Mikuni Question

[Mike Hufnagel]

What do you think would be better a 34mm Mikuni Flat slide or a 36mm Mikuni VM on a 250 with reeds?  Any thoughts?

74 Yamaha TY 250
75 Jackpiner w/ 250 eng.
80 Ktm Mc 400
82 KTM GS250II (import)
82 KTM 495
2) 84 Yam RZ350
98 KTM 300mxc
00 KTM Duke 2
06 KTM 950 Adv.
08 Suzuki DR70Z

[Mike Hufnagel]

PS. It's on a 74 KTM motor with GEM reeds installed.

74 Yamaha TY 250
75 Jackpiner w/ 250 eng.
80 Ktm Mc 400
82 KTM GS250II (import)
82 KTM 495
2) 84 Yam RZ350
98 KTM 300mxc
00 KTM Duke 2
06 KTM 950 Adv.
08 Suzuki DR70Z

[firstturn]

Mike,
  What are you going to do with the bike...MX, Enduro or Trail Riding?

Ron Carbaugh

[brian kirby]

I would use the 36 VM, a 34mm of any type is too small, and a flat slide is not vintage legal.

Brian

[Mike Hufnagel]

I would be riding hare scrambles, enduros & trails.

The VM carb. is a bored 36 (out to 36.5) really. I got the flat slide off my buddies stock motored/non reed 250. Not sure what year the flat slide is but it appears to be an older model.

74 Yamaha TY 250
75 Jackpiner w/ 250 eng.
80 Ktm Mc 400
82 KTM GS250II (import)
82 KTM 495
2) 84 Yam RZ350
98 KTM 300mxc
00 KTM Duke 2
06 KTM 950 Adv.
08 Suzuki DR70Z

[Mike Hufnagel]

Another ps.

It's a TM  , not a TMX Mikuni.

74 Yamaha TY 250
75 Jackpiner w/ 250 eng.
80 Ktm Mc 400
82 KTM GS250II (import)
82 KTM 495
2) 84 Yam RZ350
98 KTM 300mxc
00 KTM Duke 2
06 KTM 950 Adv.
08 Suzuki DR70Z

[skiracer]

I have a 36 Mikuni on my 250 MC5, and love it.  It is such an improvement over the original Bing.

[brian kirby]

A 34mm is too small for a 250, a 34 is the right size for a 175. If AHRMA legality is a consideration, no flat slide carb is vintage legal and only the Lectron is legal for Historic or GP, the Mikuni TM is only legal in Ultima. Your best choice, both from a performance and a rules standpoint is the VM36.

Brian

[tomale]

I agree with Brian, I actually bought a 34 that had been bored out to a 36  The reason for using the smaller carb is to allow more room for the float bowl... I was shocked how much of a differance it made I actually had to gear the bike up because it revved so quick that I was shifting too often and I was not using all of the power band. It pulls so hard down low, my competitor thought that I was riding a 400. the bike really rips..

Thom Green,Still crazy after all these years!
76' 250 MC5 (orginal owner)74'
250 hare scrambler (project bike)

[firstturn]

Mike,
  If you are going to be ridding scrambles the obvious choice is the 36.  As Thom stated I have seen bored out 34 carbs that work fin, but there is no sense for all the extra work when you can just buy a 36.

Ron Carbaugh

[Mike Hufnagel]

Thanks for the info! Looks Like I'll be going with the 36.5mm

74 Yamaha TY 250
75 Jackpiner w/ 250 eng.
80 Ktm Mc 400
82 KTM GS250II (import)
82 KTM 495
2) 84 Yam RZ350
98 KTM 300mxc
00 KTM Duke 2
06 KTM 950 Adv.
08 Suzuki DR70Z

[Big Mac]

Report back with results for fitting a 36 in there, length issues, cutting the intake spigot shorter(?) and adapting for the wrong-sizes on both ends for intake and carb boot sizes. Please.

[skiracer]

quote:Originally posted by Big Mac

Report back with results for fitting a 36 in there, length issues, cutting the intake spigot shorter(?) and adapting for the wrong-sizes on both ends for intake and carb boot sizes. Please.

Hey Big Mac,  When I did my conversion, I had to do a couple of things: (1) I had to cut the intake side on the carb down about 3/8".   (2) I modified my airbox also.  I cut back the flange on the box, installed a flat plate over the opening, and then made a new flange for the stock rubber to fit.  I picked up about an 1 1/4" of space, which on these bikes is almost a mile.  It was worth all the work.  I love the way the bike performs as stated above.  Regards, James

[Mike Hufnagel]

quote:Report back with results for fitting a 36 in there, length issues, cutting the intake spigot shorter(?) and adapting for the wrong-sizes on both ends for intake and carb boot sizes. Please

Finaly got the sucker on. Haven't really test ran it yet, but at least it fires up. Here's the scoop.

Carb was already cut on intake side & carb was bored out .5mm. Intake side was cut right at the end of the flare leaving about a 3/8" flat for boot mounting. Since the bike has a set of GEM reeds on it a nice size dent had to be put in the expansion chamber for clearence problems (I don't think I would have to have done that if there were no reeds). It is a custom chamber that is actually pretty big and not reallt a 250 pipe.All internals from a new carb were put into the modified carb. I had a spare intake boot from a later model 400 that was perfect for mounting the carb with no mods. A new stock airbox boot was used but I had put it in hot water to soften it up and used a heat gun to make it even more pliable and slid it over a beer bottle to obtain proper dimensions.(Note: It was a Belgian beer of good quality and very tasty).

I think skiracer's idea for the airbox side is better, as the airbox boot is flattened a bit.


Hope that helps.

74 Yamaha TY 250
75 Jackpiner w/ 250 eng.
80 Ktm Mc 400
82 KTM GS250II (import)
82 KTM 495
2) 84 Yam RZ350
98 KTM 300mxc
00 KTM Duke 2
06 KTM 950 Adv.
08 Suzuki DR70Z

[tomale]

thats great Mike, I sure like the way my 250 runs with a mikuni on it..

Thom Green,Still crazy after all these years!
76' 250 MC5 (orginal owner)74'
250 hare scrambler (project bike)