Topic: carb boring

[bucky katt]

i saw on the campbells dr gas xpipe site that they do carburetor boring and adding a 4th fuel circuit. is it worth it to me to spend around 400 dollars or so to get the stock kehins bored and another fuel circuit done? i really cant spend the money on cr's or mikuni flatslides. or should i just keep the carbs stock?

[fishhead]

I'd get the Mikuni VM 29 smooth bore adaptors and put on a set of VM 28's (KZ 900/1000) instead. It will probably cost about the same as the boring, but there are more parts available for the Mikuni's. (JMO) the Mikuni is a better carb.

[bucky katt]

ah ok, i didnt think that was a possible swap, in that case...............i'll start looking at carbs from a kawi

[fishhead]

Heres a few pics.

VM 28's on a CB 750

2nd pic shows various Kaw carbs

 Left side top to bottom
 1)VM 22
 2) VM 24
 These 2 are for the smaller Kaws (650/750) and have 3 horizontal ribs cast into the slide area. Don't use these on the 750.
 3) VM 28
Middle
 1) Early Z-1 900 (has removable nut on bottom of bowl for easy jet changes)
 2) 74-74 Z-1 900 (no removable nuts on bowls)
These 2 carbs are harder to sync because of the CB 500/550 style external sync adjusters.
 3) VM 26
 Right side
 1) VM 26
 2) VM 28
 3) Early Z-1 carb bored out to 29.5 mm (it still isnt a smooth bore).

  The early Z-1 carb is the best of the bunch (JMO), but even on the Z,they require/suggest the slides to be milled down .030 to change the slide cut out to get rid of a stumble over top of idle, The 74-75 Z slides can also be put in the early Z carbs to remedy this.The early Z carbs are usually the most expensive of the bunch and the 74-75 Z carbs arent much cheaper.
 On the right side column, the easiest way to tell the VM 26 from the VM 28 is the thickness of the carbs mounting flanges. It's hard to tell them apart, but when looking at the carbs, the 28 have a thinner carb mounting flange than the 26's do.
 There are other varients of the VM. but the pic above covers most of them.

[RRRToolSolutions]

Jeff,

I ran the stock carbs on my 836 when I first built it and had very good results after jetting and the K&N's. This was the first time around - 600 miles before the Carillos, the Dyna 2000 rev limiter, the heavy-duty upper/lower studs, and full balancing. In fact, the low-end and mid range were better than they are today with the CR's. The only thing I noticed is that the tire would fall a few hundred rpm lower. These were both at rpms well above the stock rod's limits. None of the changes I made to the bottom end the 2nd time around had any performance enhancing objectives - I simply wanted to enjoy every bit of the rpm that the porting, titanium valvetrain, and Carillos would allow.

Unless you really want 10,000 rpm and have done a lot of work to make power on top, I would not spend the money. From 2,000~8,500 rpm, I think my properly jetted stock carb were doing great. Seaweb has those carbs today on his tracy.

Oh, get with me to talk about helmets -

Regards,
Gordon