I am stumped

[79XS11F]

I have been syncing them but it's really a waist of time while she's missing. All timing parts work freely. The bike is stored in a dry heated space.
Anyway. I just took the carbs off AGAIN and I am switching out the brass floats to the plastic ones that were in it when I originally got the bike. I noticed that one of the needle valve bodies was loose. Hmmm, I check the sealing gasket which is made of some sort of fiber and it, like all the others appears deformed and try to slip up over the valve body so I have replaced them with alloy washers. This might be the entire issue even if she wasn't leaking fuel. I now however, can't remember if I set those plastic floats the same as the brass ones. They are the floats that came with the bike when I first got it and I did all my original work from the manual so I will guess that they had been set to the factory spec. I'll keep you posted.
Rob

[XJOK2PLAY]

Hey, Rob...

Feel your frustration.

Just for the sake of saying it's been done...

Start the bike and get it warmed up good.
Get a spray bottle of water, spray on each header to check for steam.
If all 4 pipes steam, each cylinder is firing. Or not...if you find one that doesn't steam.

If that passes... Proceed to test 2...
If not, check ignition, and complete test 2...
After dark, start the bike. Turn off all lights. Look for any arcing around the spark plug wires that may be shorting to ground around the engine. Bad wires, or bad coil? Test for strong fire... (Blue arc to ground.)

If that passes...proceed to test 3.
'79 F's were bad about breaking the wire at the timing plate.
Now, I know you said you've checked this before, but you might check it again. This single broken wire has fooled many of us before...and will cause the bike to run like total crap. Couldn't hurt... Use a DVOM, check continuity as you flex the wire around, engine and key off, of course. Sometimes the insulation will fake you out.

If that passes...proceed to test 4.
Synching carbs. In the past, I have had lots of issues with carbs, but the one problem that carbs out of synch will always exhibit... erratic idle problems, and vacuum advances that dance around wildly. No matter how perfect you may get the idle set, the next throttle blip may make it surge up dramatically.
Also, increased popping on decel. I found that adjusting each bank to their highest vacuum readings FIRST, then adjusting them equally to one another yielded the best result. That's my personal findings, though. YMMV.

Test 5... Ignition timing perfect? Off one tooth?

As was said by others previously though, if all else fails when trying to troubleshoot a troublesome engine problem, go back to the baseline tests.

Air/Fuel, fire, compression, timing, exhaust.
If it's in time, intake draws fuel and air, in the proper amounts, it's properly compressed, ignition, in the proper amount occurs at the proper time, and then the exhaust valve opens...it should run.

I know you already know this. Please don't take this the wrong way... I have to remind myself like this sometimes too when I get stuck.
Sometimes, I can't see the forrest for the trees...so to speak, ya know?

If, after all these tests, it still runs like puke...it might be time to try a known perfect condition loaner set of carbs from another bike...just to eliminate the possibility of some little carb passage that's still blocked.

When I was a fleet mechanic, and we'd get one in that had us baffled, it was always a process of elimination...no matter how improbable, or simple. Whatever you overlooked, or ruled out as improbable...was probably the problem.
I saw it happen to many good mechanics...more than once.

Basically, just presenting the obvious list...in hopes that it might help.

[XJOK2PLAY]

Just noticed you posted while I was typing...

Keeping my fingers and toes crossed for ya!

Hope you found it in the carbs.

[79XS11F]

No change, still missing, RPMs float when given a little twist, sync is holding by would still need a fine tuning if the miss can be corrected. I am beginning to think it's not a carb problem after all.
Number 2 is the coolest cylinder with the lazar thermometer. but all the plugs look the same and a little lean. Black without soot on the base ring and a little white on the tips. No carbon deposits. SO, tomorrow I will take the carbs off AGAIN, off the rack, full strip down and bench test the fuel levels in each one, re-rack and install them. If that does not do the trick I will consider the carbs as NOT being the problem and then start looking for an ignition issue. Perhaps I will pull all the timing guts out and replace it with the timing from the 79 special I have here. Maybe I should do that before I pull the carbs again just to eliminate that as a potential issue.
Rob

[TopCatGr58]

Hey Rob,

Just a little thing to think about. You say it can be synched, but then after synch, still missing. How OLD are the synch port caps??? They can age, harden, and actually LEAK a bit. I remember someone posting about chasing a carb problem until they found/figured out it was the old synch caps. JAT!

T.C.

[79XS11F]

Hey TC, the caps and retaining holders are new within a year. It's missing even while syncing it when she's hooked up to the hoses. It'll miss and the needle on #2 will go out of whack then back to it's synced position, then miss again. The missing is occasional. The only thing that has me thinking it a carb issue is the way the RPMs float after giving the throttle a quick twist up to the 4 to 5K range. Than she'll settle down to rough idle rather slowly. Then I will set the idle again, only to have the idle be way off the next time I give the throttle another quick twist.
It's got to be carbs but I have cleaned them several times now and air flows through every passage freely as does spray carb cleaner. In fact, the only thing I have not cleaned is the chock system because the carbs must be off the rack for that so they will be done next with the bench fuel level tests
Could the chock system cause this much trouble if they are in deed blocked of not clean enough?
Rob

[donebysunday]

Choke/enrichener can/will stick if not cleaned once in a while or left to sit gets sticky. Could be sticking open slightly choking/enrichening the cylinder to where it won't idle and hang up in the rpms.

[79XS11F]

I had guessed that the chock system. if not clean or sticky would only have an effect on the the fuel system if it were engaged. In any case i will be cleaning those while I have the carbs off the rack
Rob

[79XS11F]

Almost forgot, I am running premium fuel in this bike. I was told by a mechanic friend that running premium fuel would be best because here in Canada there is no ethanol in premium fuel. That being said we know that premium fuel does not ignite as readily as regular fuel and the lad next door told me that he was running premium fuel in his bike from the early 80s and he had issues with it including not being able to get the engine to idle at factory spec RPMs. Could I be having the same issue? Could the premium fuel be part of the problem?
Rob

[donebysunday]

If it truly is non E premium sitting for a few years should not affect it's degrade as much or corrosion/chemical reaction with the parts turning the fuel green. Let my 70 GTO sit for 3 years with 1/2 tank of Sunoco 260 and fired right up when an emergency caused me to put it back on the road. Still would have some problem with evaporation but did not experience any difficulties with MMO added, it's unbelievable what this stuff can do to clean the fuel system tank/carbs/valves/pistons.

Almost forgot, I am running premium fuel in this bike. I was told by a mechanic friend that running premium fuel would be best because here in Canada there is no ethanol in premium fuel. That being said we know that premium fuel does not ignite as readily as regular fuel and the lad next door told me that he was running premium fuel in his bike from the early 80s and he had issues with it including not being able to get the engine to idle at factory spec RPMs. Could I be having the same issue? Could the premium fuel be part of the problem?
Rob

[XJOK2PLAY]

Rob,
JAT, have you tried another spark plug in #2?
Maybe it's a bad plug? Had that happen to me once.
New set of plugs, one was factory defective internally.

If not, and #2 is quite a bit cooler at the header than the others, I'd focus on that cylinder... (ignition, fuel, compression...)
I wouldn't think it would be a coil problem, but perhaps a wire.
Coil should affect 2 cylinders, I would think...but ya never know.

If it's ignition miss, it will show up on your vacuum guage when it happens.

Header temp trick is a good indicator of cylinder performance, and helps identify which one's giving you the problem, most times.

[XJOK2PLAY]

Also,
Will an inductive timing light, clamped around each plug wire, one at a time work on an 11? Anybody ever try this before?

It's a great test tool for vehicles to determine if it's fuel or ignition causing the problem. Never tried it on an 11 before.
I know the 11 uses a dual "waste-spark" type coil system...
So not sure.

If it would work, you should be able to see a correlation with missing light pulses occurring when the engine misses.

I know on car ignitions, it's a quick way of telling if the problem's fuel or ignition.

Someone more knowledgable than me might know the answer...

JAT

[mack]

Hi Rob

Been a while since I've seen you. Check the diaphram for holes in that #2 carb or at least verify the lip is seated properly.
Did you get the Katana restored? Hope to see you at next years rally. Coming up to Ottawa next Friday to drop my daughter off at Carleton U. Pm me your address again, I know your close so I could drop by and have a listen. I can bring a set of known carbs with me for you to try. Then we'd know if it's carbs or ignition. You could chase your tail for weeks. I busted my right hand so wrenching is out for me but sometimes two heads.......

[bikerphil]

Also,
Will an inductive timing light, clamped around each plug wire, one at a time work on an 11? Anybody ever try this before?

I have tried this and it does work well for finding a misfire. You can usually hear the misfire and see the light missing pulses when you find the problem cylinder.

[BA80]

I have tried this and it does work well for finding a misfire. You can usually hear the misfire and see the light missing pulses when you find the problem cylinder.

IF the problem is in the coil or wire.