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brucey

Montesa 4RT Dragging Clutch Advice

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O.k, I know it's been covered many times but I'm looking for something I may have missed.

I recently replaced my 2014 clutch plates with a set of Apico friction plates and dimpled discs.  I also used the correct Elf oil.  However I continue to get enough clutch drag to have to put it in neutral to start (Just like my Tiger Cub!).  Selecting gears becomes difficult once the bike is hot and neutral is pretty much impossible to find at any time with the engine running.

I currently have the clutch out and have polished out some very shallow marks in the clutch basket fingers with 800 wet and dry. (mainly on the drive side).  I will also dress all the fingers on the virtually new Apico plates to see if that helps.

I have read all the posts on this subject and am at a loss as to what else I can do.  The hydraulics and slave cylinder all appear to be working perfectly. 

A guy at a recent trial said he removed several clutch plates from his 315 to cure his clutch drag problems!

I have to say the problem is taking the fun out of riding what should be a very nice bike. 

Any further advice before I put it back together would be gratefully received.

 

Bruce.

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I have tried various oils, don't have the gear selection problems, and neutral is sometimes hard to find (as on many trials bikes) but don't have actual clutch drag in that I have to release the lever a fair way before drive starts to be taken up.

Having said that, I long ago gave up any expectation of the thing starting in gear. It will do once in a while for no apparent reason but generally I don't bother trying.  It beats me how the might of Honda can't produce a clutch that consistently permits starting in gear but you may just have to get used to living with it.

Edited by 2stroke4stroke

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17 minutes ago, 2stroke4stroke said:

I have tried various oils, don't have the gear selection problems, and neutral is sometimes hard to find (as on many trials bikes) but don't have actual clutch drag in that I have to release the lever a fair way before drive starts to be taken up.

Having said that, I long ago gave up any expectation of the thing starting in gear. It will do once in a while for no apparent reason but generally I don't bother trying.  It beats me how the might of Honda can't produce a clutch that consistently permits starting in gear but you may just have to get used to living with it.

2/4/ thanks for your reply.  When I say 'clutch drag' I mean it doesn't appear to completely disengage when the clutch lever is pulled in.  I can feel the bike trying to move slightly when the engine is running, the bike is in gear (1st) and the clutch lever is pulled fully in.

There doesn't appear to be any adjustment apart from the lever to master cylinder free movement.  Mine is set to around 1mm.

I appreciate that I should only use the clutch occasionally (especially on a 4 stroke bike) but the Diaphragm Clutch on my Armac Cub and the Friction Plate Clutch on my other Cub are both far better! 

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I had the same problem and fixed it by adjusting the lever. I have to use four fingers and press the lever into the grip and I can start it in neutral. I also use a folding lever that allows me to adjust the lever farther out.

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does the release point seem a long way in on the clutch lever - would be good to determine if its an actuator problem or is it an actual clutch issue.

maybe master cyl has been rebuilt with the wrong piston or something silly.

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I'm new to the 4RT, but have a lifetime of working on bikes.  The correct clutch pack thickness is important to proper operation of all clutches.  Honda does not provide that specification, but does give a range for the individual plates.  My 2016 workshop manual specifies the nominal friction plate thickness as 3.22 to 3.38mm, with a service limit of 3.15mm.

In my opinion, 1mm of lever freeplay is too much.  The freeplay must be non-zero under all temperature conditions, but I prefer the minimum.  I use my clutch constantly.  My bike shifts flawlessly, but I can't select neutral without the bike rolling -- not a big deal. 

I would also suggest bleeding the clutch hydraulics.

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10 hours ago, brucey said:

O.k, I know it's been covered many times but I'm looking for something I may have missed.

I recently replaced my 2014 clutch plates with a set of Apico friction plates and dimpled discs.  I also used the correct Elf oil.  However I continue to get enough clutch drag to have to put it in neutral to start (Just like my Tiger Cub!).  Selecting gears becomes difficult once the bike is hot and neutral is pretty much impossible to find at any time with the engine running.

I currently have the clutch out and have polished out some very shallow marks in the clutch basket fingers with 800 wet and dry. (mainly on the drive side).  I will also dress all the fingers on the virtually new Apico plates to see if that helps.

I have read all the posts on this subject and am at a loss as to what else I can do.  The hydraulics and slave cylinder all appear to be working perfectly. 

A guy at a recent trial said he removed several clutch plates from his 315 to cure his clutch drag problems!

I have to say the problem is taking the fun out of riding what should be a very nice bike. 

Any further advice before I put it back together would be gratefully received.

 

Bruce.

I had the same problem, a right head banger, I fully stripped the whole clutch system, filed edges, cleaned every part, replaced all clutch seals, installed new Apico dimpled plates & fibres (chamfered all sharp edges) & filled with fresh dot 4 & ELF HTX oil, resulting in absolutely zero change to the clutch dragging issue! Just before scrapping the bike I ended up giving it another go, installed new cork EBC clutch plates, changing the oil to Rock Oil gear pro 75W, drilling a 4mm hole in each of the outer alloy clutch basket fingers & an additional 3mm hole in the inner alloy clutch hub (next to & in-line  with the existing hole) the result was best feeling clutch ever, still easy to find neutral after 2 hours of riding, no drag whatsoever, also no slip on the big sections - I run only 4 standard clutch springs rather than 6 for a more progressive feel & it’s a full 300cc!

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Thanks Gaspgasp, it sounds like something to try.  Slightly gutted I have spent 2 nights filing all the edges on my Apico clutch plates though.  However I'm prepared to try EBC fibre plates if there is a good chance of improving the problem 🙂

Can you confirm a couple of things:

I'm assuming you still used your Apico dimpled plates with the EBC friction plates.

The 3mm holes in the inner alloy hub are spaced in a spiral pastern.  How close to the existing hole did you drill the additional hole? and do you remember which side of the existing hole you drilled it?

I'm assuming you drilled the 4mm hole in the outer basket fingers in the middle of the thickest part near the base of the fingers (about 10mm from the base).  Is this right.  Are these holes to allow the oil to be flung away from the clutch plates? 

Interesting about the 4 springs although I'm not sure my OCD will allw me to choose which 2 springs to remove!

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The std clutch isn’t bad - May could be improved .

what you describe is a major fault somewhere or you are super fussy.

doing all the work indicated is fine if you are super fussy but should not be necessary unless you have a major fault / or bad set up in the actuation mechanism - master /Slave/ hose / levers etc . 

My take on it any way as a mont man for 20 years plus and an qualified engineer 

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9 hours ago, jimmyl said:

The std clutch isn’t bad - May could be improved .

what you describe is a major fault somewhere or you are super fussy.

doing all the work indicated is fine if you are super fussy but should not be necessary unless you have a major fault / or bad set up in the actuation mechanism - master /Slave/ hose / levers etc . 

My take on it any way as a mont man for 20 years plus and an qualified engineer 

Yup, I'm super fussy 🙂 However I made the assumption that the clutch on my £3.5K Montesa would be at least as good as the clutch on my previous £1.5K Gas Gas so that is my objective.

I'm pretty sure there are no major faults with the clutch but the dragging is a constant distraction from what is otherwise a beautifully (if not slightly over) engineered bike.

I'm also a Chartered Mechanical Engineer 🙂 

Bruce.

Edited by brucey

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9 hours ago, brucey said:

Thanks Gaspgasp, it sounds like something to try.  Slightly gutted I have spent 2 nights filing all the edges on my Apico clutch plates though.  However I'm prepared to try EBC fibre plates if there is a good chance of improving the problem 🙂

Can you confirm a couple of things:

I'm assuming you still used your Apico dimpled plates with the EBC friction plates.

The 3mm holes in the inner alloy hub are spaced in a spiral pastern.  How close to the existing hole did you drill the additional hole? and do you remember which side of the existing hole you drilled it?

I'm assuming you drilled the 4mm hole in the outer basket fingers in the middle of the thickest part near the base of the fingers (about 10mm from the base).  Is this right.  Are these holes to allow the oil to be flung away from the clutch plates? 

Interesting about the 4 springs although I'm not sure my OCD will allw me to choose which 2 springs to remove!

- Still kept the dimpled plates.

- Inner clutch hub drilled 3mm hole about 10mm centres with existing, on the side which had more space.

- The outer clutch basket was drilled center of each finger, which is minor compared to the after-market MX baskets with large slots milled in each finger.

I should have tried each method individually to identify the fault but didn’t have the time, spent to long with a spanner in my hand rather than riding. If you have the time try above but without the EBC cork plates & Rock Oil, it may work & save you a bit of brass.

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5 hours ago, brucey said:

I'm also a Chartered Mechanical Engineer 🙂

Excellent.  Maybe this is a good place to post the following?

I'm also very fussy and only change one thing at a time because I want to understand the effects rather than just fix a problem.  I'm running 4 clutch springs.  As expected, the force required to pull the lever decreased.  This is a good modification for me as I have a wimpy finger and use the clutch constantly.  Have not noticed any slipping, but when I do it will be time to replace the friction plates (I'll be inclined to use OE or EBC).

My bike is currently running the HTX 740.  That oil has the characteristic gearbox-specific smell which I find most unappealing.  I also think it's an odd choice for the job.  Elf says it's designed for very high performance dry clutch applications like 2-stroke GP bikes and shifter karts.  HTX 740 is a special-order item in the USA, and costs $50 per liter.  I'd like to find a substitute. 

I often use the BITOG website https://www.bobistheoilguy.com/forums/ubbthreads.php to find 40 and 100 degree C viscosity data for various oils.  There I learned that HTX 740 is a synthetic that measures 21.4 centistokes @ 40C and 7 cSt @ 100 C.  Also discovered that Valvoline Dexron-VI synthetic ATF is a possible substitute rated 29.5 cSt @ 40C and 6 cSt @100 C. (Which does not seem all that close to me.)  I bought  the Valvoline locally for $5 per quart, but have yet to try it. 

I have used my own viscosity measuring setup (shown below) to get a feeling for the difference.   I often test suspension fluids by flowing 10cc through a burette at ambient temperature.  My result for used HTX 740 was about 42 seconds @ 57 degrees F, whereas virgin Valvoline Dexron-VI came in at 62 seconds @ 57 degrees F.   Clearly the HTX is considerably less viscous at 57 degrees F, but possibly has sheared down somewhat from virgin.

 

Burette kinematic viscosity test.JPG

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I've run the dimpled steel plates, OEM fricton plates (2 ea 22201-KY2-000 cork and 4 ea 22201-NN4-B00 paper), and Dexron VI full synthetic with all 6 OEM springs.for 5 years. I've found there's no drag, better shifting, and easy to find neutral. I've also found, in my opinion, the Dexron VI lasts longer than the HTX-740. Maybe because it's formulated to work with wet clutches. But I still change it fairly frequently because it's inexpensive.

Did you measure the Apico friction plate thickness? I'm curious about whether or not they're thicker than the OEM friction plates.

Another interesting thing seen in other models.

The Japanese HRC RTL260F parts list shows the standard (2 ea 22201-KY2-000 cork and 4 ea 22201-NN4-B00 paper) and an alternate clutch pack with all 6 friction plates as 22201-KY2-000 cork.

The 300RR uses more cork plates than the 4RT / 4RT260, 4 ea 22201-KY2-000 cork and 2 ea 22201-NN4-B00 paper.

I'm thinking of trying the all cork OEM or 4 cork 300RR setup when I replace the plates, keeping the dimpled steel plates.

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