Another carb thread

[DavesXS]

I have read all I can. I have them synced up just fine. All 4 are the same.

From 2k and up it is great. Idle and throttling off idle sounds boggy. It does not spit or back fire.
I started with new 45 pilots. Had to set screws to 3 full turns out to sound decent. I been told no need for anything bigger than 42.5's in an 80xs. So I installed new 42.5's Still have to back the idle screws out 3 turns to sound decent.

It sounds like vacuum leak but when I spray starter fluid at the boots theres no change in engine idle. And a vacuum leak causes it to spit from lean condition.
Could it be I need to keep backing the idle screws out? Or is there something else to check?

Before I changed the pilots it idled and ran fine. It had the origonal 42.5's All it has now is new 42.5's Float level has not changed, carbs are clean.

I will get colortune but out of cash for now. But guys been tuning carbs for decades with out colortune so I should be able to get it "good enough" right?

Sounds boggy at idle, and when I first start to roll on the gas it sounds and feels boggy while engaging clutch, but once it gets off idle, and above 2k it will run away from ya, maybe even toting the front tire at WOT.


Dave

[DavesXS]

The originals 42.5's, idle screws were backed out 3.5 to 4 turns. But I figured it was from half clogged pilots, and in need of bigger pilots. Then I put the 45's in wich should need much less backing out of the idle screws as apposed to half clogged 42.5's right? And new 42.5's shouldn't need to be backed out as much as the old would they?

Maybe I have put too much thought into this. I dunno

[psycoreefer]

What have you done to the rest of the bike? individual filters? after market exhaust?

I've got a bad spot in the same range and going up one size on my mains helped, I suspect that is the range where the bike should be running on pilots and just coming on the needles. I plan to try raising the needles next time I have the carbs off so I guess I would suggest that.

[DavesXS]

Originally posted by psycoreefer
What have you done to the rest of the bike? individual filters? after market exhaust?

I've got a bad spot in the same range and going up one size on my mains helped, I suspect that is the range where the bike should be running on pilots and just coming on the needles. I plan to try raising the needles next time I have the carbs off so I guess I would suggest that.

k&n replicas, and 4-1 headers.
I have 117.5 mains, upped from 110's. But its my understanding they kick in at 3k. And pilots take it to 3k. Maybe transition from 2k-3k, and thats why it feels strong 2k and up? I got some 127.5 mains I am going to try once I get the idle corrected. I think needles are top end.

[DavesXS]

I might have answered my own question above.

If there is a transition taking place some where between 2-3k. That means from 2k to 3k the fuel is being increased from one jet to the other. And when it does it gets better. Suggesting that the first jet isn't feeding the fuel it needs to be great down low and idle.(still seems like a possible vacuum leak and extra air is getting in some how) But the bigger pilots would have helped that I'd have thought.

[John]

Have you ensured that the three small orifices in the top of the carb throat, right above where the top of the butterflies make contact, are clean, and not distorted? Those are also in the pilot circuit and they supply the fuel when the throttle is opened. The pilot screws only control the idle, and assist with fuel supply under 3000rpm.

[tarzan]

I have an 80 also,this is my second one.I have k&n filter and stock exhaust.It runs great with 110's and 42.5's.My old bike also ran the same jets and it had a k&n air filter and a kerker 4 into 1
exhaust.It ran good also.It was a little lean but with the idle airs out I think about 2 1/5 turns.
I know a lot of people suggest bigger jets and get theirs to work.You might consider going down a little on your mains,maybe 112.5 or 115's.It sounds to me you might be a little fat not lean.
Obviousy I could be wrong but usually when its soggy on the bottom end like you describe I have found alot of times I'm running rich.Just my .02

[DavesXS]

Originally posted by John
Have you ensured that the three small orifices in the top of the carb throat, right above where the top of the butterflies make contact, are clean, and not distorted? Those are also in the pilot circuit and they supply the fuel when the throttle is opened. The pilot screws only control the idle, and assist with fuel supply under 3000rpm.

I'll check that. Thats the kind of info does me good. If there half clogged, could explain why the 2 different sizes adjust out the same turns. If the openings only allow so much to pass.

I just figured out how to get the video clips off this camera so I'll post a sound clip of it tomorrow. Hopefully some one will recognize the way it sounds.
Thanks

[Mashermoto]

Dave,

Go here to find a place to start with your jetting:

http://www.xs11.com/forum/showthread...=&threadid=382

When you set your mixture screws, don't rely on the tach to find your maximum RPM. It just isn't accurate enough...neither are your ears Instead, get an electronic RPM reader that you can clip on the number one coil. They are cheap to buy so no excuses It also doen't really matter if you find one for other than a four cylinder engine...you just want something to more accurately indicate the change in RPM. Then start with each screw about 1.5 to 2 turns out from a soft seat. Then, working from one cylinder, turn the mixture screw .25 turn until you reach maximum RPM. Wait about 15 seconds between each .25 turn. Then move to the next cylinder and repeat.

That should get you closer than you are now.

[Axel]

colortune

IIRC , Colortune has been around for decades ... Definately takes the guesswork out of pilot settings

[DavesXS]

I took out the pilots, cleaned pilot circuit and put back the 45's.

Runs better from the start. I took carb cleaner and spritzed it at the filters. #'s 1,2 bogged like they should. But 3,4 idled up. So I started tweeking the idle mixture on 3,4 richer. Now they almost bog when spritzed. 1,2 are 3 turns out. 3,4 are as much as 4-4.5 turns out.
Why is 4,5 sucking more air? Maybe the sync?
I'm getting it figured out though.

Here is a sound clip. Not sure if you can tell now because its 10x better than last night. But when I initially hammer the throttle about 1/4 turn off an idle it has a slight hesitation. The rpms should jet straight up with no hesitation.
Excuse the exhause leak, I guess I got a header flange not seated.

http://www.youtube.com/watch?v=-k3Hb8P31ZA

[DavesXS]

I just finished tweeking 3,4

I tuned them richer untill they bogged exactly the same as 1,2 when spritzed with cleaner.

Now it idles like a champ, and no more hesitation. I'll check the sync again now.(actually after I go do these 2 jobs at noon)

Funny thing too. The "exhaust leak" or what ever it was is gone now I got 3,4 set good. Weired huh?

I'll post another clip this evening. And I'll get one taking off down the road to get a good exhaust sound demo.

[dbeardslee]

Dave - sounds like you got it licked but I'll mention this anyway. There's a post on here somewhere that describes soft and boggy on the bottom as a symptom of float height being too high.

[81xsproject]

The only reasons I see for needing that different of setting on synched carbs is an intake leak. Your possible culprits are boots, boot sync caps, idle mixture o-rings, or butterfly seals. An unlit propane torch (on but not blasting) is a good way to test different target areas. But I would dial them all back to the same turns out to do it.

[81xsproject]

I just PMed you