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PostPosted: Wed Sep 30, 2015 3:50 pm 
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Joined: Tue Sep 29, 2015 3:08 pm
Posts: 3
We got this MR 175 for our son to ride. It had been sitting a long time, we put in a lot of work and some parts and got her running pretty well. Then all of a sudden it starts running like crap. Wont rev up, no power, we went thru it with no luck of making it run better so then we took it to a bike shop. He went thru it and thinks its the carburetor. So I measure the engine side of the carb at 28mm, and have not had any luck finding a direct replacement for it. Has anyone here dealt with this issue and had any luck finding a replacement carburetor?


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PostPosted: Wed Sep 30, 2015 5:50 pm 
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Joined: Sun Nov 30, 2008 12:10 pm
Posts: 1010
Location: Connecticut, USA
The OEM Keihin carb on the MR175 (all years) has a 35mm spigot, 44mm mouth, and 98mm overall length. The Honda MT250, FL250, and '74-'75 CR125M carbs are nearly identical.

If you want to install a new replacement carb, the closest physical fit should be the Mikuni VM28 (35mm / 44mm / 95mm are the dimensions I found - if you do decide to get one, double-check the dimensions with the seller in case mine are incorrect).

http://www.ebay.com/itm/Mikuni-Geniune- ... 78&vxp=mtr

The Keihin PWK28 or PE28 would probably be my personal choice, but their dimensions (35/50/83) make installation more difficult. There are very cheap copies of these carbs available on eBay; I have no idea how well they'll work, or for how long.

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 Oct 06, 2015 7:55 am 
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Joined: Tue Sep 29, 2015 3:08 pm
Posts: 3
Thank you for your help Ray. I'll check into those.


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PostPosted: Sun Nov 08, 2015 9:37 pm 
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Joined: Sun Aug 16, 2015 11:24 am
Posts: 1
Is it the carb? Or could it be the main crank seal on the clutch side sucking oil and causing it to run like crap-ola. That was my experience with the MR 175 I got. I'm just now putting the engine back together, just today I made my own copper head gasket as they don't make the originals anymore, and if you do find one they cost an arm and a leg. The nice thing about a copper gasket is you can reuse them time and again by re- annealing them. Something to check out before you buy a carb. Or it could be the seal behind the magneto sucking air in and causing it to run lean. Both my seals were shot... go figure! Time is hard on rubber seals. (Just like it is on our bodies.) Whew, think I'll go lie down and take a nap.


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PostPosted: Thu Nov 19, 2015 3:09 pm 
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Joined: Tue Sep 29, 2015 3:08 pm
Posts: 3
Thanks for the reply fmwe4, actually just did a tear down and replaced all the engine seals hoping that was the problem. Didn't help in our case, all the seals were good. Replaced them anyways since we went to the trouble of it. Have not purchased a new carb yet but it's on the list of things to do. My son bought a newer TT125 in the mean time and he's been riding that while we have shelved the MR175 for now. You know because of the whole too much time and not enough money thing. lol Ride on!


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PostPosted: Tue May 17, 2016 12:18 am 
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Joined: Mon Jun 25, 2012 7:53 pm
Posts: 5
I just got re-acquainted with this forum and read your post. I have a 76 MR175 and recently replaced the stock carb with a new Vm28 Mikuni like the previous gent suggested. I can get you the name of the distributor ( I don't have it at the moment) It bolted on perfectly however I had trouble with the air box so I removed it and replaced it with a K/N air filter and rubber flange attached. No problem. Started on kick 2 and every time since. It now runs really well.


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