No more updates! Riding is sweet!

[Anonymous]

So with Tim and Cyber's advice, I finally got the mixture right on the carbs...a little above 3 turns out. It has good throttle response, with no hang (although still a little slow on the decline), nor idle drop below the set idle, as seen in rich mixtures.

So I deem the mixutre good. Next, carb syncing.

#1 & #2 sync together exactly just great. #3 is pretty near where #1 & #2 are.

Here's the problem: #4 (the one with the vacuum line) still has significantly less pull than the rest....and all the seals (tested with WD-40) seem fine...I mean, I wouldn't be getting good throttle response if I had no vacuum, right?

So here's what I think it could be...

1. vaccum leak, maybe not at the airbox-carb or carb-engine seals, but somewhere else?
2. something wrong with Cylinder 4, or the #4 carb?


Here might be an important peice of imformation: When turning the air/fuel mixture screws down to start over, carb #4's screws seats differently than the rest (aka, it's flat head screw is facing another direction when fully seated)

1993 Kat 600 w/ stock setup.

[UFO8MyCow]

can you get 3 & 4 to level out by adjusting the screw?

[Black_peter]

That's interesting cause after rebuilting my carbs #4 was wayyyyyy higher then the rest..
You cant get it to trim in?

Are you sure you have all the parts to the FA mix?
screw, washer, o-ring??
My o-ring actually got pushed into the passage once. Also the o-rings could get mashed up from previous monkeys...
(not to imply you are a monkey! )

[The CyberPoet]

It could be something as simple as differences in valve clearances (remember to sync with the engine hot), different jet sizing, blocked passage (how much fuel it pulls into the cylinder changes the burn which in turn changes the vacuum level when the intake valve reopens). Or it could be that the carb really is that far off -- or that the sync plate (between the carbs) isn't sitting in the right place because it got relocated during reassembly if the carb stack was apart.

That last reason bit me once on someone else's bike, and it took quite some time to figure it out... turned our that the plate the sync screw hits was in the center of the little spring instead of at one end of it.

Cheers,
=-= The CyberPoet

[Anonymous]

Is it possible to unscrew the Air/Fuel mixture screw of #4 four all the way out to see what's up?

[The CyberPoet]

Is it possible to unscrew the Air/Fuel mixture screw of #4 four all the way out to see what's up?

Yes, it can be removed simply by unscrewing. This will let you check the O-rings for the pilot screw very readily.

Cheers
=-= The CyberPoet

[md86]

Hey , if you're REALLY worried something's messed up with that cylinder , get a compression tester and check it out . If THAT'S good , then worry about the "little" things , cause THAT would be the biggest thing to worry about , IMHO . You can borrow mine if you wanna pay shipping ... Of course they aren't very expensive , and someone in your area may let you borrow one .

[stevnmd]

I don't mean to ask a stupid question or anything, but you did block off that vacuum line while doing the carb sync, right? If you didn't, that's your problem. You need to plug it or pinch it off. More than likely, I'm thinking that's your problem!

Or, am I just not recalling how to do a carb sync on a Katana? There is a normally blocked off vacuum port on carb 4 in addition to the vacuum line running to the petcock, no? I can't recall.

[stevnmd]

Yeah, I just looked at my old Kat pictures. Definitely a normally blocked off port to connect your gauges to on each carb. So, again, you did pinch off the vacuum line, right?

[md86]

I don't know about you guys , but when I did MY synch , I didn't block off that line . That was because I never really took the tank all the way off ! I just moved it to a nearby (REALLY nearby) table to eliminate the need for an aux tank which we didn't have . Just throwing out one possible explanation ...

[stevnmd]

Okay, so you had the line run to the petcock still which effectively blocked it off...

So, we still need to find out if that line was running to the petcock or just left hanging open. Still sounds like the most logical reason for poor vacuum at carb 4. Depending on HOW significantly the vacuum level was low, I can't help but think the bike would run (especially idle) like total shiat and the carbs would possibly be starved for fuel.

[md86]

Oh yeah , "something wrong" with the number 4 carb like how ? There ain't much as far as I know that would cause a drastic vacumme difference that you haven't already investigated . Steve's idear about the vacumme line was a pretty good place to start though , it sounds like ! If there are no leaks , I can't see what would be in the carbs that would cause it to read that funny . But valves or cyclinders could ...

[Black_peter]

I don't mean to ask a stupid question or anything, but you did block off that vacuum line while doing the carb sync, right? If you didn't, that's your problem. You need to plug it or pinch it off. More than likely, I'm thinking that's your problem!

Or, am I just not recalling how to do a carb sync on a Katana? There is a normally blocked off vacuum port on carb 4 in addition to the vacuum line running to the petcock, no? I can't recall.

That is what had me going!! (if it wern't for KR I would have messed it up!!!)
That line has to be pinched off other wise the vacuum leak is too high to overcome. I was getting fooled because when I did pinch the line, #4 went up to double the 123 levels.. I thought surely it couldn't be that far off but it was!....

[The CyberPoet]

On other idea:

Swap lines between carbs 3 & 4 -- the gauge may be off.

I just put a one gallon fuel can on a tall platform and run spare fuel line to the carbs to feed fuel. All four vacuum ports are blocked at the same time by the sync tool (at least on mine -- 4-way sync tool), so vacuum loss isn't the issue.

Cheers
=-= The CyberPoet

[stevnmd]

Yeah, sure... The mercury may be different for #4... Whatever...