OzVMX Forum
Marque Remarks => Yamaha => Topic started by: YZ250H on February 12, 2012, 07:41:42 pm
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Came on the YZ250C, but doesn't look like it gets along with the exhaust very well. The only stamp on it is "118"
I suspect a ring-in. Can anyone confirm or deny ??
(http://i202.photobucket.com/albums/aa49/tbarsby/012-3.jpg)
(http://i202.photobucket.com/albums/aa49/tbarsby/013-3.jpg)
(http://i202.photobucket.com/albums/aa49/tbarsby/014-2.jpg)
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need to see a front on photo but from what you have shown looks right ,they had only a poofteenth of a gap for clearance
Iain
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You might have to wait until next week-end now Iain ;D
So what was the reason for the 2 plugs ?
i think Vandy has a 2 plug head on hit RT1.
This head has the right amount of studs, but it looked to be really close to the pipe :o
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The 2 plugs came on the IT heads
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Looks like a 75 MX250B head to me
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MX 250 B the same as YZ250 C ??
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Yes the mx 250 b is the same head , twin plugs where the go till the 77D model if one got fouled switch to the other
regards Iain . ps Ill check my yz 250 c head tomorrow
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My 250C has only 1 spark plug. Thats correct as per the parts manual. There is enough clearence to fit my fingers between the head and exhaust. Pretty sure mx250b has same head as 250c, the exhaust is identical for both bikes. Could be mx250a.
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MX-A has fins cut out for exhaust clearance.
DT250 mono shock?
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[quote author=iainyz
Yes the mx 250 b is the same head , twin plugs where the go till the 77D model if one got fouled switch to the other
regards Iain . ps Ill check my yz 250 c head tomorrow
[/quote]
The Idea of the Twin plug Head was to start your Motor on an 8 plug
then Switch Over to a 10 or Race plug once you warmed the motor
up..To save Having to Change Plugs..on the Start line..
The Stig..
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That is actually a brilliant idea. I wnder why they didn't continue it on ?
A blessing for all of those that have had to change a plug .... on the start line ;D ;D
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Was the head originally a twin-plug head, or a single plug head that's modified?
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Page 57 of the mxb75 250 manual show the head with the blank in place . best photos in the yzc250 manual is page 73 on page 40 you can see the cut away through the fin in front of the dail guage
Iain
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I had a worked YZ250C many years a go with a dual plug head and 2 coils to run both plugs at the same time.
The bike went very fast and no problems with detonation or pre ignition.
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???
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Ok - I've got a photo of that head from the front. See if this helps. I found some pictures of Wayne's C on here. The shape looks to be the same. Wonder where the second plug came from :-\
(http://i202.photobucket.com/albums/aa49/tbarsby/001-4.jpg)
I have another one that came with the bike. What is that from ??
(http://i202.photobucket.com/albums/aa49/tbarsby/002-4.jpg)
(http://i202.photobucket.com/albums/aa49/tbarsby/003-3.jpg)
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Sorry YZ250H its not a yzc 250 head the C did not have any cut aways on any of the fins . the fins are to large the C ones are about 1'' max long on the ctr fin Ill post photo over the next couple of days . the single plug head looks like a YZ 250 D 1977 .
Iain
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Tentpeg, sounds like this bike of yours was some sort of factory prototype/rolling testbed. You should see how much Yamaha will buy it back for.
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Yammy won't be interested. I think it was made in North Korea or Honduras or somewhere using the early jap psyche of copy and improve, unfortunately lack of funds ruined the project
Buy a canoe
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Sorry YZ250H its not a yzc 250 head the C did not have any cut aways on any of the fins . the fins are to large the C ones are about 1'' max long on the ctr fin Ill post photo over the next couple of days . the single plug head looks like a YZ 250 D 1977 .
Iain
Yeah, thanks Iain.
I was pretty sure that second one was all wrong. That was a spare anyway so you might just see it for sale soon ;) ;D
The twin plugger, although not the correct one may just do the job. Plus I will have the bonus of the "warm up plug" system. Not building a nut and bolt resto, just a good clean rider.
Tentpeg, sounds like this bike of yours was some sort of factory prototype/rolling testbed. You should see how much Yamaha will buy it back for.
Unfortunately it looks like it might be a bitsa. Hopefully most of the remining stuff is correct or I will get crankier than I already am >:( >:( >:(
Maybe I should just sell it now and cut my losses :-\
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Nah, it's a well known fact that you need to buy 3 extra 'parts' bikes to restore the one you start with
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True, I suppose.
At least it will be a runner once assembled ;D ;D ;D
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Nah, it's a well known fact that you need to buy 3 extra 'parts' bikes to restore the one you start with
Or you could farm it out to someone that can actually fit a gear lever correctly :'(
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Nah, that would make my resto's too expensive Ted ::). Touche ;D ;D ;D
Gear lever lesson learnt well and truly. When you've got half a day to spare I will tell you all the other lessons I have learnt from screwing up things on projects ::)
Generally it is "always check the easy things first". Like checking for a leaking valve before you grab the tyre levers to pull the tyre off ::) Gear lever is another example.
Maybe I should write a book. "VMX restoration for the mechanically challenged" ;D
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OK Ive given you a bum steer ,finaly got to the shed mmmmm forked up Iain ( note to self check first before opening trap hole ) the Yz c 250 only has one plug hole its the 400 that has two . sorry for the bum steer YZ250H . Iain :-X :-X :-X :-X :-X
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No worries whatsoever Iain. Thanks for your help.
Now confirmed 250 C is one plug hole. 400 has 2.
First head is ??? Second one is YZ250D ??
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Was the head originally a twin-plug head, or a single plug head that's modified?
???
The way the second plug sits under the long fin suggests its modified - usually Yamaha would give lots of clearance around the fin - which would cut the fin entirely.
Edit: Ignore the above. It's MX250B.
The parts picture at Yamaha-motor.com clearly shows two plugs (with one slipping under the long fin), and no fins cut for exhaust clearance.
The pic is here: http://partstream.arinet.com/Image?arik=BuIO8rMsKpZ4DQ063ygX&arib=YAM&arim=iPJ6VgYfK1nym6YvnClJQw2&aria=zDANmFQpUd7dhdhylcHqvQ2&ariz=1&ariv=http%3A%2F%2Fwww.yamaha-motor.com%2Fpartviewer%2Fdefault.aspx%3Fls%3Dsport , but it will some up as "bad request" if you click on the link...
DT250B+ are all sinlge plug, and have fins cut for the exhaust.
YZ250C is single plug.
Same source confrims that the second head is YZ250D.
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Mystery solved. Thanks guys.
I might clean them both up and sell them for a deposit on a 250C head ;D ;D