carb rebuild problems

[7981GS]

Correct.

Daniel

[tom203]

Ok, 24 hr dip,bench synched, float level checked- let's give it a shot and ignore main jet for now. Petcock on prime,ignition on, activate "choke" fully, DON"T touch throttle and push start button.

[kennethleemiller]

Okay, so I get home from work yesterday evening, make a bowl of guacamole dip for my girlfriend, and head out to garage... (you gotta at least make an attempt to keep 'em happy, right)

I hook up the vent hose and the fuel line, put the tank into prime, switch her on and start cranking.. I've been trying to avoid using the choke, just because I don't want to just dump a ton of gas into to chambers, it seems like I've had better luck just starting it with no choke... At any rate I sat and cranked for 5 - 10 minutes with no result, so I go inside for about 1 to 1 1/2 hours, come back out, try the exact same routine, and it took a little while, but eventually fired up on it's own..

It definitely needs some fine tuning, though.. the idle was sporadic at best, it would shoot up to 5k right off the bat and then I'd chase it back down with the idle screw. If I opened the throttle it would stay rev'd and not return to idle after release. While I had the carbs in the dip I decided to figure out the slack issues I was having with my throttle, and I actually figured out a really good way to remove slack even after you've taken the adjustment as far out as it will go.. At any rate, now there is zero slack in the throttle cable, so I think I may need to back that off a little, I've heard it's best to maintain 1-2mm of slack.. Perhaps the throttle is being held very slightly open while at full release..

Also there were no filters on while performing this initial start up... I was thinking the lack of air flow resistance might also be a cause of the high revs... I wanted to rubber band some lint free rags across the mouths, but I didn't have any rubber bands..

I think with a vacuum sync, filters installed, some fine tuning of the air/fuel screws, and some experimentation with the jets, I will be able to find that perfect formula... Was just super stoked last night that it actually fired up and would at least rev up when I turned the throttle... It's definitely a major improvement over when I started this thread, and this project..

Any thoughts, suggestions?? Try not to laugh too hard at my taping job on the tank, just tossing around a few ideas for a paint scheme.. haha...

[BassCliff]

Hi,

CLICK HERE and read #4.

It looks like you are on your way to a nice running GS. Yes, bench sync, air filter, vacuum sync, idle mixture screw adjustments, perhaps some jetting changes (depending on the type of air filtration you use), and you should be good to go. Your carbs look great.


Thank you for your indulgence,

BassCliff

[hikermikem]

Well, it sounds like you're making some progress... few observations.

Why the choke avoidance? That poor bike is already dangerously lean if you're running it without filters; trying to start it without using the "enriching" circuit makes no sense. How would you expect it to fire over with little to no fuel in the mixture?

Your high/hanging idle is a symptom of a LEAN mixture and/or intake leaks. Put some filters on it - these CV carbs are EXTREMELY sensitive to air leaks and NEED some restriction at the intake. The bike simply will not run without filters.

I may have missed it in one of your earlier posts, how many turns out are the mixture screws? I would start them at 2 turns out & go from there.

The throttle cable needs to have some slack to account for cable tension when turning the bars, and temp differences expanding/contracting the metal cable... the Suzuki manual calls for 1-2 mm (.040"- .080").

Make sure your battery is fully charged, intake boots aren't cracked or leaking (did you replace the intake manifold o-rings too), check the mixture screws, install air filters (or rubber-banded rag) and try again.

[kennethleemiller]

[QUOTE=hikermikem;1576601}I may have missed it in one of your earlier posts, how many turns out are the mixture screws? I would start them at 2 turns out & go from there. [/QUOTE]

Mixture screws currently at 2.5.. I always forget, is in lean and out rich? or the other way around??

I'm high-jacking some rubber bands from work today to try again with the rags..

I did replace the o-rings on the boots and while they were off examined them thoroughly, all the rubber seems to still be soft and I could visibly see any leaks, I have been seeing a set of NOS boots on Ebay, for around $150 I think, not sure if it's worth the money if mine aren't leaking anyway..

The battery is the other weak link.. I'm not charging at the moment, ran through charging system test procedure found in the stator pages, and all signs point to a bad stator, who's replacement should be on my doorstep by Thursday.. Otherwise, I've just been trickle charging during the day and trying to start it when I get home..

Thanks for the advice I'll try again tonight..

[kennethleemiller]

Your carbs look great.

Thank you.. I remember reading that #4 when I signed on here..

[7981GS]

They never work with pod filters...








I MUST be doing something wrong.

Daniel


Do Rapidray and Chef know about this? Someone should tell them also!

[BassCliff]

Hi Daniel,

They never work with pod filters...

I MUST be doing something wrong.

Nope. You've just got "the touch". You are definitely a "GS Whisperer". One day I hope this grasshopper will be able to snatch the shim from your hand.


All the best to you and yours,

Cliff

[hikermikem]

Mixture screws currently at 2.5.. I always forget, is in lean and out rich? or the other way around??

Screw turned in (CW) leans it out.

Screw turned out (CCW) richens up.

2.5 turns out should be good to start.

You will need to get the engine idling smoothly, mixture screws set correctly (highest RPM method), and have absolutely no vacuum leaks BEFORE you can do a worthwhile vacuum sync.

Inspect your stator connections closely - this is a problem area & the connectors are most likely burnt. Do all the maintenance stuff described in the stator papers (run additional grounds, RR check, clean all connections...) first before you replace the stator.

However, members here seem to use aftermarket stators from Rick's.

Good luck - there's no quick fixes with these old bikes. Just methodical testing & repair.

[tom203]

kennethleemiller said....
"I've been trying to avoid using the choke, just because I don't want to just dump a ton of gas into to chambers, it seems like I've had better luck just starting it with no choke"

Cold, my 650 would show no interest in coming to life without full "choke"- It would crank itself out. But with full "choke", it starts instantly, even after two weeks of being ignored. This enrichment system ain't going to "just dump a ton of gas into chambers"- the system supplies a shot of air/fuel mixture to compensate for the designed lean idle carb circuit.

[kennethleemiller]

Second attempt, choke activated this time and rags in place... Fired right up beautifully (thanks Tom), went up to 5k, then gradually came back down to a little over 1500.. Stayed there for about a minute, and then fizzled.. subsequent attempts yield a slow start and inability to sustain itself... I'll try again before I go to bed just to see if it acts the same as when I first started..

[7981GS]

This bike, had been sitting for over ten years.
Got it to run with no exhaust the night before so...
I installed a set of pipes and a tiny funnel filled with gas after the carbs were filled and,

http://www.youtube.com/watch?v=TcMWTHTkts4

[kennethleemiller]

Not much better on the bed time try... guess there's always tomorrow...

Oh and 7981.. I appreciate the sarcasm.. if anything I take it as encouragement.. you seem to be quite an accomplished technician and professor of these motorcycles, although I think you'll agree, the 650's have considerably less elbow room under the tank than the 1100's...

[7981GS]

There are plenty of knowledgeable GSer's in the state of Texas.
Perhaps one or two of them are near you? (I know, a VERY BIG State.)
How about posting what city you are in/near?

Daniel