I'm preparing for next seasons cross country racing here in Oklahoma and I'm trying to dial in the stock shocks on my YFZ. Ridley and Pudljumper gave me the lowdown on the general idea of adjustments but after fooling around with the shocks a bit and seeing how easy it is to adjust the compression and rebound on the YFZ's remote resevoir shocks (all you need is a screw driver) as compared to the preload on the springs, I'm wondering if leaving the preload where it is (how it came from the dealer) and only adjusting the rebound and compression (to almost full soft on both adjustments on all 3 shocks) will do the trick for cross country racing. Basically how important is preload?

It almost seemed as if it was already at the limit of the manufacturer's suggested spring height on the front springs. According to the service manual, with the front end elevated so that the tires are not touching the ground, standard spring length is 255 mm while the max spring length is 256.5 mm and the minimum spring length is 245 mm. So according to those specs it seems the preload is already nearly as soft as Yamaha says the max limit is (If I am assuming correct that a longer spring means softer suspension).

 

ttt

Ridley?

Pudljumper?

anyone have a response/opinion?

 

It depends on how heavy you are. Pre-load should be set-up so that if you lift the quad off the ground, measure the distance bet. the rear axle and a stationary point straight above it. Then put on all your gear and sit on the quad in riding position. Have a buddy measure from the same spot, and the difference should be 30% of your total travel. For example since the yfz has 10" of travel in the rear, there should be roughly 3" difference from fully extended with no weight on the axle and rider on the machine. Do the same to the front end by measuring from the rear a-arm bolt and the ground. Only your front end should only sag about 20-25% of total front travel which is 9" stock, so the difference should be bet. 2-2.5". This will put more weight to the rear end under acceleration. You can set the ride height lower if you choose, but for XC, it is necessary to stay soft, yet keep your chassis clearance so you aren't getting high sided in transitions or hill peaks. MX riders can sit much lower to the ground because they don't have the stumps and rocks to worry about. Hope this helps a little!

 

Pudl
Mate see I told you Ridley was nice, you just have to keep him off the Polaris forum [img]i/expressions/face-icon-small-wink.gif[/img]

Geoff.

 

Ridley,

Two questions for you.
If you are running 18" tyres on the back, what gearing have you got?
I've got 15/38 with 20'' on the back but I'm changing to 18" next week.
Air box mod, do you recommend one ?

Thanks from down under, Geoff.

 

Yeah, it's nice to be noticed by the advice, and not necessarily the signature below it!! I always try to keep an open mind about everything in the atv world. Every product and quad has it's place and purpose. The yfz loves the track, and I feel the pred was more suited for trail...unfortunately I'm in love with the track now!!! [img]i/expressions/face-icon-small-smile.gif[/img]

Aussie, quit putting words in my mouth...lol! I don't know what airbox mod you are talking about...take off lid?!? Bout the only other thing you could do is put on a clamp on, and that prob. won't create the air velocity that an airbox can! Race on "mate"! [img]i/expressions/face-icon-small-wink.gif[/img]

 

Pudl,
Clamp on won't fit .
The UM alloy air box was what I was talking about.
I can't see how it can help.
What may help is using the snorkel off the 400ex as it is larger.

Thoughts?

Geoff.

 

That might work. I would also try a pro-design air intake system with either the UNI filter or K&N. K&N adds lots of power, but use an outerwear in dusty conditions. I've seen gains of 1-2 hp just by adding the K&N...awesome air filter, but iwould definately use an outerwear with it!! Try that first. I belive Alba racing has the pro-design kit for $100, comes with a larger billet opening in the box, the K&N that attaches with a hose clamp (much more secure), and also comes with the outerwear. Pro-design kit, that's the link, check it out aussie!

 

mate I allready have the pd kit but with the foam not k/n paper.

Geoff.

 

Well, I guess I don't know what to tell you though. If money is burning a hole in your pocket, try it out and let us know. I've never really liked foam filters and have always had excellent results with K&N filters as long as I use the outerwears. I've been running them in my quads for 5 years now and have not had a single problem with any of them!