Two simple carb part questions

[avizpls]

I have a 1994 M900 with the Mikunis.

I have two questions. The first, I have been wondering for a while but avoided asking because its mentioned often enough that I feel I should have figured it out just be reading around by now. But I haven't.

1) Where EXACTLY is this vacuum shut off component? Part of the carb? Along the fuel line? Before/after pump? Unless its integral to the carbs, I don't think i have one.

2) Is there a  cheaper place to get the main diaphragm assembly? I can get it from my dealer for $111 but I see now that the rubber piece is detachable. I feel like i can pick just that up for cheap! The main diaphragm controls the jet needle and is torn on mine. So I have a nasty mid throttle hesitation.


thanks

[Howie]

If you have a vacuum shut off it is here:



I think your '94 has a manual valve.

You might try SUDCO directly since they are a Mikuni importer  http://www.sudco.com   or your local Yamaha dealer since they used the same carbs on the old TDM.

[avizpls]

Yup, manual shutoff.

Thanks for that pic!

[avizpls]

OK, also I need to ID the needle I have in my carbs.

I spoke with DynoJet and Factory Pro. DynoJet needles have 6 positions and Factory has 5. My needle has 7 positions.

Does anyone know what brand a 7 position needle is? I plan on installing it the same way as a DynoJet would be.
(Plastic washer, eclip, metal washer, plastic adapter, spring)

[ScottRNelson]

OK, also I need to ID the needle I have in my carbs.

I would suggest that you throw them out and get a set of needles from Factory Pro.  Then you'll be sure that you have the right ones.  They worked quite a bit better than the stock needles in the Monster that I used to have.

[avizpls]

well they're definitely not stock. I understand the stock ones have no adjustment positions.

[koko64]

OK, also I need to ID the needle I have in my carbs.

I spoke with DynoJet and Factory Pro. DynoJet needles have 6 positions and Factory has 5. My needle has 7 positions.

Does anyone know what brand a 7 position needle is? I plan on installing it the same way as a DynoJet would be.
(Plastic washer, eclip, metal washer, plastic adapter, spring)

I had an older Dynojet kit and the needles had 7 notches. The current kit has 6 notches on the needles when I compared them.
The taper is a little more aggressive on the DJ needles than the FP ones. Both kits are excellent for the compromise that is the stock Mikuni CV carb. The DJ springs are also softer letting the slide open faster. If you are not sure, buy the FP kit coz it's got Ti needles which should last, and make sure to get FP needle jets as they will last being stainless rather than the stock ones which oval out and cause rough, rich running.

Check your main jets they may have a little "dj" scribed on them and that will tell you. The jet numbers will also be different (larger). The DJ jet sizing system does not match the stock or FP system. There is a good chart on this site you can search for.

If you are short on cash, buy the FP needle jets and fit them.

Oh and reading the numbers on the main jets may require a magnifying glass if you're over 40!

When I saw the difference in notches I asked someone who had long term experience with both types of kits.

[ScottRNelson]

Oh and reading the numbers on the main jets may require a magnifying glass if you're over 40!

I use the SuperMacro setting on my Canon camera for that.

This is the microprinting on the back of a $5 bill as an example of how small it can photograph:


I have photos of jets too, but not handy right now.  A couple of days ago I had to find out what odds and ends of jets I had for a Honda XR and had to get out the magic camera to see the numbers.

[koko64]

G'day Scott
I could use a gizmo like that! (I still think we need an old fart smiley).

Avispls
I was thinking about what other mods have been done. You know, pipes, air box/pods. Since the bike sounds like it came to you with the jet kit, you may want to look up the DJ site and scope the instructions that come with your models kit. Then you could check out the recommended needle pos-ns and main jet sizes for the level of mods you have without buying a whole new kit. When comparing the new and old DJ needles, (the notches are counted from the top), the 1st notch on the 7 notch needle was the extra one, so count from notch number 2 when looking up the specs you should run. They got rid of that first notch on the new version of the needles. In other words, the old number 2 notch is the new number one.

If your main jets are not correct according to the suggested specs, then you could buy the equivalent jets from someone on the Forum for next to nothing or a local store. Just remember that stock Mikuni jets are numbered different to the DJ jets.

If your bike has shiny, stainless looking needle jets, then leave them. If they are the stock brass ones, then change them to the Factory Pro stainless ones, best thing I ever did. I went through two sets of stock needle jets in 10,000 miles.

Oh, and set your float levels to 14mm. They can be way out from the Ducati factory. The Factory Pro and Ducati Suite sites show you how.

Just sayin'.

[ScottRNelson]

G'day Scott
I could use a gizmo like that! (I still think we need an old fart smiley).

[koko64]

 

[koko64]

Dear Moderators
May we please have an ol' fart smiley made available?
This would cater to the needs of a significant section of the board membership when giving advice to those "young people" (said with quivering voice).
Or when people want to bag others for being older.

[avizpls]

<invaluable advice>

Just sayin'.

Awesome. Thanks for the tips. FWIW I'm "done" with this phase. I fixed the torn diaphragms and took it for a ride today. Its running better now than it ever has and it seems happy. I have a dyno sheet from when the diaphragms were presumably torn and it was lean in mid range, but ok at low and top. So I upped the needle one bump. I do not know what the Jet size is, and I don't know what type it is. I think its a 175, based on what a terrible shop told me (worst mistake ever paying someone to do work you should be doing yourself...but i didnt have a dyno) The part visible from the intake runner is brass.

I have a track day coming up and I don't want the bike to be in pieces for it. Ive been chasing this problem in the wrong direction so much and now that I found it I would rather play it safe and ride it thru the trackday. THEN I'll rip apart the carbs. Then it will be winter....



Thanks again and im going to go look up the dynojet recommendations now

[avizpls]

Oh, and the mods Ive done so far are

Ignitek Ignition with Stock coils
pod filters
High Comp pistons (JE 11.5:1)
Light clutch and flywheel
Staintune low mount slipons

[koko64]

Nice mods. Similar to mine. That increase in compression wakes up the motor aright.

Cheers.