Searching for low end 82 CR250

[Eurofreak]

I'd rather buy a larger rear sprocket. We'll see how it feels after the new jets are installed.
If I can, I'd rather add to the Cr cylinder's low end instead of a WR cylinder.

 

[fran...k.]

What will setting the squish do? Is that the stock setting?

Setting the vertical height of gasses above the piston at top will effect the kind of gas flow across the piston. To help out in a reliable manner long distance on a forum the guys attempting to help will most likely be asking this. The spark starts as a kernel of flame.

It is my impression that decking the cylinder, cutting off where the base gasket goes and cutting into the head for the piston top is the direction to go. A cr cylinder if different than a wr one might be more of a plane off the top difference.

I think I read most of this. Is using a modern silencer discussed. You are at least supposed to re pack your silencer before investing too much effort on tuning.

 

[Eurofreak]

Thanks Fran. I will check the stock silencer for new packing. The previous owner built it for vintage racing. It has two races on it. I'd be surprised if he didn't looking at everything else he did but...
A modern silencer was not discussed. The jetting will be here shortly and I will run it around after installing.
Regarding the squish-

Use base gaskets to set squish at .040-.045".

So this would be an increase in compression? It doesn't need any more power on top-plenty there.
I have lowered compression with base gaskets to aid starting and change port timing. Never measured it tho I understand the concept.

 

[suprize]

steel wool in the muffler will help low end a tad

 

[Picklito]

It's not really about raising the compression or increasing peak HP. It's just about getting this motor to run its best.

Ideally we would set the cylinder at a height that gives the port timing we're after, and then we'd set the head where we get the desired squish distance. Then we'd massage the bowl to get the compression ratio we want. That might require machining the top or bottom of the cylinder, or the head surfaces as fran...k mentioned. That's quite a bit more measuring, machining, and $$$ than most of us want or need for these old scoots. But these motors are actually pretty good, and just using the Cometic base gasket that lands the squish distance at .040-.045" is a really good start, and for just the cost of some gaskets. Stock, they typically are in the .060-.080" range. There's a lot left in these motors for just a base gasket.

 

[jo360]

I have run no base gasket on my 2007 cr144 and retarded the ignition looking for more everywhere but the rest of the mods rendered any comparison to stock useless but on good fuel with a squish around 1mm you should see an overall improvement providing the squish is way off say 2mm (sorry metric not imperial) currently running 1.2mm on my wr430 , jetting, squish and gearing should be enough and cheapest route for low end gains i prefer to clutch and go up on gearing you can extend the clutch actuator to give lighter pull.

 

[Bigbill]

Why not build a wr engine and install it in a cr frame?

 

[Eurofreak]

That explains it a bit. I'll give it a try. Bill, I don't want to put that much $$ in it right now. I'd rather fiddle with what I have. It won't need much to make it a lot better in the woods. Just some low end.