1975 Yamaha DT250B (Issues?!!!)

[KamakazieX]

So, I finally got my 1975 Yamaha DT250B put back together after it failing on me many times in the past.. added some go-fast parts to it..

Rebuilt the top end with Webco head, wiseco piston, boyesen reeds. - Mikuni Flat slide carb conversion (VM28 -> TM28) and an open Uni 2-stage filter. Ran 93 oct. (always sunoco just for the fact different brand gas may run different..)

I ran out of gas at the trail, used regular 87, seemed to run fine, but I had 2 very noticeable problems which f'd the rest of my day up..

First the plug shit out.. I pulled it, black and oily. But- not to the point where it would foul. It had ran fine with that plug for two weekends on "moderate driving".

If I kicked it, it made a sound like when your lawn mower goes over a tree branch..

Right now I think its the woodruff key that split- which has happened a couple times in the past (often) - I think its because I used cheap gas. Need some advice! I just put it together!

Should I retard the timing or do you guys think it was a timing issue with the cheap gas?

BTW, since the top end swap and new carb, I'm running a B6ES (B8 is stock) and the plug is a dry charcoal color if I pull it after running. (on 93 oct.)

So heres what it could be from my perception:

Oil Metering pump too rich?
Carb too rich?
Cheap last resort gas?

The fuel line is also running dry if I WOT for too long and I have no top end power. (Shits out around 6-6.5k when it should be around 7.5k running strong) It's a 1/4in line and it runs dry quick.

[KamakazieX]

Also,

from what I remember hearing in some vague comment in the past.. I can use a blaster or banshee cdi unit & flywheel on my DT? Anyone know if this is true or can measure the flywheel-mag size with a caliper? I'd be all set with a 12 volt light setup.

[SAVAGE420]

I don't know what your problem is....but is this like your bike. My buddies 75...http://www.strappe.com/dt_150dpi_100pct.jpg

[BigG]

Originally Posted by SAVAGE420

I don't know what your problem is....but is this like your bike. My buddies 75...http://www.strappe.com/dt_150dpi_100pct.jpg

What's the setup in your sig?

[zillaguy89]

Originally Posted by KamakazieX

Also,

from what I remember hearing in some vague comment in the past.. I can use a blaster or banshee cdi unit & flywheel on my DT? Anyone know if this is true or can measure the flywheel-mag size with a caliper? I'd be all set with a 12 volt light setup.

it would probably take a little machinework, but I don't see why its not possible. I would think blaster would be a better candidate cause of the similar engine designs (more similarities than a shee at least) I think you should work on that, and then let me know what works, I'd love to ditch the points and condenser setup on my 74 DT250 =)

[SAVAGE420]

What???????????

[zillaguy89]

i do know that a blaster stator plate and the stator plate for my 74 are very similar....you'd probably have to re-wire the whole bike, but it might be worth it...I don't know if the small lighting coil on a blaster could make enough power to run the turn signals and everything....you might play hell getting the pick-up coil timed right.....it would depend on a lot of things.

[KamakazieX]

Maybe the magnets in the flywheel are shot? Would that explain why a b6 is running rich on a raised comp. motor?


This is it:



It's decent enough.. - when it runs. -- If it's free, it ain't broke.

Well- I bought 4 woodruff keys so if I get stuck next time I got backups.

[SAVAGE420]

Cool man , his looks just like that when its together but its a shitty gay blue.

[KamakazieX]

Webco head on that thing is night and day.