I'm about to purchase a 2002 yz426f, and i have heard that you can swap the cams out of a 2003 450 to utilize the autodecompression system. since i am going to bump up the compression (13.5:1) on the bike, the auto decompression sure would make life easier...is there any truth to this?? if it is more than just a cam swap...what parts do i need to make the conversion? thanks a lot
Cam Swap
- Thread starter Racerdude
- Start date
B
biglou
It is possible to do, although you'll get people telling you both do and don't. I've read of guys that have been running it for a year or more with no problems. Others are looking at cam gear tooth pitch, etc. I've read that it mellows the hit out some, too.
As for parts, just a cam and reshim. There is also a Yamaha part for plugging the decomp hole in the head if you want, or just leave the stock mech there and ditch the cable.
There are a couple other threads already running on this, but they're buried in here somewhere. A quick search will get you lots more info.
As for parts, just a cam and reshim. There is also a Yamaha part for plugging the decomp hole in the head if you want, or just leave the stock mech there and ditch the cable.
There are a couple other threads already running on this, but they're buried in here somewhere. A quick search will get you lots more info.
A safer bet is the Hot Cams Auto Decompressor exhaust cam part # 4035-1E. It's made specifically for the 400 & 426 engines. If you are going to spend some money anyway you might as well get some extra performance to go along with your easier starting.
- Thread starter
- #5
even better idea rich. i was supposed to get the bike this weekend, but somethings happened, you know how it is! ill get something soon though. I dont want to do a lot to the motor, but for the price, and since im going to have to rebuild it anyway, i thought it would be a good idea to get the high compression piston, have eric do a little head work, and that hot cam should also help out, although i really just want it for the auto decompression. i cant afford a new 450 at the time, but since i have to race against them and rotax's i figured a little more in the motor department wouldnt hurt me on the half miles (right now im riding a 250 against them) one more question....since i need my bike to hook up, do what do you guys think about a light fly wheel weight, maybe 10oz, or would that really kill the power im getting from the piston and the cam? the whole reason im getting a fourstroke is so i can hook up better, i just dont want to turn it into a lightswitch like my two stroke but at the same time, everynow and then i still need hit so i can snap the tire loose to get it turned. what set up would you go with, or am i pretty close to what i need? you just thave to remember that, well, ...there is such a thing as too fast on a short track!
I rode my YZF444 with 19 ounces of additional flywheel and 19" Maxxis DTR1 tires for a while. It defintely hooked up and was easier to control going sideways with all that flywheel weight. It certainly seems to accelerate a lot harder, and respond a lot quicker without the extra weight. I'm not a dirt tracker so I can't say for sure which would translate to faster lap times, but for a slow old guy like me I would imagine the additional crank weight would prove to be best in a DTX setting, but for SuperMoto I think I'll be going with the OEM weight.
Trye Welch (Fast Forward Racing) on the Dirt Track Online website has extensive experience with the YZFs in DTX racing and could probably tell you what works well. He's a good guy who is always willing to share info. Look him up over there.
Trye Welch (Fast Forward Racing) on the Dirt Track Online website has extensive experience with the YZFs in DTX racing and could probably tell you what works well. He's a good guy who is always willing to share info. Look him up over there.
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- Thread starter
- #7
well i rode my buddies crf (which are smoother than yz's as you know) and he had a 10 on his, and it felt pretty good, i may go to twelve, but that would be the max, i really dont have money to be experimenting with setup...just try one and hope i like it..hahaha. as for tryce....him and i dont get along, id rather burn my bike to the ground than listen to his set up advice. im thinking i could ride it at stock weight till i got the money for the flywheel weight, i have pretty good throttle control (after i hit the ground enough) speaking of ground...im heading to supercamp thursday...im gonna be on it plenty. thanks rich
Racerdude said:
OK :cool:
I guess not everyone is destined to see eye to eye. :)
