engine rpms thru the roof

[joecburris]

Just put this bike back together after it sat for 8 years. Cleaned carbs/rebuilt with k &l kit. It starts but rpms go up to 7000-8000 so I shut it off. What am I doing wrong? Any help at all will be greatly appreciated! 1979 xs1100 special.

[jetmechmarty]

Did you bench sync the carburetors? That means did you set all the butterflies the same and we'll get back to that if you didn't. Is the throttle cable properly routed, or it pulling up on the throttle shaft? Did you back out the idle adjustment?

[phatts27]

I had a similar issue. It was a combination of a loose throttle shaft on #4 (that caused an un-synced carb condition which was like you described) and incorrect float heights.

When your fuel level is too high your carbs can leak and your rpm's will be very high when using the enrichener.

Check the floats, bench sync, and check for vacuum leaks.

[joecburris]

I did bench sync the carbs, I think the main problem is that I did not clean the carbs as well as I thought. I cleaned them again last night and it is running better this morning. Still very rough! Where should I start in this tuning process? I'm not a mechanic but I'm determined to get her running perfectly. Rpms are down to 2000, I think I can tune that in with patients?

[motoman]

I did bench sync the carbs, I think the main problem is that I did not clean the carbs as well as I thought. I cleaned them again last night and it is running better this morning. Still very rough! Where should I start in this tuning process? I'm not a mechanic but I'm determined to get her running perfectly. Rpms are down to 2000, I think I can tune that in with patients?

Did you use K&L float needles or replace mains and pilot jets with K&L's?.........if so, you'll chase your tail till beyond dizzy....just a 'head-up' warning.

[joecburris]

Yes! I used k&l float needles and k&l pilot needles! Why?
Is there something I don't know about this brand?

[motoman]

Yes! I used k&l float needles and k&l pilot needles! Why?
Is there something I don't know about this brand?

Yes....these and other 'off' brands don't use the same flow/sizing determination for said jetting sizes. Part of that has to do with patent rights.
If you still have the original GenuineMikuni jets(mains/pilots), use a toothpic to spin and clean the sideholes of pilot jets, compressed air blown from top-side(atomizing port) end of them. Removed the slides, bowls and main jet in order to remove the emulsion tubes(main jet holds emulsion tube in) and clean them the same way. Spray carb cleaner through all ports of carb body(eye protection needed). The K&L float needles will most likely cause a varience of RUNNING bowl fuel levels between all four carbs, even though static levels were set 'spot-on' all the same......Yea...I know......it sucks that the GenuineMikuni float needles come as whole kit, with the little fuel screen and all, and bout $45-$48 EACH kit. But 'it is what it is' if you expect that motor to run smooth as silk with ALL four cyls. doing EXACTLY the same 'work' through ALL rpm ranges.
At least use the original jets(if they are, they'll have the Mikuni 'curly' logo embossed in them, opposite the jet numbering on the Genuine Mikuni mains, and on side of pilots next to the sizing numbers(lighted magnifying glass needed for 'old age&treachery' eyes). Do that and report back the improvement that goes with the newly aquired grin.

[joecburris]

I have the original pilot jets and air jets. I will clean them along with the main nozzles (and anything else I see in there) and report back.....thanks so much, I would have never known where to even start looking!

[mack]

bench sync

Big thing here as stated is to bench sync the butterflies as has been said. The diameter of the material used is pretty important. I use lake trout fishing line (very thin) others use a stripped down bread tie, and some use the sixth string off a guitar. Start with the #3 carb and using the master idle knob, close the butterfly onto the material so that it is just touching, then sync the other butterflies to #3. That will get your motor started and it will be loping at about 800 rpm or a bit better depending on what material you used. Then you can adjust the rpm up to 1050 with the master idle and it will be good enough to start the true tuning process.

[alaskey2]

The sixth string on the guitar is the low E, pretty sure you mean the 1st string or the high e. It's counter-intuitive to count from the bottom up, but that's what someone decided.

[mack]

Ok

lets just say "the smallest guage" string then so there is no mistake. I still use lake trout line because I like to start my tuning at lower RPM's and it's even thinner than the guitar string.

[crazy steve]

Easy bench sync.... http://www.xs11.com/forum/showthread.php?t=36021

[joecburris]

Ok, finally found time to work on this. I cleaned the original pilot jets and put them back in (k&l jets out). I looked thru the posts about carb synchronization and i think i got that dialed in as best i can. Put everything back together and it runs much better. The only problem now is that it dies without choke ( enrichment ). This has to be related to pilot jet doesnt it? I havent played with idle screws yet...set at 2 1/2 turns out since carb cleaning. Runs fine with enrichment circuit open. What should i do?

[TopCatGr58]

Hey Joe,

You probably just need to turn UP the main idle screw a little bit to get it up to the ~1100 rpm range.

T.C.

[joecburris]

You were right! Turned up the main throttle screw and closed enrichment circuit. Dialed it down to 1100 rpms and I'm happy! Thanks for all the help.