MC5 Swingarm

[Lloyd Boland]

I notice this weekend some play developing in the swingarm of my MC5 (late '76-early '77). I have not pulled it appart yet, but I know I must do it this weekend. My question is, do I have to pull the engine out, or can I just loosen the nuts, support the motor and slide out the swingarm bolt? I see from the manual and the parts book a set of bearings, the bearing sleeve and 2 o-rings on both sides. Are there any special things I should look for when pulling it appart?

[tomale]

Lloyd, The swingarm pivot does not go through the engine. and yes you can remove the swingarm with out removing the engine. From the diagram it looks pretty straight forward but often times it will be alot more work. Those needle bearing and the races they run on can get stuck on the pivot bolt. Some times the bolt has to be cut out to get it apart. Do a search on this subject because I think several guys has some good ideas on how to do it without cutting it in two...

Thom Green,Still crazy after all these years!
76' 250 MC5 (orginal owner)74'
250 hare scrambler (project bike)

[Mike Lenz]

I have not ever seen play in a needle bearing swing arm. Usually they just freeze up if not maintianed.  Are you sure it is not the head of the bolt moving in the frame area where it is clamped? I have seen play there from running the bike with the clamp loose. If so a quick fix is to put some shim stock in there to take up the play.  Buy an inexpensive feeler gauge to use for shim stock. A better fix would be a new swing arm bolt as it has been the bolt that was worn in the ones I have seen.

[Lloyd Boland]

Mike and Thom, thanks for the suggestions.  I have gone threw the search and reviewed many pages regaarding the swingarm bearing.  It seems like the locktite freezing is the way to go.  After I get a chance to clean the bike this weekend, I will make sure everything is tight and see how it sets.  If I have to remove the bearings, I will let you know how it progresses.

Thanks again.  

Lloyd

[Lloyd Boland]

Had the flu last week and didn't get to cleaning and dismanteling the bike until this weekend.  Mike, the clamp was tight.  The swingarm bolt was almost completely froozen to the inner bearing sleeve.  It took alot of anti-seize and hammerring but it finally slid out.  When I took off the adjustment nut to check the bearings, all I had left were loose bearings falling out.  I could not find any pieces of the old cage left.  I think all I need is the bearing and O-rings, but I did bang up the threads a little right at the start on the swingarm bolt.  Does anyone know the type of threads on the swingarm bolt?  I was going to try a thread file but I want to get it right, I don't want to screw-up the threads on the frame.  Maybe a new bolt will be better and avoid future problems.  Anyone have an extra one in good condition?  I will also check with Al.

Thanks for the suggestions.

Lloyd

[tomale]

Yea, the pivot bolt is always a problem, I can't remember what I did when I replaced the swing arm on my 76 MC5 but believe it or not I actually found the bearings locally...I suppose it would be possible to clean up the treads but what about taking the nut and bolt to a local Bolt supply and see if they can match up the threads.

Thom Green,Still crazy after all these years!
76' 250 MC5 (orginal owner)74'
250 hare scrambler (project bike)

[454MRW]

Lloyd,
If you don't find one or get the threads on yours fixed up, I have a nice one for $20 inlcuding shipping or I can bring it to the AMA meeting if you are attending. Good ones are getting harder to find and I usually like to keep a couple extra around just in case. I also have a set of new bearings that I bought from my local NAPA dealer, but I will have to look up what I paid, them seemed pricey at the time and I ordered 3 sets. Mike [email protected]
BTW Thom, there is no nut, it screws into the threaded frame.

Michael R. Winter
I enjoy rebuilding and appreciating Pentons!
1974 250 HS Pentons-1980 KTM 175-400'S

[454MRW]

Swingarm bolt is 14mm and thread pitch is 1.50mm and ready to ship. Thanks, Mike

Michael R. Winter
I enjoy rebuilding and appreciating Pentons!
1974 250 HS Pentons-1980 KTM 175-400'S

[Lloyd Boland]

Thanks Mike.  I got a tap and cleaned the frame threads. The threads looks very good.  I actually used a thread file on the old bolt and it looks pretty good, took a nut with the same threads and it goes on and off very easily, probably could be used in a pinch if someone else needs one.

I read the repair manual at least a half dozen times.  On one side of the swing arm tube, the nut appears to be permanently attached.  I have tried without success to loosen it, but I haven't been too aggressive in trying.  Looks like it is welded to the tube.  Am I to understand that the fixed nut goes on the left side of the frame and the adjustable nut goes on the right?  I bought the wrench from Al.  The wrench is suppose to hold the nut on the right side stationary as you install and tighten the swingarm bolt?  I think I have this correct. (But what stops the tube from spinning, I just don't quit understand.)  Anyway, I am going to try to install it this weekend.

On another note, I thought it would be a good idea to replace the nylon guide that the chain sits on at the top/front part of the swingarm, just above the swingarm bolt.  I ordered one from Al several months ago.  It is different and mounts differently to the one I have on the bike.  The one I got from Al has a horizontal hole on the very back part of it for a bolt to go through horizontally to mount it.  Mine is attached by 2 small bolds that go directly down through the nylon guide into a little metal shelf type bracket that is just above the swingarm.  These bolts go straight up and down.  I could drill 2 small holes in the middle of the nylon guide and attach them to the bracket, but I just wanted to check in to see if anyone else has a similar mounting type.  The parts manual picture is like the one Al sent me, and there is no alternative listed.

Thanks again for everyones help.

Lloyd

[454MRW]

Lloyd,
The nuts on both ends of the swingarm tube should turn, and are just originally screwed onto the threaded tube. The tube turns in the needle bearings and by unscrewing the nuts with AL's tool, you barely snug (some folks say .010 clearance), the nuts against the inside of the frame after the engine mount bolt is torqued in place. This holds the tube in place and causes the needle bearings and the swingarm to turn around the tube, and prohibits the tube from turning and wearing the inside of the frame. It is probably frozen in place and may require a press to remove the tube so you can replace the needle bearings and see if the tube can be polished up on a high speed latch with emery cloth and reused, or whether you have to find another usuable one. I may have one usuable one left it you need it, as well as a pair of new bearings. Mike

Michael R. Winter
I enjoy rebuilding and appreciating Pentons!
1974 250 HS Pentons-1980 KTM 175-400'S

[Lloyd Boland]

Thanks Mike.  I will try to work on the nut that is stuck to the tube a little more this weekend and clean it up.  I got the bearings and O-rings from Al last week.  If I get it loosened up and cleaned, I should be able to put it back together.  We have a race out here next weekend at Glen Helen on 2/14/10  Thanks again for all your help.  I will let you know about the progress.
Lloyd

[tomale]

Lloyd, the nylon guide.. I have seen several versions used in this location... On the origial 76 MC5 swingarm there was no nylon quide at all.. but on my 77 MC5 swingarm there is..It seems to be just a skid and not a guide but I have seen them with both a skid and a guide..If it fits right in that location, and you can get the holes right... I sometimes have a little trouble with that... Not sure why then mount it that way.... Remember that Penton was always in the process of making changes and they often put them into production between model years so having one that is different is always a possiblity. It is one of the things that makes these bike a bit frustrating 35 years after the fact but is also one of the reasons these bike were so good...

Thom Green,Still crazy after all these years!
76' 250 MC5 (orginal owner)74'
250 hare scrambler (project bike)

[Doug Bridges]

Loyd, I had trouble getting the nut off one side of the tube also. I soaked it good with kroil and then I clamped on to the tube tightly with wood against the tube to protect it. I could not get the nut to move with standerd wrench but when I put an impact wrench on it it came right off.

Doug Bridges
73 Jackpiner
74 Jackpiner/FrankenPenton
project
82 XR200R

[garrettccovington]

Lloyd  I don't know if you saw my chain guide I made for my bike.  It's easy and works so good when I got the replacement from Andre' I decided to leave mine on.  The botom part that curls around the swing arm I used a old street bike tire cut it to fit and tappered.  I used the old metal mount and notched the tire to fit in the notch.   drilled a hole thru the tire and secured.  The top part I went to home depot and found some nylon rollers that fit and they roll perfectly.  I used the nylon rollers for the rear chain guide and it works great




72 six-day

[garrettccovington]

Lloyd
I still have my new ones from Andre.  If you need them let me know and I can have them fed-ex'd to you.  I'll be at the race next weekend, but I would like to get them to you asap to do a fit check.
Give me a call.  My bike is a 1979 ktm mc80 250.  Maybe they'll work.  Hey its worth a try!

Gary
909-973-2234
[email protected]

72 six-day