Thursday, August 13, 2009

Yamaha WR lowering link post...about the Kouba Link



Whoa, what's this? A WR lowering link post about a CRF3 Kouba Link? Well, we do stock a few of Mr. Kouba's products, and this info is informative for all off-road link users. Our reply below pertains to a beginner considering lowering his CRF250X...

"At your weight of 179 before gear (if I read that correctly) you may be borderline for needing a heavier spring. The KoubaLink CRF3 will increase your leverage ratio: this will not only lower the rear end, but it will make your bike more plush on the smaller stuff in addition to having a lower center of gravity (leads to better turning when the front forks are raised in the clamps, more on that later) and will get better traction.

The downside to this - and I bring up your weight and spring rate - is easier bottoming. Yes, you should bottom once or twice every ride but this bottoming I speak of with the stock spring (again, at your weight minus gear) may lead to wallowing and a mushy ride no matter how you try to compensate with compression.

As for rubber marks on the underside of your fender. No worries. Take a look at the underside of any of the bikes on the starting line of an AMA National, even a WORCS, not just a MX race. Big black marks. Let me rephrase that: GIANT black rubber marks. And not once have I seen a rear wheel come through the rear fender. No, you and I are not pros; my point being is every major pro team changes their linkage for each track. Heck, I know several privateer teams running Pro Circuit and other companies' "lowering links": they're more performance links because they're all one inch or less. They don't want a shorter bike like you and the CRF3 idea, they're going for the increased traction, decreased weight transfer to the front on hard braking, lessening the rear end stepping out on rough corner entry, etc. while maining full travel. And yes, they too will have more plushness and a slight increase in bottoming. Disclaimer: every team I've spoken to with non-oem links have their spring rate properly set up and their sag reset.

The first thing you need to do with any lowering link no matter the amount (shorter ones such as the Kouba 7/8" or Pro Circuit's sub-one inch or Devol, etc) is reset sag. A linkage bike such as your CRF requires approximately 1/3 sag of total travel. Honda's guidelines allow for a few mm each way for personal preference.

I have ridden a CRF3 equipped bike with the forks raised a large amount. I don't have the exact amount but I'd say they were a good 12 to 18mm (.5 to .75 inches...they were visually more raised than my forks which are usually 3 to 6mm on my dirt and 10mm on my dualsport). Mind you, there is no need for a 1:1 lowering of fork vs rear end because changes to rake/trail (fork) affect geometry at a different rate than changes to the rear being lowered. I reset sag for my weight, kept the forks at the owner's setting and proceeded to ride the snot, er, ride the bike all day. It was very "balanced" and did not headshake like a wet dog nor understeer like a NHRA dragster trying to make its way through a Wal Mart parking lot."

Saturday, August 8, 2009

Yamaha WR lowering link "link" of the day

Rick Ramsey fetched himself a new Yamaha WR250R from the Gunnison, Colorado, dealer today. His Yamaha WR section is relatively new, but knowing his passion for tinkering, you can bet it'll be full of useful info in no time flat!

Rick's site: HERE

Wednesday, August 5, 2009

Yamaha WR lowering WR250X




Question about Yamaha WR lowering on Supermotojunkie.com as related to raising the forks on the WR250X.

"10mm is the most popular starting point to raise the forks in the triple clamps; the most you can move the forks SAFELY on this bike is 18mm. There is no 1:1 ratio of fork/rear end lowering because changes to rake/trail (the fork) affect geometry at a different rate than changes to the rear.

Extensive testing showed us that 2 inches (just a hair under, really) is the most you can lower the rear of the R and X while still maintaining a "balanced" ride up front. Anything more than 2 inches total in rear and the forks cannot safely be raised to give a ride capable of withstanding race-type speeds and handling. This is not to say a very very short leisurely rider could not get away with more lowering.

Depending on rider preference you just slide the forks up or down a few millimeters. As you may or may not know, 6mm is approximately 1/4 inch. But 10mm is a great starting point. Too much and the bike headshakes and oversteers. Not enough and it turns like a NHRA dragster and understeers. Thankfully it takes just a few bolts to make the fork height changes; please retorque the clamp bolts correctly.

As someone else noted, 1/3 of total travel is used for sag, give or take a few millimeter. The "give or take" is, again, based on personal preference.

And as the installation instructions note, make sure your chain is properly tightened (approximately 45-50mm of slack measured at the middle/bottom of the chain when the bike is off the stand....someone please correct me if I'm a bit off on this comment)."

Sunday, August 2, 2009

WR lowering: sag

Yamaha WR lowering post of the day: how to set sag.

Seems to be a very popular question. The most important part of any suspension yet so many don't do it.

Click HERE.

Thursday, July 2, 2009

WR lowering post of the day



WR lowering post of the day in regard to the misconception that lowering links decrease travel.

All the bikes I have seen with stock links that have a rubber mark on the rear fender have been bottomed hard and are a long way into the neoprene shock stop. Mfg's advertise the total travel assuming the shock stop is not on the shock shaft, so to get the rubber marks on the rear fender that stop has to be compressed pretty hard, also you have to consider the sub frame and fender flex. The way to measure usable travel is remove the rear shock spring, cycle the swing arm thru its arc until the weight of the bike is lifted with the shock stop. That travel measured will be about 30% less than the advertised travel. Longer links increase the leverage ratio slightly so that in turn increases both the total and usable travel. They also allow the tire to hit the fender sooner and harder as the stop does not have to be compressed as far. I would not say that a bike is under sprung from the factory because the tire is hittng the fender, first compare the race sag and the free sag to figure the correct spring rate.