How to Rebuild and Check for Leaks?

[ekabil]

I have an 82 GS1100GL and I am a bit of a beginner. Especially with carbs. This bike is new to me, and I think there is gas in the oil (the smell comes and goes), and so for these two reasons I want to go in to the carbs and replace what I can.
If I get a rebuild kit from Z1, I will need four, and they are $25 each. This is too much Since the bike runs fine, I think the jets are ok. Basically I don't think I need most of what is in that kit.
But, what do you suggest? I have also been told to check the float needle valve and make sure it moves without sticking so that no fuel is brought in to the carb when it is full. If this were broken then fuel would continue flowing and possibly get in to the engine, right?
Either way I can't go wrong replacing the rubber bits while I am taking them apart. However, I am not sure what I'll need. I have read through the tutorial for Mikuni BS carbs, for '80 and after, and also looked at cycleorings.com per the guide. I do not know the quantity to order from there however.

So if you were going to rebuild the carbs, only to clean them and replace the parts that can wear away and not because they don't work, what rings and seals would you use? I will probably get the gaskets from Z1 if I need them, but do I need to take the carbs apart that far to check the float needle valve?

I should also add that the bike runs very well, there are no flat spots, it idles fine, accelerates fine, and cruises fine. There is just a slight smell of gasoline from the oil cap hole. And mileage seems to suffer greatly at high RPM, say above 6,000. This may have been the result of the drag from the windshield which I have since taken off and the bike seems to run better strangely.

[MisterCinders]

Check your petcock to make sure it's not leaking.

To do the carbs, don't order those kits. Your brass bits should be fine. Just order an o-ring kit from cycleorings and the bowl gaskets from Z1.

You will need to disassemble the carbs completely to dip them for cleaning. If the needle valves are failing such that gas is flooding the engine, the parts are not likely to be broken. Instead, they may be gummed up and sticking such that they don't close. Could also be that your floats are sticking, and keeping the needle valves from closing. When you pull the carbs apart, you can clean and inspect the needles and seats. You probably don't need new parts, just clean them.

HTH

[Steve]

If I get a rebuild kit from Z1, I will need four, and they are $25 each. This is too much. Since the bike runs fine, I think the jets are ok. Basically I don't think I need most of what is in that kit.

Just like a former First Lady used to say, "just say NO". You do not need "rebuild kits". You are correct, your jets are just fine, the ones that come in the kit are usually suspect.

But, what do you suggest? I have also been told to check the float needle valve and make sure it moves without sticking so that no fuel is brought in to the carb when it is full. If this were broken then fuel would continue flowing and possibly get in to the engine, right?

For fuel to run unchecked into the engine, you need to have TWO failures at the same time. 1. The petcock needs to be leaking. 2. The float valves need to be leaking. When the engine is running, the petcock is turned ON, so it's all up to the float valves.

I have read through the tutorial for Mikuni BS carbs, for '80 and after, and also looked at cycleorings.com per the guide. I do not know the quantity to order from there however.

You will need ONE o-ring kit for your carbs. However, a couple other items that are highly-recommended, but separate, are: the drain screw o-rings (for another penny), intake boot o-rings (a couple bucks more) and the stainless bolts that hold the intake boots (another couple of bucks). All together, I thinks it's less than $25 for everything at cycleorings.com.

So if you were going to rebuild the carbs, only to clean them and replace the parts that can wear away and not because they don't work, what rings and seals would you use? I will probably get the gaskets from Z1 if I need them, but do I need to take the carbs apart that far to check the float needle valve?

Float bowl gaskets are a good choice. Not always necessary, but nice to have on-hand, just in case. You do not need to take the carbs apart to check the float needle valves. While you are in there, be sure to check the float height, especially if you change the needles.

Since the bike appears to be "running right", it might not be necessary to strip the carbs down fully and dip them, although it certainly won't hurt anything. If nothing else, it gives peace of mind that the carbs are CLEAN and done RIGHT, and you know that you have a stable platform from which you can make any adjustments necessary. Of course, if you decide to break the rack and do a full "strip and dip", you will have to get a can of dip (about $25) and a carb sync tool ($100+), but you will eventually need the tool, anyway, just for normal maintenance.

And mileage seems to suffer greatly at high RPM, say above 6,000. This may have been the result of the drag from the windshield which I have since taken off and the bike seems to run better strangely.

If I remember correctly, 6000 RPM in top gear is about 90 mph, so yeah, mileage is going to 'suffer' just a bit. How is your mileage in the more-sane area of 55-65 mph? Should be at least 40.

.

[MisterCinders]

For fuel to run unchecked into the engine, you need to have TWO failures at the same time. 1. The petcock needs to be leaking. 2. The float valves need to be leaking. When the engine is running, the petcock is turned ON, so it's all up to the float valves.


.

Unless the petcock failure allows fuel into the vacuum line. Then even the tightest float valves won't stop the flood (since the fuel comes through a different path).

[Steve]

Unless the petcock failure allows fuel into the vacuum line. Then even the tightest float valves won't stop the flood (since the fuel comes through a different path).

True enough, sorry I missed it.

But YOU caught it.

.

[MisterCinders]

True enough, sorry I missed it.

But YOU caught it.

.

Blind squirrels, broken clocks, etc.

[ekabil]

On average I'm getting about 35 mpg. However my 11 mi one way daily commute has only one stretch that isn't stop and go, a 5 mile bridge. 35 seems ok for this type of riding, plus I try to go on 15-20 mi interstate drives every few days to stretch the engine. That's something that feels right to do even if I was never necessarily advised to do it. You know what I mean?

35 mpg isn't indicative of a definite gas leak is it?

[loud et]

On average I'm getting about 35 mpg. However my 11 mi one way daily commute has only one stretch that isn't stop and go, a 5 mile bridge. 35 seems ok for this type of riding, plus I try to go on 15-20 mi interstate drives every few days to stretch the engine. That's something that feels right to do even if I was never necessarily advised to do it. You know what I mean?

35 mpg isn't indicative of a definite gas leak is it?

No, 35 mpg would be no reason to suspect a gas leak. Tire pressure, intensity of riding, wind conditions, airbox seal, intake o ring leaks, coil spark intensity, plug condition, etc etc.....a dozen or more factors affect your mileage.
Step one with any old GS is to do a absolute proper and complete carb teardown, dip and o ring rebuild. Then that factor can be removed from all issues concerning how your bike runs.
You can test your petcock, by sucking on the vaccum line to see if it properly starts and stops the fuel flow. If you suck, it flows, when you stop, the fuel line will dribble/drain quick and after 20 seconds you should have no further drips. (this is done into a container) You can leave the fuel supply line into an empty jar and see if the petcock leaks overnight. That will tell you if it is leaking into your crankcase.
LIke has been said, get the carb o ring kit (14$) the intake o rings set of 4 (6$) and the stainless steel bolt set(4$). This is from cycle orings.
An absolute must to make your fuel delivery system right.
After that, bench sync the carbs, seal the airbox, reassemble and vaccuum sync. I know it sounds like a lot, I am waiting for the exact order for my 550. ....But know what? ...when your bike is running half a$$, its just no fun. Ruling out the basic carb and fuel issues lets you move on to the next step in having a great running GS.

[ekabil]

damn fine advice