Hello All, I have started the rebuild of my pilots clutch (Torque Limiter). This is covered in the manual section 11, Transmission /Torque Limiter. As most already know I'm in the process of having some new springs made for proper fitment since the factory one are long gone. We (the board) has found a replacements for the Metal and the Fiber plates and as of yet to find the correct spring. There is other springs out there that will work however not factory fitment.

First of all here is some pics of my clutch ( torque Limiter Assembly)and some numbers. A lot more to come including a work sheet for all to use.

We or I can post links to the other discussions as a cross reference to this post. As we all know our clutches are getting old now and most are adding power. We should give Honda a Hugh at-a-boy for the design as it has been mostly maintenance free for 25 years and counting.

Well that's all the commentary for now and time for some pics to base the work off of. Do not worry your head will be hurting as I go so get you aspirin ready.

Would like to also thank all that posted info to aid in this endeavor, Great Big Thanks.

more pics

more pics

more pics,

Info to come:
Each, Springs free Length
Each, Clutch Plate Thickness ( driven plate, metal)
Each, Clutch Disc Thickness (drive plate,fiber)
Clutch Stack Thickness (stacked Height)
Work sheet related to Numbers.

Good stuff!

I never thought of the same "clutch grooves" posing a problem for the Pilot like they do on the 2-stroke quads. Those grooves can get so bad the clutch pack will start to stick when it tries to compress and float. On a manual-trans quad, this can cause stretched clutch cables, chipped gears, broken clutch cable perch, broken clutch levers, sticking gear changes, and a not-so-fun afternoon. Folks think they can file the grooves away, but this just creates slop and accelerates wear.

Pardon my complete ignorance here since I don't own a pilot but why does the pilot have a clutch ??
Aren't they centrifugal driven like the fl350? They don't have gears do they? So why a clutch?

Its one of the best things about the pilot. The clutch is designed to slip when the rear wheels hit the ground after being in the air and spinning. This allows you to hit hard after the jump and keep the gas on, and the shock does not get transferred through the driveline. what a awesome design! so its really not a true clutch - it is a torque limiter.

No, great question, the only function of this clutch is to provide slippage in the input shaft to the trans gears so when you come off a big jump with the throttle wide open then land and get good traction the shock loading on the trans does not split the trans or break gears.

They had problems with the 350 breaking transmissions, during the 350 recall they changed something inside the trans that was suppose to make it stronger then in the Pilot they added the torque clutch or slipper clutch.

Once I was riding in Florida on a power line road that had about 3 miles of nothing but whoops, I was testing my FOX air shock by running a few miles of whoops fast and hard as I could then get out and feel the temp of the shocks, I also put my hand on the cover of the trans where the torque clutch is, it gets very hot to the touch really fast the rest of the trans does not, I assume the heat is from the clutches slipping when hitting the whoops.

This is what I like to see, Great questions and good answers and good information provided. Keep it up.

I thought I would share my take on the spring for discussion and review. I then will move forward to other parts.
Yes, DMoneyAllstar the outer plate will be addressed. Please all, feel free to add any advise as to what should and how to address it.

Ok, here we go.
Please remember I’m not a professional in any way, just a back yard hacker. So take this for what it’s worth and proceed at your own risk.
As I stated I was going to provide info on the springs, plates etc. I will start with the old removed springs from my torque limiter (clutch). In this case the clutch in the Pilot transmission is a wet clutch. What I did was measure each springs Free Length or Height after it was removed from the clutch assembly. This Free Length is the linier spring’s relaxed length with no load on it. We should cover some basics here so all can follow along. What is a spring? A spring is an energy storage device, at its Free Length there no energy stored in this device. There is no force acting upon it or any force acting upon an adjacent part. We call this static or at rest. The springs force for this straight weight (linier) spring is rated as inch lbs or a given amount of pound per inch of travel before coil bind. Every inch the spring is compresses the amount of stored energy is a fixed amount based on wire diameter and the overall dimension and the material the spring is made of. When dealing with the clutch spring we should also give attention to the springs rated load at a given height or the springs Load Set Point. Once the load set point is reached future load can over stress the spring. Over stressing the spring will only shorten the life of the spring. This will also allow the spring to get closer to its solid height (coil bind) which will cause spring set. When spring set takes place the free length of the spring changes at its static position. The spring’s free length is now shorter than before. In turn the compressed length also changes for a fixed amount of travel and the force is now less than before set. In order to combat this one would have to design the spring with set in it. This is where collecting data and developing a chart to work with will help or aid in the design of a new spring for the Pilot clutch application. Since we do not have Honda’s specs we have to come up with our own.
In order to design a spring for this application we have to find out set parameters for the manufacture to engineer the spring. We need to know the min and max outside diameter, min and maximum wire diameter, working load height, working load in pounds and operating temperature. What we want is a spring that will be installed that will not take set or be over stresses during its life and provide adequate prolonged load as the plates and disk wear. So why is the free length (height) important as related to the service limits listed in the manual? Well as the free length changes the amount of in lbs decreases so the force acting upon the adjacent parts decrease and fall out of spec and allow the clutch pack to slip and accelerate wear on their parts not to mention the performance fo the machine.
Thanks to Baz, Mass, “H” and Nitro we have some base numbers to work with very valuable information as related to the about statements and explains the numbers measured. We have a base number for rate and load. We also have base numbers for ID, OD and Free length new and old and compare to the manual which list the specs. We also have plate thickness which is not listed in the book so we can build a work sheet to run all the numbers. If you go and review the clutch post (insert link) one can see the numbers. If you look at what Baz measured new in way of pounds per MM with a new spring at 26.5 mm free length (height) and Barnett/Mas with a used spring at 25.07MM. You can see the spring has taken set.
To Quote Mas-Racing: “The Used spring from nitro sport tested at 152 lbs at ¾” or 19.05 mm. The spring Baz tested was at 170lbs at 19 mm. It has lost a lot of its tension then. Nitrosport’s spring was also under the Honda service limit for length before compression so you would have to take that into consideration.”
The difference in free length before and after spring set will have an effect upon pounds at a given amount of travel. Now Why? Well we know the free length has changed, the spring rate has not changed so why. What has taken place is the pitch or the distance between the coils has been reduced so the solid height has been reduced and the effective (max) rate for a given height has changed and the stress has increased. Or could just be the difference in testers and or spring in manufacturing.
What if we design a spring with set in it so it provides a given amount of force within its max rate at a given height (travel) with an adjustment factor based on pack thickness and wear. Also design in a force greater than stock and without too much force as to possibly render the Torque Limiter ineffective.
Any way here is my clutch springs free length.
(1) 26.12 mm
(2) 25.98 mm
(3) 26.06 mm
(4) 26.03 mm
Average free length 26.0475 mm, Note here spring manufacturing can be +/ 10%. Yes the book does say replace all if any is below service limits of 26.0 mm. In my case #2 is below the specs. Would you say these springs have taken set?
FYI on the spring as related to max recommended load, if the spring was replaced with a new stock measured and built a spring without spring set built in. The spring would have a maximum rate load of 118 lbs at .185” (.185x25.4=4.699 mm) of travel. The pilot spring is being compressed (traveling) between 5.7 and 6.9 mm which are beyond the 4.699 max numbers given in the above example. This tells me, not only will the spring take set the stress will be beyond the limit of the spring and premature failure will accrue over time.

As always please correct me if I miss quoted or stated miss information.
Thank you, Adnoh

Did some number crunching and came up with so numbers on my clutch. I had to tweak my work sheet based on new numbers.

What was measured as the compressed length (travel) of 20 mm and what I measured on mine which was 21 mm. Not saying 20 is wrong just not what mine measures as shown in my pics. Baz measured his NEW spring at 21 mm and it was 120 lbs. SO I used that as a guide. The math (back yard hacker math that is)also supports the 120 Lbs area for the spring.
So I worked up a new spring so that after set it would give me around 124.59 pounds using my old plate and disk and a touch higher with new ones. This also give me an additional 46 pounds of shim distance if a higher poundage is needed with out the spring being over stressed passed it's max travle. I know that may not sound like a lot however its a 39 % increase. I' working with this as not to over do the poundage and stress the transmission. Here's a couple of pics of the work sheet to show the numbers.

forgot the pdf,s sorry

Purchased 100 spring today and should have next week. Fiber and steel clutch plates on the way as well. Pics and write up to follow as I get the work done. I will be busy for the next couple of weeks. here is a spreed sheet you can use to play with.
Here the Quote they sent me:
"We quote:

C.815x.148OTx1.000
Custom compression spring, .815 OD, .148 OT wire, 1.000 free length, 5.2 total coils, ends closed and ground, plain finish
Spring rate of 725.83 lbs./inch
Load point of 167 lbs. at 0.770 compressed (solid) height (.230 travel)
NOTE: This load point is overstressed and the spring will take a set. We will manufacture such that free length after set is 1.000

50 – 5.95 each
75 – 4.36 each
100 – 3.98 each
+ 116.00 lot charge for performing the set
Ship 1 week.

Block tolerances on prints do not apply as all tolerances are to Spring Manufacturers Institute specifications. The quantities for custom made springs can vary +/- 10%. We have a $10 handling fee for direct shipments and for carriers other than UPS or LTL truck line."

I call the MFG and altered the order. I decided to do the set my self.

Quote"
Order completed by phone.
Confirmed.
100 – 3.98 each
Protech responsible for set.
Ship 1 week.

Thank you for your order!"

here is a print on what I came up with for others to use if they want.

What source is good for the metal and fiber plates? Also if I read this right you didn't order 100 springs, if others want em go through your source you used? Contact? I want to get all this stuff on hand to have.
Keep the info coming, Thx EZ

EZ, I did order 100 spring. I ordered the with out set to save the 116.00 dollars. I can set them my self it just takes time. The print was for others to view or use if would like. I did not want any one to feel obligated to buying springs that I had made. There is one line spring calculators that will guide one to having them made with defaults through out the process to keep one from making a mistake.

viewtopic.php?f=1&t=13073&p=128849#p128849
The springs I had made will not work according to what Lee posted see above link.

Call change the order?

No I can not at this time as there is production. When I talked to there engineer about the stock numbers he said no way with out it taking set and it was way over stressed. He also told me the max safe poundage was 118lbs. The stress was at 90% of the material strength. That is why I changed the configuration. After ruining several sets of numbers and discussion on the application we came up with what I ordered. Ever spring calculator I used came up with the same thing. I do wonder why BAZ's new spring measured less than 26.9 or 27 mm.

The only thing that comes to mind is the material. Maybe lee can way in on that. I check my springs installed length several time and came up with the 20.95 mm or 21 mm with the parts I had in the clutch assembly. I do have all new plates on there way and I then can measure the new parts and compare to the old ones. I will play with the number again and see.

There has to be an answer. The numbers do not lie. Maybe some on else can measure up there in order to make sense of it all and call around and ask.

I know I will use the new spring in mine and see what happens. Like I stated in the beginning I will measure each spring and monitor it as well.

If you downloaded my work sheet, change the installed length to 20. It comes up to 154 lbs
The spring I had made can go up to 167 pounds at .230 travle or installed height of 19.558 mm. Granted this is at solid and not good. The big question is the stress on the at 20 mm installed height. I will need to calculate it and verify it with the mfg. I bet it will be around 40 to 50 %.

Back to square 1 for those wanting springs.

Andoh.

I guess I am confused if you can get 154 lbs at 20mm and the numbers Lee provided said design was 155 lbs whats the problem, then adding a shim takes them to 167lbs sounds like a place to start for the high HP machines.

I havent seen any problems on my 440 Pilot (guessing 70 hp) all I have ever changed was the factory frictions (once and old ones were still with in spec) reused all the rest of the parts, its had plenty of abuse and countless whoops, bumps and jumps at WOT (Wide Open Throttle).

I think where guys will have a problem will be when the clutches start to slip because of too much wear and HP being applied like any other clutch once they slip they die really quick, dark oil will be the first sign, that's where the shim or stronger springs would come into play, I change my trans oil after every ride trip where I use 10 gallons of gas or more, also use to change my balancer oil too on the Honda Engine, been using Mobil1 15-50W for years, I cant see any reason why not to recommend it to others, same oil I use in all my ATV gear boxes and use in my 1999 400EX since new.

good point "H", I just every one to be informed.

Pics of the springs and receipt.

Holy shit they are expensive...

Install and test them, install then find a long whoop section like the entrance to the dunes at Little Sahara Dunes at the North camp grounds (Cow Boy Camp?) run that WOT (Wide Open Throttle) a few times in and out with other Pilots (when dune cops are not around lol) then stop and feel the trans for temps and compare with the stock Pilots, feel the cover and around the torque clutch area as well as the rest of the trans, any suspicion that the clutch might be slipping or something is not normal STOP!!!! You don't want to burn up the clutches or plates, think its not slipping enough like the trans is much colder than the stock springs, rethink what your doing...

End of trip trans oil change should also tell a story?

Thanks.

What did you think of? Are you going to go ahead and try em out?
I'm in for what I committed to regardless. Don't wanna see you stuck with that expense. I depend on guys like you and this forum so I don't have a 600 pound paperweight.

How funny "H" I have done that many times. Never noticed a speed limit. I have been through that section at 50 to 60 from start to stop. Opppppps. Yes data will be collected to share. I got enough part to rebuild the clutch a few times or so. Burning a set up no big deal at this point as long as I do not damage anything else. As they go away the rpm's should peak way out and my vapor red light should go solid.

Ez, Yes I'm gona try them as I have nothing to loose at this point. The math is in line so testing will be the next step.

I did take ten out of the package and started measuring them up. I built a work sheet to analyze the data. It will be link to the work book and access for quick reference.

So here is some pics and the pdf's of the work sheet and the sorted data into sets that I did so far.

What I will do is take all the spring measure them, set them, than remeasure them, and log the information. I than will tag each on and place the 10 in a bag and make the bag 1-10, 11-20 etc. I than will take the work sheet using the sort feature and log them into sets. Then I will start the testing with the valve spring tester and add that to the work sheet. After all the springs are done I will start on plates, fiber and steel and build me a clutch to test.

more pics