Quote from: Egaeus on February 25, 2007, 12:05:55 PM
So I caught a break in the rain, and took it for a spin.  The purpose was to warm it up for rebalancing since I'd had the carbs apart and cleaned that bit of gunk out, but I couldn't help but notice that the symptoms were the same, or worse.  I had to keep reminding myself not to panic. 

So I got it home, balanced the carbs, and went back out before the serious rain got here.  It runs great.  Doesn't miss a lick.  Just in time for the rain.

Great job!
I always wander to resync carbs and do all this job, do you have to disassable the bike to take carbs out for each tiny little adjustment or is there another way to do that?

To synchronize the carbs you have to take the frame covers loose, and take the seat and tank off. I take the frame covers off, but you don't have to.  It is done while running, so you need to hook the tank up at about the same height so that fuel will flow.  I will post a short, small video that I took yesterday of my carb balancer in use that I took in anticipation of my bike not running right.  I didn't need to post it for that, but I will do so when I get home.

Okay, so cleaning out the choke didn't fix the problem.  Between rain, darkness, cold, and going out of town, I finally got around to putting the bike completely back together, and I rode for a bit and it starting having the same symptoms after a few miles.  It's running sporadically on one cylinder, and backfiring out of the exhaust again. 

Funny thing is that now, since the choke is working 100%, it actually has an effect on the bike.  When I pull back the choke, the bike starts running correctly.  The missing goes away, and the backfiring stops.  Switching to PRI has no effect.  When I am idling warm, without choke I idle at a normal speed, but with choke it goes up to ~5000 rpm.

So the jets are as clean as new, the emulsion tubes are clear, and the fuel level in both carbs is at the correct height.  I'm at a loss.  I'm thinking vacuum leak, but where?  The boots are flexible and the clamps are tight and the frame petcock is working fine, so where could it be leaking?

A quick shot of starting fluid at the boots while running will tell ya, if she speeds up, that's it.

You need to prove some things beyond reasonable doubt first....

Float level needs to be seen at the exact point in time of the problem occuring. You need to connect some clear tubing to the float drain stub, open the screw and bend the tube upwards above the carb. The fuel will level off in the clear tubing to show the float level in the carb at ANY time!
If you want to set up the tubes properly you can use right angled tube connectors to go around the carb. I use pet store aquarium pump connectors, they seem to be petrol proof! The tubing should be proper clear fuel line if you can get it, otherwise expect it to melt after 5 minutes. Don't use silicon rubber tubing, it melts!
MAKE SURE THIS TUBING IS SECURE!
Run the bike on 'prime'. When the problem happens, very quickly switch to 'on' and kill the engine. Then check the float level. If it's ok you can rule it out. Be careful that the tubes don't fall off or move or fuel will go everywhere and torch your bike and yourself.

Your 'choke effect' can be VERY misleading!! There could be many causes to this fault.

Okay, so I got some starting fluid and rode the bike to work so it'd be warm when I got home to work on it.  I took videos.  I also got some clear weed eater fuel line so I can check the fuel level while running (the aquarium line's ID is too large, it falls off).  I will do the fuel level test later, but I went ahead and checked for vacuum leaks.  I, however, am a dumbass.  See the video....

The videos

Balanced carbs on the 25th

Still balanced today

I check for vacuum leaks

f%$k! I'm a dumbass

That's okay, I never throw things away

So if you have any ideas as to why the starting fluid caused my right cylinder to quit running instead of the predicted behavior, I'd be interested in hearing them.  Obviously, the rest will have to wait until tomorrow....

Okay, the vacuum leak is fixed.  It was a vacuum leak.  I still don't know why it caused the cylinder to quit running, but anyway....

It's running worse now, believe it or not.  It's still sputtering and backfiring out of the exhaust. 

I'm willing to believe that the vacuum leak out of the top cover would cause a problem during normal operation.  However, when balancing the carbs, the aquarium line is much tighter than the cap that's on there.  The carbs should be balanced.

I ran it on one cylinder at a time again.  It's having the same problems on both cylinders (cutting out, backfiring).  Having fixed the vacuum leak, I'm now back to my original hypothesis: fuel starvation. 

Reasons:
- Problem only occurs on the road.  Idling, it runs fine.  The fuel level while running in neutral is 1-2 mm above the float bowl mating surface. 
- Problem occurs with both cylinders. 
- There is some fuel flow restriction from the fuel filter.
- The choke provides more fuel, and alleviates the problem.  Sometimes, it helps more than others, which I suspect to be because the fuel level gets too low for the choke to help as much

After lunch, I am going to bypass the fuel filter and see if that fixes the problem.  To the filter, the flow is reasonable, though the petcock is a little restrictive.  I think that may be the problem, since the tank is in pretty bad shape.

Woohoo!  Update and progress.  I bypassed the fuel filter.  It helped, but didn't fix the problem.  So I rode back home, got a screwdriver and the clear weed eater fuel line, and rode with my petcock ON.

(unimportant part) I started having severe symptoms of fuel starvation and I ended up on the sidewalk and after checking the fuel level in the left carb and finding it low, I remembered that I was low on gas and it should have been on RES.  I then let the float bowls fill up in PRI, turned it to RES, and set off again.

So when I started getting the normal mild symptoms, I rode it for a bit, and when convenient, I cut the ignition, shifted into neutral, and coasted into a "road to nowhere" and checked the fuel level.  Left was dead on.  Right was about 1/2 cm low. 

So it's the right cylinder that's giving me problems.  I presume the left cylinder backfiring by itself was due to unburned gas from the right cylinder in the hot exhaust.  So much for that diagnostic methodology.

Now, I have a very, very limited set of possible causes.  I haven't pulled the carburetors (for the thousandth time) and checked, but it should be a simple case of garbage or dried fuel in the line from the T to the needle valve, or a sticking needle valve. 

So now the obvious question:  If there's no blockage, how do I prevent the needle valve from sticking?  Is there something I can put on it to make it less prone to sticking? 

So I hear that this engine is bulletproof.  I'm about ready to put that to the test....

Or in other words, cleaning the float valve assembly had no effect.  In thinking back, I may have had the bike on the side stand when I checked the fuel level.  Anyway, the fuel level is correct for both sides, and I still have the problem. 

Maybe a rebalance is called for since I disassembled the carbs, but I need a new top cover for my carburetor first.

Beyond that, I'm stuck.

Hmmmm... doesn't sound like fuel level.... 1/2 cm shouldn't matter much.

Slightly Low float bowl levels will affect the first 1/2 turn of the throttle and not so much w.o.t (wide open throttle) -this is because the main jet is lower down in the float bowl and generally not as fussy.
You balanced the carbs while you had the air leak!! this will need doing again, but to be honest- unbalanced carbs aren't going to cause this fault. during W.O.T the balance doesnt really matter that much. Not enough to give you this problem.
From the video, it looked like you were spraying the EZ start with the carb balancing caps off. I can't tell, but this will really REALLY mess things up if you're riding with them off!

I'm not sure after all these posts, what the symptoms now are??
Running one cyclinder at a time will give you erratic "farting" anyway!

There are numerous causes to what I think your symptoms are..
Bearing in mind I'm not sure what they CURRENTLY are, here's some suggestions:

Slightly blown head gasket, partially duff spark plug, intake manifold leak, main jet missing/fallen out, mid jet and main jet put in the wrong holes, HT leads breaking down, partial fault with electronic ignition, blocked emulsifier jets may have been missed.... er... lots of things!
How about you Drive the bike on PRIME with the float tubing attached (and new plugs), but switch to ON and immediately stop the engine when the fault shows in that order.

Have you re-done the EZ start test, since you fixed the leak?
Also bear in mind that when you have a leak, the engine will quite possibly tick over faster than if you didn't have a leak.

Carburettors are set up for max power and then 'richened' a little to avoid over-heating. More air can speed them up!
This problem sounds like a real Buddha Loves You! you have my sympathies.

When the problem occurs, is one side hotter than the other? I usually spit on the head near the plugs on each side to tell.

If the spits sticks and boils it's ok, if it beads off like mercury -it's too hot!!! are both sides the same?

I'm no expert, but I fault-find things for a living....

If you don't mind, please re-list the most up-to-date symptoms as accurately and in depth as possible, explaining whether it occured after a re-build!

Quote from: johnlaughland on March 12, 2007, 10:04:39 AM
Hmmmm... doesn't sound like fuel level.... 1/2 cm shouldn't matter much.

Slightly Low float bowl levels will affect the first 1/2 turn of the throttle and not so much w.o.t (wide open throttle) -this is because the main jet is lower down in the float bowl and generally not as fussy.
You balanced the carbs while you had the air leak!! this will need doing again, but to be honest- unbalanced carbs aren't going to cause this fault. during W.O.T the balance doesnt really matter that much. Not enough to give you this problem.
From the video, it looked like you were spraying the EZ start with the carb balancing caps off. I can't tell, but this will really REALLY mess things up if you're riding with them off!

I'm not sure after all these posts, what the symptoms now are??
Running one cyclinder at a time will give you erratic "farting" anyway!

There are numerous causes to what I think your symptoms are..
Bearing in mind I'm not sure what they CURRENTLY are, here's some suggestions:

Slightly blown head gasket, partially duff spark plug, intake manifold leak, main jet missing/fallen out, mid jet and main jet put in the wrong holes, HT leads breaking down, partial fault with electronic ignition, blocked emulsifier jets may have been missed.... er... lots of things!
How about you Drive the bike on PRIME with the float tubing attached (and new plugs), but switch to ON and immediately stop the engine when the fault shows in that order.

Have you re-done the EZ start test, since you fixed the leak?
Also bear in mind that when you have a leak, the engine will quite possibly tick over faster than if you didn't have a leak.

Carburettors are set up for max power and then 'richened' a little to avoid over-heating. More air can speed them up!
This problem sounds like a real Buddha Loves You! you have my sympathies.

When the problem occurs, is one side hotter than the other? I usually spit on the head near the plugs on each side to tell.

If the spits sticks and boils it's ok, if it beads off like mercury -it's too hot!!! are both sides the same?

I'm no expert, but I fault-find things for a living....

If you don't mind, please re-list the most up-to-date symptoms as accurately and in depth as possible, explaining whether it occured after a re-build!

Symptoms are:

One cylinder (I believe it's the right) is missing when I try to maintain speed.  An example is in 4th gear at 45 mph (~5k rpm).  When I maintain this speed, It jerks and bucks.  It's a mild form of the jerking and bucking caused when you are, say, running in ON when you should be running in RES.  Or, in other words, only one cylinder is cutting out.  If I let off the throttle or lay into the throttle, it stops the jerking and bucking.  Sometimes, it will backfire out of the exhaust, especially if I have been keeping it constant for a relatively long time.  This started sometime in October or November.  I don't remember that I did anything to it, but that was 5 months ago.

As far as your post:

I balanced the carbs when I had the air leak, but the air leak was on the top vacuum cap.  It would not have been leaking when the carbs were balanced, as the carb balancer would have sealed where the cap was leaking.

The caps were on when I sprayed the starting fluid.  Don't worry, I know better than *that* at least.

I did retest with starting fluid.  The leak was sealed with the RTV silicone. 

As far as the suggestions, here are my responses:

Head gasket: no signs of an oil leak.  I believe I've heard that it will seep oil if it's leaking.
Spark Plugs: changed with no effect
Carbs: Jets are intact.  There is no mid jet on 89-2000 carbs.  All holes in the emulsion tubes are clear.
Ignition: I can't say for sure.  However, seeing as it seems to be related to the throttle input, I don't think it is.  I've checked the spark on both sides, and it's a good spark with the spark tester set at 20kV.  The spark looks identical on both sides.

How will running on PRI do any good?  It seems that running on ON will be the more appropriate course of action.  PRI has no effect on the symptoms.  While I didn't run with the tube on and the drain screw out (a good way to lose the drain screw), I did kill the engine when the symptoms were present and coast the rest of the way to my stopping place, so the state of the fuel level at the time of the problem should have preserved.

Edit: changed when it will backfire.  It backfires both when I let off the throttle or accelerate.  I noticed a backfire when accelerating today on the way home from work.

Okay, another factoid that I didn't bring up earlier because of a mistake I made.  Last night, out of desperation, I tested the compression again.  I failed to do it correctly and didn't open the throttle.  Needless to say, I didn't get a good reading.  What I got was 85 psi on the right and 110 on the left.  I about had a heart attack until I got out the Clymer manual and realized that I did it wrong.

Today, I did it correctly and got 145 on the right, and 146 on the left. 

Now, what would cause the incorrect readings to be so different?  My guess is imbalanced carburetors or a vacuum leak (Whee!  Circles!).  Why?  Because obviously the left carb can take in much more air than the right to get such a higher reading.  But how can that be?  Everyone saw that the carbs were balanced, and that I found one vacuum leak (and it was fixed, though you didn't see that part). 

Well, I'm inspecting my homemade differential manometer and I'm noticing that the aquarium line is looking a bit yellow and feeling a bit hard.  I'm going to feel really stupid if the second vacuum leak isn't on my bike at all, but rather on my balancer.  I'm going to seal it up with RTV silicone and try the balancing again.  Before I do that though, I have to get a new top cap, as you can plainly see that the replacement isn't going to yield good results.

Quote from: Egaeus on March 12, 2007, 11:31:54 AM
An example is in 4th gear at 45 mph (~5k rpm).  When I maintain this speed, It jerks and bucks.  It's a mild form of the jerking and bucking caused when you are, say, running in ON when you should be running in RES.  Or, in other words, only one cylinder is cutting out.  If I let off the throttle or lay into the throttle, it stops the jerking and bucking. 

Just looking at the quoted material my first instinct would be to check valve clearances.  If that's not it, then it's hard not to notice that the problem zone seems to be approximately where the pilot circuit transitions to the main jet.  So, when you cleaned the carbs did you check for blockage by squirting carb cleaner through the straw and into the pilot air jet at the carb mouth to see if the fluid squirts out all of the pinhole jets in the roof of the carb throat aft of the venturi?  

Well, these would be obvious culprits but this thread and its relatives are too much to sort through to know all the troubleshooting that's already been tried.             

Running on primary just overrides any other vacuum problem. It is possible to have TWO faults, which really confuses things.
This is why it's never worth changing more than one thing to find a fault.

-You adjust ONE thing and if it don't cure it, you PUT IT BACK AGAIN!!!

-There's nothing Worse than creating two faults!!!
-Cuz then, you may cure the original problem only to think you haven't!!!

I know this from bitter experience of having to fix electronics that other engineers had their mitts on first!

A partial fuel block will fill up quite quick when there's no demand and only show itself at high demand/ speed.
Switching to ON just before turning the engine off should give you a 'snapshot'of the fuel levels.

Sounds like you have a mid-carb problem, probably lean, since the power comes back in at W.O.T. and backfires a bit on overrun.

Hmmm... could it be the carb diaphragm? That might explain it....

A small hole would not matter at tickover or show at W.O.T, but maybe it wouldn't lift the slide enough at mid throttle??? I'm not sure what the symptoms would be cuz I've never had it.....

Next time you have the carbs out, put them to your mouth like a trumpet, seal the other end with your hand and gently blow. The throttle slides should lift up to the highest point and only drop down when you let the air back out. compare the two. If one behaves differently to the other then have a look at the diaphragms. Don't blow too hard!

I know this isn't very technical but hey, I'm a bodger!

Someone friendly near you should lend you their carbs for a day! I

I don't know what else it could be, but I'm no mechanic, I'm an electronic fault finder...!

PS - you can test the vacuum gauge by connecting Both to the same cyclinder and see if they read the same! (T-link needed)

Valves? Mine ran like crap when the valves were wacked. You can check the slides by taking the tank and the air filter/airbox off and running the motor, you'll be able to watch the slides for a few minutes before you run out of gas...if your vac is incorrect the slides won't lift the same. Dunno? Just tryn to through that out..

For the record, the valves are right on the money.  They don't even tick they're so perfect. 

As far as my most recent theory, once I took the carb balancer off of its 2x4, it literally fell apart. There's no way it was sealing.  I sealed it up last night and now it will hold a vacuum without any significant leakage except between the two sides (the sensitivity adjustment won't make a perfect seal).  However, the total pressure in the device stays constant as far as I can tell. 

So I finally balanced my carburetors with the new and improved carb balancer.  I took videos of it, so you can critique my method.  I did it as a how-to.

Calibration 1
Calibration 2
Balancing the carburetors
Check for leaks

So after all of that, I went for a long test ride to see if it helped.  Well, the symptoms on the road seem a little less severe, but definitely still present.  At idle, it seems that is misses worse than before.  Since it's doing this at idle more severely, I was able to take a video.  I tested the spark on the video as well, so you can see it.
still not working

One step forward...three or four steps back.

So out of sheer desperation, I rechecked my valve clearance.  There are two valves L-In and R-Ex that were ever so slightly out of adjustment (.09 mm and somewhere just under .038).  I switched the shims between those two (a 258 and 260...for the third time, long story) and remeasured, and I'm happy that they're correct now.  No effect.

You heard how well it was running when I balanced my carbs, right?  And you heard how bad it was running in the night video right?  Now I can't balance my carburetors.  Just ain't happening.  It's so off that I can't get it to do anything.  I did my best, and gave up on it.  I did determine that when the bike starts missing, the right develops more vacuum than the left.  I have overthought the significance of that, and I still haven't decided which cylinder that indicates is misfiring. 

While I was checking the valve clearance, I did triple check my timing.  It's correct. 

And while riding yesterday, I put it on PRI at a stoplight and turned it off to see if that helped the idle.  It didn't.  I left it on PRI, and this morning, I had a puddle of gasoline.  Now the needle valve isn't sealing?  WTF?!?!  When I rebuilt the carb, I didn't replace the needle valves because they looked new.  They still do.  I don't know what's going on....

I'm really getting sick of this thing.

Hows your carburettor breather hose. Check to ensure it's not blocked.



If it is you will have an air lock in your float bowls.

Heh, yeah I saw your thread this morning and about jumped up and down because I found something different to check.  Believe me, I'm going to check that thing as soon as I get home.  I'm going to feel dumb if that's it considering that I've been trying to fix this off and on for over a month.