650 seca carb fuel level

Q-Assuming that all aspects of my low mile bone stock 82 650 seca are checked, and adjusted to spec with the possible exception of the float/fuel levels, how would an engine running with equal however too high fuel levels run? Start up? Idle? Over-rev? plug condition? mileage? other?
Thanks,
E.S.

:?:

 

Welcome to the site !!

Higher fuel level would tend to make it run rich and get poor fuel economy, all things being equal, however, since the Pilot circuit is adjustable, a person could tune it to idle, start, and low-speed cruise just like it had a "Normal" float setting (within reason)

You can check your float levels with them on the bike using the clear-tube method, and get a friend to help put the bike on Mainstand with the rear tire hanging off your driveway and front elevated on blocks, to "level" the carbs.

Some reference w/pics
http://www.xj4ever.com/setting%20fuel%20levels.pdf

 

thanks for the quick reply. I have gone completely through this bike, rear brakes to battery to fuse block to new air filter, ignition component testing and all mechanical adjustments. New jets and float valves, inspected the needles for irregular wear, carefully went over the diaphragms and all the carb intake/manifold boots and replaced the intake manifold gaskets to eliminate possible air leaks finally setting floats with carbs level on bench with clear tubes to 3mm below body/bowl intersection and a carb synch.

I suspect that the fuel level is too high as the bike has a hard time starting and the plugs are uniformly sooty and black after a run. Also, the engine revs up to 4-5K when started and comes back to a good idle after about 1 minute without using the enrichment lever. Bike seems to run well once going.

No doubt I messed something up, maybe the fuel level should be 4 or 5 mm?

 

Why would you need all new jets?? Did you change jet sizes??

Have you tried turning your Pilot screws in??

Also, I added the reference above while you were typing.

 

Nope. 3mm exactly. 4mm is within tolerance, but at the extreme of the low side. 5mm would be too low and you would have stumbling, etc. 2mm and you would flood the plugs

TtR is correct, you didn't list the pilot screws as something you touched on the carbs. These passages have to be cleaned out as well. Then a colortune or plug chops to adjust the screws.

Your plugs should be a nice shade of brown-paper-bag when the mixture is adjusted correctly.

 

Hi, yes I have un-plugged the idle screws and cleaned everything out. I had them at 1.5 turns out from seated and got a lot of black smoke at start up and idle, then re-set them at 1.5, 1.25 and one turn out, running with cleaned plugs, less black smoke but still sooty plugs and hard starting. Now they are at .75 turns out with new plugs, gapped at .028. and running it I still have sooty plugs. Have not ran it at high RPM's and chopped and inspected yet.

Bike seems to idle well however still have the high rev at start up and some reluctance to rev down when riding/shifting. Sounded like air leaks to me, not sure where leaks would be coming from as intake manifold boots are in good shape, with new vacuum caps, vacuum line to petcock and new gaskets that were also lightly coated with Hylomar, all tightened down at clamps.

 

Two very good possibilities:

Enrichment plungers not fully seating when OFF (or their little rubber "stoppers" are damaged) OR the soot is from something other than unburned fuel; like OIL.

If it's burning oil and the compression numbers are fine, it could be a bad valve stem seal.

 

(Enrichment plungers not fully seating when OFF (or their little rubber "stoppers" are damaged) OR the soot is from something other than unburned fuel; like OIL.)

No, not oil, definitely running too rich. Seems uniformly on all cylinders based on the similarity of the spark plug conditions. Damaged rubber stoppers on the enrichment plungers? All the plungers move freely and are not hanging up. Are the rubber stoppers internal as part of the plunger assemblies or are you referring to the sealing boots at the top? I don't recall.

I think I may want to recheck fuel levels, leveled carbs on the bench and set them on the low side of 'in spec'.

btw, I replaced all of the main and idle jets just to confirm the PO didn't drill them out or mess them up in any way. Also I inspected the top of the emulsion tubes where they meet the needles and everything appeared clean and round. I read that ovalized emulsion tubes and needle wear are common on V-twin Yamahas with Hitachi carbs.

Regarding possible air leaks, are there any obvious locations other then the intake manifolds to check? Maybe throttle shaft seals?

 

Perhaps a possible cause to my carb tuning issues?

I believe that there is supposed to be a cover plate that goes over the top of the the 2 air jets in the chamber beneath the diaphragm. My carbs did not have this part, however the PO did have someone go over the carbs in the bike's recent past who may have forgot to re-intall them. Was this part installed on all XJ's and what does it do? Is it possible that the threaded hole for the plate's securing screw may enter into other parts of the carb ie-it is not a blind hole? Other possible issues with exposing the air jets to this area?

 

I think it is a blind hole, and I think the carbs will work the same without this cover installed.

Any air leaks would tend to make you run leaner.

Did you try a lower float setting yet??
Did you try going for a short ride with the air filter removed?? (no dirt roads 8O )

 

Yeah, I seem to be battling 2 things at once. One is the high rpm at start up leveling back to a good idle in about 1 minute, while also not revving down quickly enough between shifts...air leak maybe?

the other is that it is running too rick with fouled plugs (all 4 evenly), heavy fuel consumption and a difficult restart when cold.

I am hoping that the two are related and one fix will fix all.

A's: I did check my fuel levels and they were are all set at 4mm below the carb/bowl interface area, spot on to the low side of 'in spec'.

Have not yet run the bike since however really nothing has changed. The The air filter is brand new. Is your thought that running without an air filter would lean out the mixture (noticeably?) to confirm that it is running too rich? Maybe there is a 'very difficult' to clean passage in the carb bodies that I overlooked and they're plugged up?

 

And your valve clearances are in spec; and you've done a vacuum sync with the YICS blocked?

Just checking.

 

What size did you buy??

Did you get the air jets in the wrong holes??
What else would make the Pilot system run rich??

 

valves are all in spec, and there is no YICS on this model to block.

new Hitachi jet sizes are 110 main, and 40 idle.

Air jet sizes as installed under the vacuum diaphragm are 50 front (closest to engine) and 195 rear (closest to air box)

 

Did you make your carbs go "clunk" ?? (clunk test)
http://s82.photobucket.com/albums/j255/ ... CN4501.mp4

I'm gettin' low on ideas . . .

 

Ahhh, the clunk test. Just to knock one more possibility off of my list, I have now preformed 'the clunk test' with good clunking results. Nothing hanging up with the tops removed. I am assuming that a slower slider return with the spring and top installed is normal.

...regarding jets sizes and air jet placement noted earlier...does all seem right?

And noted your site with the clunk vid, I noticed the pic of the 4 carbs with the tops removed and 'air jet' covers in place....to confirm, no cover shouldn't effect performance?

 

Ahhh, the clunk test. Just to knock one more possibility off of my list, I have now preformed 'the clunk test' with good clunking results. Nothing hanging up with the tops removed. I am assuming that a slower slider return with the spring and top installed is normal.

...regarding jets sizes and air jet placement noted earlier...does all seem right?

And noted your site with the clunk vid, I noticed the pic of the 4 carbs with the tops removed and 'air jet' covers in place....to confirm, no cover shouldn't effect performance?

 

oops, dbl posted.

OK, 'if' not carb related, than perhaps something electrical that causes a weak spark? How would a weak spark effect the performance?
-Fuse box was updated
-All plugs are firing
-I did test the resistance on both circuits of the coils, and the caps separately according to values in my Clymer manual, all
-Wiring from engine, to cdi to coils all 'look' good without any noticeable pinches or frays.
-all connectors in ignition system cleaned with a shmear of electrical grease for good measure.
-I checked the timing with a timing light, appeared spot on.
-Possible out of tolerance ignition pick-ups?
-Anything else that would effect all 4 cylinders equally?

 

OK, any additional thoughts would be great as I 'think' that I've checked into about everything that can be checked.

Anything that may cause a weak spark on all 4 plugs?

Air and Fuel jets all sound correct in sizes and placement?

Air Jet cover plate might make a difference in carb performance?

What else might make the pilot system run rich?

Are there replacement parts for the Enrichment Plunger rubber seals?

Are there any typically difficult to clean out passages in the carb body?

Thanks and much appreciated, I can't wait to ride this Seca with good reliability!