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Clutches..... wet multi-plate clutces..... they are wondeful pieces of equipment....
over the years there was an escallation of the number of plates used in the multi plate arrangement....and this was done to increase the surface area of the clutch plates to increase clutch holding power...instead of merely jacking up the spring pressure...and thus lever effort needed to work the clutch....
more & more plates is why motocross bikes have better clutch hookup combined with super easy lever pressures.... in the past here used to be springs so heavy that you would get arm pump from clutch use in a lap or 2...not so now.....
but that's the MX Bikes....not the Quads....
the bike clutches rarely need anything beyond the OEM setup for anything off-road.... the rear tire will typically break traction long before the engine would overpower the friction grip of the clutch pack....
not so on quads...think about how much more the quads have going on behind the engine than the dirt bike versions do:
1) double row axle carriers (yes, more bearings does = more firction)....
2) a comapratively HUGE axle to turn..... and you know you're just going to buy a wider\heavier one as soon as you can afford it... 2+2"
3) not one, but 2: BIG \ FAT \ MEATY\ HEAVY\ EARTH GRABBING tires....not to mention the 2 wheels they are mounted on
so...an azzload more weight to accelerate in the assembly... PLUS an azzload more tire connection to the terra firma we ride on
now... the ATV world is also way more engine building\ power obsessed than out dirt biking brethren...so we build big\ powerful engines to power all of that extra driveline stuff mentioned above.....
and what's still in the middle between of all that power, and all of thet driveline weight and traction??
your poor oem clutch...that was originally designed to handle the needs of the dirt bike....
and still, the oem clutches do an amazing job.....
In My Experience (not IMO)... the oem clutches are typically he best quality...none of the oem's want the warranty hassle, or bad reputaion...that would come from inferior clutch components....
and my own favorite clutch setup is the OEM clutch pack...with the steel plates sandblasted for extra grip.... without adding springs that would ruin the nice\easy clutch pull...and if i still need more spring pressure, i will try adding only half of the springs as extra pressure untis first...no sense going stiffer than necessary....
and seriously... the oem clutches with bead blasted steels will really hold tight with a lot of abuse....
i can usually see clutch slip during my frequent dyno sessions...long before it becomes a real world problem....
on a dyno graph... a slipping clutch will give a distinct, characteristic torque curve....the clutch will have a certain amount of torque it will transfer during the rise in rpms...of course the rest will be lost in slip\friction.... then once the torque increase per rpm is going to plateau, the clutch pack will finally "re-hook"..and what you will see is a funny, "hang-nail" like spike as the clutch stops slipping and snaps some interia momentarily into the reading....those graphs read less than actual torque up to that point...and a falsely high torque peak at that point... easy to spot a slipping clutch on a dyno graph...
anywhoo.....
on to this year in the michigan dunes (Silver Lake).... this season has seen more rains than any i can remember...the dunes have constantly had wet sand... that is, that parts that haven't been completely under water..LOL...for real...
so... this year is the year that clutches are taking an exceptional beating.... between a well built engine and good paddle tires in heavy wet sand...somethings gotta give....and it will be the clutch pack....
evidence of a slipping clutch is when you have increasing clutch lever free play.... slip = heat...and heat expands the plates thickness...and that shows up as increased free play.... which comes back into correct adjustment when the assembly cools down....
this year, just a couple passes has added enough slip and heat to my clutch packs (TRX and YFZ)...that the lever free play goes up by about an inch..... not good... and that is with bead blasted steels...plus 3 out of 6 springs with heavy pressure......
Sooooooooooooooo...... what's next?
centrifically assisted clutch pack pressure.... a centrifically weighted assy that put pressure over and above the spring pressure.....
such as the Direct Drive company's Lockout pressure plate assembly ...sold & used by site sponsor KBR...
there have been many centrifically assisted clutches ,for many years in the automotive industry.... the idea works well....
in all cases there will be some sort of weighted assembly that puts more clamping force on the clutch pack as RPMs\centrifical force increases.....AND it also means that there will be more lever effort needed to operate the clutch as rpm increases .... you can't magically add clamping pressure to the pack and not feel it when pressing against it to unclamp the pack....
lower rpm will not feel much added lever effort at all....high rpm will see the most
now... while it WILL work....KBR and many, many others have solved all sorts of clutch issues from clamping to reliability to longevity with the Direct Drive units.....clamping force increases with rpm...but clutches really slip worst during the steep part of the rise in the torque curve... so, in a magic world...it would be nice to have added clamping (and thus lever effort) only during steep torque rise through the midrange (which would also necessitate that your clutch be throttle position sensitive)....that aint happening.....
and..they do add flywheel weight to your rotating engine assy...which could be either good or bad depending on particulars.... just mentioning that it does....
so... i put direct drive clutches on both my trx and yfz..... incredibly detailed units, with CRAZY good tricked out eye appeal via the clear covers..... and quite a bargain price in out world too....
the yfz unit fits great all the way around..... no problems or special stuff needed...
the trx unit would require a special kickstarter offset for kick start models....and it requires quite a bit of brake lever cutting to get the brake lever even CLOSE to to original pedal height...not thrilled about that, but what are you going to do?
i'll see how they work next week when we have the Venom Test & Tune day at Bob's Raceway....and i'll put some pics up of the units fairly soon... hard to imagine more eye appeal on an engine part....
over the years there was an escallation of the number of plates used in the multi plate arrangement....and this was done to increase the surface area of the clutch plates to increase clutch holding power...instead of merely jacking up the spring pressure...and thus lever effort needed to work the clutch....
more & more plates is why motocross bikes have better clutch hookup combined with super easy lever pressures.... in the past here used to be springs so heavy that you would get arm pump from clutch use in a lap or 2...not so now.....
but that's the MX Bikes....not the Quads....
the bike clutches rarely need anything beyond the OEM setup for anything off-road.... the rear tire will typically break traction long before the engine would overpower the friction grip of the clutch pack....
not so on quads...think about how much more the quads have going on behind the engine than the dirt bike versions do:
1) double row axle carriers (yes, more bearings does = more firction)....
2) a comapratively HUGE axle to turn..... and you know you're just going to buy a wider\heavier one as soon as you can afford it... 2+2"
3) not one, but 2: BIG \ FAT \ MEATY\ HEAVY\ EARTH GRABBING tires....not to mention the 2 wheels they are mounted on
so...an azzload more weight to accelerate in the assembly... PLUS an azzload more tire connection to the terra firma we ride on
now... the ATV world is also way more engine building\ power obsessed than out dirt biking brethren...so we build big\ powerful engines to power all of that extra driveline stuff mentioned above.....
and what's still in the middle between of all that power, and all of thet driveline weight and traction??
your poor oem clutch...that was originally designed to handle the needs of the dirt bike....
and still, the oem clutches do an amazing job.....
In My Experience (not IMO)... the oem clutches are typically he best quality...none of the oem's want the warranty hassle, or bad reputaion...that would come from inferior clutch components....
and my own favorite clutch setup is the OEM clutch pack...with the steel plates sandblasted for extra grip.... without adding springs that would ruin the nice\easy clutch pull...and if i still need more spring pressure, i will try adding only half of the springs as extra pressure untis first...no sense going stiffer than necessary....
and seriously... the oem clutches with bead blasted steels will really hold tight with a lot of abuse....
i can usually see clutch slip during my frequent dyno sessions...long before it becomes a real world problem....
on a dyno graph... a slipping clutch will give a distinct, characteristic torque curve....the clutch will have a certain amount of torque it will transfer during the rise in rpms...of course the rest will be lost in slip\friction.... then once the torque increase per rpm is going to plateau, the clutch pack will finally "re-hook"..and what you will see is a funny, "hang-nail" like spike as the clutch stops slipping and snaps some interia momentarily into the reading....those graphs read less than actual torque up to that point...and a falsely high torque peak at that point... easy to spot a slipping clutch on a dyno graph...
anywhoo.....
on to this year in the michigan dunes (Silver Lake).... this season has seen more rains than any i can remember...the dunes have constantly had wet sand... that is, that parts that haven't been completely under water..LOL...for real...
so... this year is the year that clutches are taking an exceptional beating.... between a well built engine and good paddle tires in heavy wet sand...somethings gotta give....and it will be the clutch pack....
evidence of a slipping clutch is when you have increasing clutch lever free play.... slip = heat...and heat expands the plates thickness...and that shows up as increased free play.... which comes back into correct adjustment when the assembly cools down....
this year, just a couple passes has added enough slip and heat to my clutch packs (TRX and YFZ)...that the lever free play goes up by about an inch..... not good... and that is with bead blasted steels...plus 3 out of 6 springs with heavy pressure......
Sooooooooooooooo...... what's next?
centrifically assisted clutch pack pressure.... a centrifically weighted assy that put pressure over and above the spring pressure.....
such as the Direct Drive company's Lockout pressure plate assembly ...sold & used by site sponsor KBR...
there have been many centrifically assisted clutches ,for many years in the automotive industry.... the idea works well....
in all cases there will be some sort of weighted assembly that puts more clamping force on the clutch pack as RPMs\centrifical force increases.....AND it also means that there will be more lever effort needed to operate the clutch as rpm increases .... you can't magically add clamping pressure to the pack and not feel it when pressing against it to unclamp the pack....
lower rpm will not feel much added lever effort at all....high rpm will see the most
now... while it WILL work....KBR and many, many others have solved all sorts of clutch issues from clamping to reliability to longevity with the Direct Drive units.....clamping force increases with rpm...but clutches really slip worst during the steep part of the rise in the torque curve... so, in a magic world...it would be nice to have added clamping (and thus lever effort) only during steep torque rise through the midrange (which would also necessitate that your clutch be throttle position sensitive)....that aint happening.....
and..they do add flywheel weight to your rotating engine assy...which could be either good or bad depending on particulars.... just mentioning that it does....
so... i put direct drive clutches on both my trx and yfz..... incredibly detailed units, with CRAZY good tricked out eye appeal via the clear covers..... and quite a bargain price in out world too....
the yfz unit fits great all the way around..... no problems or special stuff needed...
the trx unit would require a special kickstarter offset for kick start models....and it requires quite a bit of brake lever cutting to get the brake lever even CLOSE to to original pedal height...not thrilled about that, but what are you going to do?
i'll see how they work next week when we have the Venom Test & Tune day at Bob's Raceway....and i'll put some pics up of the units fairly soon... hard to imagine more eye appeal on an engine part....
