1973 Penton Hare Scrambler clutch

[Andreas Piepke]

Hi All,

After putting my 1973 Hare Scrambler I found a number of issues I need to correct, one of them is that the clutch doesn't separate. I took the clutch cover off again and noticed that the pressure plate lifts off only on one side.

This observation makes me wonder whether one or some of the springs has a larger spring constant than the others. I can't remedy this by backing out the nuts on top of the springs with the lowest travel.

I measured a distance of 42.0 mm between the clutch arm and the clutch actuator housing. I guess this is close enough to the recommended value. The clutch contains 7 friction plates (each 2.4 mm), 8 steel plates (each 1.4 mm), and one steel ring 3.05 mm.

There is one issue I found: each of the two clutch rods is only 102.4 mm long. Between the two rods are two coupled steels balls of 11.4 mm length. The combined length of 216.2 mm falls short of the recommended length of 222 mm I found in some other post on this forum.
Could this be a problem or is the fact that I have the correct arm clearance sufficient to conclude that there is enough travel when pulling the clutch lever? As usual your input and knowledge is very welcome!

Thanks!

Andreas

P.S.: Before putting the clutch in I lightly filed the outer cage so the driving plates don't hang up on the groves left by previous use.

[ALB]

Andreas,

Remove the arm assy from the clutch actuator. Look at the pin inside the barrel of the assy that pushes the rod. Is the pin round or worn flat???
A high percentage of these pins are worn flat from all the years of use. A little bit of wear make a big difference on how far the rods get pushed to release the clutch plates. Replacing the pin with a new one could solve your problem.

If the arm assy is loose or wabbly in the actuator housing - it will not allow the rods to push the pressure plate enough. If this is the case, then the clutch actuator (bearing plate) will have to be replaced.



Alan Buehner

[Andreas Piepke]

Thanks for the feed back Al! I had the actuator arm out at some point to remove dirt and grease it. I didn't spot excessive wear but then maybe I don't quite know what to look for. I'll take it apart again and post a picture so you and others can give me your opinion on the wear.
Do you see an issue in the somewhat short actuator rod and the fact that it has two coupled spheres instead of one shown in the parts lists?
In the end I may have no choice but take the springs back out to understand whether or not they are all of the same type.

Thanks again!

Andreas

[Andreas Piepke]

Al, here a picture of my clutch actuator arm:



There is some wear but it seems rather minimal to me or am I not looking at the right thing? Your feedback would be very welcome!

Andreas

[adrian_goold]

Here is a video of my mc5 clutch while I have it apart.
Compare to yours.

http://youtu.be/vVArVLrkzdY


Regards,
Adrian Goold #101
http://www.ozktm.com

'73 175 Rebuilt|'74.5 250 Rebuilt|'74.5 400 Restoring|'76 MC5 250 Restoring|'76 MC5 400 Restoring|'78 250 in pieces|'81 250 Now Racing| '81 495 Now Racing|'84 125 Selling|'07 KTM 300| 74 CZ 250|74 CR250M x2|

[Kip Kern]

Andreas
The rods should be 108mm each with one 6mm ball between them for a total of 222mm.  Your clutch nuts are screwed in too tight, they should be in just enough for a 1mm cotter key to slide in the head slot through the nut and no more.  Make sure they are all the same as far as threads protruding through the nuts, around 2 threads.  The cotter key or wire (some use) should just pass through the nut and slot but lie in the slot, not stick above where the nut can still turn.  If the actuator is good, rods are correct then you can measure the arm play as in the book.  This play is adjusted by different thicknesses of pressure plates and nothing else.  Have to play with it to get the 40-45mm on the actuator arm but that is it.  Also, make sure you have the plates stacked correctly and correct number as in the manual.  It doesn't help that the manual indicates that there is no one way to assemble the clutch but that is the nature of the beast.  You will get it!

[Andreas Piepke]

Thanks for your input! I made a little video of the clutch operation:

https://www.youtube.com/watch?v=h_nuYGUIa1I

As you can see the problem is that the pressure plate should translate outward while in reality it translates and rotates. As it doesn't lift off locally (in the video in the back) the clutch doesn't separate. Before making this video I backed all screws out until the nuts are only 2 mm in from the end of the bolts. This is the minimum to get the pins in. This is why I my top suspect is that some springs are not right. Perhaps the previous owner "mixed and matched". I found a bunch of things in the bike that weren't right.
The clearance between the clutch mechanism lever and the engine is with 42 mm OK. The wrong length of the actuator rod shouldn't matter as the overall position seems to be according to specs.
I tried to follow the assembly instructions for the clutch. But this is not easy as they are not very clear. This is an older 1973 engine and I found 7 friction plates and 8 steel plates plus a steel ring in there. I put the steel ring in first, as the manual says. I am wondering whether I should remove one steel plate as the manual talks about 7 steel disks and not 8. Any experience out there whether there were models with 8 steel disks?

Thanks again for your help!

Andreas

[BrianTaylor]

Andreas

if you rotated the clutch 90 degrees the 180,then 270  would it always pull to the front ?

Brian Taylor

[Andreas Piepke]

No when I rotate the clutch it always binds at the same screws/springs.

Andreas

[DKWRACER]

You might have a clue there, binding at the same screws. Measure the spring wire thickness on all the springs, you might have 400cc mixed in with 250cc...keep us informed...Tom Brosius

[DKWRACER]

PS, the manual states two different spring wire lengths for the diferent cc motors, FYI....Tom Brosius

[Andreas Piepke]

So I took the clutch apart again:



As one can see from above image it contains 7 sintered bronze friction plates and 8 steel plates. The stack starts and ends with a steel plate. In addition there is a steel ring without spines at the bottom.
1) The manual talks about fiber friction plates. Mine are bronze. Are these possibly the wrong plates? I measure a thickness of 2.4 mm for the friction plates. One is 2.3 mm, so uniformity is good.
2) The clutch had 8 steel plates with 1.4 mm thickness installed. Is this possibly one too much as the manual states there should be only 7 steel plates? The stack of plates is seen on this image:

Would anybody know the correct distance between the plates and the rim of the inner clutch wheel?
3) The pressure plate that was installed when I took the engine apart has part number 51 32 006 099. According the parts listing this could be for a 175 ccm engine. I have a second 250 ccm 1976 vintage scrap engine, its pressure plate has part number 51 32 006 599. I am wondering whether they are both wrong or these parts were interchangeable.
4) The 8 clutch spring have a quite uniform length between 35.9 mmm and 36.2 mm. They all have a wire diameter of 1.6 mm. The manual states that the 250/400 ccm models had the same springs of 38.5 mm length (the 175 ccm ones were with 40.5 mm a bit longer), the parts listing gives the wire diameter as 1.7 mm for the 250/400 ccm and 1.5 mm for the 175 ccm. Therefore the springs seem all of the same and correct type.

I am a little puzzled as what the problem with the clutch operation is. Perhaps I should measure the actual force constant of the springs, just to be sure. Chances for this to be the issue are probably low.

Thanks for your continued interest and input!

Andreas

[Mickey Sergeant]

What if you moved the springs that seem to bind to a different location. Mark were it was binding and see if it binds in same location or ware you moved springs. That might tell you if it's the springs.

Mickey

[Keith Meatyard]

Looks like in the video that one of the outermost plates are hanging up on one side.  Could be either a steel plate which moves axial along the center hub splines is hanging up on the spline, or one of the friction plates' tabs is hanging up in it's respective slot in the basket.

Keith Meatyard

[Andreas Piepke]

Hi Keith,

This is a plausible explanation. I filed the outer basket to prevent hanging. I didn't do that with the inner hub. It does have a deep scratch in one of the spines. I'll try to polish it. After taking the inner hub out I tested the motion of the plates by hand and couldn't feel any resistance or hanging. I'll try to smoothen the surfaces again.

Thanks!

Andreas