I don't have those. That was in the set of cases that I ordered off of ebay.

So our CDI limits the RPM? To me it always felt like the engine just kept going until the valves floated.

 

It always felt like that to me too, but my understanding is all cdi's limit rpms. The engine may keep revving past the power peak and then power will drop off, but still not hit the limit. The limit would come into play if you miss a gear or in neutral.

Here's one for a yfz450 with a 16k limit www.dynaonline.com/skins/downloads/instruct/dfs7-12p.pdf‎


I think the limiter is like a low-pass crossover in audio. You can adjust the crossover point, but can't select an all-pass.

 

It is a 4 valve engine. They could be using better (lighter) materials, better combustion chamber design, better intake and exhaust ports, better cam profiles,

There have been a lot of technology improvements since the 80's. I would bet that our engine was designed no later than 1984. And it most likely was just a carryover of a previous design that they adapted for use in an ATV. They probably didn't use a computer program to optimize every aspect of the engine like they should be doing today.

Look at the GM Small block 350 vs the GM Gen IV engines. From the outside they look very similar, even on paper they spec out similarly. But they have implemented enough changes to the point where the Gen IV engines come from the factory with almost double the hp of the old SBC engines, and they are running a lot cleaner and getting better gas mileage. The displacement has stayed relatively the same.

 

If you wanna see factory HP, look at the 60s lol

Yup, the 230 is just a bunch of old stuff they slapped together one day just to see if anyone would buy it. No doubt computers have helped us along, but when I was researching muffler designs, I was fascinated at what I was reading from 1940s military and nasa tests. Oh and 1920's patents. You'd be amazed at how much "new" technology is really really old.

I have a 2005 250ex that is a pushrod engine. The old 80's 250x was a 4-valve OHC engine. Why did they downgraded to pushrods on a sport quad? I had a 250x for a while. It wasn't all that much different from the 230 powerwise. The engine is way bigger. The head is massive in comparison. Its about 30lbs heavier overall.

Here's another thought: The nascar engines are putting out 830hp at 5860cc, so that's .1416 hp/cc. Multiply by 250cc and you have a 250cc, pushrod, 2-valve head engine churning out 35hp. Imagine what these guys could do without a phonebook sized rulebook of restrictions.

I'm sure those guys would love to have a 4-valve, DOHC head with variable valve timing, but damn, look what they can do with half that.

 

IMO, They downgraded because the market no longer considers 250cc 4 stroke quads to be sport quads. They are entry level quads designed for youth. The 400 is their sport quad and the one that gets all the attention now.

Even Suzuki's 250 "sport quad" uses an engine that is more closely related to our 1984 engine then the engine in the current drz. If they use an older engine technology they can sell it for a lot less money.

Here you go.
38hp from a stock rmz250. I believe that's a four stroke engine.
MXA'S 2012 SUZUKI RM-Z250 MOTOCROSS TEST: IS IT JUST ANOTHER REHEATED 2011 MODEL? | News | Motocross Action Magazine

My guess is that most of that power comes from a higher rpm, and much more aggressive cam profiles, like you said earlier.

 

Power can only come from high rpm. You have to supercharge engines to get more power over simply a swept volume. You can either use a supercharger, a turbocharger, or principles of fluid dynamics and pipe/port design to supercharge the air. The latter can only happen with high rpms (or extremely small ports, which would be silly).

So the higher your engine design can rev, the more advantage of supercharging you can take. That's the only reason DOHC and 4 valves is worth anything.

 

Here's 600hp from 2000cc Ford Unveils Global Rallycross

Turbos are cool. Here's a 230 turbo that beats a 240cc 2-stroke.
Have to figure at least 40hp for the blaster. Possibly close to 50. I guess that answers my question if my engine can handle being 280cc.

 

There's a company that will make custom titanium wrist pins. Trick Titanium | Proven Combinations For Winning

I believe their pricing is somewhere around $150 for one, and they go down quickly if you can get more than one person to buy in. Kind of expensive, but if you're after every last ounce....

I've seen people mention titanium valves, but I don't see these anywhere. Do you know of a company that makes them, other than the one that I linked above?

 

I don't know anyone who makes valves. If I was willing to pay $150 for a pin, I would find someone to make a piston the right way. Wiseco did pretty much everything wrong.

 

How much would a custom piston run you. Sounds like that Wiseco piston is the major factor keeping you from having the motivation to finish your engine? If so, a custom piston might be worth the expense if it gets you excited to work on it again. It would be cheaper to do it now, then to tear the engine apart again and do it later.