Carb sync and valve adjust-still not too happy

[BassCliff]

Hi guys,

EDIT: 1981 GS650G

I traveled down to help a friend put the finishing touches on his bike, Mr. ssanderson111. He has cleaned the carbs, Kreemed the tank, painted his body work, and in general done a fine job of getting his bike all spiffy. I brought shims and a Carbtune and was just going to help him do the final tweaks. But I must say that I'm a little disappointed with the results. Steve is a great guy and we had fun working on his bike. Here he's taking valve clearance measurements.

And here's Steve cleaning gasket off the head.

After the valve adjustments and carb sync the bike would start fine and idle fine. We'd go for a little spin and after about a half mile the bike would want to die. We'd go back to the garage, hook up the temporary tank, it would start right up. I'd make some minor adjustments to the idle mixture screws and idle knob and it would start, idle, and rev fine in the garage. Using the "highest idle method" the idle mixture screws are all about 2.5 turns out. We went for another little test spin and within a half mile it would stall again.

We noticed that the airbox boots for #2 and #3 were dangerously close to slipping off the carbs. We did our best to get them attached firmly thinking that they were moving off the carbs and causing a very lean condition. Steve says he'll order new airbox boots.

What else, besides replacing the airbox boots, should we try?

Issue #2: There was also a glitch with the valve adjustment. Everything went well except for exhaust #2. When first measured it was less than .04mm so we stuck in the next smallest shim. When we remeasured the clearance was more than .4mm! So we put the original shim back in and remeasured. The clearance was still more than .4mm. We went all the way up to 3 sizes larger than original (original was 2.65x, went up to 2.80) and the clearance was still near .5mm. Nuts I say!

With the advice of a couple of other members who said that the bucket could be temporarily stuck, we went back to one size smaller than the original shim and buttoned it back up. When we started the motor, it made a definite clacking sound but quieted down quite a bit as we ran the motor. I don't think it's as quiet as it should be and it makes more noise than my motor, and I like to run my clearances really loose. I don't have a compression tester. Steve said the bike was down on power and that has me a little concerned. We noticed white smoke from the left exhaust (the #1 and #2 exhaust) when revving it up.

Thanks to Mr. Nessism and Ms. SqDancerLynn1 for letting me call them on the weekend to ask their opinions.

Does anyone else have any thoughts as to this sticky bucket?

I hated to leave Steve (ssanderson111) with a bike that was not running as well as I thought it should but I just ran out of time. Steve was very gracious and we're going to get together again when he has replaced the airbox boots. Steve said he cleaned the gas cap (I thought of the venting issue). Steve also disassembled and cleaned the carbs, replacing the O-rings with a kit from Robert Barr. We noticed that his petcock wanted to leak and I'm wondering if it is flowing properly. Steve did Kreem the tank and I'm hoping that it didn't flake or peel and get stuck in the carbs. I did not take off the petcock for inspection, but it seemed to flow OK when we dumped some gas into the temporary tank.

I'll stop rambling now. Let me know if you have questions. Thank you for your thoughts.


Thank you for your indulgence,

BassCliff

 

[Nessism]

Could be a tank vent or petcock issue if it starts and runs well but then dies after a mile or so. Maybe try cracking the gas cap after it starts to act up and listen for a vacuum sucking sound in the gas tank?

Not sure what to suggest about a sticky valve/bucket. Maybe pull out the cam and then the buckets to see how sticky it really is? Fair bit of work there so maybe a last resort.

 

[7981GS]

When the tank was coated did he make certain that something was in the vent hole around the filler neck to keep it open?
If it got coated shut, there is your problem. (No venting.)

Daniel

 

[wkmpt]

If you think the bucket might be hanging up, I have scads of them. If you think you might need a couple, let me know, if you'll cover the shipping I'll just give you a few.

 

[Guest]

When the tank was coated did he make certain that something was in the vent hole around the filler neck to keep it open?
If it got coated shut, there is your problem. (No venting.)

Daniel

I was thinking the same thing, hopefully it's just that simple...

Did it also stumble when the petcock was left on prime? Perhaps the petcock is bad (or vaccum line isn't secured).

 

[landshark]

Im sure you guys all know more than me, but my immediate thought was the vent on the gas cap too, i saw it happen to a mate with a cheap billet cap he bought from China, exactly the same thing.

 

[tas850g]

The bike runs well the the temp tank but when you put the oem tank on that's when it only runs for a few minutes then dies? Sounds like something is up with the tank/petcock.

Mine did this exact same thing after cleaning the carbs. At some point after the cleaning the petcock vacuum failed. However, I was able to run the bike on prime only. Have tried running the bike with the tank on pri only?

 

[BassCliff]

Hi,

Thank you folks! I forgot all about the vent hole in the filler neck. We'll start there and proceed with the other suggestions. I appreciate your thoughts. Thanks!

Thank you for your indulgence,

BassCliff

 

[Graham]

Check the carb vent hoses. It?s rare but they can get clogged.

 

[ssanderson111]

Hi Guys! I'm the lucky owner of the problem bike at hand! I LOVE my GS and can't wait to get her back in tip top shape. Thanks for your advice!

I just checked the vent hole in the filler neck. Sure enough, plugged up with Kreem. I unplugged the hole with ease. Hopefully that was the only problem.

The airbox boots should be shipped out tomorrow. Hopefully they'll be here by midweek and I can get them on the bike asap.

I cleaned the carb vent hoses a few weeks ago when I deep cleaned the whole rack. So, they should be clear.

The airbox was sealed with weather stripping a few weeks ago as well, so that shouldn't be a problem.


Hopefully the freed up vent hole and new airbox boots will solve the problem. I'm wondering if these problems could also be leading to the reduced power experienced on our two short test runs yesterday? I'm guessing the carbs will need to be synced again with the new boots installed? Could the #2 exhaust bucket issue be causing the lack of power?

Thanks again!

 

[jwhelan65]

I have this exact same problem have yet to figure it out on an 80 750E

 

[GSexpress]

If the shim bucket is sticking, The shim tool will be hard to incert and leaver the bucket down and then it will come out too easy. If it's real easy going and out, it could be a weak or broken valve spring. That could lead to early valve float on that cylinder and a bent valve.

It definately sounds like a tank venting issue. But it couldn't hurt to check the "O" rings on the carb manifolds. Double check the vent and vacuum hose routing. I had a bike once that would run fine while I had the tank loose and the seat open, but when buttoned up it would quit running. The tank was pinching the vacuum line to the petcock when tightened up.

 

[BassCliff]

I just checked the vent hole in the filler neck. Sure enough, plugged up with Kreem. I unplugged the hole with ease. Hopefully that was the only problem.

Steve,

Have you taken a test ride since clearing the vent?

Tyfyi,

Cliff

 

[ssanderson111]

Not yet....too busy studying. I might be able to putt around the parking lot during lunch today. I'll keep everyone updated.

 

[ssanderson111]

Update: The vent hole was plugged up, so I unplugged it last night. Moments ago, I started the bike (started right up), let it idle for a few minutes (idled just fine), then started riding around my complex. It ran (but not well) for 1/8 of a mile and died. I can get it to start and keep running, but only if the choke is all the way out. With the choke all the way out, lots of white smoke is coming from the left exhaust (#1/#2 exhaust). Even with the gas cap removed, the bike still would not stay running without the choke all the way out.

 

[BassCliff]

If you think the bucket might be hanging up, I have scads of them. If you think you might need a couple, let me know, if you'll cover the shipping I'll just give you a few.

Hi Matt,

PM sent. Thank you!


Cliff

 

[SqDancerLynn1]

With choke out it runs. That says you still have carb problems or maybe lack of fuel. Have you checked the petcock, tried running on prime..

 

[ssanderson111]

With choke out it won't die.....but it also won't rev up past 4-5,000 rpm. That was with the petcock set to "on". I'll try it with the petcock set to "pri" later today.

 

[robertbarr]

At this point I'd suspect the petcock screen, especially following the tank liner work.

I had a similar problem that developed on an '82 850, and it drove me nearly batty (OK, short drive...) until I finally pulled the petcock for the umpteenth time and gutted the screen. That solved the problem.

I don't know WHY that solved the problem, because I had tried checking the flow rate (into a fuel can) and it flowed fine -- full tank or nearly empty, made no difference. On the bike, under operating conditions, it would starve the carbs so much that the bike would stumble a bit and die. The lower the fuel level in the tank, the more likely it was to happen.

I dubbed the operation a 'screen-ectomy'.

Just one more idea for ya.

RB

 

[ssanderson111]

Robert, are you suggesting that I remove the screen from the plastic skeleton completely, while leaving the skeleton attached to the petcock? Or should I completely remove the whole filter (for lack of a better word? it looks like a filter!)?