Trey is dying - AND NOW LIVES AGAIN!

[adidasguy]

As for Trey, I think he's dead.

History: He had bad PO. Recently, put in LeFe battery and MosFet regulator. That went OK. Did a SeaFoam to all bikes. Junior is super! Trey was OK for a while. Then checked oil. A little low. added some. Now is at the "F" on the stick, so maybe a half a cup too much. Not too much that I would  think it would cause any problems.

For a while, he has been getting harder to start the longer he sits. Seem as if the carbs were either flooding (due to bad carbs) or draining (due to a slow fuel leak).

There was fuel showing around the intake boots to the carbs, so there was excess fuel from somewhere. Looking in the airbox, I saw fuel all over the carb air intake.

Hadn't been run for a week so he needed some attention. No power. None at all. He would rev just fine in neutral. When running, even at 6k RPM in 2nd gear hard to go 20 mph.

Probably Trey was ready to go bad and some say SeaFoaming simply sped up his demise (not a complaint, it just sped up the clock).

Today we adjusted his carbs. They looked pretty clean and the needles were good, but replaced them and the seats, anyway. Then everything was wet with fuel. Intake and output of the carbs. Put on the extra set of carbs (from running bike and we didn't do anything to them just as a control in case we screwed up the other carbs) and still runs like before. Backfiring through air box, clicking of valves or something. So maybe his valves suddenly went bad? No power. Then once in a while there is power for a few seconds (running around the block as a test). Probably intake valves are sticky. What else would cause backfiring through carbs & airbox? If intake valve stuck open and the plug fires, wouldn't that be the only way you would get a backfire through the airbox? Then the metallic ping, could that be the valve closing suddenly when the plug fires?

Thinking of sending one set of carbs to PJ Motorsports in Oregon to be professionally adjusted - that would eliminate that as a variable. They charge $100+parts and take about a week. I really doubt the carbs are the main problem. I'm thinking it is the valves or something worse.

So could the valves suddenly attention and the top end need work?

I'm thinking that it does. The occasional tink of metal (valves snapping shut?) and the backfiring through the air box would indicate the intake valves are not closing before the plug fires. That's my guess.

While I'm an expert on electricity, I do admit I am new at carbs and valves (in my family, we did not work on cars so I do not have that background).

Should I (1)do another heavy SeaFoam dose or (2)take the top end off and check things or (3)part out Trey......and spend my time on the new bike build?

Is Trey dead? Is there hope?

[ghostrider_23]

While I am no carb expert either I do understand engines. As you already know, you will need air for intake, fuel, combustion & spark for power. If I read your thread correctly it sound like you maybe getting fuel in the oil? You may try a cylinder leak down test to see if you have bad rings causing blow-by into the oil case. That test will also let you see if the valves & seats are good as well that could be forcing fuel back through the carbs into the airbox when the compression stroke is formed. Other than that sounds like it's time to rebuild your carbs and do a video inspection while you're at it. lol.

You can rent a cylinder leak down tool from any auto store. Take the spark plug out and screw in the leak down tester. Make sure the piston is on BDC, use a little compressed air to fill up the cylinder and read the gauge. Let it sit for awhile and if your gauge is still at the same psi you're good. if the psi is less you have leakage from either the rings or the valves & seats.

Please reaf & refer to the instruction booket when renting because I'm sure I left a couple of safety steps out and do not need to get flamed by others. I am giving you the general rundown.

Good luck and let us know how it goes.

[bigfatcat]

Old bike = possibly bad ignition module. I've had similar symptoms - backfire, power loss, no run, etc - with bad modules.

[noiseguy]

If you're confident that the carbs are OK (if you took them apart and cleaned them, they are likely OK though the presence of fuel concerns me) then start checking the electrical system for issues, esp if you have a spare bike to trade parts from. Start at the pickups and work back.

Typically, backfiring is a timing issue, not a carb issue. The intermittent symptoms also sound electrical in nature (a skipped tooth on the cams would not be intermittent.)

If that doesn't work, pull the head cover and look at the valves... though I doubt you've issues there. Check chain, sprocket... or anything amiss.

[adidasguy]

Spare parts? Does a parts whore have spare parts?
I'll try the ignition module.
2 sets of csrbs and similar issue, so doubt it is the carbs.
Either ignition control or valves.
Or it is just cold and Trey doesn't like 40* weather.

Update: ICU: not the problem. Swapped and no change. Seems to be running on the right cylinder. Changed left coil- no change. Changed left plug: no change.

Unplug left - no change. Unplug right: dies. So that means left cylinder not working.

Interesting: unplug right and try to start with full choke and it will eventually start up with only the left cylinder. So what gives? Left cylinder going out or left left side valves? Intake not opening?

I guess when I have a warm day, take the top cover off and see what the valves and ships are up to? Re-check a set of carbs and see if the carbs are screwed up?

I'm thinking of sending off a set of carbs to PJ Motorsports in Oregon to be professionally fix up a set. I think the set we worked on got really screwed up and the spare set, which we didn't work on, may have a poorly function left side.

[twinrat]

check your inlet shims probably to tight .

[Jared]

When you say you changed the needles and seats...you mean new ones or ones out of other old carbs...?Replace the float needles etc with new if you haven't. Physically clean the carbs-take them off the bike and clean all the orifices/jets/air passages etc.
Check the floats to make sure they float.Verify/correct float height if needed. Fuel leaking out an intake boot...stuck/bad float is what I immediately think.  The intakes boots look cracked (since you mentioned them..)?They new?-that can be a BIG air leak.They can look ok and be bad...(buy new if they are needed).

Ethanol/additives in gas and bikes sitting  sucks for carbs...

If you can get the engine warm enough- What's the compression on both cylinders? (look at the valve clearances before you warm it up).

Did you check the signal generator....? You said you swapped plugs and coils...New plugs??...get spark but no fire on left cylinder?with the air filter out- shoot some gumout (EDIT) CARB (/EDIT) cleaner into the airbox towards the right carb inlet and try to start the bike....see if it fires off on both cylinders for a second ...
Good luck.

[ghostrider_23]

Like Jared said and is easyenough to do, run a compression check on both cylinders and compare the readings. You did check the spark output and ensure that there was spark going to the plug correct???

After the compression test is done it will either be rings or valve. If you are getting spark & fuel into the right cylinder it sounds like you have no compression in that cylinder.

[gsJack]

Pull the plugs and give it a quick finger in the hole compression check, if you get a loud pop from both cylinders the problem is not valves.  Only takes a minute or two and it's always a good starting point.

[ohgood]

+1

low compression can lead you to think it's an electrics/fuel problem initially. instead of a thud thud thud vrooom like on normal startup it will thaw up thawup thawup and not fire nicely. check the valve clearances after you do a compression test.

i'll remember the sound my drz made forever, when the rings gave up.

[noiseguy]

Check compression, of course. Make sure you have enough.

Bike is running on one cylinder, with the left picking up intermittently... this still sounds electrical . So we've probably ruled out the ICU... methinks you have another wiring issue somewhere between the pickups and the ICU. Have you pulled your right side inspection cover to see what's happening in there? Trace back the wires to the ICU and make sure everything's solid. Then, the pulse up to the coils from the ICU. Check it with a small 12V bulb or noid light (used to test fuel injector pulse.)

[gsJack]

The only problem I've had causing my 02 GS to run on one cylinder is the plug wire coming loose in the coil, should be bonded in tight.  adidasguy has already checked this by switching coils above.

Other GS'ers here have had the problem caused by both carb problems and in a couple of cases a bad pickup coil.  Maybe time for a parts whore to swich the pickup assembly with a known good one.

The way I learned it 64 years ago working in a garage was to check compression and then spark and finally carbs in that order when you have no idea what's wrong with a vehicle.  Cars have changed a lot since then but the GS500 has not.   

[ghostrider_23]

Damn GSJack,

Quote,"The way I learned it 64 years ago workig in a garage" 

How old are you?

I think I've seen a video you did on youtube and you don't look over 64 + 5 or 7 years of childhood making around 70 to 72

[numus]

Did you check the battery to see if you are having an abnormal voltage drop? Also check around the starter solenoid harness... That is where the majority of my problems came from (the main power harness goes thru here and mine started to melt so connections because intermittent).. I pulled the entire harness and wired both the battery positive and the positive coming off the rectifer to an inline fuse and wired that directly to the positive post of the battery. All the starter solenoid does now is star tht ebike off the switch, nothing else runs thru there... 
You can also do a voltage check on the coils themselves to make sure the connection is good and also that your CDI isn't bad... If you have 2 meters i would check both LH and RH coil.. i believe LH reads inverse of RH (electronic tach taps off RH) and make sure they are the same...

I only add this part because of a recent issue with the Katana and loss of power.. Turns out I had a fuel line kink. It started to restrict fuel flow and I started to drop cylinders. On some turns it must have jared the line the right way and it opened up a little and would restore power... Just another thing to possibly look at...

[mister]

- Check to see you have left side spark first.
- If no spark, swap out lead with one you know is working.
- Add correct milk as required

Michael

[gsJack]

Damn GSJack,
How old are you?

Looking forward to riding my 02 GS on my 80th birthday next summer.   

[adidasguy]

Swapped ICU
Swapped coil
Swapped plug
Do have spark (ouch!)
Did quickie valve clearance check (was cold in the 30's and late at night) 0.04-0.05 so within spec (0.03-0.08) but on the tight side. Will do a more proper check when in the 40's

Didn't do thumb compression check yet.  Valve bucket does go up and down smoothly as engine rotated, so I don't think the valve is stuck (could be damaged). Will check mixture screws, though unlikely 2 sets of carbs would both be lean on the left side (but possible).

Here's the odd one:
Unplug left wire, runs the same.
Unplug right, dies
Put on full choke with only left plug and runs the same as no choke with only right plug.

Gas is good. Had to fill up after only 100 miles when testing and running around the block. Problem came on slowly over a couple weeks where it would get harder to start unless full choke.

Will do more testing and go over the suggestions for what I have not checked when it gets above 40.

[Bluesmudge]

Left valve could be bent and still look fine going up and down (Mine did  ). Do the compression check with your finger that GSJack has suggested.

[ghostrider_23]

Adidas is going to try everything first and then do the compression test last. lol

[adidasguy]

I'm did the electrical first, as I know electrical the best and electrical things are a piece of cake for me.
Now moving on the the mechanical.
I knew Trey had a bad PO and never had a valve adjustment. So went checking valves, since I was going to do that anyway and was next on my to-do list.
Not necessarily doing things in a backwards order, but going through things first that I know needed to be done and were going to get fixed first. 
If I find compression is the problem, that IS on the list as there are gaskets with minor leaks and the whole top end WILL be taken off this winter for a complete overhaul.
Hope this makes sense --- doing easy things first on the list to see if he will run, before weather warms up (or I get a heater in the bike cave) and do the complete engine overhaul.
If warm this weekend or some evening, the finger test will be done along with a proper valve clearance check.
Bent or bad valve would not surprise me as it came on slowly over a 3 week period. A valve burning or bending could reach the current state in 50 miles of riding.
I'll pull the carbs (now only takes about 1 minute to remove them, 2 minutes to put back on), because I remember seeing the intake valves looked different and will take pictures. Tempted to insert a camera in the spark plug hole and see what the top of the inside of the cylinder looks like - that's the video nerdiness in me.

As an added note - I really want to get on to the bike build so the easier I can fix Trey to run a few months before the tear down, the better.

UPDATE
OK - went to 36* bike cave (needs a heater!). Every other turn of the engine the ffffffffffffttt on each side with thumb over spark plug hole feels the same.

More update
Brought original carbs inside to replace the screws with SS ones, just because I was bored tonight and it is 34* outside. Found the mixture screws were 4 turns out. That won;t explain his current problem with the left cylinder, but could explain all the gas in the carb air intake and dripping from the airbox boots (which were not properly connected so all the extra air leaking in might explain why the PO cranked up the mixture. Don't you love bad PO's?)