Carb Rejetting on '81 CB750c

[ezridermn]

Hi Gang,

I am going to rejet the carbs on my 1981 Honda CB750c. I am running an aftermarket Mac 4 into 1 exhaust and 4 K&N pod filters. I found a Dynojet kit that provides the parts to do what they call a stage three jetting which is said to be for my type of setup.

First question is has anyone rejetted their carbs with this kit? If so how does it run now? Also, where do you live, as you know altitude plays into fuel mixtures? I live in the Minneapolis area which is about 500 ft. above sea level.

Also, I would like any advice you might have regarding doing the actual work on the carbs. The directions raise a couple of questions. They have you drill out your slide lift holes. What does that accomplish and is there any risk to ruining the carbs doing it?

The other area which I am a bit more concerned about is the fuel mixture plug/screw. I will detail what the directions say and then ask my questions.

"Locate the fuel mixture plug. If you see a screw head then proceed to the adjusting procedure. With the 5/32 drill bit provided carefully drill through the plug. Note: The mixture screw is directly underneath this plug, be ready to pull back on the drill the instant you break through. Use the screw provided to secure and remove the plug. Carefully turn the mixture screw clockwise until lightly seated, then back out 3.5 turns."
OK questions. If there is a screw head is all I have to do is seat it and then back out 3.5 turns and I am good to go? If not do I take the screw out and then drill? If there is just a plug head how do I identify where it is? I am confused by the statement to use the screw provided to secure and remove the plug. If you drilled it out then why would use a screw to get it out? Also, the kit doesn't seem to contain a screw for this use.

I have attached a PDF of the installation instructions to this post.

Here is a link to the item on the Dennis Kirk website:
https://www.denniskirk.com/dynojet/stage-1-and-3-jet-kit.p171842.prd/171692.sku

If anyone can help me better understand this issue before I go after the carbs I would really appreciate it!

 

[DesmoBro]

Not sure if you have messed around with it yet....I am currently messing around with Jet Sizes, And i think with smaller needles and a bigger hole (the drilled hole) you end up with More Gas in the mixture which is what you'll want. I havn't bought the Jet kit yet but it seems like the Way to go. I upgraded just the Main Jets and havn't noticed any difference while driving ( still runs like crap) So i'm about to drop the $100 on a Jet kit

 

[crazypj]

EPA mandate means you have 'tamper proof plugs' on fuel mixture screws.
You drill a small hole so you can get plugs out without damaging carb body
Do you have a service manual?
It's standard procedure and shown 'in the book'
Don't know whats in the kit but the Honda 3 jet carbs are real difficult to get right, stage 3 is semi-race, you may find it doesn't actually work too well on the street at part throttle?
Just checked link, did you read this
'Expect a power increase of 10-15 percent, short stroke high RPM motors are susceptible to compromised driveability as a result'
To be quite honest, there are not enough parts to make carbs work properly
PJ