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Please help me on a Mikuni for a 79 CR250
https://vintagedirtbikeforums.alp-sys.com/viewtopic.php?f=21&t=3832		 Page 1 of 1
Author:  mxgirl75 [ Wed Oct 10, 2012 12:42 pm ]
Post subject:  Please help me on a Mikuni for a 79 CR250
Does anyone have experience putting a Mikuni on a 79 CR250? What is entailed? Is it bolt on? I know I can get a pre-jetted one from either Sudco or Vintage Iron. Vintage Iron claims it is a bolt on affair.

Please help me, I would like to make a good decision on this.

Kristi
Author:  Dave [ Thu Oct 11, 2012 6:32 pm ]
Post subject:  Re: Please help me on a Mikuni for a 79 CR250
it is a bolt on as far as i know but the jetting in the replacement Mikuni is a good starting point if you get one pre jetted for a 1979 CR250.

you still may need to rejet and make adjustments here and there though due to the Altitude and temperature differences to get it spot on.

i plan to put a Mikuni on my 1979 CR250R sometime or i may go with a 38mm Kehin Air Striker possibly.
Author:  mxgirl75 [ Thu Oct 11, 2012 11:13 pm ]
Post subject:  Re: Please help me on a Mikuni for a 79 CR250
Thanks Dave for the info!
Author:  redrocket190 [ Fri Oct 12, 2012 10:45 pm ]
Post subject:  Re: Please help me on a Mikuni for a 79 CR250
You may want to have some length machined off the bell side. It is longer than the Keihin and will be challenging to get into the air box boot without. Match them up and take them to a machine shop. This is my jetting from Southern California.

Pilot 35
Air screw 1.75 out
Slide 2.5
Needle Jet 159-P8
Needle 6FJ6
Clip #2
Main 360-380
Float height 19mm
Author:  mxgirl75 [ Sat Oct 13, 2012 12:00 pm ]
Post subject:  Re: Please help me on a Mikuni for a 79 CR250
Thanks for the info Michael, I am moving to the Twin Air filter, the stock setup has to be the biggest pain I have ever seen for an air filter. If it is still to long, I can take it and have a little bit machined off on the bell side.
Author:  redrocket190 [ Sun Oct 14, 2012 8:17 am ]
Post subject:  Re: Please help me on a Mikuni for a 79 CR250
When you remove all the OEM air filter cage, boot etc. to mount the Twin Air filter, let us know how you support the new filter in the air box.
Author:  mxgirl75 [ Sun Oct 14, 2012 7:31 pm ]
Post subject:  Re: Please help me on a Mikuni for a 79 CR250
An Oetieker clamp on the inlet side from Aircraft Spruance. Works like a charm and no problems with a carb coming off.
Author:  redrocket190 [ Mon Oct 15, 2012 7:50 am ]
Post subject:  Re: Please help me on a Mikuni for a 79 CR250
Photo?
Author:  b-joe [ Mon Oct 15, 2012 9:54 am ]
Post subject:  Re: Please help me on a Mikuni for a 79 CR250
i´m using the twinair filters for about 20 years now without any fixing and have no problems.
Author:  redrocket190 [ Mon Oct 15, 2012 1:50 pm ]
Post subject:  Re: Please help me on a Mikuni for a 79 CR250
I use Twin Air filters in all my bikes except the Elsinore where I am lucky to have a supply of OEM filters. My question was about mounting the filter in the air box and was a) simply curiosity and b) based on what I saw years back. So.. when you use the Twin Air it has an air boot attached and mounts direct to the carb, all the OEM cage / boot etc. is not needed. Given that the air boot on the Twin Air is smaller than the hole in the front of the air box, how is it supported? Or is this not an issue.
Author:  mxgirl75 [ Tue Oct 16, 2012 1:55 am ]
Post subject:  Re: Please help me on a Mikuni for a 79 CR250
I know a guy who loaned his CR480 to Chuck Sun with the stock hose clamp on the engine side of the carb and the Twin Air mounted, the carb came loose and came off, ending Chuck Sun's race. Since then he has run the Oetiker clamp with no issues at all. There are no problems with the Twin Air not supported. Since my bike is out of commission right now with an air leak somewhere, I have not gotten the chance to run the bike with the Twin Air yet.
Author:  b-joe [ Tue Oct 16, 2012 12:37 pm ]
Post subject:  Re: Please help me on a Mikuni for a 79 CR250
at first you have to cut the boot to the right length.

Image

if not it looks like this shit. :(

Image

sorry, i have no pic here where you can see inside the airbox. maybe later.

Image

the twinair filter is very easy to change, no leaks are possible, best filter for a racer.
Author:  redrocket190 [ Wed Oct 17, 2012 9:30 am ]
Post subject:  Re: Please help me on a Mikuni for a 79 CR250
It would seem that once the air boot is cut shorter, the size of the filter means it sits snug against the front of the air box and supports itself. Nice.

I am interested in your running a hydraulic clutch - which one? I have these on all my other bikes and love them.

Never seen anyone running the rubber sound-deadening blocks between the fins before. Shades of the Yamaha IT line...
Author:  b-joe [ Wed Oct 17, 2012 11:18 am ]
Post subject:  Re: Please help me on a Mikuni for a 79 CR250
redrocket190 wrote:
It would seem that once the air boot is cut shorter, the size of the filter means it sits snug against the front of the air box and supports itself. Nice.

yes, it supports itself

redrocket190 wrote:
I am interested in your running a hydraulic clutch - which one? I have these on all my other bikes and love them.

it´s a magura hymec for KTM LC4 models. the only extra thing you need is the small collar to fit it to the original cableholder.
i made this collar by myself on a lathe.

redrocket190 wrote:
Never seen anyone running the rubber sound-deadening blocks between the fins before. Shades of the Yamaha IT line...

this bike was made by honda germany for Hans Werner Pohl for isdt races. to be road legal it had to be quiter, so they put the rubbers between the fins and addeted an suzuki rm250 silencer to the original muffler.
honda gave him two bikes, one for spare.
this is the second one, here without the rubbers, guess they got lost over the years or were removed when the cylinder was replated.
i got the first bike at 1989 and found the second one last november not far away where i live. :D

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