in dirtrider magazine they rated the cr450f over the 426; it won in every category except for power. the 450 has smoother power, but the 426 has more power and revs higher, they also said that you need to shift more on the 450 beucase it has impressive low end, but not much over rev. i think that the crf450 bike is very impressive, but not becuase of its engine, it is impressive becuase of its handling. i would personally go with a 426 or drz400 motor. The drz400 motor puts out less power stock, but much more can be done to it than to the 426, it is also more reliable when put in a heavier quad chassis. In dirtrider mag they had a drz400 with a 436 big bore kit(by the way, the drz400 can be bored out to 470cc) yoshimura pipe, yoshimura ignition module(rev limiter set at 11,500rpm) yoshimura cams, and k@n filter. It was dynoed at 60 horsepower. either way, you will def be better off with a fourstroke than the 250 two stroke.

 

If you really want power, go with the KTM 520 Motor. Is has more power than the Honda or the Yamaha and has an electric start to boot. As well, the power delivery is smoother that the 426.

I draged a 426 on the main straight at SIR (Seattle International Raceway) and not only did the KTM pull the 426 (by several bike lengths) but the 426 topped out at 80mph and the KTM topped at 106mph.

Geared the same, the 426 would be absolutely shamed in a drag with the 520.

 

How much hp could you get out of a 426 if bored to 440 and camed? I think that the drz 400 idea is a good one. The one that was built for Doug Gust was awesome. It even has electric start, and zukiscott said they got 60 hp out of the drz by boring and caming it.

 

A 426 that has been stroked out to a 440 will put out slightly more power, but the 426 doesn't like to be stroked, when the yz400f first came out some racers tried this and wound up grenading there motors; now i'm not saying that the 426 is not a reliable motor, i'm just saying that it can't handle alot of internal motor mods. Then again though, with a motor that puts out that kind of power who needs mods? raptorlover, as far as doug gusts machine goes, i would give my left nut to have that thing in my garage, i would be happy if the z400 puts out half the power that gust's quad put out, hopefully we'll see yamaha get into the mix now with a 400 class machine.

 

To me the CR450 motor would be the better choice since you can destroke it to 440 or have it sleeved down. The Yamaha and Suzuki both have to built up. Honestly, I dont think any motor likes to be stroked it seems to be a recipe for disaster. Of course with my recent experiences I dont have alot of faith in big bores either.

Nothing against the DRZ motor, but isnt it a little more low tech than the YZF or CRF. I know the DRZ is not in the same league as the YZF or CRF in dirtbike form. If I was going to go through the trouble of doing a conversion the DRZ would not even be considered.

To me the beauty of doing a converion would be that you could leave the motor in relative stock trim and still have one of the fastest quads at the track and also on of the most reliable.

Adam Smith

99 400EX

 

A CR500 engine in a 400ex frame=awesome!!

 

adam, your right the drz isn't in th esame league as the yzf and crf, but that is becuase both the yzf and crf are motocross bikes, the drz is an enduro/trail bike. both the yzf and crf motors are pretty much tuned to the max from the factory, the drz is very restricted from the factory; this makes it a great quad motor as it leaves you the potential to build the motor that you want and to also make more power. As far as boring and stroking motors making them not relieable; every motor reacts different to this, all depending on deck height and how much material is in between the cylinder wall and water jackets. if the deck height is very short on your motor than stroking forces you to run a piston with a shorter over all height, this squishes the rings closer together and causes height to increase, the piston to become unstable at very high rpm, and the motor will consume more oil. Neither the crf, drz, or yzf would respond well to stroking as they all have short deck heights. As far as overboring, of the 3 motors the drz has the greatest overbore ability, suzuki def over enginnered this cylinder. As far as the drz being lower tech you are def wrong, the drz is a dual overhead cam four valve motor with a 10,500 rpm redline stock, the reason it puts out less power(but more low end tourqe is because it is detuned. Of the 3 motors the crf and drz are the best choice for a quad as there transmissions are much stronger than the yzf's, although they are heavier motors. Also, deboring a 4 valve motor is not a good idea, in order for your intake charge to evenly distribute a 4 valve motor needs a very large bore, the larger the better the intake charge up to a certain point ofcourse; much the same reason that a 281 cubic inch cobra motor makes in excess of 100 hp more when it has the sole modification of being bored out to 306 cubic inches.

 

I just want to clear up one thing. I want to know where these hp readings are coming from on these three bikes? The hp readings are either coming from the crank or the rear wheels. The crf is 49 horse, the 426 is 46 horses, and the drz is 40 horses. I just want to know where these numbers are being mesured at.

 

the horsepower numbers on all 3 motors is measured at the crank

 

i am thinking about building a quad, where do i go to get some good prices on a new cr450f engine or maybe even the yzf426? any help would be great