cb360 thinking about going with mikunis vm 32's any thoughts? good, bad?

[tonuppirate]

tired of fooling around with my keihins and thinking about going with a set of mikuni vm 32's from ebay. just wondering if any of you have done this swap and what experiences you have had with it.

installation issues
reliability issues
performance
compatibility
can you get velocity stacks for these?
any other things I might need to know
the company says these are pre jetted and set up for my bike, was planning to buy from sportingforless. they seem to have everything in the kit except the intake manifolds which I'll have to buy separately, and I'll have to make the cables to length myself. for 299 it doesn't seem like such a bad deal.
thoughts? advice? much appreciated.
TP

 

[crazypj]

28's or 30's work much better on the street (and probably for racing?)
Much easier to get smaller size carbs working properly.
I've run my 391cc conversion with 26mm carbs, it only does about 120mph though.
Only issue is fitting, I modified carbs and manifolds, don't remember which ones I used (it was at least 20 yrs ago)
Everyone is fixated with oversize carbs, they can be made to work, but never very efficiently

PJ

 

[tonuppirate]

the only reason I wanted to go with the 32's is they come pre-setup, and as a set, with all the parts. I wouldn't know where to even begin to look for 26's, 28's or 30's or whatever you would recommend for my particular setup.

120mph??? I can only get my bike up to about 75mph max! is that normal for a stock cb360? it seems a little slow to me. I'm only about 160lbs. so the bike is not dragging around a lot of "extra weight" at 70 MPH i'm running at about 7k rpm. I'm wondering if the PO did something funky with the sprockets, but, I'm not exactly blasting off the line either. I don't expect much out of a 40 year old 360, but topping out at 75mph seems a bit slow to me.
what do you think?
TP

 

[Wee Todd]

changing carbs is not going to get you any faster,,you have some issues if it only attains 75 mph,,stock cb350 twin is 16-36 so check your gearing,,does it idle??have you done a compression check,,,is it timed to spec etc etc.........the bike should easily "DO THE TON" ;D

 

[Rocan]

changing carbs is not going to get you any faster,,you have some issues if it only attains 75 mph,,stock cb350 twin is 16-36 so check your gearing,,does it idle??have you done a compression check,,,is it timed to spec etc etc.........the bike should easily "DO THE TON" ;D

i wouldnt say do the ton easily... but it definitely should be able to hit it or at least get up past 90...

set everything to factory spec.

 

[crazypj]

It will do over the ton stock, but, you will need a tailwind, slight downgrade and be head down arse up.
With stock (high) bars, sitting upright, about 80~85 flat out
It wont do it by changing gear at 7,000rpm, you have to hit redline and it will probably be faster in 5th than 6th gear.
If diaphragms are good in you Kei-hin carbs, you would be better off keeping them. (I'm working on some modifications/jet changes)
As for 32's, some may be better jetted than others but no-one sells Mikuni's 'correctly jetted', no matter what the ads say.
Most come with 190 main and 45 pilot jets
140~160 hex main and 25~35 pilot will at least let it run, but, it will be rich mid-range, particularly when cruising at 'fixed' throttle (wrong type of needle jet/'emulsion tube')
The kit price is actually pretty good, but, it won't be 'plug and play'

 

[tonuppirate]

I don't have stock bars, but they are not true cafe bars either, a couple of inches above the triple trees. looking forward to your fix for the keihins, as it seems screwing around with the mikunis is gonna be more trouble than its worth. should i rejet the keihins? i'm running 100 and 68 right now, it seems no matter what these bikes like to run rich in the mid range. keep me posted on your keihin fix, it seems the 32's would just be dumping gas for no good reason. I'll check the gearing in case the PO did something weird with that. don't have a compression tester, but the bike idles fine, and timing was checked about 500 miles ago. engine is pretty tight no signs of smoke from the exhaust. although i get a lot of popping from the carbs on decel.
TP

 

[Big R]

Hey Tonup, the popping on decel - I think it was BobJohnson that had that same problem with his 450 and posted it in the help section as well.

 

[crazypj]

UPDATE
I got a formula for carb sizing from guy in work.
On a CB360,
At 11,000 rpm,
You NEED... 31mm carb.
A full race 12,500 rpm CB350 motor needs 31.66mm carbs, 32mm is close enough
If your not revving that high, a smaller carb will be better.
At 9,500rpm, CB360 wants a 28.8mm carb, 28mm isn't going to restrict motor at all (motor's only about 80% volumetric efficient at high rpm)
Smaller carbs will give better throttle response at lower rpm
So, theoretical size matches empirical data. 8)
Get 28's or 30's for stock motor.
It would run fine with 22mm carbs (80% of 28 if my math isn't too far off) but, you won't have 'big carb' bragging rights then ;D

PJ

 

[tonuppirate]

like i said i think I'll stick with the keihins, what size are those BTW? maybe a rejet? any suggestions? I'm looking at rearsets now and might switch out the bars to a lower profile. I'll check the sprockets this weekend to see if the PO did anything weird with them. its running really well right now, just no power in the top end. i'd like to crack a ton just once to prove that my little 360 has the balls to do it. but, i'm not planning on making it a regular occurrence. BTW how's that fork brace coming along?
TP

 

[tonuppirate]

another random thought, my buddy who is into nortons runs a single carb setup for his twin. has anyone tried anything similar with the parallel twin hondas? seems like it would solve a multitude of issues.

 

[joevirus563]

tired of fooling around with my keihins and thinking about going with a set of mikuni vm 32's from ebay. just wondering if any of you have done this swap and what experiences you have had with it.

installation issues
reliability issues
performance
compatibility
can you get velocity stacks for these?
any other things I might need to know
the company says these are pre jetted and set up for my bike, was planning to buy from sportingforless. they seem to have everything in the kit except the intake manifolds which I'll have to buy separately, and I'll have to make the cables to length myself. for 299 it doesn't seem like such a bad deal.
thoughts? advice? much appreciated.
TP

I'm setting up 2 VM32 for my cb450... Take a look around the web... cuz vm32 look a little oversize for your motor.
THey use VM32 with racing spec...

 

[Rusnak_322]

another random thought, my buddy who is into nortons runs a single carb setup for his twin. has anyone tried anything similar with the parallel twin hondas? seems like it would solve a multitude of issues.

Harleys also do that.
I had a Honda XL-250 (street legal XR250) that was a single cylinder but with twin carbs.
Twin carbs will allow straighter flow into the head. A single carb will require the air to turn and probably not flow as well at high RPM.

 

[crazypj]

Just remembered, single carb doesn't work so well on a 180 twin, can't remember why exactly, something about charge robbing (guess it would be OK if you wanted it to sound like a baby Harley?)