Hi all, I'm currently converting an old Honda farm bike to trials form.

The bike is a monoshock  but as the linkage assembly was badly seized up and made from steel I had to cut it to disassemble. The shock unit is also quite heavy so will be chucked away.

Some advice wanted please; what would be a good setup to use/modify? I was thinking direct mount so as to avoid clearance issues with linkage. Cheap and commonly available would be ideal.

If I used a shock designed for linkage, would I get enough rear wheel wheel travel? I know there's lots of variables: mounting position relevant to swingarm pivot, swingarm length, angle of shock etc.

I'm thinking a linear rate spring would be best but again I guess it depends largely on other factors? Does monoshock angle (pds setup) have any effect on traction?

Lots of questions and I expect some experimentation will have to take place in order to answer them but any help will be much appreciated

 

I've converted a couple of mono's to twinshock with few problems. I used the shortest shocks from NJB which work well

Many years ago there was a chap who used the very plush Fournales air shock to convert a Bultaco or two.

No linkage, which was the same as the JCM bikes.

Air shock...hadn't thought of that. Maybe I could fill it with hydrogen and make those rear wheel hops with much less effort

Edited October 17, 20205 yr by theoldstuff

It's a pity downhill MTB shocks aren't rated for the weight of a motorbike.

 

If it was me, I'd be thinking of remaking the linkage (namely, drawing up a pattern and getting a local machinist to knock it up), or going to twinshock.  A system without a linkage might put some interesting strain on the mounting points.

Please post photos - these projects are always interesting to see!

Mr Gollner got the measurements right!

Spoiler

 

 

If I have to I'll make some alloy linkages but would prefer to go direct mount.

Picking up an alloy body kdx200 shock unit tomorrow so that'll be at least a lightweight starting point.

Will be reinforcing swingarm at mount point so time for some experimenting coming up.

That TLR is really cool setup, keeps the weight low too.

I will post some pics in next day or two.

This is my majesty, as you can see it's been some  what altered.  I personally  think not for the better.  It does not work . Hope you have better look with yours . I never did this  and I am in the process  of removing it all.  

Yamagodden, do you have any more photos of that setup? The shock looks like its mounted really close to the pivot point if its a direct mount. Going back to twinshock?

It's on a linkage  but  must have been direct mount at some time.

Looks very Suzuki full floater like in design from what I can see, that front pair of plates would be strange for a upper shock mount with the slotted holes but I think you're right. Definitely needs returning to stock which looks to be a fairly big job

Not that bigger job , just made a jig to drill rear shock  mounts out.  You can see the old mounts  and they were cut off  . Have got a swing arm to swop over  from the home made one that's fitted. Biggest job is removing the extra bits welded  round the seat tubes ect.  Sam brownlee informed me they used a AR50 Kawasaki  shock  .l

Thanks Yamagodden, always good to see other setups.

Got my shock unit the other day (supposedly a kdx unit) but is way too big and heavy unfortunately so back to the drawing board.

In the meantime I've been converting from electric start to kick only; removal of battery, starter motor, starter clutch, associated wiring, and cutting/epoxying stator cover. Also lacing up some old alloy rims to replace the rusty old steel ones.

Original dry weight of 125kg has been reduced to less than 90kg thus far. Would be happy if final product is 80kg, pretty close to a modified tlr perhaps?

Keep it up theoldstuff.  You have done well  to loose   that much of the bike. I spoke to mick Andrew's and he put holes everywhere  in components.   

That's some serious weight loss!  For light weight cheap shocks would a used modern trials shock do the trick?