Carb adjusting 78 xs11. Pods, 4into1. HELP.

[Diskman01]

Here goes...

Purchased my 78 XS11 in March of this year (2011). Ran OK but had some issues. Fixed the bad electrical gremlins and started working on the "too lean" condition at speed and the gaspy low end. Spark plugs were extremely lean.

Decided to re-jet due to the pods and 4 into 1 that a PO installed. I went up from 137.50 mains to 147.50. Still seemed weak all around so I bought some 152s for the mains. Still running lean on the top end. Low end was better though.

Pulled the diaphragms and found that the main needles were all set 1 notch LEAN. Made for a bi** to tune. Went BACK to the 147.50 jets. lol

I adjusted the floats that the PO adjusted from about 80MM down to 25MM from the gasket surface. Now the low end is terrible and a low end and very black plugs. Very very black plugs. Engine loads up and will die cruising at 30-40MPH.

Now what? I hate to adjust the floats to the rediculous height again but that seemed to run the best. The little "tang" was bent at least 45 degrees down.

Whats everyone running their floats at? Obviously 25MM on my 78 is waaaay too rich.

Ideas? Do the idle screws on the tops if the carbs make a difference on the low end rich at all? Or just idle speed?

Should I mess with the screws some more or pull the carbs and re-adjust the floats way leaner?

[Rasputin]

Put your needles back to the center position. Drop you mains back to stock. Up your Pilot jets one size from stock. Start with 2 turns out on the mixture screws. be sure to synch and colortune or do it by ear then recheck your synch. You are way too rich from my experience with these.

[DGXSER]

You have so many things tweaked it is hard to figure what is what if you ask me. Like Ras stated, set it all back to the basic beginning point. Stock jetting (or one up on pilots as Ras suggested) middle needle position, stock mains, set mixture screws to 1-1/2 or 2 turns from LIGHTLY seated.

Try that and see what you get.

[TopCatGr58]

Hey Diskman,

What TYPE/brand of PODS?? There are the EMGO cheap ones that have a prominent LIP on the inside mounting edge that can interfere with the air flow thru the inlet bell ports and can artificially richen things up!

Also, the 78 should have SCREWS that cap off the Pilot jet tower inside the float bowl, but wanted to make sure yours has them installed. If they are not there, that too would cause excessive richness because the pilot jets are supposed to be fed by the little tunnel between the MAIN tower and pilot tower, and NOT directly from the BOWL!

Also, you've got the UPPER "T" fittings connected to free flowing VENTS/tubes. They can not be connected to each other without being "T'd" to a vent source, otherwise the carbs will flood. The lower "T"s are the fuel inlets.

Finally, your carbs ARE 78 series aren't they, with the 2 sets of inlet "T"s, and also only 3 ports along with the arced slide port, and the pilot jet/Idle SCREW should be large and accessible on the front outside of the carb body. IF it only has 1 set of "T"s down low for fuel, and 4 round ports on the inlet bell, and the pilot jet screw is down inside the body, then they are the later series.

You said it had 137.5 mains, so we're assuming they are the 78 series, but stranger things have happened with PO's!?
T.C.

[tw1980]

These things can drive you crazy.I know you don't want to hear this but I would recommend pulling each carb.THOROUGHLY clean.By soaking in carb cleaner and blowing out ALL ports.Be sure to check all the holes in the emulsion valves.Put everything back to stock then resync and start over.Make small adjustments at a time.Start with main jet.When you get that right and only after you get it right then set the needle jets.Then you can set the pilot screws.I think if you follow that procedure you'll get it right much quicker.Good luck. Terry

[brcree]

Pods

I agree with all....ditch the pods...and go back to stock! Your bike wont run any faster with the pods for the hassle you will have to go through to make them work. The engineers put allot of time into making these things run well...unless you have great expertise with carbs....pods are a crap shoot!

[Diskman01]

Yep. They are the cheap pods that the PO installed. I did the rubber extension a while ago so they are NOT interfering with the carb inlet holes.

Regular 78 SX11. The carbs have the screw adjusters located next to the intake boots on the head. All are OK.

I already put the needles BACK to stock (middle clip) last week. That's when I pulled my 150 Main jets and dropped back to 147.5. 147.5 seem great for my top end.

The carbs are close to stock now. THAT'S what's frustrating. Put them back to stock a few days ago and Im getting really rich at 30-40MPH now.

Needle at middle setting, 147.5 jets (works at speed), original pilots, floats at 25MM.

Would the low speed screws have anything to to with this or are they only effect idle?

Should I adjust the floats leaner? They are at 25 now. Would 23MM make a difference possibly?

Carbs have been removed 4 times and completely cleaned. Trust me. They are clear and clean. Freshly cleaned tank, new filters and fresh gas.

I have an aitbox, but installation is impossible with the hardened boots. Should be able to get the pods to play nice.

[Diskman01]

Hey Diskman,


Also, you've got the UPPER "T" fittings connected to free flowing VENTS/tubes. They can not be connected to each other without being "T'd" to a vent source, otherwise the carbs will flood. The lower "T"s are the fuel inlets.

Finally, your carbs ARE 78 series aren't they, with the 2 sets of inlet "T"s, and also only 3 ports along with the arced slide port, and the pilot jet/Idle SCREW should be large and accessible on the front outside of the carb body. IF it only has 1 set of "T"s down low for fuel, and 4 round ports on the inlet bell, and the pilot jet screw is down inside the body, then they are the later series.

You said it had 137.5 mains, so we're assuming they are the 78 series, but stranger things have happened with PO's!?
T.C.

I have the vents hooked to 2 tubes that go up under the seat a bit. Yeah, the original mains were 137.5 but a tad too lean on the top end so I installed 147.5s. They seem to work at top end so I will stick with 147.5s.

Yep, I have the jet/idle screws. Will those make it run really rich at 30-40MPH if they are out too far or do I need to fiddle with the floats? The floats are at 25MM now..

[natemoen]

I cant see how it would even be possible to get the floats to 80mm! How are you measuring the floats? Should be measured with the carbs upside down with the gasket removed measuring to the highest part of the float body. Set them to 25.7 +/- 1mm (the closer the better though). When measuring this way going with a lower number richens the mix and going with a higher number leans the mix. most people that play with the float levels usually end up going back to the stock level eventually anyways so just set it at the 25.7 and leave it.

147.5 is huge in comparison to stock and I think it is way too big for your setup. Go back to stock with the proper float height and the needle set to the center notch and start over.

[Diskman01]

I cant see how it would even be possible to get the floats to 80mm! How are you measuring the floats? Should be measured with the carbs upside down with the gasket removed measuring to the highest part of the float body. Set them to 25.7 +/- 1mm (the closer the better though). When measuring this way going with a lower number richens the mix and going with a higher number leans the mix. most people that play with the float levels usually end up going back to the stock level eventually anyways so just set it at the 25.7 and leave it.

147.5 is huge in comparison to stock and I think it is way too big for your setup. Go back to stock with the proper float height and the needle set to the center notch and start over.

I made an "L" out of some scrap aluminum that's 25MM from on the inside and measured from the gasket surface (removed) to the highest point of the float upsidedown. I can guarantee that I am at 25MM.

Will toss the original 137.5s in this afternoon and see. I originally used the jet calculator on here somewhere. 4 into 1 and PODS. At the time I didnt know the needles were set lean too. lol.

[cywelchjr]

I didn't catch it in there. Do you have the screws covering the low speed jets inside the carb bowls? They screw in over the low speed jets in the early carbs and if they are missing they WILL make the carbs VERY rich in the mid range as it makes the main venturi just sucks fuel directly from the bowl instead of through a jet, this really screws up the mixture as the mains try to come into play as they are being bypassed. This screw is of critical importance, it's supposed to make fuel going to the low speed jet go through the main jet, but without that screw, the low speed jet is fine, but the venturi gets unmetered fuel that didn't go through any jet at all, just through that cross passage. DAMHIK. It's not a pretty running bike if this happens, and you CANNOT tune around it, it MUST be plugged with the screw on the early carbs and the rubber plug for the early 80 hybrid carbs.

[Diskman01]

Ok, after putting the mains back to 137.5, the floats double checked to 25MM it seems to run great on the interstate. In town at 35MPH, it will load up with fuel and die. PLug foul up badly.

Ideas? Float levels? Run them less than 25MM?

[DGXSER]

What pilot jets are you running? Do you have the pilot jet cover screws in place as Cy mentioned? What position are your needle jets at?

[cywelchjr]

And where are your idle mixture screws set to? Those set the idle mixture not the idle speed. It sounds like you need to do a proper carb sync, part of which is a proper idle mixture adjustment as it sounds like the idle mixture is off, maybe way off, which affects the low to mid range throttle settings.

[natemoen]

What kind of rpms are you at when have this happen?