Topic: Bigger K8 slow jets (SOLVED!!!)

[Buffo]

OK...I need bigger slow jets on my 1978 CB750K8.

Does anyone have any used pressed in slow jets they could sell me?

I also want to buy a set of the screw in slow jets. #38  I have never seen the screw in kind. Is the whole jet one piece or is it like the main where only the head gets changed?

I need jets

BTEAS

[Sam Green Racing]

Donald,

Stop messing obout, Go buy some CR specials and go man go.

[Buffo]

I may at some point. But right now I would like to see if I could make these work. I am only a hair off on the slow.

[Sam Green Racing]

Don't get your hair off with me and it's not my fault your a bit slow.   

[TwoTired]

While I haven't done it. It would seem like these could be made to work in your carbs.

http://www.rageperformance.com/carburetorparts.asp

Keihin Slow Jets
N424-22-XXX
Fits some PE Series Carbs

Or here:
http://www.rageperformance.com/carburetorparts.asp

Since your carbs weren't made to have the slow jets replaced, you may have to tap the positions to accept screw in types.  Once you find a type that has the same height as what you need, you can grind down a tap to rework the carb body so that it can accept a screw in type.

The only alternative I can imagine is to drill out your existing jets.  You may have to turn your I.M.S. back in, though.

If your current ones are #35 ( 0.35 millimeter = 0.0137795 inch)
Perhaps # 38  (0.38 millimeter = 0.0149606 inch)  About a #79 drill bit
Or #40 (0.40 millimeter = 0.015748 inch)  About a #78 Drill bit
The hardware store usually sells an xacto micro drill set w/stand that has these sizes.

Cheers,

[Buffo]

Well...I have talked to the carb guru at motorcyclecarbs.com.

The CRS carbs will not work on a 1978 CB750K8 easily. There are serious mounting issues and he knows people who bought them and are having a real hard time getting the jetting right.

On the bright side...he will drill my slows out for $5. a piece. ACCURATELY. I do not think I could do the job as well as him. It is what he does for a living.

I would like to get 2 more sets of slow jets. Have them drilled at different sizes and have one original set.

Please...anyone with spare slow jets...please...wont you help the children? 

BTEAS

[dusterdude]

don,since you are both egotistical and stupid,you could drop 500.00 on the twin mikuni setup and tell us how they work.yea,sorta like a guinea pig.yea thats the ticket.

[Cvillechopper]

I just went through the slow jet issue with my 78 750k and ended up getting lucky (in regards to the jets) at my local dealer.  Old school guy had an old plastic bin with a bunch of old jets in it.  There was a set a #38 screw-in type jets that were an exact match (length, emulsion tube, etc).  The best part was that they tapped themselves into the carb body with a light pressure while turning.  The owner of the shop said he thought they were from a 77 cb750, but couldn't remember for sure.  Don't know if this helps or shows my reluctance to do things the conventional/ right way....

[Buffo]

thanks 2tired...i have called that company and I am waiting for an answer.

the site said that part# N424-21XXX fits MOST PD carbs. Are the earlier 750 carbs "PD" as well, just another version or are they something else?

It would be nice it there was a simple solution.

I like how some folks on this site remind me of some of my family...
very willing to spend my money! 

BTEAS

[Buffo]

Well...Cville, You stumbled onto the correct coarse of action!!!

The fine folks at motorcyclecarbs.com started experimenting on a set of K8 carbs of thier own and came up with what Cvill did and 2tired recomended. Screw in slow jets of the #38.

Cville, He said that you/we are going to put a good dab ob locktite BLUE on the threads. He said that they (at least the ones he tried and is sending me) went in real nice, but he would be more comfortable if they were locktite BLUED. FYI

BTEAS

[Cvillechopper]

That's a great idea.  I didn't think about them backing out, but with all of the vibration I'm sure they need a bit of re-enforcement. 

[MRieck]

Well...I have talked to the carb guru at motorcyclecarbs.com.

The CRS carbs will not work on a 1978 CB750K8 easily. There are serious mounting issues and he knows people who bought them and are having a real hard time getting the jetting right.

On the bright side...he will drill my slows out for $5. a piece. ACCURATELY. I do not think I could do the job as well as him. It is what he does for a living.

I would like to get 2 more sets of slow jets. Have them drilled at different sizes and have one original set.

Please...anyone with spare slow jets...please...wont you help the children? 

BTEAS

The problem with the CR's and the F2/F3 and later K's is the larger ID of the carb insulator(or more commenly known as the "boot"). DOHC adaptors for the CR's are supposed to work on these bikes. Jetting is always a problem if the person doing it doesn't know exactly what they are doing.

[dusterdude]

so don,does this mean you`re not gonna try the mikunis?damnit jim.

[bhkrause]

Well...Cville, You stumbled onto the correct coarse of action!!!

The fine folks at motorcyclecarbs.com started experimenting on a set of K8 carbs of thier own and came up with what Cvill did and 2tired recomended. Screw in slow jets of the #38.

Cville, He said that you/we are going to put a good dab ob locktite BLUE on the threads. He said that they (at least the ones he tried and is sending me) went in real nice, but he would be more comfortable if they were locktite BLUED. FYI

BTEAS

Holy Shmokes!!!  This is too good not to put in the FAQS or Technical library.  Somebody get details of this and post it permanently for all F-heads to see, it's been a trouble spot for a long time!!!!!!!

[Buffo]

when I get the jets in I will post the part numbers for all to use.

BTEAS

[eurban]

Buffo did you ever post the results of your experience with installing screw in type slow jets?  Would like to know how well this ended up working out and the exact parts that you used.  Thanks