Vintage Dirt Bike Q & A

Hopefully you won't be cursing me later on for this...

Have you gotten the kickstarter issue resolved? I went back over the posts and couldn't find where it had been repaired or otherwise dealt with. I sure wouldn't forget about it and hope it won't be a problem, because in all likelihood it will be.

In my experience, flywheels and ignition rotors cling to crankshafts with the absolute grip of death, especially if a little rust is present. If you can borrow an automotive claw-type puller and if the claws can either reach the rear of the flywheel or fit inside the cutouts, this may work - otherwise you may have to bit the bullet and get the proper 27mm LH-thread internal puller.

Last week I tried removing a '77 CR125 rotor without a puller (a 26mm RH-thread internal - they don't exist) by tapping the crankshaft a bit, then I came to my senses and used the claw puller; I had to really lean on the puller bolt, too. I could have "tapped" it right through the cases and it wouln't have budged.

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

Ray

Currently I have left the kick started on as is. so I can still kick it over until i get it going nicely then I will just remove the kick start arm and leave it like that. If I need to pull the gear out then I will But the oil is still fresh and I don't really want to waste time until I get it running well. And if I were to sell it then I think I could get more being able to kick it over on the spot. There is a parts store close to my house I will head over there after work and see what is out there. Its simple to understand plus I always wanted a gear/flywheel puller to add to my collection of tools. This bike is a real pain in my ass. By the end of may if I don't get it running well then I may just have to pass it on to another person and take what I can get for it. I really do like the feel and size of the bike just this motor is pissing me off. I will keep you posted!

Well Ray you were right the flywheel had the grip of death going and it was not even rusted. I was able to get it off with a universal gear puller. I found that the plate that holds the points in had come loose so I tightened up the screws and pit it back together. Now it spudders quite a bit but I was not able to get it started as it must have flooded because gas was dripping out of the exhaust so I will need to check the float level and go from there. These 2 strokes are very simple I think I will get it going very soon now.

Ok, So I have gone through the whole bike. I started with the points, cleaned them with sand paper and checked the gap and timing all seemed in decent shape. I then cleaned up the carb checking the jets for clean passage. I checked the spark and it is much better with the cleaned points(blue spark).

So the moment of truth came to start it up. It was 11pm at night and I know this bike is very loud so taking it for a spin was out of the question but I still kicked it over and on the first kick it fired right up but when I gassed it, it sounded like it was getting way to much gas. I shut it down as my garage was filled with smoke and it was time for bed. The next day I got all ready to take it out but could not get it going again it just floods and gas starts to drip out of the exhaust. So now I am stuck again I adjusted the float level but still will not start and floods.

I think I need to rebuild the carb with new parts but the keyster carb kit seems to not have the proper needle for the mr175 carb should my next step to get a carb kit or???

Once again, it's great you at least got an MR with a working ignition. If yours had a good carb too, it would have been like winning the lottery.


I've never bought a Keyster carb kit, but the guy I talked to on the phone there once was super helpful. I can tell you for certain that the carb kit in the following eBay auction has the correct float-valve needle (the MT250 carb is nearly identical to the MR175's):

http://cgi.ebay.com/ebaymotors/HONDA-NE ... ccessories

ALWAYS REPLACE THE FLOAT VALVE NEEDLE AND SEAT AS A SET!

If you got a Keyster kit, I would definitely replace the stock slide needle with the Keyster one. My carb had the same symptoms as yours during initial testing, and it turned out both the slide needle and needle jet (the main jet screws into it, and the slide needle fits inside it - if you already know this, my apologies) were completely worn out. If this is the case with your carb - as it is with many vintage carbs - the bike will never run really well unless it's fixed (new slide needle & needle jet), or at least 'kludged' (replace slide needle or build up the old one's worn straight section with solder and sand flat, remove .5mm from slide cutaway). A #48 pilot jet and #118 main jet will help a lot; the stock jetting is just too rich and will screw you up for the foreseeable future unless these are changed (main jets are 99101-357, slow/pilot jets are N424-24):

http://jetsrus.com/a_jets_by_carburetor ... ection.htm

And before I forget - you mentioned having a copper head gasket in an earlier post. These are .020" thinner than the stock gasket, and will increase compression quite a bit - which is a very good thing in these 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