'81 GS550L Idle Issue

[Mith]

Quick Rundow:

I've cleaned the carbs several times. Float Bowl hieght has been set and checked numerous times, complete carb rebuild kit (proper size), new intake orings, new airbox boots and clamps, new petcock, valves have been adjusted, new valve seals, valves have been lapped and seated, new exhaust seals, relay mod, spark plug caps, stator paper tests all pass.

The bike starts at the touch of the starter button, the only problem is that it doesn't idle real smooth and exhaust pipe 1 doesn't get hot as fast. Once it starts to get warm I can hear it try to smooth out when cylinder 1 starts to fire. If I take it out on the road it runs like a champ, better than it ever had before I did all this work. When I get back home it idles way too high and all cylinders are firing. If I shut it down and check the plugs they are all a nice light brown.

I'll admit that when I did the carb rebuild, having never done it before I didn't realize that the float bowls had a small orifice in it. I believe that I may have opened up the orifice on carb 1 float bowl. It may be getting too much fuel while idling. Does this make sense? If I pull the plug for cylinder 1 after letting it idle for a bit then it's black.

If I need a float bowl does anyone have one for a BS32 they could part with?

I feel that I'm very close to having this bike back in service!

Best Regards to all;
Pete

[Larry D]

Not sure what you mean by the float bowl having an orifice in it...... I was having similiar problems, except it was my #4 carb. I found out that the idle adjust screw tip was broken off in the carb. I didn't notice it while cleaning the carbs.

[Mith]

I replaced all the internal parts to the carbs when I rebuilt and cleaned them so I know there are no broken jets. I'm referring to the pilot circuit in the float bowl. There appears to be a small passageway (orifice) at the bottom of the hole where the pickup tube goes down into the float bowl. When I cleaned all the float bowls I didn't realize that the passageway had an orifice in it and I think I ended up reaming it with the pick I was using to clean the gunk out of it. Now when the bike idles, the number 1 cylinder doesn't run consistantly and the plug is black and wet. When I ride the bike it runs fine and the plug is a nice brown color just like the others. This is why I think I may have damaged the orifice in the floatbowl. I hope that one of the more knowledgeable members here can tell me if my theory even sounds plausible.

[ta2ooz]

it sounds to me you are having a spark issue at low rpm cold.possibly a hairline crack in a plug that seals up when warm

[Steve]

That orifice in the float bowl is not for the pilot circuit, it's for the enrichener circuit (the 'choke'). Unless you ran a drill bit down there, you probably did not hurt anything. It would be worse if you reamed out the hole in the tip of the tube that sticks down into that orifice.

Now, I just have to ask, ... you say that you "cleaned the carbs several times". Did any of those times involve dipping the carbs (prefereably overnight) in carb cleaner dip? Since you had to do it "several times", it sounds like you were trying some shortcuts, and you are learning that there are no shortcuts when it comes to cleaning the carbs. Do it right, do it once.

You mentioned "carb rebuild kit (proper size)". Do you mean those K&L kits or whatever brand? If so, did you keep your old parts? Those (expensive) kits often contain parts of questionable quality and do not have all the o-rings that you need to do the carbs properly. Except in extreme cases of wear (not very common), it is far better to re-use your stock brass pieces and just replace all the o-rings with a kit from fellow GSR member Robert Barr. You can order his kit at www.cycleorings.com.

Everything else that you mentioned that you did to get the bike to run sounds just fine, but one thing I did not see mentioned was "carb sync". If the carbs are not synchronized, the effect of the imbalance will be most noticeable at idle speeds. It is possible that your #1 carb is just not opening at the same time as the others.

Another thing I did not see mentioned was fine-tuning the idle mixture screws. Start with them all between 2 and 3 full turns out from lightly seated, then, when the engine is warm, turn each one slowly, listening for highest idle speed. If there is not increase in idle speed, turn it in slowly until the engine starts to slow down, then back it out about 1/4 turn.

.

[Mith]

Thanks for your response Steve, I'm still learning. I purchased the carb rebuild kits from Dennis-Kirk. Probably spent too much at the time. I verified the sizes of the jets as I replaced them. I did install all new orings (which came with the kit). I did bench sync the carbs prior to installing them and had the screws set at 2.5 turns. I did dip the carbs when I cleaned them (the second time as I did try to do a 'quick' dip the first time). When the bike was idling I did turn the screws, looking for the rpm to increase and that did happen on cylinders 2,3,4 but number one didn't seem to make a difference. I'll try it again though and see if turning it in causes it to decrease. I haven't done a sync yet as I don't have gauges, I've been reading all the various postings about what gauges to get, there seems to be a lot of disagreement about it! I will also swap a couple of spark plugs to see if it is a faulty plug. Do you suppose that the number 1 carb is still dirty? Which ports are used with the idle circuit if not the pickup tube that goes into the float bowl?

Thanks for the great information!
Pete

[Steve]

Sorry to say, but yes, you did pay too much for your carb kits. No matter what you paid. I have seen prices ranging from $15 to $25 for each kit (you need four of them), and the price for a complete o-ring kit from cycleorings.com is just under $15. It includes ALL the o-rings that you need and NONE of those questionable brass pieces. Yeah, the numbers on those brass pieces that you got probably match, but the question remains whether they are accurate. The Chinese drills used to make the holes might not be as accurate as the originals.

The idle (pilot) circuit is fed fuel from the pilot fuel jet, which is the one under the rubber plug right next to the main jet. It is also fed air by the pilot air jet, which is the one that is in the intake throat. Those two jets pre-set a mixture, then the idle mixture adjustment screw (the one on top of the carb outlet) will control how much of that pre-set mixture gets to the engine. The passageway from the pilot fuel jet to the adjustment screw is not very big and there is NO way to clean it by poking anything through it. The only way is to soften the gunk with an overnight dip, then spraying carb cleaner through the passages, followed by a blast of compressed air to make sure it's clean. There is an o-ring around the bottom of that adjustment screw, and I have not seen a "rebuild kit" yet that included that o-ring. It is also possible that the tip of that adjustment screw has broken off in the carb body. If you remove the screw, you should see a very small hole down into the carb throat. If you can't, you will have to press the broken tip out of there.

With your uneven firing when cold, then higher idle when warm, it sounds like you have a broken screw tip in there, especially if turning the screw makes no difference. You can remove that screw without removing the carbs from the bike to inspect it. You can remove the screw from #4 for comparison.

.

[DimitriT]

I haven't done a sync yet as I don't have gauges, I've been reading all the various postings about what gauges to get, there seems to be a lot of disagreement about it!

Pete,

don't bother wasting time and money until you get the sync done.

The best gages I've seen are the carbtune gages. I'm not
sure they are the most precise (I think mercury sticks may
be slightly more precise) but they are the easiest to use and
give great results.

It sounds like you've addresses the other tuning issues so this
is likely the problem.

[Mith]

I have my bike idling nicely now. I had to adjust the air mixture screws more carefully. I was being too conservative last time. I wasn't turning them enough. Once they were dialed in it really came to life and I had to turn the main idle down again. I let it cool off for about 5.5hrs and it started right up and I was able to take it off of choke after about a minute. Thanks for all the great advice, I've been sitting in the forums gallery for the last year reading everyones posts and using what I've learned to get my bike back in service.

One more question: Is there a US distributor for the Morgan Carbtune? I'm ready for one and would rather not have to order it from overseas.

Thanks to All;
Pete