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315 clutch fix


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I've had the 315 for years and tried all the fixes, but didn't find them effective long term. My Father and his colleague suggested this and were kind enough to make it for me. By removing 2 fibre and 2 steel plates but keeping the same amount of lift (x), you get a bigger space between the plates when disengaging the clutch. ie standard = x / 13 plates is a smaller number than modified = x / 9 plates. It's just enough to be able to select neutral with the engine running and no more stalling in gear with the clutch disengaged.

Done a few hours practice and a trial with this set up and it's carried my 15 stone around the fun route with no sign of any slipping. It had 5w 30 fully synthetic van oil, which worked fine. Just changed it for some 15w 50 fully synthetic that I use that for another bike, will report back if any problems show up.


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What was the original problem that could not be solved?   The issues with the 315 clutch have been spoke about and solved for quite some time now.

While the above modification is quite ingenues I do think the clutch would slip or wear out the fibers plates or indeed warp the metal plates with a more aggressive rider on it.

You are still 15 stone and expecting less square inches of surface clutch area to pull you around with no degradation on clutch wear due to extra heat being generated in a smaller square surface area???

This modification also throws the weight further out to the periphery of the clutch housing causing all sort of problems and balance issue which in turn may cause bearing issues and clutch chatter. 

The oil in the clutch is not juts a lubricant it also draws away the heat from the clutch plates to keep them kool and the clutch feel consistent.

You have the same amount oil in the clutch with the fewer plates sharing the load so the oil will be hotter and therefore it makes it harder to keep a consistent clutch feel. 

Due to the weight being further out it will have more centripetal effect and won't let the plates separate as much.

There is also extra mass with the weight being further out and it will have an effect on how the clutch takes up and on the outer basket fingers.

My points are all mute if you are riding simple basic sections etc but a for a higher level rider not a good idea at all.












Edited by billyt
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On 1/29/2019 at 6:44 AM, nigel dabster said:

the 315 clutch works well elf htx helps and a fresh set of plates would have been an easier solution im sure.

I've owned two 315 and they were both had clutches that dragged badly. A new set of dimpled steels would stop it for an hour or two and the htx oil would only really cause it to temporarily drag less. Polishing the tabs on the fibre plates would improve things temporarily. I'm pretty sure that the root problem is not being able to separate the plates sufficiently with the amount of lift available.


On 1/29/2019 at 5:37 AM, billyt said:

My points are all mute if you are riding simple basic sections

:lol: Probably the worst rider in the club, but still enjoy trying. I did wonder if the spacer might be better situated in the bottom of the basket closer to the bearing, but all seems ok, no strange noises or behaviours. The clutch is common to the CR250 motocrosser, so honda would have designed it with the surface area to handle more than twice the power and much more prolonged use and heat and I wouldn't be too worried about removing 4 / 13 plates from the stack even if the bike was being used by a hard route rider. With the bike being nearly 20 years old, slightly thicker oil in the gearbox is probably a good thing. Ability to disengage the clutch properly just makes the bike more enjoyable to ride, especially with the queues at most trials. tbh even if the worst happened and it catastrophically destroyed the bottom end it wouldn't be the end of the world, sometimes worth taking a risk to try new things.

Edited by caravan_monster
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1 hour ago, caravan_monster said:

... The clutch is common to the CR250 motocrosser ...

Doesn't the CR250 clutch have 8 friction plates rather than the 7 in the 315R clutch pack. That said, the 4-stroke 300RR only uses 6 friction plates.

Aside from that, if it's working for you and you're not noticing any increased vibration, no need to change.

FWIW, a more common way to reduce drag & stick, and smooth out the clutch action a little, in 315R or 4RT bikes is with dimpled steel plates.

Edited by sportsawyer
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