Low-idle problem on recently bought 83 GS650 G, many previous owners

[KnowsNothing90]

Ok, thanks for the feedback Steve. I checked out the link and now I understand why you guys are pushing for getting the o-rings replaced and what they are/do, as they put it in the link:

"Either way, you wind up with a temperamental engine; it'll run fine under some conditions, but it'll be crabby & lethargic other times. A classic symptom is an unstable idle speed. If your bike's idle runs way up after it's warm, this is the likely cause. It can be hard-starting and will run hot. It leans out the mixture, can cause your valves to burn, and generally causes annoyance. It is an absolute waste of time trying to tune a motorcycle with an intake leak, as you're aiming at a moving target."

[Redman]

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.......................I nudged it a bit on monday and it significantly affected the idle speed and is located between the 2nd and 3rd carbs like you said. How does this knob regulate the idle speed, does it control the amount of fuel going in or is it a different type of mechanical adjustment??
[ATTACH=CONFIG]59298[/ATTACH]

It is pretty much just an adjustment to hold the carb throttle open a little bit, much the same as holding the throttle grip open a little bit.
Now that you understand that, please go back to the 3rd line of post #3.


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[KnowsNothing90]

Thanks a million to all of you for your feedback, as pretty much a total newbie I appreciate it very much! I cancelled my insurance since it was registered in Ontario (which is way more expensive than where I am now in Halifax, Canada). I've been working alot and took a break on the motorcycle, but I've got some time off over the break and as things slow down over the winter at work (i'm helping out a small arborist company at the moment) so I will be getting back at it very soon.

The plan is to take the carburetor apart and clean it over the winter based on the info I can find on how to do this from the forums. Then, once I replace the o-rings and perhaps the bowl gaskets, as mentioned in the "Carb-rebuild-vs-cleaning" thread:

"What most carbs that are not running well need is a cleaning of the small passages and new o-rings. So you need o-rings (search for "Cycle ORings" ~$15 total) and probably new bowl gaskets and a bucket of carb dip."

Then I should be able to do a vacuum test on each of the 4 carbs and be able to figure out if there are any other issues that need to be resolved before I can get the carbs tuned properly for spring of next year. This bike was so fun to ride when it was in working order, so hopefully the o-rings and bushings are the main source of the idling problems. I think pretty much everything else on the bike needs to be gone over with a fine tooth comb before it's a solid reliable ride based on what I've been reading on here about previous owners and used motorcycles, and the transmission is also probably suspect but I'm willing to put the time in myself to minimise the costs of getting it professionally worked in (which I will make sure to do after I'm done tinkering around)!

[Steve]

Then I should be able to do a vacuum test on each of the 4 carbs and be able to figure out if there are any other issues that need to be resolved before I can get the carbs tuned properly for spring of next year.

Please brace yourself.
You can not simply do "a vacuum test on each of the 4 carbs". When you do a vacuum synchronization (sync), you will need to connect to all four carbs at the same time. The forum favorite is the Morgan Carbtune. The price changes from time to time, based on the exchange rate, as it comes from England. At today's rate, the 80GBP translates to $136CAD.

What makes you think the transmission is "suspect"? They are rather bullet-proof, so I doubt there are problems there.

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[KnowsNothing90]

The reason I'm thinking the transmission could be suspect is because when I was riding east from the Toronto area I made it to a small town North of Montreal driving pretty much without any long stops (probably ~4-6 hours, i was already a few hours east of Toronto when I left). Up to this point it had been mostly open road and highway driving but in this small town we ended up in stop and go bumper to bumper traffic (which is when I first ran into real problems with the bike, see post 1). At this point the bike was acting very erratically in first gear (cutting out, idling high etc).

Once I got it back home a friend of ours readjusted the clutch (also mentioned in post 1) but there was also another issue, which is the point I am getting at, when I shifted out of first gear the bike would lurch forward (even after the clutch adjustment). So, based on this our friend (the retired aircraft mechanic) figured that during this long ride the first gear must have fused with something else in the transmission (probably the clutch plate?). He was able to address the issues with a quick fix at the time, that is we shifted the bike out of first gear while it had the front tire set against the wall of our house. After we did this a few times the first gear did become "unstuck" and was no longer jumping forward when I shifted it out of first. Maybe this "quick fix" did unfuse the first gear from the clutch plate (or whatever it was sticking on) and might not cause me any more issues, but that was the reason I thought maybe I should try and take a good look at the transmission.

Probably not a conventional way to address transmission problems, but it was shifting fine afterwards and could very well be back to normal functioning. I was just thinking that maybe all this could have damaged the first gear or clutch plate and it could be a liability going forward - what's you take on this?

[KnowsNothing90]

Thanks for the feedback! A friend of mine had said that you have to do the vacuum test on all 4 carbs at the same time, the way worded it definitely did sound like I was going to try to test each separately as you interpreted it though. This friend (not the same aircraft mechanic guy) custom built bike back in the day and is a pretty handy (although unlicensed) mechanic who has a hydraulic lift in his garage and know the in and outs of most vehicles (especially older stuff). He had suggested that I could small glass baby food containers with water in them to built 4 cheap vacuum testing doodads myself. Obviously they would not be nearly as accurate as the real thing but would give a decent idea of which cylinder(s) were having issues.

In any case, $136 sounds like a very reasonable price to me to buy the real thing, and probably a good investment moving forward as I'm guessing it could be used on pretty much any motorcycle engine (or would it be any naturally carburated engine)?