More power for DRZ 400 SM – DR-Z 400 – ThumperTalk

26 Mar 2015 | Author: | Comments Off on More power for DRZ 400 SM – DR-Z 400 – ThumperTalk
Suzuki DR-Z 400 SM


Posted 10 August 2011 – 11:46 AM

I am a new owner of a DRZ 400 SM. I have been looking at the forums trying to see what is out there to get more performance out of this bike. It is fun, but needs more.

First want to educate and clear up some things. I have been a high end engine builder for almost 40 years. An engine is an air pump.

You have to get more air out the exhaust before you stuff more in the intake. And the more you compress the air, within the limits of the fuel and spark advance, the more power you will make.

The pistons available for these engines are all over the map. After investigating them all, and I mean all. CP is by far the best. Moose may be second. JE is the next.

Not enough difference between those to matter. The others have no business in an engine that you are going to increase power.

Exhaust systems. When an exhaust valve opens, the gas leaves between 1,200 and 1,400 feet per second. That is over super sonic.

You don’t want to create shock waves in super sonic flow because that adds tremendous drag. Every weld with a bump inside makes a shock wave. Every bulge in the pipe makes a shock wave. The only way a bulge is going to add power is if something else in the exhaust system is wrong.

AN exhaust system won’t flow more air unless it is a larger diameter or it has larger radius bends. It has to flow more air if it makes more power.

I can’t find enough camshaft information to make an educated choice. Lift, duration and lobe separation angle are not enough to determine what cam to select. Does anyone actually have profile information? I would like to see profiles for Hot Cams.

Megacycle, E model, and whoever else makes them. What Kawasaki cams are equivalent to the DRZ 400 E model? Does Kawasaki make a better set of cams than the Suzuki E model?

FCR carb on the SM engine. First, do they actually fit? Are there electrical changes that need to be done? Do you need a different boot on either side of the carb? Are the throttle cables different?

As is the case with virtually every motorcycle, the intake tract length is too short. If it could be lengthened, the power band would be broader, especially in the lower revs, and fuel economy would improve.

Suzuki DR-Z 400 SM
Suzuki DR-Z 400 SM

Is there a service where I can send out my cylinder and get it bored and then get a quality nikasil treatment back on it? It looks like 94 mm is about the maximum and still keep a stable and round cylinder wall while it is running. Who has the best record on cylinder life?

Can the DRZ 400 SM flywheel and electrics run on the DRZ 400 E model?

Can the DRZ 400 E model engine just plug into the SM frame?

Would anything else need changed to make this swap?

Has anyone ever installed a 450 motocross engine in a DRZ 400 SM?

I figured out to shim the inside of the forks and rear shocks to lower the bike two inches, the right way. And I got the appropriate springs, at least at first. As I get used to it though, and go faster it seems to need stiffer springs and stiffer compression settings on the forks and shocks.

I use mine off road a lot. Has anyone really settled down on fork spring rates for a 145 pound rider with the bike lowered two inches?

And finally, not knowing the history of these bikes; Is piston rattle normal? There are times when I think it is a little louder than I would expect. The rattle is usually under just certain load conditions, and not there all the time.

Suzuki DR-Z 400 SM
Suzuki DR-Z 400 SM
Suzuki DR-Z 400 SM
Suzuki DR-Z 400 SM

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