Making a 250 Behave Like a 200

[stpauls]

20 hours ago, guy53 said:

The slow throttle and a little bigger rear sprocket are in my opinion the only mod you can make without playing with carburation

Guy 

A slow throttle certainly softens the engine's response to the throttle. 

However, putting a bigger rear sprocket on a bike certainly reduces the speed, but unfortunately it also INCREASES the power at the back wheel, which is probably not what the rider desires!

[micm]

A softened 250 motor will still feel intimidating, even if you make it a bit gutless.

I suggest you buy a recent 125 instead. Loads around. Doesn't matter which make. It will feel 'lighter' due to less engine torque reaction (I think). 

When she's happy with that, upgrade her!

[trapezeartist]

3 hours ago, sirdabalot said:

I've had 200 and 250 Evo's and found the 250 with the additional flywheel weight and semi slow throttle (QA tube dremelled to a SA tubes diameter over the 1st half of movement) more forgiving than the 200. Standard the 200 span up to quick on muddy rocks, I tried fitting the 250s additional weight but it was awful, too sleepy, like trying to accelerate through dry sand. 

Interesting.

[guy53]

stpauls your right in saying that there will more power to the rear wheel but you will need more throttle ( rev ) to feel the '' kick ''. at least that was my feeling with my bike.

Guy

[lineaway]

5 hours ago, stpauls said:

A slow throttle certainly softens the engine's response to the throttle. 

However, putting a bigger rear sprocket on a bike certainly reduces the speed, but unfortunately it also INCREASES the power at the back wheel, which is probably not what the rider desires!

Actually it is just the opposite. The new bikes come geared fairly tall. They spin due to this style of gearing. With the gearing lowered, once you are on the throttle you will not spin. You are now tracking at a slow pace. 

[stpauls]

5 hours ago, lineaway said:

RActually it is just the opposite. The new bikes come geared fairly tall. They spin due to this style of gearing. With the gearing lowered, once you are on the throttle you will not spin. You are now tracking at a slow pace. 

Rubbish!

Edited December 20, 2018 by stpauls

[guy53]

lineaway my exact feeling

Guy

 

But I'm sure I'm wrong!!

[lineaway]

4 hours ago, stpauls said:

Rubbish!

Actually you are partly right. I tried lot`s of gear choices. It came with 10 cs, I tried a 9 and 11. Worthless. I even rode for awhile with a 10 and 39. The problem on the Beta is the gap between 1st and second. So I just went for gearing 2nd. With 9 and 44 I usually never use first, but every so often having a super low first works a treat. (The 10 and 39, first worked great but again second became worthless.) 

[Sir Real Ed]

On 12/19/2018 at 6:53 AM, lineaway said:

 The 250  is a low compression bike in the first place, look at the Factory specs. I run 9 and 44 sprockets. Not for a low first, but for a great 2nd gear. My 3rd gear is exactly the same as a stock second, and 4th is just barely taller than the stock third. It gives you such a broad range having 4 workable gears in a section.

Thanks Lineaway.  Just got my 250 Beta, so I don't have any options on stock gearing, but I like your line of thinking.

[Sir Real Ed]

22 hours ago, mcman56 said:

I spent quite a bit of time experimenting with a 250 Rev3.  (It is surprising what some people will do for entertainment.)

- Instead of welding a washer in the inlet of the exhaust pipe, I made a spacer with smaller ID that fit between cylinder and pipe so it was removable.  The pipe still cleared the fender but did not slide into the muffler quite so far.  It softened the power quite a bit but also made it bog proof.  You could use large amounts of throttle at low RPM and it would just chug along.  If you are interested I may still have this spacer.  I don't remember if I changed jetting.  

- In the US, Betas come without flywheel weights so adding one would soften power.

- I made a carb spacer with small boost bottle.  If you run the Mikuni manifold with a Keihin carb, you pick up an extra 1/2" to insert a spacer with port for boost bottle.  IIRC this produced the same bog proof low end chug power but did not soften the overall power much. 

- A 26 mm OKO carb ran the same as a 28 mm Keihin but the response was just a tiny bit softer.

mcman56,

do you remember the ID, OD, and thickness of the spacer you made?

Quote

 

 

Edited December 20, 2018 by Sir Real Ed

[mcman56]

I just looked it up.  The outside of the spacer was shaped just like the exhaust flange with the two holes.  The ID was 1.42" but I don't remember where that came from, probably some percent of the unrestricted area.  It was 1/4" thick aluminum.  I'll look for the actual part. 

[mcman56]

I pulled out the parts.  The smallest was thin and 1.3" ID.  That must be the one I remember.  The tapered part fits in the pipe.  See picture.  Send me a PM with your address, I can should be able to mail it.  I have no use for it now.  

 

 

[Sir Real Ed]

On 12/20/2018 at 9:54 PM, mcman56 said:

I pulled out the parts.  The smallest was thin and 1.3" ID.  That must be the one I remember.  The tapered part fits in the pipe.  See picture.  Send me a PM with your address, I can should be able to mail it.  I have no use for it now.  

 

 

Very interesting.  I tried to send you a PM, but the response was you can not receive PM's for some reason.  send your email address to me at jebeehler@comcast.net and I'll send you my address.  thanks.

[mcman56]

Message sent but does anyone know how to allow PMs. I looked at my profile but don’t see any settings for that