Progress on the sidevalve 4 stroke?

R

Rob_NZ

New member
Any new news on how gasgas are progressing with that?

Ive seen the videos and drawings etc - example here:
http://www.gasgas.com/4stroke.htm

Im hoping they can make this a success. It would be great to have a low complexity four stroke, with moderate power and a long service life available in an enduro bike, not just the trials bikes.

Im hoping long service life will be one of the design parameters.
 
Rob_NZ said:
Any new news on how gasgas are progressing with that?

Ive seen the videos and drawings etc - example here:
http://www.gasgas.com/4stroke.htm

Im hoping they can make this a success. It would be great to have a low complexity four stroke, with moderate power and a long service life available in an enduro bike, not just the trials bikes.

Im hoping long service life will be one of the design parameters.
Click to expand...

If you look at the original press release about Gas Gas hiring Cervantes, I think it said he would ride a 2T the first year and then help develop a 4T the second year. Maybe it's the same engine in a off road frame?
 
I think that the 4 strokes are dead in trials.
Wouldn't surprise me to see GG drop the 4 stroke in trials.

Sales are just way down on 4 strokes trials bikes and this would surely dictate company direction.

Just my 2c
 
i don't understand why gg would design a sidevalve - it seems like just a work around so they wouldn't have to redesign frame.....they're not very efficient, but they are smalller/cheaper/easier to build...
 
IMHO I think a 4 stroke engine isn't a very good idea for a trials bike but if you're going to try it the side valve engine design is a brilliant choice.

The disadvantage of a 4 stroke is extra weight at a higher place in the chassis. The side valve engine will have a minimal weight gain at a very low point in the chassis. The side valve engine design is inefficient just as Stainless suggests but the consequence of this is a power deficit when compared to an overhead valve engine. In a trials bike application who cares about peak power?
 
Low CG, light weight, tuned for low end power, AND reliability. If your going to do a trials 4stroke this is a very good path. For a lightweight technical woods bike it wouldn't be bad either as long as big peak power was not a requirement.
 
The problem with the side valve or flathead design is that the point of diminishing return on compression ratio is about 9:1 because when you shrink the combustion chamber to gain compression you restrict the intake and exhaust flow around the valves. It will never run with the 12:1 4ts of today. 4ts already give up an advantage to the 2ts and this design gives up an advantage to the 4ts. It would be very dependable and smooth and would also run on 87 octane or about any swill you wanted to pour in it but as a competition engine it would be limited.
 
I would see it as a non competition, low cost of ownership, low center of gravity option for the enduro/trail rider.

30ish HP wouldnt be bad. Many people are still happy enough with their XR250/CRF230 or similar, with suspension improvements.

Apparently there is a class of trails/x-country riding in Japan "touring trials" that must have 4 stoke engines - which is a growing market.

It is discussed in this thread.
http://www.advrider.com/forums/showthread.php?t=609054
 
side valve progress

After reading many of the responses to the side valve four stroke I thought I would let my opinion be known. I believe there is a viable market for a LOW maintenance four stroke motor. I used to ride Honda CRF 250s and although I actually liked the power output of the machine I was changing valves like I change socks. I have been a friend of Steve Berkner and Mark Berg of Go Fasters for years. I have ridden with and competed against Steve for many years and I finally was persuaded to try a Gas Gas 2 stroke and I have to say I am totally impressed. Both my son and I have been riding them for the past several years and they are great. One of the things I have discussed with Mark is, as I get older the slower the bike I race on the faster I can ride it. Now this is not to say I want a slow bike but when you can use 90% of the power without wasting energy I can ride a multi hour event and get better results. I do not ride trials so I can"t say how effective this motor would be for that but I do feel a LOW maintenance engine that has controlable power that makes its power in the low to mid range would be ideal for me. In joking with Mark Berg I thought an ideal name for it would be the 320 om (Old Man)
 
When news of the GasGas trials side-valve 4-stroke engine first broke a lot of us looked on thinking hey, maybe GasGas had resurected an idea that the Big 5 (Honda, Yamaha, Suzuki, Kawasai, KTM) overlooked in their strides to produce new technology 4-stoke motors.

On the surface it looked promising, at least for trials bikes, but in practice it seemed to have fallen short for problems most likely brought up in earlier posts.

Another problem I think the motor has is a side-valve motor has a tendency to be louder than an overhead cam motor and that alone may have been the final nail in the coffin of the side-valve motor making it into a mass producee competitive off-road bike.
 
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