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Mixture control valve

Virago Ninja - Wrenchin' Secrets & Help Tips! http://Virago.Ninja
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PostAuthor: club_c » Tue May 27, 2008 7:24 pm

bmack";p="100260 wrote:The light just came on, I finally understand. Thanks

I was thinking I was going to have to come down there....
clubbie 1982 XV920J shaft drive, kinda custom (sold)
1981 XV920R chain drive, complete restoration (sold)
2001 BMW R1150RT - new purchase
1985 BMW K100RS - needed much love, now done, my best resto yet
1985 BMW K100RT - needs freshening up. I'm sensing a trend...

must......stop..........buying......bikes.........
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PostAuthor: racingbrat » Sat May 31, 2008 9:21 pm

That valve looks really good in the trash can gets rid of alot of problems .
1983 Virago
Home made forwards
1983 920 Motor swap
Shaved Seat
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1980 XS 850 Dual disk front end
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PostAuthor: Matthew » Sun Jun 01, 2008 2:28 am

been kickin mine around the shop for years, along with the seat tube for the air box. Thats one we haven't talked of in a long time.

Folks with 81-83 bikes there is a rubber tube that runs from the air box to up under the seat. Well at speed or under load that tube can pull so hard it sort of suction cups to the seat pan, blocking off your air flow.

Yank and toss in the corner.
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Re: Mixture control valve

PostAuthor: lakepirate48 » Mon Jun 16, 2008 8:05 pm

what is the procedure to determine if it is working.I just took mine off to check it( blowing and sucking) both of which I cant do...seems froze

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Re: Mixture control valve

PostAuthor: ss350z » Fri Sep 05, 2008 8:06 am

From Dr. Pisstons Webpage

http://www.drpisston.com/


5. Mixture Control Valve

All Viragos and RH and RJ models from 1981 to 1985 had a gizmo on them called a "mixture control valve" MCI), commonly known as a "gulp" valve. This valve opens by vacuum developed on sharp deceleration (when you "chopped" the throttle closed) and was supposed to provide a little puff of air to the front cylinder to offset a momentary rich condition in that manifold as droplets of fuel are sucked off the walls. This valve never really did anything positive (that is measurable or noticible) and was probably put on there by Yamaha to impress the EPA boys that they had some smog equipment on their bikes so they could get an import license. Over time these valves can leak and dump air into your front cylinder when you don't need it, making for a lean condition. I would recommed that if you have this valve on your bike that you remove it and cap the ports in the front carburetor holder.
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PostAuthor: ss350z » Fri Sep 05, 2008 8:13 am

Not sure why it posted with 2 s's, but it seems to work either way.

http://www.drpisston.com/

hmmm maybe something with the site programming?

w w w. d r p i s t o n. c o m
1981 xv750 a work in progress-(almost there)
1981 xv920r It's Alive, but still lots more work !
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Re: Mixture control valve

PostAuthor: qniswonger » Tue May 26, 2015 2:36 pm

ya i was reading up on it... that valve is also called an "anti-backfire valve" by some mechanics... and like the post above says.. it allows air into the front cylinder on deceleration to keep a lean condition in the cylinder so there isnt a backfire...
'04 VSTAR 1100 Classic
14036
'83 XV750 Midnight Virago (custom)
14040

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