs, you've probably done the worst thing to those carbs..

Without the right carb synch, that bike will not run, or idle.

Buy another set of ebay or take it to a shop and have your visa ready.

[waterman]

Don't be so quick to give up on your carbs. When setting carb floats, measure from contact with float valves. Measure from the notched curve area not from the flat hinged area. I hope this make sense; if not, do a search on float height.

I would set your idle mixture screws around 2 full turns out and verify that you have gas in bowls (open drain screws to check for gas). The throttle butterflies will not have to be open much at idle, paper thickness maybe. From here your carbs should get it running. Of course this assumes alot--stock carb jets, stock exhaust, good ignition, decent compression, yada yada yada..

Try with good flowing gas tank, full choke, and fully charged battery. Once running then you can worry about fine tuning mixture screws for best idle and synch for smooth operation.

[robertbarr]

You're not getting fuel, for a reason that's common to all 4 carbs. That much is obvious. If you were getting fuel, even in just a couple of cylinders, you'd get some life out of it. It might not run well, but it'd run.

The next time it's set up to try to start, put a shallow container under a carb and open the drain screw. If you get several ounces of fuel, OK. Try the other three. I'd bet there's no fuel, or very little fuel, in the bowls.

[nabrams]

Unless you've actually broken something there's no reason to get new carbs. Just adjust everything to where it needs to be. Of course, you need to verify fuel flow at all points (out of petcock into carbs first - use a transparent gas line).

Having said that:
Instead of going about the process piece-meal, why don't you search for the many posts on this forum (some by me) that list the many "sanity-check" steps/verifications needed when restoring a bike that's been sitting (based on what you've said, you definitely should consider your bike as belonging to this category) - and then actually DO the checks.
This will save you MANY hours of frustration and TONS of money.
If you're a beginner (in terms of mechanical skill) you're looking at between 30 and 60 hours of work and a couple of hundred dollars for purchasing tools you'll need (besides whatever parts you need for the bike). In the end you'll have a reliable machine for a fraction of the cost of a new bike.

By the way: I know many have seen me give this same speech to many of the newcomers. I think they need to see the big picture besides tackling their immediate/first problem.

[Dave8338]

Sounds like some good advice already given...I'd add, order a new petcock, as your first step! This will remove any doubt to that ever troubled part of the equation. It sounds like your getting fuel to the bowls but how much? Follow the suggestions posted above. I suspect your choke circuit is messing with you. Next, as for your air/fuel screw (they are actually an air screw) lightly; "LIGHTLY" seat them and then back them out 1.5 turns...this will at least get you close. Also, ditch the starting fluid, and mix up a small batch of 2-stroke fuel (40/1) in a spray bottle and use that to nurse this thing along until you get everything sorted out. Nothing worse on a non-runner that either! :shock:

You can try the carb cleaner in the spray can, but most likely, you should tear the carbs apart (it's not that hard) and dip them.

If you haven't bought a book for your bike, spend the money and save the time!

Take your time and you'll get it!

[rick1234567]

Hey thanks for all the posts everyone - I guess a little background would be in order - I think I'm pretty decent mechanically - rebuilt a bike engine (the cx500- (no carb trouble - just crankshaft, rods , bearings, y'know the little maintenance stuff) and lots of car experience (fuel injection only) - just basically an idiot when it comes to carbs- So thanks for all the info - I am planning on ordering the petcock tomorrow - and definitely still need a good book... while I'm waiting is it reasonable to use the other tank to troubleshoot?

To address some of the above - when I pulled the carbs off there appeared to be a lot of gas in the carbs - all 4 (this is after the other tank had been on) - but there had still been no dice.

Oh yeah and I had gone through the "cleaning your carbs" pdf - dip and everything before trying to start

I pulled them back off to make sure no tank grit had gotten back in the carbs and it looked Ok and the bowls had gas.(now pulling jets etc/ spraying passages to make sure)

So is there anything that sticks out in terms of adjustment/ i.e. first thing to check when the carbs are back on?

So far I think the plan is to put back on, verify gas in all the bowls - and make sure the air screw is around reasonable : I still don't know what lightly means on this ( screw in all the way with not much force until it stops - then back out?) or is there some point you should feel adifference in resistance.

definitely plan to check the posts on the sitting bike checklist - what is the best to search - "sanity check" Wow this turned out long - but thanks again for all the help.

Oh yeah and thanks for the heads up on the ether

[SAN]

carb trouble

Sounds like some good advice already given...I'd add, order a new petcock, as your first step! This will remove any doubt to that ever troubled part of the equation. It sounds like your getting fuel to the bowls but how much? Follow the suggestions posted above. I suspect your choke circuit is messing with you. Next, as for your air/fuel screw (they are actually an air screw) lightly; "LIGHTLY" seat them and then back them out 1.5 turns...this will at least get you close. Also, ditch the starting fluid, and mix up a small batch of 2-stroke fuel (40/1) in a spray bottle and use that to nurse this thing along until you get everything sorted out. Nothing worse on a non-runner that either! :shock:

You can try the carb cleaner in the spray can, but most likely, you should tear the carbs apart (it's not that hard) and dip them.

If you haven't bought a book for your bike, spend the money and save the time!

Take your time and you'll get it!

The mixture screws pepole refer to are fuel flow screws not air, read note #2 carb rebuild. counter clockwise, richer. clockwise,leaner. have you blown air into bowl vent tubes to push pull fuel into bowls. good luck!

[Steve]

To me, it sounds like the idle speed is just not quite high enough.

But, since you already have the carbs off the bike, you may as well do a bench sync. Your #3 carb is the 'master' carb. Remember, they are numbered from clutch hand to throttle hand. Adjust the master idle speed screw until a 1/16" drill bit or other small piece of wire just barely slides past the butterfly valve. Move the drill bit to carb #2. There is an adjuster screw with a lock nut between carbs 3&2. Loosen the lock nut, turn the adjuster so there is about the same amount of drag as there was with carb 3. Snug the lock nut, but don't tighten it all the way, yet. Repeat for carb #1, then #4. When you are done, go back to make sure nothing changed and they all have the same amount of drag. NOW go back and tighten the lock nuts and check again to make sure nothing changed. Turn the idle screw counter-clockwise until the butterflies no longer move, then go back clockwise about a turn. Install the carbs, connect the cables, hoses and airbox. Prime the float bowls, use the choke, start the bike. BE READY TO HIT THE KILL SWITCH IF THE ENGINE RACES. If the idle is too high, reduce the idle speed setting, try again. Obviously, if it's too low, raise the idle setting.


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