Beta Evo 250 Low Compression Head Insert.

[stpauls]

Has anyone used a lower compression head insert to make the power softer on a Beta Evo 250 T?  Opinion?

Edited August 18, 2015 by stpauls

[goudrons]

There are easier and cheaper ways of softening the power delivery than messing with the head.

 

Beta dealers in the US have been offering SS models (Super Smooth).

 

Apart from a few other alterations, they fit a flywheel weight (standard on UK bikes before 2015??), replace the fast action throttle (white tube) with slow action (black tube) and replace the 11t gearbox sprocket with a 10T.

 

 

[slicktop]

The tophat washers on the clutch pack can be rearrainged to adjust engagement too. Beta offers thinner clutch discs too. This really helped smooth out the power delivery on my 300.

[inchhigh]

A friend of mine put one on a 290 evo and it transformed it.

[totty79]

The 250 has the lowest compression of the range at just 8.9:1, I wouldn't expect to be able to reduce this by enough to make a significant difference - although I've never tried.

 

Not all evo's have the tophat clutch washers, I think it's only 300s, my 2012 250 does not have them. Swapping out the two thicker clutch plates did help smooth out clutch engagement on my 250, which does help make the bike feel less aggressive. 

 

[stpauls]

There are easier and cheaper ways of softening the power delivery than messing with the head.

 

Beta dealers in the US have been offering SS models (Super Smooth).

 

Apart from a few other alterations, they fit a flywheel weight (standard on UK bikes before 2015??), replace the fast action throttle (white tube) with slow action (black tube) and replace the 11t gearbox sprocket with a 10T.

I have the flywheel weight. slow throttle and a 10 tooth front sprocket.

[goudrons]

I have the flywheel weight. slow throttle and a 10 tooth front sprocket.

 

And it's still a handful?

[dan williams]

I have a 300 that I put a low compression S3 head on. It also has VForce carbon reeds and I dropped one tooth on the countershaft. I also had some custom clutch washers made with less preload and replaced the two thicker fiber plates with the thinner plates.

As someone pointed out the 250 has a lower compression ratio so I'm not sure how much of a change you will see. On my bike it mellowed out the hit that occurred at mid throttle. It also made the bike easier to kick over. It does seem to have limited the ability to run at high revs/low load as the bike burbles wide open on fireroads.

If you want the bottom grunt enhanced I highly recommend the carbon fiber reeds. My bike pulls a gear higher on hills and is almost impossible to stall. this is literally the first thing I do to any new bike.

[goudrons]

My '14 300 came without a flywheel weight and after riding a '07 Rev3 250 for so long is was like trying to tame a lion at first, particularly that mid throttle hit.

Seems the transition off the pilot circuit to main jet can be pretty brutal.

 

While soucing a weight I stuck on a slow action throttle and it did smooth out that hit and make the power delivery smoother, but I didn't like all the travel I had to put into the grip when I did need to wind it on. (I'm lazy).

 

The weight, back to the fast action and some practise (often overlooked) and it soon started to feel right.

 

After all those mods and you're still finding it a bit too firey, you could try retarding the timing slightly.

Carefully mark the postion on the stator as it is now, then rotate it back a mm and try it, it should flatten the power curve off in the higher rpm range.

 

Or perhaps consider a thicker (or two) cylinder base gasket, this will increase the squish gap slightly at a fraction of the cost of an insert.

If you remove the barrel and head together, you shouldn't need to replace the head gasket either.

(Also grease the base gaskets both sides, that way when it comes to splitting the barrel next time, you should be able to reuse them as they'll not stick and tear)

Edited August 19, 2015 by goudrons