Carb Questions, Nothing Unusual

[Aaron]

Heya fellas, need some help again. Up until the last week or so the bike (80 SG stock) was starting easily and running fine. Except, acceleration was smooth and easy up to 5500 rpm. Then it acted like it was overloaded, maybe not getting enough fuel, cranky about running that speed. Even being limited to 5500, i could easily keep up with and pass traffic on the highway. But my top speed was only ~75 in fifth. "Easy!" I though. "I'll just get a rebuild kit from ol' georgefix and clean the crap out of em, put in new stock everything and sync em up." So i did all of the rebuilding to rediculous meticulous standards and put em on the bike. Then i built a vacuum gauge using a darn close copy of the method found in tech tips. All going well, but i can't start the bike to tune it. I pulled the plugs and they are all black. They aren't particularly sooty and they are dry, but definately black. Im not sure how long its been running rich though as i haven't checked them any time recently. Id like to see a pic of the stock pilot jet for an 80SG if anyone has one. I cant seem to remember what number was on the ones i put in were, but i know what they looked like. George seemed to send me a bunch of stuff i didnt need. The needles were for a 78-79 and he sent me four 125 mains, four 120 mains, and only two 110s. I just wanna be certain i put the right stuff in there. Since i only have two 110s, i put them on the outside and put two of the mains i pulled out back in. They looked like 112.5s? The holes looked in decent enough condition, and they weren't much larger than stock so i figured they'd be fine for awhile. The original needles were in great condition, so i reused those. There were no new air jets. My diaphrams are in great condition. The pilot jets i pulled out are marked 60 and have no holes in the side. The ones i replaced them with had holes, but i dont recall the size. Anyway, if that doesn't explain the situation, ask away. Thanks for the help guys.

[motoman]

If all else stock(airbox, exhaust) 110's all across IS stock for 80 and 81 Specials, and IS what should be run IF all else is stock. Main jetting is FIRST to do so it pulls hard, smooth and equally quick up to redline. This will get U started, only if intake and exhaust are stock. Just an FYI, the staggered jetting was done on the Venturer(81) model only, but the Standard also uses different metering rods than the Special did for 80-81 models. The XJ(Maxim) had even different metering rods and main jetting was and is 112.5 mains all across. Also, your main jets and pilot jets should show the Mikuni logo in order to be Genuine Mikuni, as this can give U tuning fits if not........BTDT!

[BA80]

Check the PICKUP COIL WIRES.

[skids]

Your pilot jets should be of the air-bleed variety. Stocker had six holes in the sides. No 60 pilots seem awfully big (42.5 Mic's were stock). Normally, at high rpms, the pilots have less influence, but if they are way too big, maybe they do. There is a nice comparison of emulsion tubes and pilot jets if you do a search. You will see that there are some significant differences with the pilot jet types...

Emulsion tubes are pretty durable and generally can just be cleaned. The big, round main jets are what I go with, although I was told that the smallers diameter ones are compatible as well.

[skids]

PS, you didn't set your float levels too high did you?

[Aaron]

I did not change my float height since it was running as well as it was before i rebuilt the carbs. I fear i may have to check them. It seem as though i do have all stock insides in the carbs now other than those two 112.5 mains. My emulsion tubes are clean as a new whistle. I stripped everything down to individual components and ran em through the part washer at work.

[DGXSER]

First, do you have stock exhaust and stock air box?? Those are critical to properly jetting the carbs.

Stock jetting for the 80 model year was 120 across the board mains with 42.5 pilot jets. Also check your pilot air jets (in the inlet bell of the carb at the 8 o'clock position). Should be 180 or 185s.

Where did you set your mixtures screws? about 2 turns out is a good starting point, maybe 1-1/2.

Did you disassmeble the slides, pull the needles out of the slides? If you did, are you certain you got them put back in the right order? First time through my 81 carbs on Thunderstruck, (my first SH, departed friend), I misassembled the needle valve in one slide, that carb would foul out at the stop light with the mixture screw all but seated. It took me two months or so to figure that one out. The spring holds the needle down when properly assembled, I had the spring in first, lifting the needle, which effectively kicked in the main jet at idle.

[Aaron]

It's all stock other than color and tires. I've been in these carbs a few times before and have become quite comfortable digging around in them. Especially after all the reading up on em i've done on this site. 80 should be 110' across the board, not 120's. Im not sure where the adjustment screws are at after all the trying to sync i did today. Im gonna reset everything back to zero tomorrow and give it another shot. The needles are operating quite smoothly and seem to seat as they should. I just cant get it to start. Any other suggestions?

[DGXSER]

Make sure your turning the right screw for idle versus synching. The way you stated your not sure where the mixture screws are after all the synching made it sound like your trying to synch by changing the mixture screw. There is a separate screw lower, between the carb bodies, at the throttle shafts for synching.

[Aaron]

Yeah, i meant idle mix screw. Sorry. Anyways, im thinking they may still be set for those larger pilots and mains that were in there. It seemed as if a p.o put maxim stuff in these special carbs. Or maybe i just de-jetted som maxim carbs without knoing it...

[natemoen]

The XJ has a cable operate choke, so of had the standard rod and lever for the choke they were XS carbs (unless someone in the past changed it over.)

[Aaron]

Oh really? The choke on my carbs is/was cable operated. There is no cable so i just have to reach down and yank on it by hand though. What were the stock pilot jets in the XJ carbs?

[DGXSER]

Pilot jets for the 79 through 82 were 42.5. Also have 6 holes in the sides of the jet.

[Aaron]

I wonder what the heck was up with those #60 non-air bleed pilots i pulled out then. Any other differences between the XJ carbs and SG carbs besides choke and main jet sizes?

[bikerphil]

The stock pilot jet sizes for the XJ are 47.5, they are 42.5 for all year XS carbs except for the 78 which used 45's.