Topic: Rich carb, I think

[jimbo]

Funny thing I have noticed...  Now that I have my bike on the road, I actually have more questions than when I was rebuilding it.  Well, here's my latest.  When I start my 74 550, it runs great.  I usually don't even use choke it does so good.  On initial start, no smoke or anything.  After I take it on a ride, it starts smoking.  This afternoon, I was out about 30 minutes or so.  Smoke seems to be fuel related.  I pulled the plugs and they look like all of the carbs are running rich.  I have played with my mixture screws.  I started out with 1 full turn.  Then moved to 1 1/2 turn now, I am at 2 full turns and it doesn't make a difference.  Bike even reacts like it is running rich.  Flat acceleration sometimes.  I have to let the engine breath in between shifts.

What am I missing here?  I did a full rebuild on all carbs during the past winter.  Soaked them in carb cleaner, blew out passages.  Replaced needle valves & jets.  Slide needle is on the middle clip on all carbs.  Should I tear the carbs back down and if so, what should I check for?

When it runs good, it runs great.  It moves right down the road with you.

[hymodyne]

If needles don't affect much change, there might still be gunk in your carbs.

 a Plug chop is frequently recommended on this site, although finding a stretch of road on which to perform it requires  I've found difficult.

information about exaust config, air filter selection,timing and compression will yield reliable answers from posts here.

hym 

 

[MetalHead550]

Youre definitly running rich.  First indication is that you can fire it up and idle without choke and it runs good cold then crappy warm.  My first guess would be the floats are set to high.   Is your air filter clean?  Are you sure you have the correct plugs?

[jimbo]

Air filter looks good.  I even poped it out and tried it without it with the same results.  I am running the stock air box.  I haven't timed it yet.  I may try static timing it this weekend.  I just changed the plugs.  I had Champion that Autozone had crossed over and I saw a recomendation to stay with the NGK D7ES so I put new ones in.  Finding a good long stretch of road for a plug chop is hard to do here also (Eastern KY)

Also, factory 4 to 4 exhaust.  I kept the exhaust and air box stock to avoid problems necessitating changing jet sizes.  I haven't done a compression test yet but probably should.  When it runs good, it's great so I didn't think of doing the compression test.

[jimbo]

Youre definitly running rich.  First indication is that you can fire it up and idle without choke and it runs good cold then crappy warm.  My first guess would be the floats are set to high.   Is your air filter clean?  Are you sure you have the correct plugs?

When I rebuilt the carbs, I checked float height and thought it was weird that none of the 4 needed adjusting.  I may not have measured correctly.  I remember having problems grasping what the repair manual said about where to take the measurement.  Do the carbs need to come back off for float height or can I just drop the bowls and check still on the bike?

[TwoTired]

Running too rich can wash the oil off the cylinder wall and accelerate wear.
Your bike's symptom are indicative of running too rich.
A dirty or restrictive air filter can make it run too rich.  You didn't state which type you have.  If stock, then try a Uni filter unless you are operating in dusty conditions.
The exhaust type and filter type also effects the mixture requirements.  If not stock, the factory carb settings likely won't apply.  But, the stock carb settings for your bike are listed in a chart in the FAQ.

Are you sure your choke is adjusted so all carbs are completely open?

Do you know what parts came in your carb kit.  There are different needle taper profiles for the CB500, Cb550K and CB550F.  I'm guessing from your description that your slows should be #38, the needle ought to have the CB550F profile, and Mains should be #100.  I'd put the needle clips in the second groove from the top.  Then clean the plugs, run it and check the deposits again for improvement.

You really should need to apply choke to start it.  If you are strating out rich enough to start without it, then when it gets warm it will be too rich as it can burn much more efficiently hot and doesn't need the extra fuel to run.

I agree you should tell us the Spark plug numbers you are using, and it won't hurt to tell us what you set your float height at.   Fuel bowls too full can make things run richer, too.

Lastly, there are emuslion tubes between the needle jet and the main jet that have small holes drilled in them crossways.  These premix air before it is fed to the carb throat.  If these holes are plugged things will run richer, also.  They aren't that easy to remove and clean.  But, maybe you did anyway.

Are all your spark plug looking like they are running the same mixture for all cylinders?

Cheers,