7602 clutch slave piston fitment

Discussion in '7602 Racing' started by 7point62, Sep 17, 2009.

  1. 7point62 Husqvarna
    AA Class

    Location:
    Southwest England
    Husqvarna Motorcycle:
    2004 TE450
    Other Motorcycles:
    2001 Kawasaki TR250
    I finally got around to fitting the new slave piston today and had an unforseen problem (and a couple of thoughts about why some folks may be having trouble with their clutches...)

    Anyway, the old piston popped out easy enough, so I applied a little oil to the new piston and quad ring, slid it in - and it stuck fast! I had to bleed the system to force it out. A closer inspection (and some careful measurment) showed that the bore was oval, caused by the mounting flange being very slightly concave. It looked like the sealing o-ring between the slave and motor wasn't seated properly at some point as it appeared to have been nipped, but luckily we have spare stuff like that on the farm! The stock piston, although not visibly worn is a touch smaller, so didn't stick in the bore. The damage to the o-ring was slight and wasn't apparent 'til I removed it, but the slave is pretty fragile, so it may have been enough to bend it.

    There was no alternative but to remove the cylinder, support the flange with a big socket and gently press the thing flat until the piston (minus quad ring) fitted properly. Luckily it straightened pretty easily. :banana:

    Assembly second time around went fine. I reverse bled the system, using a syringe on the bleed nipple to force oil (5W fork oil, 'cos I had some spare) up to the master cylinder and chase the air out. I pushed the piston all the way into the cylinder a few times get rid of the little bit of air that was trapped in the cylinder (you'll hear it coming out of the master cylinder relief port), then all I had to do was fit the cylinder and other hardware and set the oil level. I'll give it a good workout tomorrow. :)

    Thoughts / conclusions:

    1) I should have inspected the cylinder condition more closely before attempting assembly.

    2) The piston assy should move freely enough to allow the spring behind it to return it to the clutch pushrod. I believe this could be one of the reasons for suddenly "losing the lever". Perhaps the piston can be forced back by crankcase pressure or whatever. If the piston's not touching the pushrod you'll have no clutch. I also think this is why thin oil in the clutch system is important - the hose bore and relief port are small, so the lower the oil visco, the easier everything will settle. Perhaps a slightly stronger spring would help.

    3)When refitting the slave check the o-ring for condition and correct seating and tighten the screws evenly so it pulls the slave onto the engine squarely. Oh, and don't trap the wire from the gear position sensor.

    Sorry for the long, bloggy post but maybe it'll save someone from a similar hassle.

    Edit: I hasten to add that none of the aggro was due to the new piston! It was dark by the time I finished, but I'll bed it in tomorrow and see if it's cured the occasional snatchy clutch disengagement I've been experiencing.
    MotoMarc36 likes this.
  2. Joliet Husqvarna
    AA Class

    Location:
    Vista, CA
    I'm getting ready to do this myself, so I appreciate you taking the time to write it up. Ken
  3. krieg Husqvarna
    Pro Class

    Location:
    Matthews, NC
    Husqvarna Motorcycle:
    Many in the past
    Other Motorcycles:
    '12 Triumph Scrambler
    Great post. My 7602 piston went in with no issues and is doing fine. :thumbsup:
  4. Colo moto CH Sponsor

    Location:
    La Jara, Colorado
    Husqvarna Motorcycle:
    7602racing.com
    7.62,

    Thank you very much for taking the time to do this writeup. As you mentioned, our piston is just ever so slightly larger diameter than the stocker. I did this to try and minimize the amount the piston can kick side to side in the cylinder bore. The target diameter was .002" larger than the stock piston (less than the thickness of a sheet of paper). Obviously the larger piston combined with the oval cylinder caused your problem. I have had 1 other customer have similar issues. I went through all the finished production pistons and scrapped any of them that were on the large side of the target diameter so this shouldn't be a problem from now on.


    If you don't mind, could you explain in better detail how you went about straightening the cylinder for any other husky riders who may have this problem?

    Thanks again for the great write up.

    Clay
  5. 7point62 Husqvarna
    AA Class

    Location:
    Southwest England
    Husqvarna Motorcycle:
    2004 TE450
    Other Motorcycles:
    2001 Kawasaki TR250
    Hi Clay,

    I fried my camera a while ago so I had to resort to pen and paper. As you can see I got a "D" in art...

    [IMG]

    I used a socket that was slightly smaller than the width of the flange at it's widest point (although I guess a couple of pieces of identical thickness soft metal or even hardwood could be used) the idea is to support the ends of the flange about level with the bolt holes while allowing the centre to flex. I needed a small piece of aluminium packing to be able to apply pressure to the centre of the part of the cylinder that faces outside on the bike (as in the drawing there's a piece of the casting to one side that protrudes and I didn't want to apply pressure to that).

    Easy does it! Most people won't have a press but gentle nip in a vice will do the job just as well. I only needed to give it a couple of tweaks, checking the fit each time with the new piston (minus quad ring). I cannot stress highly enough that softly softly is the idea here as the cylinder is mostly fresh air and bends very easily. ;)

    As Colo says there's only a couple thousandths of an inch in it, so the usual disclaimer applies. Please don't blame me if it breaks!

    For anyone without measuring gear the tell-tale that the bore is oval is that when the piston sticks it will be gripped on opposite points of it's circumference so you will be able to rock it at 90 degrees to those points only.

    I suppose the alternative would have been to try and polish out the high spots with 400grit and kerosene and finishing with 1200 grit, but I didn't fancy that as I was concerned about breaking through what looked like a hard anodised surface, plus it probably would have taken a while. I was pretty much resigned to buying a new cylinder anyway, so straightening it was a bonus. Still, as almost all the other installs have gone without a hitch I don't think that potential purchasers of the piston upgrade need worry unduly.

    Hope this helps!
    MotoMarc36 likes this.
  6. Colo moto CH Sponsor

    Location:
    La Jara, Colorado
    Husqvarna Motorcycle:
    7602racing.com
    7.62,

    Thanks a ton for your artwork. I really appreciate you taking the time to draw that up and clarify the process.

    Head on down to the local pub and have the bar tender pull up a pint of Spitfire as a reward for such fine work. :cheers:
  7. 7point62 Husqvarna
    AA Class

    Location:
    Southwest England
    Husqvarna Motorcycle:
    2004 TE450
    Other Motorcycles:
    2001 Kawasaki TR250
    Cheers mate, I'll do that later!
  8. 7point62 Husqvarna
    AA Class

    Location:
    Southwest England
    Husqvarna Motorcycle:
    2004 TE450
    Other Motorcycles:
    2001 Kawasaki TR250
    "Oh, yeah, so does it actually work?"

    Just like a couple of other people have experienced, the lever pull was a bit heavier to start with, but it's either getting easier or I'm getting used to it. I can still pull the lever back to the bar with one finger easy enough though. The clutch bite happens a bit further out but there's been none of the jerky off/on thing that was bugging me before, which is the main reason I bought this little fella.

    Considering how janky my cylinder was I'm well pleased.
    MotoMarc36 likes this.
  9. Dirtdame Administrator

    Location:
    Escondido, California
    Husqvarna Motorcycle:
    07 TE450,11 WR300,13 WR125,18 FE501
    Other Motorcycles:
    KDX200,Hodaka100,MV Agusta Brutale
    I still want to get one of these units soon. A couple of summers ago, the fluid in the slave cylinder was pretty dark, indicating some wear, but I checked it last month and it was pretty clean, indicating that not much more wear has occurred. Still gonna get one....:cool:
  10. robertaccio Contributing Member

    Location:
    San Diego, Ca
    Husqvarna Motorcycle:
    2017 TX300
    Other Motorcycles:
    92BetaZero260, 01YamahaYZ125
    wow that bending thing is amazing! glad it works with the upgrade piston! very cool work.
    I am still freaking that mine is 100% OEM after 110hrs lots of clutch slipping/feeding (my technical ride style).
    MotoMarc36 likes this.
  11. 7point62 Husqvarna
    AA Class

    Location:
    Southwest England
    Husqvarna Motorcycle:
    2004 TE450
    Other Motorcycles:
    2001 Kawasaki TR250
    It's giving me a nosebleed just thinking about it TBH. The"fix" got me out of a jam, but I think my Husky deserves a little better, so I'll pony up for a new one as soon as possible. The 7602 piston will be fitted to the new 'un though.

    I suspect mine is original too, so five+ years isn't bad.
  12. krieg Husqvarna
    Pro Class

    Location:
    Matthews, NC
    Husqvarna Motorcycle:
    Many in the past
    Other Motorcycles:
    '12 Triumph Scrambler
    I replaced mine on a brand new bike with less than 3 hours. After purging the milky goo from the fluid in the system and installing Clay's magic piston, my clutch feels better than new. :thumbsup:
  13. 7point62 Husqvarna
    AA Class

    Location:
    Southwest England
    Husqvarna Motorcycle:
    2004 TE450
    Other Motorcycles:
    2001 Kawasaki TR250
    It's a little puzzling that a few owners have reported emulsified clutch fluid on nearly new bikes. It seems that once it's changed out then it stays ok. Strange. Comments?
  14. krieg Husqvarna
    Pro Class

    Location:
    Matthews, NC
    Husqvarna Motorcycle:
    Many in the past
    Other Motorcycles:
    '12 Triumph Scrambler
    That's exactly what I thought. The goo in mine was limited to slave cylinder itself and not the reservoir, but the goo was very evident... looked much like a white, homogeneous "blob" floating around in the slave cylinder.
  15. petem Husqvarna
    A Class

    Location:
    Andover, UK
    Mine looked exactly like that too but only in the reservoir as far as I could see. Mine's also still a low hours bike - makes you wonder how that's happening so early on. :confused:
    Must check it again soon to see if there's any more white goo. Since replacing the seal at the lever and doing a flush/bleed it has been better but when the engine's hot it still needs the span adjuster screwed all the way in so that I can just about disengage the clutch.
  16. krieg Husqvarna
    Pro Class

    Location:
    Matthews, NC
    Husqvarna Motorcycle:
    Many in the past
    Other Motorcycles:
    '12 Triumph Scrambler
    I'll be checking mine again soon as well. But I've had no issues at all in 3+ hours of riding since the fluid purge and piston replacement. In fact, the clutch has been 150% better than new. Crossing my fingers. :thumbsup:
  17. wingnut Husqvarna
    B Class

    Location:
    Barrie, Ontario
    I replaced my slave piston before I even rode my 09 txc 250. So when I took the piston out the fluid in the cylinder had what looked like white grease particles. Since I hadn't used my clutch yet it hadn't yet become mixed to a milky color.
    BTW 7602 I haven't had any clutch issues, not that I shouldn't have with a brand new bike, but for piece of mind down the road, priceless.:cheers:
  18. Colo moto CH Sponsor

    Location:
    La Jara, Colorado
    Husqvarna Motorcycle:
    7602racing.com
    I'm wondering if they use a white lithium grease when assembling the clutch. Or if one on the parts is sent from the manufacturer packed in the stuff.
  19. wingnut Husqvarna
    B Class

    Location:
    Barrie, Ontario
    Thats what it looked like. It was if they used it on the piston then after installing everything they filled the clutch with fluid.:excuseme:
  20. gestion01 Husqvarna
    A Class

    Location:
    Montreal
    Could not make the 7602 piston work. It keeps getting stuck. Maybe i have an oval cylinder?

    In any case I have to change the cylinder. For some reason the groove where the clip keeps the piston from falling out is busted.

    The Clip is holding on by a millimeter...:eek: but it works with the stock piston. It's been like that since? i don't know for sure, first time I pulled the cylinder off in 60hrs.

    Another session will be needed to sort this thing out. :banghead: Good old cable clutch!