I just was wondering , what ever became of the side valve/ flat-head 4 stroke engine? We saw a few short videos of a trials bike using this engine, but it was still going thru R&D? I think that would capture some peoples' attention (and market share) more than a Yamaha engine in a GasGas chassis. Just my random two cents. Jim
What ever happend to????
- Thread starter iajim
- Start date
I'm going a bit on a limb here, but I'll make the bold statement, this will not happen. Books have been written and pages could be posted of text explaining why but the flathead died for a good reason, it was replaced with designs with far great thermal effeciency than any flathead could ever achieve regardless of modification.
I was extremely surprised to see this post and did find some nice writeups about this offering, nothing technical, but it surprised me with the technology today that development dollars would be spent on revisiting the flathead. They weren't talking old school sidevalves either, they were wrapping this engine up over 10k rpm, a far cry from an old ford and beyond what all but the most proficeint flathead players ever moved air through that design. But we are talking horsepower here and you guys are discussing torque, and that is BMEP, thermal efficiency and volumetric efficiency. BMEP can be addressed to a certain extent with engineering work on valve timing and compression, but the engine by design is severely limited when moving into thermal and volumetric efficiency.
When the market calls for it and we truly find current offerings lacking, you will more likely see small displacement 4 cycle engines of a long stroke design, utilizing direct injection and variable valve timing to overcome the necessary compromise for low end torque and high end horsepower. The ultimate monster for the application would naturally be a diesel, but even the hyper diesels of today's technology have currently maxed materials out to the point where they still would not accomplish a viable engine within the weight requirements of the two wheel off road market.
There is my opinion! take it as intended, I'm sitting at home listening to Andy griffith show for the umpteenth time till the kids go to bed and ran out of things to browse on ebay...........
I was extremely surprised to see this post and did find some nice writeups about this offering, nothing technical, but it surprised me with the technology today that development dollars would be spent on revisiting the flathead. They weren't talking old school sidevalves either, they were wrapping this engine up over 10k rpm, a far cry from an old ford and beyond what all but the most proficeint flathead players ever moved air through that design. But we are talking horsepower here and you guys are discussing torque, and that is BMEP, thermal efficiency and volumetric efficiency. BMEP can be addressed to a certain extent with engineering work on valve timing and compression, but the engine by design is severely limited when moving into thermal and volumetric efficiency.
When the market calls for it and we truly find current offerings lacking, you will more likely see small displacement 4 cycle engines of a long stroke design, utilizing direct injection and variable valve timing to overcome the necessary compromise for low end torque and high end horsepower. The ultimate monster for the application would naturally be a diesel, but even the hyper diesels of today's technology have currently maxed materials out to the point where they still would not accomplish a viable engine within the weight requirements of the two wheel off road market.
There is my opinion! take it as intended, I'm sitting at home listening to Andy griffith show for the umpteenth time till the kids go to bed and ran out of things to browse on ebay...........
gasser
New member
I don't know if GG met their design goals or not but if they came close that side valve 4stroke would be perfect to put in a bike similar to KTM's (gas driven) Freeride. It's smaller engine size would allow a much lower seat height and lower center of gravity. Very important advantages for a bike used for play riding and trials. It would also be much cheaper to produce and sell which is also very important in the play bike market.
I guess what piqued my interest in this subject was an article in the current( May) issue of Cycle World. The "TDC" article written by Kevin Cameron. The article concerns itself with the side valve Harley's, which were losing ground to the smaller/lighter/ hi revving english twins. The solution was quarter inch thick head gaskets. It was described as having a 3:1 compression ratio yet it made just as much power. The culprit had been restrictions in the head not the valve train. This was all 1960's technology, but the thinking still applies. Something was needed, all the other flathead hot-rods, Auburn, Hudson, had that "something". They did the exact opposite of what logic would dictate and came up with a vast improvement. I don't know if the flat head has reached it's peak, I just hope they stay with the developement.
