Vintage Dirt Bike Q & A

I have been working on my MR250 on and off for a few years now and finally went a head and got a Mikuni 36mm. First time starting with the Mikuni and it was a world of difference. Only problem with the Mikuni is how the throttle cable comes into the carb. On my Keihn there was a 45 degree bend on the top of the cap. With the Mikuni there is just a short straight stub in the cap making my throttle cable too long. I have tried but can't figure out a way to use the 45 from the old cap with the new cap. What have others done? I have also thought about getting a universal throttle cable stop to go up in the twist grip and cut the cable to desired length. I would rather not do this because I don't want to wreck the cable. My other problem is with the exhaust. Where the pipe meets up with the flange at the head is there supposed to be some sort of a exhaust donut in there? I have looked on various websites with parts but none of them give all the parts of the diagram and I don't want to order something if it is wrong. If it is just a donut gasket I would think I could just go to an auto parts store and get one cheaper. I can post pictures if it would help clear up my question.
Thank you, Michael.

Good luck on finding an exact fit throttle cable.
What I do is desolder the brass ferrule on the end of the insert that goes into the carburetor slide and move it up to the length you need. Using flux, I resolder it there and cut the cable a bit longer and then slowly, very slowly, grind the cable to be flush with the bottom of the ferrell.

As for the exhaust save your money.
Buy high temp silicone (red or copper) and use that instead.
Be sure to clean both surfaces to be oil-free and apply just enough silicon to not squeeze into the expansion chamber when you install it. Let it sit 24 hours and you will never have an exhaust leak there again. You can never say that about the original parts for this Junction.

Rick

Could you remove the elbow from the original carb top and fix it to the new carb? With effort,they will come out.

I ended up going with desoldering the end and resoldering it at the right length. With a little effort it worked great. I also did the gasket maker and it seemed to work. My next question is if anybody has sealed the inside of the fuel tank? I cleaned it out the best I could but I still feel overtime the rust and debris will continue to contaminate. What brand dealer did you use? How did you prep the tank?
Thanks.

I ended up going with desoldering the end and resoldering it at the right length. With a little effort it worked great. I also did the gasket maker and it seemed to work. My next question is if anybody has sealed the inside of the fuel tank? I cleaned it out the best I could but I still feel overtime the rust and debris will continue to contaminate. What brand dealer did you use? How did you prep the tank?
Thanks.

Kreem makes an A and B kit. A will remove the rust and dry the metal,B will dry the inside of the tank. If the rust is pretty light I just use the A-B kit and get the rust out. Then I put some premix in the tank. If it's pretty rusty then I coat the tank. It's a do-it-yourself deal that works excellent as long as you don't rush. I usually let the tank soak over night with the rust remover solution in it. If I have to coat it I pour the stuff in and rotate the tank every 30 minutes for the first few hours to evenly coat everything. DO NOT let the coating on the paint! Instructions say to let it dry for X amount of time but I always let it dry for 4-5 days. I've never had one fail doing this.

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