It is possible! Htey keep claiming that they are 690's on Alchohol but something just doesn't compute here. How does a 690 on alchohol beat an 830 with 25h.p. shot of n.o.s.?![img]i/expressions/face-icon-small-confused.gif[/img]

 

Thats the million dollar question!!

I t is not that simple! I dont care what they say.



It cool to keep some secrets, but dont lie! just say I cant tell ya.





Bigger.

 

I would think it would be possible to put in a 105 piston, and destroke the Crank to come up with 690cc's. Of course you would have to deck the head and Jug to get your compression back, but that shouldnt be that hard. teh only problem I can fore see is the timing chain lenght, but that wouldnt stop someonr like sparks. With a nice MIX, I should be a Runner!





Bigger.

 

The stock DS makes peak power at about 6200rpm. It definately needs to be short shifted to go fast because power falls off quickly after 7000rpm. As mentioned earlier the low rpm is deceiving because you hear a motor barely wound up but your going 70mph! When we first started racing the DS it took awhile to get used to shifting early, you actually shift early compared to other engines because they have to be wound tighter to make any power. The DS makes alot of HP and TQ at fairly low rpm which means it stays together longer and has great potential when built properly. Keep in mind my 15,000rpm engine is only 198cc and doesnt even make as much power as a bone stock DS.

The reason the new yzf, crf, and sparks bikes have that Bap Bap Brap sound is because of their ultra light engine components. I serously doubt they are destroking. A stroked engine when built properly should rap quicker than a destroked engine, because of the leverage gained against the crank pin. It should not turn as many rpm however because the crank pin has farther to travel.

Any engine component that has to travel, stop, and travel back the other way should be as light as possible. Example: piston, pin, rings, valves, retainers, locks. Not much of this has been looked into for the DS. Most people just want a "big bore" or throw some cams at it and dont consider the light weight components as well.

I am building a stock bore DS motor for myself this winter and have a goal of 70HP on gas which I probably wont reach but I'm going to try. I will address the most over looked things when engine building; Light weight piston and pin, light weight valves, locks and retainers, piston ring seal, volumetric efficiency, header length,etc.

MrHorsepower

 

That should'nt be to impossible.

DSmike's Yellow DS has 70 hp on a stock bore,stock valve engine, on alky. I would guess he would only loose 3-4 hp going to Race gas.

So I'm sure with the improvements you plan on making, you coud make that 3-4hp back.



Good luck!



Bigger.