Vintage Dirt Bike Q & A

Bought this bike at a farm sale, the owner passed away, it starts and everything, but no manual came. I asked a few guys there if they knew what the mix was on it, but I got 3 different answers(32:1 20:1, whatever smokes a little ect.). If someone knows that would be great. Thanks alot

Ringer

The ratio depends on the oil and the size of the bike not its age. For a 250 c.c. use Bel-Ray MC-1 at 50:1 or something like Spectro or Maxima at 32:1 or 40:1. The difference in ratio only affects the jetting by less than one main jet size. Do not run anything at 20:1 modern oils are far superior today and you will struggle to get the motor hot enough to burn all the oil and then its gloop all over the place

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Michael Stiles
1979 Honda CR250R Elsinore | 2006 Husqvarna SM510R | 2007 Service Honda CR500R-AF

Not to mention that back in the day we were running leaded gas. I have a few CR250s from 73-83 and I run Maxima at 40:1 in all of them with no problems.

Thanks alot guys, at the moment where I live its hard to get anything else besides wally-world brand 2 cycle oil. I use to use Castrol in my 82 Kawasaki 250.

Also, I finished rebuilding the carb and started to inspect the the rubber intake manifold and it appears to have cracks in it. I have called everywhere to i try and find one but they are out, do you guys know of any good used/new parts dealers that might have one?

If not dont worry about it. Thanks a lot,

Ringer

Would't the MR have an oil pump? This brings up another question. If todays oils are so different what are we supose to run in a 74 MT250 with an oil pump? I'm currently using 2 cycle outboard oil.

ringer - search the swap section, i've found most of what i needed on this site - el gueche

I run a little under 50:1 in my MR250. I noticed that with my current carb settings that mine does not perform at its peak If the mixture is to fat. When I was running under 40:1 initially ( bike sat for 2 years), it would not pull the front tire on the power band. Now with my new ratio, it will pull the tire with a crack of the throttle!

Yeah I kinda went between 50:1 and 40:1 and found that my bike responds better. No, my MR doesnt have a separate oiler on it. I was able to find the intake for it. Thanks guys.

But some bad luck this weekend, was riding in out of pastures and across a gravel road and a peice of sand was kind enough to get in the rear brake line and manage to cease my rear break from working. So to keep from wrecking. when I pushed down on it and it would not respond, the break pedal broke. Well at least I didnt wreck. Are these parts kinda standard enough I can stop by the local bike shop and get some or are they hard to find?

Thanks again,

Ringer

Wow! Guess it must have been all that adrenaline. My break pedal on my MT250 is pretty strong. Are you sure it was sand in the cable that caused the problem? There is not a lot of travel on my MT before the break pedal hits the foot peg mount. Maybe your MR has the same problem? Found my replacement on Ebay. In my case, the return stop was broken from too many falls, causing it to hit the case. Look closely at any replacement to make sure everything is straight and intact. If it were available at a bike shop it would be very expensive. I paid about $15 for mine. ThereÌre steel on the MT. Is yours aluminum?

Yeah its aluminum/alloy of some type, my brother wanted to mig it but I dont think it will work, broke when i was hammering it to keep from wreckin it into a fence. Well the cable wont move in or out with out some major pressure on it.

Here is a listing for a used one. I have never purchase from them but the price is right http://www.bikeboneyard.com/76%20mr-250.html You should replace the cable with a new one. Your bike shop should be able to help you with that. You could also post a message on the swap meet here. Good luck

Yeah I found that the other day, I am almost ready just purchase the whole damn bike for spare parts. But Brendan there, found everything I needed for about $50 bucks for the pedal, brake cable, and rubber intake. Lot cheaper than going to the nearest watering hole and having them hunt around for it.