Topic: 550 not running well...Not sure what to check next.

[elquenada]

Background Info:  '75 550 all stock setup recently re-ringed and gasketed.  Original 4-4 exhaust, original airbox (with UNI filter NU-4055).  Valve clearences are set, cam chain is new and freshly adjusted, new spark plugs.

The Problem:  Bike was running ok but carbs were leaking gas so I pulled them out to fix the float levels 2 days ago.  I bench-synched the carbs and got them back on the bike.  I started the bike up and it idled pretty well after a few trys.  I took it for a test drive around the block and the throttle felt really flat; the engine wanted to bog out unless I gave it a ton of gas.

After the ride I decided to take a step back and double check the dyna-s timing.  I put a timing light to it and made some adjustments.  I took the bike for another ride and  WOW it was fantastic.  The throttle was really responsive and the bike was riding great.

Then...I stopped for gas.  When I started back up the bike felt flat again.  It bogged down and stalled out at the next light.  I decided to synch the carbs.

Where im at now: Synching didn't help, the bike idles a little rough and now it stalls and bogs out as soon as I release the clutch. I checked my plugs and found that 1&4 sooty while 2 & 3 look relativley tan.  I double checked the resistance of my coils, wires and caps and they all tested ok.  Dont know where to go from here, any help would be appreciated.  Sorry for the novel .

[OldSchool_IsCool]

Could the timing have slipped?

[elquenada]

i guess it could have but i think more likely one of the carb adjustment screws did.  I found that the #4 carb adjuster wouldnt tighten down completely.  But this was way after the fact and after many other carb synch adjustments.  I'll have to go back and double check everything.  Not today though I've got other problems now...

[TwoTired]

Did you check for fuel contamination?
The pilot jets are only 0.016 in. in diameter.  Doesn't take much to plug them up.  And if it is loose, the debris can fall out allowing the bike to run well again for a while, till the debris finds the tiny hole to plug again.

Also, have you checked the head pipes for even heat when the problem does occur?  A cold one allows focus on 1/4 of the engine.

You could drain each carb and catch the release in a clean container.   Chunky bits are unwelcome.

Check spark plug deposits.  Tha'st your window into the combustion chamber.  Dark fluffy soot can lead to misfire conditions.  At any rate, unequal deposits can refine/confine where to look for issues.

[elquenada]

Did you check for fuel contamination?
The pilot jets are only 0.016 in. in diameter.  Doesn't take much to plug them up.  And if it is loose, the debris can fall out allowing the bike to run well again for a while, till the debris finds the tiny hole to plug again.

Also, have you checked the head pipes for even heat when the problem does occur?  A cold one allows focus on 1/4 of the engine.

You could drain each carb and catch the release in a clean container.   Chunky bits are unwelcome.

Check spark plug deposits.  Tha'st your window into the combustion chamber.  Dark fluffy soot can lead to misfire conditions.  At any rate, unequal deposits can refine/confine where to look for issues.

could be bits of junk in fuel though I doubt it cause I just replaced the petcock screen with a new one and cleaned out my carb bowls.  I have not checked the head pipes for heating will definietely have to look into that.  Lastly, the spark plugs 1 & 4 are full of soot, meanwhile 2 & 3 are pretty tan. 

at any rate I'll have to wait until tomorrow till i fire it up again.  I'll update then.