Ok, time to fix some leaks for good. Help!

[TRC]

A couple nagging leak issues on my '75 GT550!

First up are the float bowls which, despite very careful meticulous cleaning with a Dremel brass wire brush and brand new factory gaskets, still leak. Sigh. Now what are my options? I've got another new set and the energy to pull the carbs again and replace them but what's the point just to have them leak as before? I hate to coat the new ones lightly with something like Permatex #2 prior to installing them, but I'm short of other ideas.

Next up are the oil injection lines. Same deal - made sure they were clean and used new factory gaskets on both side of the bolts yet several leak same as before. No idea what to do here to get these things to stop leaking. Any suggestions?

BTW, I've only had the bike for a little over a year and have put a ton of work into it. Since ownership it has seemingly randomly fouled plugs which has meant it has sat lonely in the back of my garage mostly while I ride my modern bike. Not being one to give up, I'm back at resolving the remaining issues and decided almost randomly to check the oil pump adjustment. Well I couldn't believe it that while doing so, the dang thing would stick open if I released the throttle right about where the markers line up. I actually yelled "eureka!" out loud. Some squirts of high-temp silicon spray on the lever and the sticking is gone. Need to do some tests now but I'll be surprised if my random fouled plug issue isn't a thing of the past.

[Alan H]

Sometimes the oil pump doesn't return when the engine is stopped. It will go back when running.

I would suggest that either the fuel levels are slightly high, or the float valves are leaking. Make sure the valves aren't worn and there's a thin gasket under them where they screw into the carb. Do all 3 carbs leak or just one? Have you got standard airbox or pod filters. The standard airbox supports the back of the carbs so they sit level properly.

[TRC]

Thanks for the ideas. I thought that may very well be the case with the pump but it was rather gummy sticking pretty good. After a test ride last night I pulled the left plug, the problem child, and it was pretty black and on its way to carbon fouled. That has been the pattern - always the left plug, sometimes I pull it and it looks good, other times it carbon fouls. Mostly fouls really. The other plugs are always good. Up next I will test the coil and wire - easy enough and should have done it previously. The bike has been converted to electronic ignition.

The carbs have pods. The bike had been sitting for several month and the leaking from the bowls is minimal in that time, but leaking slightly none-the-less. Float levels are correct, set them all when the new gaskets were installed. Will note the washer you mention - can't recall on that one.

[jabcb]

Suzuki discontinued the plastic oil line washers that worked well & now sell aluminum washers. I haven’t had any long term luck with the aluminum washers. But the stat-o-seal washers have worked great so far.
I get them from McMaster-Carr. Very reasonably priced but they charge for shipping.
https://www.mcmaster.com/#stat-o-seal-washers/=18ohfnl

The fuel level should be below the float bowl gasket when the bike is on the centerstand.
I use this fuel level tool to check the actual fuel level: https://www.z1enterprises.com/fuel-leve ... uzuki.html

Recently one of my GT750s had an intermittent overflow of the left carb when parked on the sidestand. Ranged from sometimes nothing to sometimes pouring out of the overflow. Using the tool I verified that the fuel levels were correct without removing the carbs. So I switched out the petcock & the problem was solved.

When does it leak? If it leaks only the sidestand, then you might have a warped float bowl. I’m currently trying to deal with this problem on a T250/T350.

[TRC]

Thanks, I'll give those washers a try! Yeah, aluminum ones in my experience as well are mostly useless.

It doesn't have a centerstand so always on a sidestand. Two of the three are leaking slightly - left and center- and definitely from the bowl gaskets. If warped, what to do?

That fuel level tool is out of stock but sure I can find one elsewhere. Sounds handy and couldn't hurt.

[TRC]

Happen to know which size of those washers are needed?

[jabcb]

My answer is a work in progress.

I have a topic on this on the Suzuki GS forum. I sometimes use that site for generic questions because they have a lot more traffic than this one.
http://www.thegsresources.com/_forum/sh ... -bowl-tips

I used 180 grit sandpaper on a flat surface to make the float bowl surface flat again.
Use circular motion. If your float bowls have an overflow tube, then cut a hole in the sandpaper so that you don’t damage the tube.
You may need a deeper opening if the overflow tubes stick out a lot.

The expert recommended 80 grit paper — I don’t know if that makes a difference.

I expected the gaskets made out of PF-4N to be the best option because its a modern material, but the gaskets I bought are the wrong shape and will not work.

The T350 has used float bowl gaskets. I wanted to give it a try after sanding them & didn’t have any new ones at the time.
Currently the T350 has a slight petcock leak. The float bowls leak a smidgen - just enough to make the bowl surface slightly wet and evaporate before making any drops that land on the motor.

Now have new K&L gaskets, which are a good match for stock.
Probably will try the K&L gaskets + a different petcock.

[jabcb]

Happen to know which size of those washers are needed?

M6

[TRC]

Excellent, thanks! The washers have been ordered.

Yesterday I checked the coils, took apart the left spark wire cap and cleaned the innards and cut a 1/4' off the lead, re-adjusted the timing, switched the plugs to 7s instead of 8s. Took a pretty decent length test ride and bike idled and ran really well. Went to my favorite long up hill stretch and at the top killed the motor and pulled the left plug which looked good. Ok, one of these things had a positive effect.

On the timing... I have the install documentation for the electronic ignition which the PO printed but there is no info on how to actually set it and no brand indication anywhere so trying to find additional info is impossible. Generally not an issue as it's pretty straight forward (tiny LEDs indicate when it will fire for each cylinder) but there's one thing that I'm not 100% sure on. When I turn the engine over until the right cylinder marker tab indicator comes around (stamped "R"), does that indicator mean that it is at TDC when it lines up or does it mean "this is when the spark should fire"? How I have the timing set is assuming that it means "this is when it should fire" but want to be completely sure. I could have stuck a stir-stick down the plug hole and tried to determine it, but figured I'd ask some experts instead.

[jabcb]

The R/L/C markers are when it should fire.
A somewhat more accurate method is to use a dial indicator to find TDC & then use the dial indicator to set timing per the mm before TDC spec.

Which electronic ignition system do you have?

[TRC]

Thanks again for the info. Good to have confirmation on what the indicator tab means. That's the problem, I don't know what electronic ignition system it is! The printed documentation has no brand listed anywhere on it and neither does the hardware. Would a picture help ID it?

Off to put some miles on it and check the plugs some more (spare plug in pocket lol).

[TRC]

Back from a 20 mile ride - left plug turning black and that's with the air/fuel mix screw out 2 and 1/4 turns. Blarg. No signs of crank seal issues such as hanging RPMs off throttle or other such nonsense - it's running very consistently, it's just too rich in that left carb. Middle one likes to run lean but dialing in the screw gets it right, the right carb is good near 1.5 turns out as expected.

What next? I guess I'll get what I need to do a compression test. If compression is good then that left carb is going to need to be totally stripped, dunked or boiled in lemon juice or something (maybe both lol), and rebuilt. Fun fun.

[Alan H]

Favourite is the fuel level is slightly high in that carb, or perhaps the choke hasn't fully dropped in it.

You didn't expect this to work at first attempt did you?
God loves a trier!!

[TRC]

First attempt? Ha! I've done a leak down test, pulled the carbs I don't know how many times, coils, spark wire, voltage regulator, timing, battery. I feel like I've gone around in circles half a dozen times at least.

I guess my plan of action is:
Will do a compression test.
If good will do a leak down test again.
If good will pull the carbs and check left carb float level again.
If good will strip, dunk, rebuild left carb.

If that doesn't fix it will put it on the curb with a free sign.

[TRC]

Left cylinder compression test = 160. Well that's good at least.

Ok, so when I said I tested the coil, here's what I did and did not do specifically. First, I pulled apart the plug that all of the coils connect to. With my multimeter I tested the reading for each of the coils at the plug connector. They all came back about the same reading so figured that with this first test the left one is as good as the others. Then I was a little stumped. You can't remove the spark wire from the coil so how can you test the wire itself? Seemed impossible. As I said before, I did trim off 1/4" of the left side wire, took apart the cap and cleaned the innards. I am getting spark but I suppose it is still possible that the left coil isn't outputting what it should but I don't know how to test it given how these are built. It turns out I have a complete extra set of coils that came with the bike that I had forgotten about. No idea if they are good or not and don't know how to test if they are. Any ideas other than to switch them out and see what happens?

Really though I'm back to thinking the issue is with the carburetor heh.