Vintage Dirt Bike Q & A

I'm wondering if there's anything I can or should do to improve my mt - was thinking along the lines of lighter wheels, forks, & triple trees. if so what would be a good fit? I'm putting progressives on the rear and if I can lighten it a little well ok?

There are actually a couple easy mods for the bike to help in the motor/engine department.

If you're riding yours on the street, not sure how much you will be interested in doing, but if you are riding it strictly off-road there are def some mods.

First - take the flywheel off, and have someone turn it. Don't take it as thin as it will go, just tell the machinest to take about half the excess metal off. You will see how thick the metal is very easily. I can't remember off the top of my head how much lighter it is that way, but it's substantial and noticable in the throttle response and the bike doesn't want to stall.

If you want to take the airbox out it's a nightmare, but I put a foam weenie on mine because I happened to have one, and it appeared to help quite a bit. I need to check my jetting to see if I need to go richer though as it's def flowing more air!

A friend on here "Rick" spotted a "Hooker Header" on eBay and I snagged it. Haven't mounted it yet, but will when it warms up. The stocker is heavy and I'm sure is very restrictive - I've actually seen some full race MT exhausts on there (eBay). I'm sure they would help but be loud.

Last but not least there are two ways to play with the head. You can mill the head 20,000ths and pick up mid range, and it will rev quicker. It appeared to even have more top end because it could "pull it" easier. My next step is to mill the head another 10,000s to give me 30,000ths total from stock and either add a base gasket to lift the exhaust port (but I feel that wont be enough) or lift the exhaust port a small amount - 1mm is what I'm going to try.

I figure the increased compression can make up for the taller exhaust port and I should pick up some top end at the loss of some midrange.

Those are the easiest mods I've found. I'd like to find a 2mm larger carb, or have this one bored 1mm or 2mm if it can handle it. We'll have to wait on that one though - just like the Hooker header, I haven't had time to mess with that much.

Good luck.
Mike
BTW, you def have to run 92/93 octane gas with the milled head. I actually use a little Maxima "Hi-Test" with mine too since I'm riding off-road only on this bike. It's only about $5.99 and can treat 10 gallons of fuel.

You could mount a CR250M front end including the forks and the aluminum triple tree to save a little weight. Honda CR250M wheels would be lighter especially the rear since the one piece hub and the aluminum rims are quite a bit lighter than the MTs hub and steel rims. For the time and money I would skip the front end mods and try to find MR250 front and rear wheels. They are the aluminum hub and rim types and the front uses the same conical type front hub. It is a bolt on swap. Alot of weight saved for not that much money or hassle.