Vintage Dirt Bike Q & A

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 Post subject: 76 mr175
PostPosted: Fri Nov 20, 2015 5:40 am 
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Joined: Thu Nov 19, 2015 7:13 pm
Posts: 3
hello, and thank you for letting me join
i have a 76 mr175 that i have had for years and only gotten to ride a few times ... main problem being that my buddy tried to start it and did not have the flywheel bolted on ... it did not snap the key, it snapped the crank away from where the key goes in it ... then he tried to weld it in place so at least we could ride it till i could find another crank and flywheel ... it ran about 5 seconds then it broke the weld and spun out of time just enough to not run and it locked in place ... this was a fun little bike and i would like to get it fixed ... as i do not have a press, i will need a crank with a good rod already on it and the flywheel ... i will also need a clutch basket as one of the "posts" is broken ... i will be needing the parts when i get my tax return in a few months so i wanted to try to locate the parts now and get some prices with shipping ... if the price was right, i would buy the full bottom end and just swap out my jug ... i do not want to have to scrap this old bike


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 Post subject: Re: 76 mr175
PostPosted: Tue Dec 15, 2015 6:38 pm 
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Joined: Tue Jan 27, 2004 8:51 pm
Posts: 136
Location: Gilbert, AZ
Ebay for a used crank and clutch basket.
Otherwise try crankworks in Tempe AZ. Phil may be able to TIG weld your keyway and cut a new one. MAY...

Rick


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 Post subject: Re: 76 mr175
PostPosted: Wed Dec 16, 2015 11:21 am 
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Joined: Sun Nov 30, 2008 12:10 pm
Posts: 1010
Location: Connecticut, USA
Welcome!

The MR175 can be very hard on flywheel keys - my original one was nearly sheared in half. I've found decent complete motors on eBay for less than $200 - sometimes less than $50 - but right now (12/16/15) doesn't seem to be a good time for either motors or cranks over there. Just for what it's worth, my buddy is currently running an aftermarket Powerdynamo ignition on his MR175 with no key at all (!), and it hasn't slipped so far (both tapers are perfect, though).

The MR175 ignition can be a real horrorshow after 2K miles or so, although most of them work OK early on. The MT125 ignition fits the motor cases & ignition cover, but you'll have to adapt the cable to the MR harness. I'm using CR125M ignitions on both my 175's, which make them feel more like 250's down low.

Re the clutch - I'm not sure if by 'posts' you mean the threaded posts in the hub, or what I call the 'fingers' in the basket/primary gear that engage the clutch plates. The '75-'78 CR125M or '75-'76 MT125 clutch hubs (with smaller center hole) will work, but only the MR basket will fit unless you change out the basket and drive gear to the CR125M setup, which is what I've done in both my motors.

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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