Running Lean

Helix · Post by **Helix** » Tue Apr 21, 2009 1:04 pm

My Bike is running lean. The spark plug is white not brown.

Any suggestions, carb was rebuilt

jaybob · Post by **jaybob** » Tue Apr 21, 2009 1:13 pm

Yes it sounds like your bike is lean. Need more details:

What bike, model and year?
Any modifications?
What altitude?
What did the carb rebuild consist of?

Helix · Post by **Helix** » Tue Apr 21, 2009 1:36 pm

Late 74 GT550
No Mods
Keyster carb kit
Not sure altitude by I am near Toronto

jkevinlilly · Post by **jkevinlilly** » Tue Apr 21, 2009 1:46 pm

Did you use everything in the Keyster carb kits? The jets normally do not work so well. If you did, try putting the originals back in, and remember the middle one is different in size from the outer two, due to the way the exhaust is set up. Also, check to make sure you are not getting air leaks around any of the connections between the airbox and the carb intakes, if you are sucking air in somewhere it could be an issue.

Kevin

Helix · Post by **Helix** » Tue Apr 21, 2009 3:13 pm

I replaced the outer two main jets but used the original middle one.
I do not have any leaks from what I can tell.

But

When I rebuit the carbs I did not pay to much attention the the slider pins.
Could this be the issue and if so should I adjust the notch up or down

jaybob · Post by **jaybob** » Tue Apr 21, 2009 3:27 pm

Do all of the spark plugs look the same?

Yes if you adjust the jet needles higher by putting the clip into a lower groove you will richen up the midrange.

Here is a link for some instructions and adjustment procedures if you tear into the needles.

http://www.3cyl.com/~tripleed/suzigtcarb/

Helix · Post by **Helix** » Tue Apr 21, 2009 5:26 pm

Yes all spark plugs look the same
I will adjust the needles on Fiday to see how that works

Also I am using NGK 7s at was pure white.

Changes to NGK 8 at got a little better but still enough

tz375 · Post by **tz375** » Tue Apr 21, 2009 7:19 pm

Try swapping the needles back for the stock ones in the stock clip position and see if that improves things

Some Keyster needels are way off spec and it's possible that yours are. Stock 550 needels are an unusual spec and are pretty lean, so if the keysters are even slightly larger, you would have a problem.

tz375 · Post by **tz375** » Tue Apr 21, 2009 7:24 pm

Helix,

I just noticed your other posting. The bike has not run in 13 years. So tell me how clean the petcock is and the fuel lines into the carbs and the needles and seats. Is the breather in the fuel tank clean, is the timing absolutely spot on?

I'm not questioning you ability, just trying to determine what was done and what might have been skipped or "underdone".

After 13 years of non use, lots of things change.

Helix · Post by **Helix** » Tue Apr 21, 2009 8:07 pm

Fuel lines are new and clean.
The petcock is another matter, I am not sure how to clean it, is there a filter and where is it. Do I have to replace seal in order to clean it.

All the needles and seats are new.

What's the breather in the tank?

Timming is spot on and is converted to electronic Boyer Brandson.

I am definitly going to swap back the original needles.
Was hoping to not have to.

tz375 · Post by **tz375** » Tue Apr 21, 2009 9:10 pm

I'd drain the tank and then remove teh petcock. The filter is on top, inside the fuel tank. As you drain the tank you'll get a good idea how well the petcock flows and if the fuel starts to stop (so to speak) and then sort of gulps out, the small hole in the filler cap that lets in air as the fuel is used up is clogged.

Are your carbs on rack? IF so it takes a lot of time to strip and clean them or to adjust the needles. Once they are off it would be good to check the choke circuits to ensure they actually close off. Blow through every passageway and compare that to the other two carbs - circuit at a time. You would be surprised how different they can be.

With needles out, try to measure them at say 10mm up from the tip and compare the diameter to a stock needle at EXACTLY the same spot.

Make sure the vacuum hose is connected to teh petcock and there are no air leaks anywhere.

Helix · Post by **Helix** » Wed Apr 22, 2009 7:11 am

If I remove the petcock from the tank,can I use the same seal?

Yes the carbs are on a rack. I will pull them on thursday and report back what I find

jaybob · Post by **jaybob** » Wed Apr 22, 2009 7:20 am

The percock is sealed with a rubber o-ring. It would be best to use a new one. However you may get lucky and it may re-seal again for the short term. Long term I would replace with a new one.

Buffalo-guy · Post by **Buffalo-guy** » Wed Apr 22, 2009 12:26 pm

Helix wrote:Late 74 GT550
No Mods
Keyster carb kit
Not sure altitude by I am near Toronto

Helix. I personally have not had any success using Keyster carb kits. The manufacturing tolerances just don't seem to measure up to factory Mikuni. My wifes 380 ran dismally with Keyster kits installed, and returned to good running order when refitted with original jetting and needles. I don't know if thats a common thing, but I won't risk the money and effort to try them again. Good luck with it. Cheers.
Fred

rngdng · Post by **rngdng** » Fri Apr 24, 2009 5:21 am

I've had trouble with the Keyster slide needles.

Lane