I have a B model 250 with the original Mikuni that I've been trying to setup for a few years. The motor as a .005 inch head gasket, is on 3rd os, the exhaust port is '' lifted'' .020 inch, the rest of the ports are not modified, not really polish but clean. There is no modified reed valve. I run Shell super gaz with a good oil at 50:1. I fitted a Uni Filter and the motor is equipped with a Wes exhaust. I played with the timing without any real improvement.I have been fiddling with the needle eight, low speed and main jet, air screw etc. but the motor is always running hot at close throttle to 1/4 open . I fitted a VM 26mm played with it all of one summer and went back to the original Mikuni. I am thinking maybe an OKO carb might cure the problem, any experience ?
You should also have a look at your cable and it's routing, I know they are different, but the clutch on my TY 250 is smooth and predictable. I change the cable and keep it well lubricated, I also use a longer lever. It is very light to a point that some of my friend thought I ad taken spring out.
I don't think numbers are important here as electric motor do not delivers power the same way a combustion motor does, and by the way, the first mono where laughed at.
There might be 10,000 km of off road trails in the FQMHR but I ride either a Ty 250 or a Beta Rev with no light or turn signal, and frankly I'm not interested in riding full throttle in a field. As for the ATAQ, they are a great bunch of guys that organise competitions, and there is also a vintage trial group that also organise comp that I attend and really enjoy. But I like to ride ( trial terrain ) not compete. I like to ride just for fun. As for you Leosantanalg, don't throw the line too far, you might see me coming around one Saturday morning. I went to Vermont last year to meet the guys, the Vermont Plonker, and I can promise you that if I still have my bike I will be back this year.
I had time to do a little work on the motor yesterday, as you mentioned David, the crankshaft on the clutch side is different. From what I have measured, they would be interchangeable if you use the primary drive gear of the same year as the crank if you do not use the oil pump. Also the axle main 14t ( 434-17411-00 A model ) and the clutch ass'y won't be interchangeable. I don't have anything to check the weight of the crankshaft , but the A model look heavier, that maybe one of the reasons Yamaha added weight on the flywheel ( they sure overdone it ). On that subject, I always take the ring on the flywheel and use an A model flywheel on my B.
I split the base and I think I had reasons to fear. I only have A model parts list but I'm sure everybody will understand. On the output shaft ( on witch the chain sprocket goes ) called in the manual part 17 axle drive, the last gear, part 18, gear 2nd wheel is not free as I was expecting it, So is that shaft on a D model interchangeable with one from an A model ? I could use the complete shaft ( with all the gears )
canada280i I found the one on Kijiji this weeckend, it's a bit more expensive then the one ( I hope it's not the same ) I was offered. I don't fell '' the love ''.
250 B carb
in Yamaha
Posted
I have a B model 250 with the original Mikuni that I've been trying to setup for a few years. The motor as a .005 inch head gasket, is on 3rd os, the exhaust port is '' lifted'' .020 inch, the rest of the ports are not modified, not really polish but clean. There is no modified reed valve. I run Shell super gaz with a good oil at 50:1. I fitted a Uni Filter and the motor is equipped with a Wes exhaust. I played with the timing without any real improvement.I have been fiddling with the needle eight, low speed and main jet, air screw etc. but the motor is always running hot at close throttle to 1/4 open . I fitted a VM 26mm played with it all of one summer and went back to the original Mikuni. I am thinking maybe an OKO carb might cure the problem, any experience ?
Guy