Mikuni experts, your answers please...

[lane1feathers]

G'day boys (and girls) just want to get my head around these mikunis before I go ahead with the conversion. I think I've got it sussed...let me know if I'm on the right track...please.

This is obviously the fuel inlet, it has a filter!

There is a T piece similar just behind inlet, this must be fuel return?

My index finger is pointing to the vacuum nipple (which gets plugged) and my middle finger is pointing to the bowl overflow (which has pipe going to atmosphere or bottle ) the 2 hoses with filters are breathers (going to canisters) Now the tube running across the front has a brass pipe inside of it and the rubber is broken at the end. Has this got something to do with balancing?

[paso750]

Lane, here you have the carb sections of the TDM/TRX Haynes manual and the TDM850 factory manual.
https://www.box.com/s/8puax6a9md5hffvqvg3a

Does it say BDST38 on them ? I`m just wondering about one or two small differences (like the throttle position sensor) and because some Yamahas used a BDSR38 (of which I don`t know the difference).

The T connection with the filter is the fuel inlet. The one behind it is the fuel overflow that leads to one of the black plastic containers. (The breather tubes with the filters lead to the other)

The carb has no fuel return. You should keep the Y connection for the fuel return in the fuel line.

Those two brass tubes on each body should be for the carb heater system and connected to each other so can be ignored. But to be sure blow through them or remove the float chamber cover to check.

On the Yamahas the Mikuni is mounted reverse compared to the Duc. On a Duc the pilot screw (the one you`re pointing at in the last pic) shows to the front of the bike and collects dirt. A good thing is to take a clear fuel line, heat one end, squash it with some pliers so one end is sealed. Then cut it off and push it over the pilot screw (tube) to protect it.

The synchronisation screw is in the middle below the fuel overflow connection shown on pic 2.

What I don`t know is what that horizontal tube is which is connected to the left float chamber cover.

I find it very interesting that the Yamaha Mikuni has a throttle adjuster cable.

G.

[lane1feathers]

Ha, ha...crikey! Close, but no donut! If that was an exam, I failed... Thanks for all that G.
I'm away on the mines for a couple of weeks so I'll let you know about the numbers when I get home and dis-assemble to clean before I tackle the conversion. I'm running open carbon fibre mufflers and will be using UNI foam filters. I'll chase the mikuni threads on the forum to determine which jets should be used

[paso750]

I`m afraid you won`t find the jetting info here and even if an open exhaust and foam filters can require a different one.
The best is you start with the one you have or a 900SS jetting and go from there.

[higgy]

gotta start somewhere, check the sudco mikuni manual and calculate a good start point

[lane1feathers]

Cheers, will do, thanks guys

[koko64]

What kind of air filter set up are you going to run?

The differences compared to the Duc version are interesting. Maybe some improvements hopefully.

If you can only fit K&N pod filters let me know because I have some jetting settings for a 900 motor (M900) with pods as well as open airbox, etc. It will at least put you in the ballpark. I did quite a bit of dyno testing with pods and airbox mods.

Some of those hoses like still air. The two cannister hoses and the breather hose from the second T piece should be out of turbulent air. The SS and Monsters had pods they breathed into. A redbull can or something could work.

Loving this forum. I cant find one P750 for sale down here and 906/907s are going for 6900-9000 grand!

[paso750]

it would be an interesting project to see if the injection system of later TDM models would fit maybe in combination with a power commander (I wonder if the dimensions are the same as a Mikuni carb)


G.

[lane1feathers]

G'day koko, I will be running UNI foam pod filters (to support the Aussie economy) as these fit, are cheap, and are easily avail from everywhere. I've just got myself a stage two dynojet kit off eBay for it. I have the D&D open mufflers so that should be the right set up. A good place to start anyway
I have a couple of canisters for the breather tubes and bowl overflow line. They are from a monster (small, black, triangular) and a vacuum fuel pump as well. These were courtesy of the ever generous Gerhard (paso750) Thanks again G.
The conversion has been postponed until I get a wet week on my R&R (I work FIFO) where I'm not busy with everything else! It's running fine for the moment...except for the stumbles and flat spot on take off...and i need it to get to and from the airport. When it comes off the road I'll be doing fork seals, braided brake lines, swing arm bearings, rear sprocket, steering head bearings, LED light strip under headlight, and a few other bits including a good wash and polish so I will need a few days with no interruptions.

[koko64]

Sounds a good plan.

With pods and open mufflers, a baseline would be say 160-165main jets (170-175 DJ jets), needle where the kit tells you for open airbox and 40 slow/idle jets. Thats a good starting point. Since pods dont flow as well as a good open airbox, the 165/(175 DJ) jets might be too rich. Im not sure with your water cooled bike and the K&N would flow better than the foam Uni filter so try 160(170).
Set the floats at 14mm as they are usually out!
Remember Dynojet have their own jet sizing scale, 160 Mikuni = 170 DJ (roughly).

You'll be saving a few Watts for your battery, ignition and head light going to a vacuum fuel pump. The hexagonal pump flows heaps at a safe 3psi. Its a high flow rate at low pressure. Thats my plan for the P750 (when I can find one). Maybe I should be open to buying a 906. If you hear of any please let me know.

Good luck.

[paso750]

http://www.4strokes.com/tech/carbjetxover.asp

koko, how much do you want to spend ?

[koko64]

Im looking for something that needs work, so not much!
I need a project!. I have seen Pasos cost more than the ST2!

I want to rebuild one and try stuff. I have a thing for the air cooled motor, but would be interested in a 906 with a dead motor as I would fit a 900Ss/M900 motor. I love the twin air ducted oil radiator concept. I also feel familiar with the Kokusan ignition system.

I will be patient for the right opportunity.

[Fraser]

Lane,

The DynoJet Stage 2 kit, with Uni Pods and an open exhaust should work just fine. Have that same set up on my P750 and she runs very strongly.

Cheers,

Fraser.

[lane1feathers]

Koko, thanks for the tip re; DJ jetting being different, I didn't know that
Even old, busted arse Paso's are fetching stupid coin nowadays. Either people are now realizing that they are an appreciating asset, or they know they can make a small fortune if they spend a little time and effort parting it out Hell, I paid $4k for mine it owes me $7500 now and still isn't finished. (Actually, probably closer to $8k )

Fraser, thanks for that info, I figured I'd be pretty close with the stage two

[paso750]

Lane, there`s a problem noone noticed yet including you and me. I`ve often read the Mikuni BDST38 from the Yamaha was the same as the one Ducati used and I`ve written that here a few times myself convinced it was true. Now I`m very much in doubt.
On the Yamaha the carb sits behind the engine and is hence reversed. The bracket for the throttle cables is not on the side of the float chambers as it is on a Ducati. So when mounting that carb on a Duc, the throttle cable connections are on the rear and it`s not possible to turn the carb around. (How could I ever miss this ? ) I wonder if it`s possible to change the linkage/throttle bracket otherwise the only way I see is long throttle cables.

G.