what size factory jets for rejetting?

Hiya. So I need to rejet my 83 vf750f but the dynojet kit is $100+ and requires drilling. I'm looking for a cheaper alternative to smooth out acceleration until I decide on a more permanent solution. I know I can go pick up jets at a dealer, but my question is what sizes should I get, or how many should I go up from what I have now (stock)? From the collector back the exhaust has been opened up with 2" of pipe roughly the length of the stock slipons with baffles inserted in the chrome tips. The airbox has also been completely removed and single pod filters attached to each carb. Now, with this done, how many size should I go up with what jets? Should I shim the needles and if so how much and with what exactly? I need as much help as possible that is as specific as possible so that I don't make a silly mistake. I guarantee I will fall in love with whomever helps me out. Thanks a million. :smile:

 

Any ideas? The lean condition is not helping my bike to run cooler so I would like to try and put new jets in soon. Running a little rich wouldnt be too terrible but I was thinking of going up maybe 2 sizes on the jets? I suppose I'll give it a shot with 2 sizes up on each if I don't hear a better idea soon. I want to try and get it right for the most part on the first try as taking everything off is such a pain. Thanks in advance.

 

It's a bit of a crap shoot doing it this way with home made exhaust and such. You're going about it the right way, but be prepared for a lot of assembly and disassembly and back again.
No love needed though, thanks-

 

"I want to try and get it right for the most part on the first try as taking everything off is such a pain."

Good luck with that. Most carb work requires several tries to get it right that I have found. I have a Stage 1 Dyno Jet kit in my bike. I put it in years ago. So memory is lost to what I did. But I still have the instructions and original jets/needles. The original jets are marked 128. The kit jets are marked 122. The kit needles are smaller in diameter than stock and parts list shows a 110 vs stock which is marked 1HB. By how much I don't know. They had to be quite a bit thinner in order to get a richer A/F ratio. I do know the kit also has .020 thick washers in case the needles needed to be raised. They note that the washers are 1/2 step thickness (.020) and you should start with a full step (2 washers under each needle. Then go to 1/2 step for mileage. They also supplied a 7/64 drill bit to enlarge the slide lift holes. Don't remember if I drilled them or not. Holes are for faster slide action. The instructions state for individual air filters to use stage 3 kit. Don't know what's in a stage 3 kit. But either kit will work with slip on's. The reason for the stage 1 kit is I went with a K&N filter and it ran lean. Now that I've muddied up the waters, I would try to raise the needles by .040 first and see what happens. Then drill out the jets by .001 or .002 Depending if the motor feels lean or real lean. If it get to rich then drop the needles by .020. This of coarse is a SWAG (scientific wild ass guess). Good luck and let us know what you finally come up with.

 

no one can answer this as it can only be determined by experimental means, that is, test and repeat, test and repeat.
you will need to look at you sparkplug color many times to determine mixture strength.

start going up in main jet size until you just begin to trail off on power, meaning that you're finally running too rich; then go back one size.
open up mixture screws 1/2 to 1 turn

never mind the needles until you have found the best main jets FIRST.

 

Excellent. I feel like these are reasonable ideas. I know it is silly to think I could get it right the first time but what I want is to get the rough starting point right. What I mean by that is that staying with stock is not helping, so it must be larger than stock but smaller than say 10 jets up? I figured two jets up is a good starting point and I'll work from there. Should I try another starting point?

Oh, and when I do change the jet sizes, which jets do I change? I feel retarded for not remembering but I think there are two or maybe three jets in the carb? Would I change just the main jet or the other(s) as well? If I did change them, would I go up the same number of steps for each or stagger them in some way? Again, a rough idea is what I'm looking for as I'm not expecting you to know my bike from my vague description.

I went to the closest Honda dealership today and I was told that the jets cost about $13 each. Christ, going with the dynojet kit would be a much cheaper, more reliable alternative if they're that expensive. I think the lady was retarded as jets shouldnt be more than a couple bucks but dealerships do have a way of sucking every last penny out of you. I also talked with the snobbiest douchebag tech whose only advice was to put my bike back to stock or sell it for scrap. He believes that messing with a Honda is "a sin against humanity." I don't understand people that arent interested in shaping the world around them to fit their needs, with only one life to live, customization makes it worthwhile. Ah, but I digress.

Anyway, I will call another dealer and find out if the jets are really such a silly price but just in case, where can I find jets that I might choose by size easily enough to fit my needs?

Oh, and if you havent noticed, this has been one of my first posts here on the site as I have been a member for a very limited amount of time but plan on staying around for a while. I just want to say thanks to everyone who has been kind enough to help a brutha out. If anyone is even the slightest bit interested I'll try to get some pics up so that you can have a better understanding of the mess I got myself into by not leaving well enough alone. Thanks again.