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."