High compression and non-firing cylinder

[fenderfreek]

There's no reason to stick a wire through something I can see through. If it were clogged, I'd be most willing to point that out.

You didn't, however, point out that you could see through there. That's all anyone has asked for - what you did to make your conclusions and verify these things. It takes it from guessing and postulating to mere logical deduction.

All of my "O" rings are new and I've cleaned my carbs as best I know how. So much for bikes, you fellas have bigger problems.

Again, this is the first time you've pointed this out. You'd be surprised how many people's definition of "clean" carbs means taking them off and blasting a little aerosol carb cleaner in there.

OK, so one of you can "swap out" a rack of carbs in 10 minutes? Who, in his right mind would believe that?

I'm hardly adept this, but it doesn't take more than 20-30 minutes for me. I would consider it an hour well spent if it solved the problem. If not, you at least know what's *not* wrong with it. It wouldn't surprise me if a seasoned bike mechanic could do it in half the time as me.

Now, the other one's importance in life is based upon 7500 posts which often simply parrot answers already provided? At the same time, you know how good of a job others do cleaning their carbs? Is this your life's work? God, I hope not.

No, but covering your bases is always a good thing. Better to over-scrutinize a problem than possibly miss or ignore critical details. It's called being "thorough".

I'm not in the 'clique' and I don't miss it a bit! Your foul self-important attitudes have led to this forum losing so many people who once had a lot of enthusiasm. You don't have any interest in GS motorcycles; you only have interest in your selfish desire to be appreciated.

Gaining members every day because people come here and get their bikes fixed by this "clique". If you can't appreciate someone being thorough in their assessment of your situation(without seeing the bike and what you did, no less), then you should probably grab the phonebook and find a bike mechanic. If taking a time-proven critical approach to someone's methods is being "self-important" to you, then I wouldn't go around asking for advice, because you'll meet a lot of "self-important" people.

 

[Guest]

Frustration

Frustration

My frustration arose because of the fact that I did a perfect job cleaning the carbs, including everything that was mentioned. They were dipped and soaked at length. I've got a little tool that pushes through the jet holes. This time, I put in 2 new OEM pilot jets, including #4. I replaced the "O" rings (I always do) but even if I hadn't, the only one that could cause this sort of problem would be the #4 needle jet ""O" ring (unless all the gas leaked out of the others getting there).

If anyone can exchange the carbs on a stock GS750L in 10 minutes, put it on Utube. I'd love to see it and I'm sure many others would, as well. I think I work a little slower than many of you but I also think it would be a truly amazing feat.:dancing:

I'll try to be more tolerant in the future and when I get this figured out, I'll report back (even if there's a problem with the carb).:lol:

 

[Dave8338]

You didn't, however, point out that you could see through there. That's all anyone has asked for - what you did to make your conclusions and verify these things. It takes it from guessing and postulating to mere logical deduction.



Again, this is the first time you've pointed this out. You'd be surprised how many people's definition of "clean" carbs means taking them off and blasting a little aerosol carb cleaner in there.



I'm hardly adept this, but it doesn't take more than 20-30 minutes for me. I would consider it an hour well spent if it solved the problem. If not, you at least know what's *not* wrong with it. It wouldn't surprise me if a seasoned bike mechanic could do it in half the time as me.



No, but covering your bases is always a good thing. Better to over-scrutinize a problem than possibly miss or ignore critical details. It's called being "thorough".



Gaining members every day because people come here and get their bikes fixed by this "clique". If you can't appreciate someone being thorough in their assessment of your situation(without seeing the bike and what you did, no less), then you should probably grab the phonebook and find a bike mechanic. If taking a time-proven critical approach to someone's methods is being "self-important" to you, then I wouldn't go around asking for advice, because you'll meet a lot of "self-important" people.

Now THAT...was VERY well written. Nice job! :clap:

Rockford, the carb issue is one of the most frequently asked questions here in the tech section. As a matter of fact, my first question was about the CV carbs as I had never worked on a set before. Hollys, Carters, Rochesters, tillotsons, Keihins and any number of 2-stroke set ups, too many times to remember but nothing specific to the Mik CV setup.

These bikes are notorious for running lean, as a matter of a finely tuned carb and EPA import regs in the 80's...that's just how they are. When you introduce even the slightest restriction in fuel flow or just slightly more air as a result of cracked o-rings, The bike will let you know.

Something as simple as an over-oiled air filter will cause a GS to run rich.
A leak/ crack in an intake o-ring or rubber mount will cause a lean condition most noticeable at an idle (usually higher than the base of 1100 RPM's) An airbox not sealed tightly will cause a lean condition through out the RPM range.

All of this may be known to you. Some may not. Those that have replied to your post are among the best on the fourm as it relates to carb issues. It's not that anyone is trying to belittle you or your abilities, but we are trying to aid in solving the problem that your bike is having. I think I can safely speak for all here in that we LOVE the GS bikes to life...not death.

Any and all questions are welcome. Mods (4-1 pipe or pods) make the fine tuning just that much more critical.

Now lets get that bike up and on all four. :-\\\

 

[Guest]

Thanks

Thanks

Thanks! #4 isn't running lean; it's not running at all, I don't think. I set my air screws when I synched it and the plugs still look perfect. I'm convinced that the problem is elsewhere based on a whole bunch of reasons including the fact that the problem existed both before and after the last carb rebuild.

My best suspicion right now is that it may be a valve. They shouldn't need adjusting based on how long and how many miles it's been since I did it last but, who knows? Maybe something went wrong.

 

[Nessism]

If the compression is 170 psi in that cylinder the problem is not the valves.

 

[Dave8338]

Have you pulled the fuel drain plug on the bottom of the #4 carb?

Can you get the bike to run on all four when you mist the air box with fuel?
(I like to use my two stroke mix --little better for things when they're running dry)

Your valves won't be the problem if your compression #'s are that good. It sure sounds fuel (the lack of it) related to me...:-k If you had valves that were too tight or rings that were stuck, the compression #'s would be much lower.

 

[Guest]

Thank you

Thank you

If the compression is 170 psi in that cylinder the problem is not the valves.

Thank you. I'm glad to learn that.

 

[Guest]

Fuel

Fuel

Have you pulled the fuel drain plug on the bottom of the #4 carb?

Can you get the bike to run on all four when you mist the air box with fuel?
(I like to use my two stroke mix --little better for things when they're running dry)

Your valves won't be the problem if your compression #'s are that good. It sure sounds fuel (the lack of it) related to me...:-k If you had valves that were too tight or rings that were stuck, the compression #'s would be much lower.

Yeah, I've pulled the float bowl and there's plenty of fuel getting to it. (I compared it with #1.) I agree that it sounds like a fuel problem. I haven't tried the fuel mist deal but it sounds like a good idea. I'm assuming my idle would increase a little if the cylinder is currently starved.

I guess if the idle goes up, that would mean a carb problem and I'd have to go out and find a crow to eat!

 

[hampshirehog]

You can always squirt a teaspoon of petrol into the motor via the plug hole. If that cylinder fires you'll know for sure it's carbs (which it really sounds like it is).

Either that or pop in a Colortune - you'll see if you're getting a spark under compression.

 

[Steve]

I just read through this for the first time and am a bit surprised at the attitudes that are starting to show.

I am also a bit confused by some of the statements that Rockford is making:

My frustration arose because of the fact that I did a perfect job cleaning the carbs, including everything that was mentioned. They were dipped and soaked at length. I've got a little tool that pushes through the jet holes. This time, I put in 2 new OEM pilot jets, including #4. I replaced the "O" rings (I always do) but even if I hadn't, the only one that could cause this sort of problem would be the #4 needle jet ""O" ring (unless all the gas leaked out of the others getting there).

If anyone can exchange the carbs on a stock GS750L in 10 minutes, put it on Utube. I'd love to see it and I'm sure many others would, as well. I think I work a little slower than many of you but I also think it would be a truly amazing feat.:dancing:

I'll try to be more tolerant in the future and when I get this figured out, I'll report back (even if there's a problem with the carb).:lol:

Unless something has been changed, your '81 bike should have CV carbs. The needle jets do not have o-rings.

Haven't tried it on a 750L but I have done the carbs on my wife's 850L in about 15 minutes. I have no intention of putting it on YouTube.

There's no reason to stick a wire through something I can see through. If it were clogged, I'd be most willing to point that out. All of my "O" rings are new and I've cleaned my carbs as best I know how. So much for bikes, you fellas have bigger problems.

OK, so one of you can "swap out" a rack of carbs in 10 minutes? Who, in his right mind would believe that?

Now, the other one's importance in life is based upon 7500 posts which often simply parrot answers already provided? At the same time, you know how good of a job others do cleaning their carbs? Is this your life's work? God, I hope not.

I'm not in the 'clique' and I don't miss it a bit! Your foul self-important attitudes have led to this forum losing so many people who once had a lot of enthusiasm. You don't have any interest in GS motorcycles; you only have interest in your selfish desire to be appreciated.

Actually, there is a reason to stick a wire through there. I have found that if there is any moisture at all in a jet hole and you look at a light through the hole, it appears bigger than it acually is. I prefer to use a strand of copper wire as it is less likely to scratch the brass jet. This will ensure that there is no crud in the jet, slightly reducing its diameter and its ability to meter fuel flow.

Nice to know you have cleaned the carbs "as best I know how". Our problem is that we hear this pretty much every day from a lot of new people that are trying to resurrect an old bike. They have no idea what they are doing, and think that merely removing the float bowls and spritzing some spray in there constitutes "cleaning the carbs". We have no idea if you fall in that category. So far, you have only mentioned cleaning the carbs, but never mentioned how, so we don't know if they were properly dipped and re-o-ringed.

Yes, many of us do have bigger problems, but we tend not to bring them to this board as they don't have anything to do with GS motorcycles. And, evidently, we are not the only ones with bigger problems.

There is a "clique" here? I must not be in it, either. I have never been invited, in fact, I have never heard of one.

Thanks! #4 isn't running lean; it's not running at all, I don't think. I set my air screws when I synched it and the plugs still look perfect. I'm convinced that the problem is elsewhere based on a whole bunch of reasons including the fact that the problem existed both before and after the last carb rebuild.

My best suspicion right now is that it may be a valve. They shouldn't need adjusting based on how long and how many miles it's been since I did it last but, who knows? Maybe something went wrong.

The problem may have existed before the last carb rebuild, but it might be caused by something that is plugging a passage in the carbs. If, by chance, the carbs were not thoroughly cleaned to remove that blockage, the problem would still exist. I'm not saying that your carbs are dirty, but merely pointing out that although you are convinced the problem lies somewhere else, it might still be in the carbs.

I don't think the problem is with the valves, either, but I am just curious ... how long and how many miles since they were adjusted?

.

 

[Guest]

I am also a bit confused by some of the statements that Rockford is making:
Unless something has been changed, your '81 bike should have CV carbs. The needle jets do not have o-rings. More correctly, I should have said needle valve "O" ring; my bad!

Haven't tried it on a 750L but I have done the carbs on my wife's 850L in about 15 minutes. I have no intention of putting it on YouTube. It takes me longer than 15 minutes to remove the seat, remove the tank, loosen and move back the air box, disconnect the choke cable, disconnect the throttle cable and remove the carbs. Getting everything back together takes me even longer. You are obviously very quick and talented and I commend you for that.

Actually, there is a reason to stick a wire through there. I have found that if there is any moisture at all in a jet hole and you look at a light through the hole, it appears bigger than it acually is. That's interesting! I've found if there's moisture in the jet that you can't see through the hole (or holes) at all. I prefer to use a strand of copper wire as it is less likely to scratch the brass jet. This will ensure that there is no crud in the jet, slightly reducing its diameter and its ability to meter fuel flow. There's no need to stick anything through a new OEM jet, for obvious reasons, although I did inspect it as anyone would. (You must have missed the part about a new jet.)

Nice to know you have cleaned the carbs "as best I know how". Our problem is that we hear this pretty much every day from a lot of new people that are trying to resurrect an old bike. They have no idea what they are doing, and think that merely removing the float bowls and spritzing some spray in there constitutes "cleaning the carbs". We have no idea if you fall in that category. So far, you have only mentioned cleaning the carbs, but never mentioned how, so we don't know if they were properly dipped and re-o-ringed. I mentioned that I'd "done it a dozen times on this bike and other bikes". I also said I'd "dipped and soaked them" but I didn't go into any more detail as I didn't think it was necessary. My bad. If you think I'm "new people", that's fine but you should realize that a lot of new people have a great deal of experience. (A lot of people who've been here for along time have very little. One thing has nothing to do with the other.)

The problem may have existed before the last carb rebuild, but it might be caused by something that is plugging a passage in the carbs. If, by chance, the carbs were not thoroughly cleaned to remove that blockage, the problem would still exist. I'm not saying that your carbs are dirty, but merely pointing out that although you are convinced the problem lies somewhere else, it might still be in the carbs. I totally agree with that but I don't think removing carbs that were just "thoroughly cleaned" (as I also mentioned) would be a very prudent first step.

I don't think the problem is with the valves, either, but I am just curious ... how long and how many miles since they were adjusted? A little over a year and 1800 miles.

Everyone else who'd like to 'take a shot' at me is welcome but I've got some company coming and may not be able to get back to you very soon. Aloha!

 

[salty_monk]

Have you tried running it in the dark? Funny question but perhaps you have a plug wire or coil that is shorting out. I had that on a bike & I'd have never have found it if I hadn't been in a dim garage looking at it one night.... I could see the fireworks. Have you tried swapping the plug & wire from 1 to 4 yet? That really only takes 5 mins! :lol:

Nessism & Tkent are just trying to help, no need to be sensitive. People out here on the west are so easily offended some times, I don't get it.

I used to be able to do a needle clip swap on my carbs on my 1000G in 20mins so I would think a simple swap over would not take much more than 10mins. TKent has a bunch of bikes & buys & sells them for fun so I would expect him to be much better at it than me. The G & L models are much simpler than the E models. Regardless, even if it takes you 2hrs it has to be worth it to be sure it's not the carbs.

It can only be fuel, air or spark. If you have those combined at the right time & an acceptable amount of compression (170 is in spec for these bikes, 185 is the max specified) then it will fire.

Dan