Ha! I came from a 660 Raptor to a Blaster. Hated the weight and expensive complexity of the Raptor. Stock Raptor or Banshee is still just less than 40 hp and 400 lbs. Put a 200 lb rider on either and you are talking 15 lbs for every HP. Not too hard to get 30-35 hp out of a Blaster, with a 200 lbs rider you have that same 15 lbs per HP ratio.
The 660/700 Raptor and any 4 stroke is very difficult and expensive to modify the engine for much more than 15% more HP. Multi cylinder engines do not "plant" very well, especially 2 stokes. The Banshee is a hoot. I recommend riding one or buying one for the thrill of it, but a single cylinder is much lighter, simpler, more traction, and cheaper to modify.
Sicivicdude is so right in thinking out what you want to do with your machine. I want light, nimble and powerful off roader. Blaster does it. If I wanted a flat track machine, weight would mean less. Banshee would be better. If I wanted wheelies and torque, 660/700 Raptor it would be (high center of gravity). If I wanted a track racer and repair expense not important, one of the 450 race machines.
I should open up another thread about where HP comes from, but basically since Harry Ricardo's day it is recognized that power can only be made by PLAN.
That would be:
Pressure, average cylinder pressure through the stroke
Length of crankshaft stroke
Area of the piston
Number of power strokes per minute. RPM x cylinders / 2 stroke or 4 stroke.
all this is divided by a constant to allow for units.
The only way to increase power production is to increase one of these factors. Luckily with a Blaster, all of these factors are easy to increase.
Working the numbers backwards, the stock Blaster produces 17hp at 8500rpm with its 195cc. That would be an average cylinder pressure of about 71psi. Modern MX engines have average cylinder pressures of about 125-140psi. This is influenced by air flow through the engine and detonation limits. All the reed valve, head mod, flow porting, triple port, air box and exhaust tricks can probably raise Blaster cylinder pressure up to about 130psi max, making about 30hp with no displacement or rpm increase.
Displacement alone is physically limited to about 245cc, this factor alone with no flow or head mod increases would raise HP to only about 20hp believe it or not. If even a moderate flow and pressure increase of say 100psi was achieved, you would see about 30hp according to the math.
RPM is a big way to increase power. Cylinder filling efficiency usually decreases with RPM but not at the same rate as power increase and the tuned effect really helps us in a 2 stroke. The Blaster is a tough little engine that should readily handle 10,000 even with a 3mm stroke. This is part of the DT200's secret to its 32hp. It makes it up in the 9500rpm range. This is where raising the ports or cylinder or a new pipe help make HP. Even most of the stroker kits with their port raising shims raise the RPM range and increase HP through RPM as much as displacement.
So, what if you put it all together? A big bore stroked Blaster tuned to maximum cylinder pressure at 9500 rpm? About 45hp, or probably almost as much as any MX250 engine built in the last 20 years. Why "almost" as much? Because this is a 40yr old piston port engine design updated to reed valves. It has limitations. 45hp in a 300 lbs bike with a 200 lbs rider is still a power to weight ratio of a Hemi powered Barracuda!
So I want 45hp, right? What are the side effects? Power produces heat (or is a byproduct of heat or whatever!) so if you are producing 45 hp you have to remove a lot of heat from the cylinder and heat. Air cooling is not so good at that, so better if you only use the 45hp in small blasts.
Also, increasing the rpm range reduces power at lower rpm. MX engines do not make much power in the rpm range that you spend most of your day driving in.
If you are only turning 7300 rpm you are probably only making about 31hp max with your mods.
Pop a 72mm cylinder on and your power will raise to 35 hp. Worth $600?
How about this. Shim your cylinder higher or tune so your rpm goes up to 8500 rpm and you will see 36hp for less than $20 worth of parts.
Tune it for 9500 rpm like a DT200 and you should be up into the 40hp range.
You may need to sprocket down to use it.
Excellent advice from everyone in this thread. Whew, lot of typing, I gotta take a frosty adult beverage break...
.........is that a bug in my drink?
Great write up! So should I just double up a stock base gasket and see what happens? Whats exactly is holding my rpm's back? Port timing & exhaust? I have a spare cylinder that I going to get the sides welded up so I can triple port the exhaust and full port the intake with boysenn ports. I'm not going to sleeve it. Just run the next size up.
The trails that are in my area are wide and long. There are only a few areas where the blaster prevails in tight cornering. I think my modded banshee would take the raptor on the trails that I ride. I am going to find out next year, lol.
I bought the Banshee. I have wanted one since I was 15. The blaster was a substitute or a learning experience to get me ready for the next one. I should be able to make 60 hp with it very easily.
Posted pics in a new thread, I dont know how to do it on a reply.
http://www.blasterforum.com/engine-mods-swaps-129/pics-my-next-build-48498/#post611128
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