250 and 305 heads

[Dick Eastman]

I was comparing the two recently; the steel "scull" on the 305 has a 61mm relief cut in it, the 250, just as cast, the valve dias. appear the same.
My friend has a 250 that has been over bored to 57mm, and has been having a difficult time finding a decent 250 head, but 305 heads are easier to locate. Can a 305 head be used on a 250, and if so, are there other differences besides the relief cut in the steel "scull"? The intakes on a 305 are also only slightly larger [about 1 mm]; are the cams/valve train different, or any other differences that would prohibit the use of a 305 head on his 250 scrambler?
I appreciate the wealth of experience on the board to help with this inquiry.
Thanks,
Dick

[G-Man]

Dick

Just the skulls and the ports. Everything else the same. Some 305/350 racers like to start with a 250 head so that they can do their own squish band.

G

[Dick Eastman]

Dick

Just the skulls and the ports. Everything else the same. Some 305/350 racers like to start with a 250 head so that they can do their own squish band.

G

Thank you kindly, Graham.

[rrietman]

I have used a stock 305 head gasket on a 250 bored 3mm over with no issues. so maybe the head itself would work as well?
Randy

[pcmenten]

Hi all. I now have a 67 Dream 305. It needs to be put back on the road but it is complete.

Thinking in terms of performance improvements for a daily drive type use, I have looked at the big bore kit. I'm also quite curious to learn more about using a 250 head to create quench. If anyone can direct me to a web site that might describe this modification, I'd appreciate that.

Very cool bikes.

[Nick]

Looks like you found a nice one!
Having used a Dream for daily transport for many years (rode it to work again just last week) on both surface streets and the highway, I would not suggest going to a big-bore kit. In stock form the Dream is under-carbureted, under-geared and the mufflers are overly restrictive. You'll enjoy significant performance and speed increases if you go to a slightly larger carb, less restrictive mufflers (I simply pulled the baffles out of mine!) and a 2-tooth smaller drive sprocket.

More gains can be achieved by modifying a Superhawk cam to suit the Dream's 360 crank. A 2-into-1 exhaust will also help.

You needn't be afraid to rev the Dream, they love to rev.

[DJM]

Not trying to be funny here but surely if you want to improve the performance of a CA77 you should be looking for a CB77?.

With a single 22mm carb, the CA is never going to fly, even with a 347cc kit fitted,

Just my .02p worth, must admit to never having owned a C77 although I'd like one. My first bike was a C92 so I'm familiar with the concept.