JMC Swingarm Wheel Spindle Removal

[DougW]

Starting to do a bit of work on the recently acquired scabby lc.

I assume that if I loosen the pinch bolts, then remove one of the cap heads that secures the eccentrics to the wheel spindle , that the other eccentric will pull off outwards with the spindle attached ?

Other side eccentric is a mirror image of the one shown.

Thinking of using a slide hammer through one of the two eccentric rotating holes to pull outward.

Plenty of old hammer rash on the poor old abused thing, don`t want to add to it !

[DougW]

5 minutes ago, Yamonda said:

I would've thought using a paddock stand then a block under the wheel it keeps it in place.

then undo the Allen the pinch bolts and the adjusters should slide out. Been years since I've had one. 

Maybe Google jmc swingarms and check out images. 

Adjusters show no immediate desire to slide out, trawled web for images and only found one image of the type I have in bits, others have a detachable section of arm.

[rossm]

1 hour ago, Yamonda said:

Give them a spray of wd40 and if you can make a a tool to gently move them. Eg solid flat bar and 3 bolts or rod to fit the holes as best as possible.

Maybe one for each side, apply brake and in gear too.

 

He's going to struggle to put it in gear and apply the brake:-)

[DougW]

5 hours ago, Yamonda said:

Is that an LC

Yes, or the remains of one.

[Thunderbolt]

I thought that the brake side eccentric was threaded on these, the sprocket side was clearance and the axle went through from that side. IYSWIM?

[DougW]

 

9 hours ago, Thunderbolt said:

I thought that the brake side eccentric was threaded on these, the sprocket side was clearance and the axle went through from that side. IYSWIM?

I think so, I will make up a tool so I can rotate the eccentrics without adding to the existing damage and have a play. Coincidentally I was talking to the last owner yesterday, he had never taken the rear wheel out !

[Thunderbolt]

2 hours ago, DougW said:

 

I think so, I will make up a tool so I can rotate the eccentrics without adding to the existing damage and have a play. Coincidentally I was talking to the last owner yesterday, he had never taken the rear wheel out !

There will be some bodgery in there no doubt.

 

[DougW]

14 minutes ago, Yamonda said:

Nah was just thinking you could drop in some wd40 or diesel, least it can only go down.

Maybe make a shroud out if plastascine or

It doesn't actually seem that corroded, the brake plate side actually slides in and out a couple of mm , I think Thunderbolt`s suggestion that one side is threaded may be correct, I will try rotating the adjusters when I have finished making up a tool.

The front wheel spindle came out fairly easily with no corrosion, the bike has been dry stored pretty well.

Edited April 16, 2020 by DougW

[CBXKevin]

I see this is an old thread, so you have probably got this sorted by now. However, I have just started sorting out an old JMC swing arm for a CBX special I plan to build. Mine has the same blue anodised eccentrics as yours.  Once the axle bolts were removed and pinch bolts loosened the eccentrics just slid out. No threaded part on the housing or the eccentrics.  At the moment that is as much as I know about JMC swingarms, need to figure out how the SA pivot bearings are meant to fit now. 

[DougW]

On 1/20/2023 at 11:52 PM, CBXKevin said:

I see this is an old thread, so you have probably got this sorted by now. However, I have just started sorting out an old JMC swing arm for a CBX special I plan to build. Mine has the same blue anodised eccentrics as yours.  Once the axle bolts were removed and pinch bolts loosened the eccentrics just slid out. No threaded part on the housing or the eccentrics.  At the moment that is as much as I know about JMC swingarms, need to figure out how the SA pivot bearings are meant to fit now. 

Thanks for the reply, the steel spindle had seized into the large alloy eccentrics, they eventually came free.

Edited January 26, 2023 by DougW

[DougW]

On 1/20/2023 at 11:52 PM, CBXKevin said:

I see this is an old thread, so you have probably got this sorted by now. However, I have just started sorting out an old JMC swing arm for a CBX special I plan to build. Mine has the same blue anodised eccentrics as yours.  Once the axle bolts were removed and pinch bolts loosened the eccentrics just slid out. No threaded part on the housing or the eccentrics.  At the moment that is as much as I know about JMC swingarms, need to figure out how the SA pivot bearings are meant to fit now. 

My JMC swing arm pivot bearings where, from memory, imperial sized taper roller bearings, and got replaced.

The LC in question had done a few thousand miles now, been used for commuting and had a go at sprinting on it.

[CBXKevin]

Good to hear you got your project completed and it sounds like you have had some good use and fun from it.
I have found it really hard to find much info on the JMC swinging arm.  Mine does have taper roller bearings, I know this because a pair of bearings were tied to it when I got it 😄,but there was no pivot spindle with it.   I have been wondered how you you could get the correct prelode for the taper roller bearings and at the same time tighten the pivot spindle nut to the correct torque. I have just found out that maybe there should be a distance sleeve between the bearings that ensures the correct preload is maintained, which would make sense, Just wondering if you have any info or can confirm that.  Finding this stuff out is all part of the fun of course. Thank for any help. 

[DougW]

I`m not that impressed with my JMC arm, it appears you cannot torque the swing arm spindle to anywhere near the original torque setting as it will over preload the taper bearings.

If I remember correctly it did have a spacer between the taper bearing seats.

So I tightened mine up as much as I thought the taper bearings would take. It still swung relatively freely at that.

The original set up also solidly clamps the spacer tube into the frame, which to me will provide extra rigidity which is not present with the JMC arm.

It seems to work ok though at my relatively pedestrian pace on road tyres.

Edited February 7, 2023 by DougW

[TLRS]

46 minutes ago, DougW said:

as it will over preload the taper bearings.

Did the jmc come with them originally? Any space for different bearings?

[DougW]

3 minutes ago, TLRS said:

Did the jmc come with them originally? Any space for different bearings?

JMC arm came originally in the bike with rusted remains of taper bearings, replaced them like for like.

My preference would be needle rollers and needle roller thrust washers, but with the idea that this bike is meant to be used for daily commuting and not join the other LC as an ongoing project, will probably stay as it is.