Vintage Dirt Bike Q & A

Ryan, you were right it was just flooded. The next morning I went out and started it up on the 2nd kick, and got some real nice RPM range (havent been able to do that for awhile_, but after maybe 5-6 seconds of revving, it will bog back down and putter with no throttle response, then about another 5-6 seconds I can rev it high again. When I'm revving it high, and I let out the clutch to go forward, it just starts the bogging down again. I think I'm going to check the crankcase for floodage today.
Thanks for your help

Your welcome. And now it sounds like the ignition timing might be off have you timed it correctly? And also did you try a new spark plug?


-Ryan

Wow. It sure has been awhile, almost a year since I posted this. Well, I still have the ol' MR, and I was just reminded of it yesterday when I was fixing up a snowmobile with a friend. He had bought some new carbs for his Yamaha, and the old ones were Mikuni VM36's. I knew I had heard about this model somewhere, but couldn't put a name on it, then I remembered about you guys talking about taking off that old Keinhin and putting on the Mikuni.

Now, obviously I will have to put on all new jets, but besides that, this should work right? As long as the body itself is a VM36, it doesnt matter what it came off of right?

I went outside to the MR after this, rocked the bike back and forth for a minute or two, kicked it, and on the second kick it started up. Was able to rev through the ranges for about 3-4 seconds, then it started the all so familiar bogging down that plagued it before. I was still able to ride it down the road and back up my driveway though. Exicted to try and get it running. I will have to refresh myself on what I had learned before though, I have forgot alot about what I have diagnosed.

Also, gave it a compression test, and got 130-135. I must have mis-calculated it the one time I got 110.

I would think any VM36 would work. But I only have two Mikuni carbs and am not an expert. Make sure you have a 2.5 slide in it. I like to run 40 pilot; 270 main; 6dh7 needle; 159q4 needle jet.

Good luck in working the MT intake manifold up & around the 36mm carb intake. Be careful it doesn't split on you.

~JM~

_________________
WWW.CADDY500.COM
The High Performance
Big Block Cadillac Forum