Power Valve Springs

[dirtbird]

I'd bet the assortment of KTM springs drop right in if you have them and want to experiment. The Beta PV system is a cross between the GG design (sub port drum valves) up top, and the KTM governer on the bottom.

We forget that 2strokes had hit before powervalves. Can you say Suzuki TM400?

Dimension-wise they do drop in. However, if you try them with your hand you'll see that all Beta springs are way softer than KTM ones, so although the actuation system design is identical to KTM the calibration must be different.

[Darkside]

I'm using the green spring in my ktm (hardest). maybe a red spring will work in the beta and it will have similar results

[GMP]

I'd bet the assortment of KTM springs drop right in if you have them and want to experiment. The Beta PV system is a cross between the GG design (sub port drum valves) up top, and the KTM governer on the bottom.

We forget that 2strokes had hit before powervalves. Can you say Suzuki TM400?

Dimension-wise they do drop in. However, if you try them with your hand you'll see that all Beta springs are way softer than KTM ones, so although the actuation system design is identical to KTM the calibration must be different.

Got it. Must be governer design, balls, lever differences then.

[celler]

Anyone with a 300 mind measuring the 2 springs. Wire diameter, number of coils diameter, length. I'd like to compare what is n the 250. Everyone sysys the 300 is so smooth. The 2 springs should crate a more progressive PV opening rate. The 250 ramps up very quickly. I come off a host of 250 mx bikes and many were more linear than the Beta in the midrange. I'm sure their is a solution.

[GMP]

'14 250s were changed I beleive for this reason. Maybe check the part #s of the various parts.

[dirtbird]

'14 250s were changed I beleive for this reason. Maybe check the part #s of the various parts.

It was the power valve's itself dimensional accuracy that changed, however part number remains the same (but the actual stock in the factory was renewed).

Although I don't find 250's powerband so aggressive, still celler's idea its not bad. I will try the 300's spring setup to check if it gets more controlled feel when the PV opens.

(outer springs are the same but the 300 uses a 2nd inside spring to control rate of opening, just like KTMs)

[celler]

I have a KTM 250 SX also so I took that apart. The primary spring is stiffer than the Beta.. Anyway I put in the KTM secondary springs and set the adjuster to 1.5 turns. I like it better than stock but I know this is far from ideal. What I have noticed if I put more preload on the spring it just loses power and delays the hit. The setup allows the powervalve to open early to maximize low mid and just delays the upper mid slightly. Now I'm real curious on the dimensions of the springs in the 300.
250 spring - All units inches
.067 wire
.612 od
11 1/2 active coils
2.55 long

2009 250 sx

Primary spring
.079 wire
.645 od
12 active coils
2.55 long

2nd spring - yellow stock
.048 wire
.418 od
5 1/2 active coils

FYI - KTM is much heavier spring force everywhere. The primary spring is also preloaded a lot more in the stock setting. KTM has different mechanics inside. To us Beta owners it is a so what.

[celler]

Went riding again and backed the adjuster out to flush. Low mid was better and transitioned better to upper mid. Noticed today Beta Steve 300rr produced best power with the secondary spring removed and the adjuster at 1.25 from full out. I checked my 250 and flush is 1 turn in from full out. If you look at the dyno curve of BETA Steve's bike from JD you will see how the lower mid is filled in nicely with the JD jetting and 1.25 from full out setting. I am running a Suzuki (NECJ) because I like the linear power these produce and they are clean running.

[GMP]

Great needle series for the GG250 as well. I have the full set of diameters and clip positions. I'm pretty happy with the stock 300 needle (N2ZJ), but I'll give the NEDJ/NECJ a try this summer.

[Knox Enduro]

I have been running mine set at flush also, I have found it to be a more linear transition as well.
I think the '13 250 also comes with the aggressive map setting as standard, I am in the process of putting on a switch.