Mikuni VM 32 question

[tonyb]

Hello I recently got a deal on some brand new vm 32 carbs.
Wondering if anyone can help me with getting the settings in the ball park.
I'm running pods with the titan performance chambers.
What size are you fellas getting good results with?
Pilot jet
Needle jet
Main jet
Needle
Needle position
Anyone using larger carbs? 34s?
Thanks
T

[Suzukidave]

I suppose these are going on the T500 ?

[tonyb]

Yes that's correct for the T500

[tonyb]

I took it apart and here is what it currently has
Main jet 200
Pilot jet 35
Air jet 2.0
Piston valve 3.0
Jet needle 6DP17 (clipped in the middle slot)
Needle jet 159, 0-6

[tonyb]

The original carb has
Main jet 97.5
Pilot jet 30
Air jet. Not sure where this is located
Piston valve 25
Jet needle 5FP17
Needle jet, can't seem to get it out (does it come out of top or bot?)

I'm basically wondering where all these should be with pods and chambered pipes
Thanks!!!

[ja-moo]

It looks close enough to run.

[jeff kushner]

I've run with my 750 with:

main 200 pilot 35
Needle 6DH4-3 Needle jet-P-0
slide 2.5 or 3 (needle position changes of course)
on VM32's with a stock porting and exp chambers

most ported 250cc (I figure you are running a 500 or 750)cylinders will run in this neighborhood:
here's some actual examples:
230 40 6F9 P-6
220 37.5 6DH4-2 P-2
220 37.5 6DH4-3 P-6

Good luck!!

jeff

[Vintageman]

Note, the t500 used 188 series needle jet and the main jet for it is the round type and has a different flow rating that the hex type which is required by the 159 series

To cross ->
http://www.ozebook.com/compendium/t500_files/mikuni.pdf" onclick="window.open(this.href);return false;

I think the Needle Jet size is a P4 or P5 for t500. It all depends on the diameter of the jet needle you have versus OEM at the start to know what size Needle jet... then it is the taper of needle.

A lot of people say start rich on main and I have done that the only to have all the injection oil washed away. Been saying this a lot lately... couple of painful $$ experiences, Takes a few hundred miles before you know too rich ... compression starts to drop, little harder to start warm ... go back and check ring gap.

Now i put a little oil in gas until correct if i feel i need to start above OEM main size.

If you are too lean of course it can cause too hot and ruin things to. However, the T500 pings if you luckily letting you know it is lean. At least mine did.

My GUESS If you had stock air box (early or late bike), stocks jets, and stock exhaust and just change pods. I think you needle to up the flow of the main jet 10-15% for good large volume pods.

[ja-moo]

A lot of people say start rich on main and I have done that the only to have all the injection oil washed away. Been saying this a lot lately... couple of painful $$ experiences, Takes a few hundred miles before you know too rich ... compression starts to drop, little harder to start warm ... go back and check ring gap.

What? One run through a couple gears will tell you if it's too rich. And you had another problem than a rich mixture, if it was rich enough to remove oil, it would have fouled plugs in a matter of a mile or so. And adding oil to the gas leans out the mixture, and ruins any chance of getting your jetting correct. Even the Sudco manual says to put in a huge main jet when tuning in the bottom circuits until you are good to 3/4 throttle......

[Vintageman]

It would foul a plug. then i back off some on size, would not foul. Unfortunately I also removed oil mix from tank at that time thinking it was this too. It ran well no worries. The recent bike was the Gt250A and I ran it hard. No other way to run it. Same with my GT185 modded (just tore this one down same issue).

Both bikes had premature ring wear after a few hundred miles and a few steps over OEM on main jet

You want to feed your engine fuel with a fire hose and no added premix, just stcok street bike injection, run it hard (mostly WOT). your bike. Just tear it down after a few hundred miles and measure ring gap or cyl ridge depth


I was schooled like sudco says too. We learn from experience, this is mine-> neither extreme is good: too rich fuel with oil injection only being one extreme.

[ja-moo]

I have road raced for years, never found a premature wear problem. Yes I run the hell out of all my motors. Not sure what your problem is.........

[Vintageman]

Problems were solved ... just trying to help a mate avoid the problem I had: increase the fuel to oil ratio has consequences.

My Tuning Advice (free so you get what you pay for )->

If you start rich or not sure premix some oil with gas until you are tuned on an injected engine only.
And, If you leave it rich on main, and just use factory oil injection, and you run WOT lot a (i.e. use the rich main circuit) your engine's top end will have premature ring and cylinder wear that simply looks like a high mileage engine when it’s not.

Cheers

Mike

[tonyb]

Ok finally getting around to some fine tuning thanks for all the help! vintageman that conversion chart really helped and thanks for the examples Jeff! I'm ordering From jets r us after I get a consensus from you fine gentlemen.
Needles: 6DH4 002-301 (clipped at middle to start?)
Pilot:40 (I'm sluggish down low and it takes a while to get back to the idle circuit.)
Main: 170. Is this too lean? It is equal to 120 round type mains that titan performance suggested)
Needle jet 159-P2 or P0?

Again this is for a titan with pods And chambered exhaust.
THANKS!!!

[titan performance]

Tony.....I'd say a 40 pilot is too big. 30 is stock, just go up one or maybe 2 sizes at most.
Try the 120 main at first, but get some 115's too. You may be able to run even leaner still, but caution is the order of the day, as melting pistons is a pain. Needle on the middle notch, at least for starters. There is a lot of oil talk here, but I don't see what that has to do with anything myself....set your pump correctly, decent quality oil....job done.