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PostPosted: Tue Nov 17, 2015 10:51 pm 
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Was so happy to see the state of the carb- could only go faster now....right?
Looking for the best place to get hold of a rebuild kit...any pointers gratefully accepted.


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'75 MT250
'78 Sportster
'81 RD350LC
'86 FZ600C
'94 CBR400RR (track bike)
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PostPosted: Wed Nov 18, 2015 7:37 am 
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Joined: Sun Nov 30, 2008 12:10 pm
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Location: Connecticut, USA
This one's pretty decent (the Honda FL250 uses a nearly-identical carb):

http://www.ebay.com/itm/K-L-Carburetor- ... hR&vxp=mtr

Ray

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'74 CR125M (175cc), '75 MR175, '82 RM250Z, '08 YZ250F, '14 Zero FX electric, '14 Zero MX electric, '18 Alta MXR electric


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PostPosted: Tue Dec 15, 2015 6:42 pm 
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Joined: Tue Jan 27, 2004 8:51 pm
Posts: 136
Location: Gilbert, AZ
Thanks Ray. I need 2 of them and that one has what I need for mine. Mainly the bowl o-ring and needle and seat.

Rick


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PostPosted: Wed Dec 16, 2015 10:30 am 
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Location: Connecticut, USA
Rick,

No problem! You may want to try that needle too - it's leaner below 1/2 throttle than the Honda ones & might give you a better idle and low-end throttle response, especially if your needle jet has a lot of hours on it.

Ray

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'74 CR125M (175cc), '75 MR175, '82 RM250Z, '08 YZ250F, '14 Zero FX electric, '14 Zero MX electric, '18 Alta MXR electric


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PostPosted: Wed Dec 16, 2015 9:35 pm 
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Joined: Tue Jan 27, 2004 8:51 pm
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Location: Gilbert, AZ
2 kits ordered.
I have a 1975 MT250 and a 1974 roller with carb.
The '75 carb ran lean when warm so I put the '74 carb on and it was flooding out.
Ended up being the O ring on the seat (needle seat).
Found one to work and did this on the original carb too but have not tried it yet.
I do notice the '74 carb gives a LOT more low end response but I will put the '75 carb on after this kit is installed.
I will report back next year (2 weeks :) ) how it works. Our prime riding time is now here in AZ. :lol:

Rick


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PostPosted: Thu Dec 31, 2015 12:06 pm 
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Ok sad question. I tore apart the carb pretty quickly, taking what I thought was enough pics. Whole thing is a little mor complicated than I'm used to and then....I came across this tiny little collar/ring thing and I've no idea where it came from. It is not pictured in any diagrams yet attached Pics from a website selling kits suggest that it might sleeve over the tickover screw?


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'75 MT250
'78 Sportster
'81 RD350LC
'86 FZ600C
'94 CBR400RR (track bike)
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PostPosted: Thu Dec 31, 2015 12:56 pm 
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Yes, that collar slips over the idle adjustment screw.

Rick, I was curious as what jet sizes you found in the 74 and 75 MT250 carbs.

Thanks
Mark


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PostPosted: Thu Dec 31, 2015 8:41 pm 
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Great. Much appreciated!
Mine's a 1975. Jets found are 119 and 58


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'75 MT250
'78 Sportster
'81 RD350LC
'86 FZ600C
'94 CBR400RR (track bike)
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PostPosted: Thu Dec 31, 2015 9:08 pm 
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Joined: Sat May 24, 2014 7:19 am
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The 75 stock jets were 115 main and 58 slow. Your picture is a little blurry but it looks more like a 115 than a 119, my eyesight is not what it used to be though.


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PostPosted: Sat Jan 02, 2016 8:41 pm 
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Double checked armed with magnifying glass and you're right: 115.
Also found another jet which I've yet to read up about.
It's on the side and 0.8..


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'75 MT250
'78 Sportster
'81 RD350LC
'86 FZ600C
'94 CBR400RR (track bike)
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PostPosted: Sun Jan 03, 2016 2:27 pm 
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Joined: Mon Mar 23, 2015 4:40 pm
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Hmm the kit has a 120 main. I've rebored to first oversize. Would it be wise to throw in the 120 or just put the 115 back in?

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'75 MT250
'78 Sportster
'81 RD350LC
'86 FZ600C
'94 CBR400RR (track bike)


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PostPosted: Wed Jan 13, 2016 10:28 pm 
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Joined: Tue Jan 27, 2004 8:51 pm
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Location: Gilbert, AZ
texasmark wrote:
Yes, that collar slips over the idle adjustment screw.

Rick, I was curious as what jet sizes you found in the 74 and 75 MT250 carbs.

Thanks
Mark

I have not measured them yet.
I decided to install as-is as it couldn't hurt at all. The '75 carb would run lean when warm...problem solved. Thanks.

I did not find the collar as shown above in my carb or in the kit. Figured it is still in the carb casting or not used. [shrugs]

At least my bike runs well now and I am not afraid to take a long ride but as it warms up more I will tinker with the jetting and dial in the points to exact specs.

Rick


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PostPosted: Sun Jan 17, 2016 12:01 pm 
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Joined: Tue Jan 27, 2004 8:51 pm
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Location: Gilbert, AZ
texasmark wrote:
Yes, that collar slips over the idle adjustment screw.

Rick, I was curious as what jet sizes you found in the 74 and 75 MT250 carbs.

Thanks
Mark

First, I have no idea if either of these carburetors have original jets in them. I live in Arizona and the elevation is around 1200 feet.

1975 MT250 carb
Main = 115
Pilot = 58
Needle = 271004

1974 MT250 carb
Main = 105
Pilot = 60
Needle = 271002

The FL250 carb kit from fleabay.
Main = 120
Pilot = 58
Needle = D96. (anyone able to translate this?)

Rick


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PostPosted: Sun Jan 17, 2016 3:24 pm 
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Joined: Sun Nov 30, 2008 12:10 pm
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Location: Connecticut, USA
Rick,

I think the idle-speed-screw collar is initially pressed into the carb body, mainly to support the screw end (the slide's constantly banging down on it, which is probably why it loosens up). On my carbs, the symptoms of the collar missing was an erratic idle; this isn't a big deal with the MR/MT motors & their big stock flywheels, but my bikes have CR tiny-rotor ignitions and it was a real PITA.

According to my MT250 info all these jets/needles are stock, except where noted:

1975 MT250 carb
Main = 115
Pilot = 58
Needle = 271004

1974 MT250 carb
Main = 105 (stock is 122)
Pilot = 60
Needle = 271002

The FL250 carb kit from fleabay.
Main = 120
Pilot = 58
Needle = D96 (similar to 271004, but slightly leaner straight section & slightly richer taper)

Ray

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'74 CR125M (175cc), '75 MR175, '82 RM250Z, '08 YZ250F, '14 Zero FX electric, '14 Zero MX electric, '18 Alta MXR electric


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PostPosted: Thu Jan 21, 2016 11:59 am 
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Joined: Tue Jan 27, 2004 8:51 pm
Posts: 136
Location: Gilbert, AZ
Thanks Ray.
With the 105 main I may be close to what I will need for this summer at my cabin at 7000'.
Is there a chart to assist me in main jetting for altitude at 7000-9000 feet?

Rick


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