X-lite Hydraulic Clutch

hi Chris-

happy to give my opinion on hydraulic clutches.

There is no magic bullet to solve clutch drag AFAIK. However there a few things you can do to mitigate things on this slightly under-designed Brembo system:

• use zeroW-40 engine oil (mobil1 0w-40 for euro cars) in the crankcase.

• change your clutch fluid (dot4 brake fluid; it's all the same, except for either Motul- highly recommended. OTOH, I use Prestone. Do not agitate the fluid when pouring)

• use the minimum of free play in the clutch lever- but you have to have some.

• protect your clutch line from header heat with an IR reflective tape or insulation.

• you gotta get all the air out of the slave. try hard- it's a bitch and that air bubble hides good. I am betting this is your problem (still)

The bad news: after all this, the clutch will still drag- but it'll be reasonable. I can e-start my 310r in gear most of the time. However, neutral is a hit-or-miss situation. Even the 449/511s have the problem using almost the same hydraulics. The old magura's have less of an issue but it is still a problem; I will say I do like the brembo system better, though.

BTW, the problem is not with clutch in and of itself; I believe the issue arises from a hydraulic system that has "just enough" travel, but really needs 1-2mm additional travel, or even more. And if there is any air in the system- forget it; 'cause you just lost that thin-thin margin of movement. Of course, if you have a notchy, worn clutch basket this may cause clutch drag also. But really we're talking about new hydraulically operated systems here.

(Also, if you're losing clutch operation after the bike heats up- definitely look for an air bubble in the slave, which would get bigger/grows with engine heat).

There are possible engineering solutions. The new thinner friction plates and steels that MXGP bikes use might make a difference. Scott Summers took 2 springs out of the clutch with no negative affects on his 450 (not workable on bikes with an odd number of springs). I suppose someone could make a reducing sleeve and piston kit for the slave cylinder (not as hard as it sounds- but beyond me); in the same vein, you could bore the master cylinder and put a slightly bigger piston in (slightly harder IMO).

I am not a fan of hydraulic actuated clutches for a few reason. And I would point out that most American pro's do not use them if they're not stock on the bike. Ryan Villipoto reverted back to a cable clutch when he raced MXGP [most mxgp clutches are hydraulic tho]. The purported advantages (less effort, self-adjusting) are not really advantages IMNSHO.

When I talk clutch "feel", I believe most people hear "reduced effort", but that's not it. It might be the steel cable transmitting the friction contact point better- but I can't say for sure... I just know I feel it. In addition, the need to adjust your clutch during a race (us casual riders don't really run across this) lets a racer gauge how long a clutch will last- in a mud race clutches go out left and right.

Also, I can and have made a cable clutch as effortless as a hydraulic clutch, by modifying the clutch arm. Finally, a cable system is way more reliable AND field-fixable then a hydraulic systems. hands down. I'd also like to see a comparison by weight, I'm not so sure a cable system is heavier.

The biggest argument against my opinion is trials riders: those guys are clutch masters. And AFAIK they all are using hydraulic clutches. Maybe its a euro bike thang.

Shifting gears is the least important thing I do with the clutch, btw. I use the clutch to take power off the rear wheel, I use it to bring the rpms up into the powerband when I'm between gear ratios or caught with my pants down in the wrong gear, I use it to bring the front end down without rolling off the throttle (e.g. steep hills). All of these efforts are with one-finger feathering, also; I shift with two fingers on the lever and I don't know why. But I start the engine in gear with 4 fingers on the clutch- which is the last clutch function but one of the most important.

Hey, Chris- do you mind if I post this? You might get some other ideas and opinions.
regards,
scott

ps- chris, one last thing to look for is for an air leak. If you see brake (clutch) fluid leaking externally, you might have air coming in (i.e., bad o-rings, banjo washers, pin hole in clutch line, etc). Be suspicious of any fluid loss.