Rejetting issues with KZ750B3

I have a completely stock KZ750B3 (twin) and I am putting a Macs 2-1 exhaust on and replacing the air filters with K&N slip-ons (Ithink that is what those individual filters are called??) So I was wondering If I could use the stock jetting or If I need to rejet? Could I just set the needle that is in the CV up higher possibly?? I ride at around 1000 feet above sea level and it rarely changes much. Also How do i go about rejetting?? I've never done it before and any tips would be much appreciated.

Does the B3 have the small main jet carried in the float bowl? If so, I would reconsider my plan to stick those pod air filters on the bike since the little main jets are not available in larger sizes that I know of. The bike will not run very well at the top of the rpm range without new and larger main jets. Your messing with the jet needle won't be of much help in this situation. You might explore drilling the small mains but if you hose them up, replacements are not readily available.

Does the B3 have the small main jet carried in the float bowl? If so, I would reconsider my plan to stick those pod air filters on the bike since the little main jets are not available in larger sizes that I know of. The bike will not run very well at the top of the rpm range without new and larger main jets. Your messing with the jet needle won't be of much help in this situation. You might explore drilling the small mains but if you hose them up, replacements are not readily available.

Becker wrote:

I have a completely stock KZ750B3 (twin) and I am putting a Macs 2-1 exhaust on and replacing the air filters with K&N slip-ons (Ithink that is what those individual filters are called??) So I was wondering If I could use the stock jetting or If I need to rejet? Could I just set the needle that is in the CV up higher possibly?? I ride at around 1000 feet above sea level and it rarely changes much. Also How do i go about rejetting?? I've never done it before and any tips would be much appreciated.

If you keep the stock airbox I can tell you EXACTLY how to jet those headers.... I put a set of Mac 2-1 on my KZ750B4. Mine has the Mikuni BS38 carbs. If yours does also, then here is the right setup:

Main jet: stock 125

Pilot Jets: go UP to #50

Needles: go to maximum rich setting (move clip to bottom slot)

I screwed with mine for a long time to get them peaked up.

If you put on air pods I have no idea how to make it run right. It probably never will run exactly right again, but they will certainly make it run leaner.

wiredgeorge wrote:

Does the B3 have the small main jet carried in the float bowl? If so, I would reconsider my plan to stick those pod air filters on the bike since the little main jets are not available in larger sizes that I know of.

True. Those jets are not available ANYWHERE. I found the "Keystar" or "Keyster" brand rebuild kits came with the correct stock main jets. I bought a set of those kits just to get the jets.

You can get the Jets from England , I have a friend that lives there and sent them to me ,, You might look online to see if you can find them in the UK ,, ,, with pods it is a 150 main and I think the 50 pilot ,, You might try the drill out method ,, just go slow .

Shoe48 wrote:

You can get the Jets from England , I have a friend that lives there and sent them to me ,, You might look online to see if you can find them in the UK ,, ,, with pods it is a 150 main and I think the 50 pilot ,, You might try the drill out method ,, just go slow .

I know some fool who drilled his main jet too far.... so, he buffed up the brass real bright and torched the jet hole full of silver solder and drilled it again with a smaller drill.

I guess I just won't go for those air pods then. But where can i find a different pilot jet?? Do I have to buy a whole kit or can I buy just one?? Should I try the manufacture first or just look online?? I kind of lost hope in buying from kawasaki after I realized how ridiculously expensive stuff from them is. Any help is greatly appreciated.

I personally wouldn't drill ANY jet much less those bitty little mains. As far as the pilots, they are available in any size. If you call z1enterprises.com they will have them or can get them in #47.5 or try bountyhunter's suggestion of a #50 which sounds a bit rich to me. I doubt a Mac 2 into 1 flows much better than a stock system... I would try using the stock set up before rejetting anyway.

wiredgeorge wrote:

I personally wouldn't drill ANY jet much less those bitty little mains.

Really good advice. BTW, when I did the calculations, the size steps in standard numbered drill sizes miss quite a few of the available jet sizes. The guys who make jets must have a really good set of drills.

wiredgeorge wrote:

If you call z1enterprises.com they will have them or can get them in #47.5 or try bountyhunter's suggestion of a #50 which sounds a bit rich to me. I doubt a Mac 2 into 1 flows much better than a stock system... I would try using the stock set up before rejetting anyway.

The stock pilots that came on my B4 were 40's and they ran way too lean even with the stock pipes. I used to have to run with the choke on until it was fully warmed up and even then it had some really bad lean spots. I kept taking it back to the dealer and complaining and he said it would be illegal for him to install richer jets because of smog laws.... but apparrently he drilled them because they say "40" on the side and the hole is the size of a "50" and the bike ran a whole lot better. I left those pilots in when I got the kerkers and went up one size on main and it ran great. When I got the MAC's I bought a full set of new pilot jets to make sure I knew the true size and the 50's do run the best on mine with the MAC's. 47.5 is rideable but a shade lean. YMMV.