Familiar troubles

[aslam]

After reading around on the board for awhile, it looks like my bike is experiencing some similar troubles as those previously discussed.  Namely:

1.  Bike seems to idle low, between 1000-1200.  Although 1200 is the spec, the bike sometimes still sounds like it's going to sputter out making me wonder whether the air/fuel ratio is optimal.
2.  When the bike is warm, the engine will decide to stay at 3-4k RPM constantly with the clutch engaged insteading of dropping back to idle at 1200.  Is it possible that the carbs need to be rejetted or synced?  This is my only guess with regard to this problem.

I haven't tried to adjust the throttle idle cable so that will be the first order of business.  As for the other problem, my only plan of attack is to take apart the carbs and clean them well while replacing the jets.

Can anyone offer some suggestions?  Thanks.

ASLAM.

[JohNLA]

A carb cleaning could not hurt but my guess would be valve clearence because mine was acting similar when my shims were below spec. Also, you should synch the carbs after doing the valves.
Good luck and keep posting.

[aslam]

Thanks for the suggestion.  I'll see about adjusting the valves.  Is it easy to adjust the valves on your own?  I have a friend who can help me clean and sync the carbs, apparently he already has the right tools.  So while we're in there I'll see if he can adjust the valves with me.

I also need to make sure the throttle & choke cable are adjusted correctly.  The choke doesn't seem to function as I would expect.  On full choke, the bike will idle at nearly 4k RPM.  Is this nominal?  According to the manual, I saw that you adjust the choke to keep the RPM at 2k during warmup and turn it off after a few minutes.

Any clarification?

ASLAM.

[JohNLA]

The choke on the GS is the most fickle thing I have experienced on any of my bikes. It can be tough to get it to idle in one spot . Almost every stop I have to adjust it until it is warm. You can blame old tech meeting modern epa emmisios. The common fix is larger pilot jets.

[aslam]

Well, I had a friend take a look at the bike last night.  The problem is as persistent as ever.  We both decided that our best first step is to take out the carbs, clean and resync them.  I recently got the bike and I think it hadn't been ridden regularly for awhile.  This may have something to do with it.  The strange thing is, the throttle is definitely totally closed and the bike still runs from 3k-5k RPM sporadically.  I'm guessing this has to do with the fuel delivery system/carbs.  We'll see what happens after I clean everything out inside the carbs.  I'll try to make sure I clean the jets well.

Hopefully soon, I can have the bike running well so that I can put the V&H full system on it, take it to the dyno and have it jetted correctly.

BTW, does anyone think these problems I have described have anything to do with the fuel petcock?  I've read about lots of other people having problems with fuel delivery from the stock petcock.  That's what I've got.

Thanks again.

ASLAM.

[500rider]

I have the same problem occasionally but I wouldn't expect it to be the petcock (although there seem to be lots of problems with them).  The petcock problem seems to be causing a vacuum leak that is causing the one cylinder to choke when the engine is under load.  But this shouldn't affect idle really (IMO).  I could be wrong though .. carbs are curious things.

JohNLA:  

can you give me a theory behind the valve clearance and why it would affect idle .. I'm curious?  I wouldn't be surprised that my valve clearance is below spec since I did not check it before last season.  I plan to do it before riding this season though.

Rob

[JohNLA]

Original symptoms

1. Anything below 1500 rpms would allow the engine to conk out.
2. Idle would jump to 3-4k rpm's. (Sometimes, engauging a little clutch could make it drop.)
3. When I would rev the throttle it would takeup to 2 or 3 seconds before the revs would drop.

I ripped apart the carbs and found very little to clean but soaked them and scrubbed them but all my problems remained. I did it again with more emphasis on the jets. Played with air screws and shims but nothing helped.
I never checked the petcock because I have never had any other problems with it (knock on wood). It has never stalled or given me anything but joy at highway speeds. My bike has never sat more than a week and half, and that has only happened twice.

Finally, I got the courage to open the engine
Should have done it long be4fore 16k miles (9k of that since September last year)
I had to replace all 4 shims. One needed to go down 3 sizes to get in spec Another was down 2 sizes and 2 were down 1 size. After I did that everything ran great

[aslam]

Do you have any idea why the valve problem would make the bike run that way?  It makes no sense to me.  It seems like there would be some problem with fuel delivery and carbs that somehow makes it run lean.  But after adjusting the valves and replacing the shims you are good??  Maybe the valve misalignment was causing it to run lean.

In any case, my first order of business will be to clean out the carbs and replace the jets.  I hear #40 non-bleeding type is the way to go for the pilot.  Once I resync the carbs I'll see how it runs.  If no improvement, I'll get the valves looked at.  However, I don't think that's a job I'm willing to do on my own.  I guess I'll take it to the shop for that.  Doing a valve job myself scares me.  

ASLAM.

[scratch]

I haven't tried to adjust the throttle idle cable so that will be the first order of business.

Are you refering to the choke cable here? Does the throttle cable have too much slack ('bout 1/8th inch rotational play at the throttle grip with the handlebars at full lock left and right)? The idle screw is the item that controls idle (although there are contributing factors).

Start with easy stuff first.

Get your bike to Srinath standard: size 40 non-bleed pilots, mix screw out 2.5-3 turns (adjust to taste), shim needle.

Use the throttle or choke to keep idle up when cold.

Idling at 4k with full choke on is normal.

Idling at 3-4k when warm indicates a lean condition, most likely you'll need to rejet.

If the shims are all too tight as John has stated, it's kinda like the valves stay open all the time, and allow alot more flow, and keep the rpm's up by themselves. I know this is kind of a lame explanation, but I'm dizzy from not eating breakfast and not getting enough sleep.

Please let us know what happens after you work on the carburetors.

[aslam]

My mistake, sorry.  I was referring to the idle screw, not cable.  I haven't ripped the bike apart yet.  That will be my project for next weekend (I'll be busy this weekend).  I have tried adjusting this idle screw without much success.  As I take the bike apart I will make sure to check the simple stuff too, i.e. choke cable & throttle cable.

It seems based on what I've seen on the board and what I know of the bike so far that I need to clean & resync the carbs... And check the valves.  The concensus agreement is that I'm running lean right now.

I'll let you know how things go.

ASLAM.

[Juanfer]

carb rebuild needed maybe?

[aslam]

Well I got the GS running great now.  According to the similar problems that JohnLA had awhile ago, I went in to check the valves while in the process of redoing the carbs.  Sure enough, all valves were out of spec.

After spending awhile figuring out how to use that valve shim tool I was able to get all the valves in to spec.  I think 3 out of the 4 valves are around 0.04mm and the last one is about 0.07mm.  The bike needed the adjustment badly, I couldn't even hear the air compress in the right cylinder when cranking the engine via generator.  After replacing the shims, there was a noticable different just in feeling the compression.

Also rejetted the carbs.  Replaced stock 37.5 pilots and 122.5 mains with 40 pilots and 127.5 mains.  Cleaned all the gunk out and reset the idle air mixture screws from 5.5 turns out ( ) to 3 turns out.  Dropped in a K&N filter into the airbox and put it all back together.

The bike still takes awhile to warm up, but runs great!  It was running so lean before that the bike was hesitating and tossing me around.  Now, it's definitely got a more adequate air/fuel mixture.

Just wanted to say thanks to all those that helped out.  The knowledge of the GS on this board is amazing and the archived information (especially on rejetting) is priceless.

Thanks  

ASLAM.

[scratch]

Good for you!

There's nothing quite like a finely tuned ride.

I just so happened to get my carbs synchronized all the way up to redline (using the vacuum balanced method) this weekend.

[aslam]

Cool.  What's the procedure for syncing the carbs?  I didn't really check the float levels or resync after cleaning and reinstalling the jets.  I would have liked to but I don't have a vacuum gauge nor do I know how to use one!  :lol:

ASLAM.

[scratch]

At this point, the best you can do is to wait until you have to play with the carbs or valves again. If you do it yourself, you can synch your crabs statically, which requires removal of the carbs and a light. Hold the carbs to the light so you can see the light at the bottom of the brass butterfly valve, and using a screwdriver, adjust the screw on the throttle linkage so you can see equal amounts of light between the two.

I mean, your bike runs fine now, so why mess with it. But, for the future, you can prepare.

[aslam]

I mean, your bike runs fine now, so why mess with it. But, for the future, you can prepare

Amen.  I ain't taking that thing apart any more than I have to.  

ASLAM.