CG125 OHV Build Oddessy

[Erskine]

Re: CG125 Decaf - trials mock-up

Steering stem swapped over thanks to advice from the usual suspects, and front end bolted up.
I dropped the forks as much as I could while still preserving the 6 1/2" travel.
It's progressing but every step throws up a new issue to be addressed.
I now need to source a chain tensioner so I can run the rear wheel as far back as adjustment will allow.

 

[crazypj]

Re: CG125 Decaf - trials mock-up

We used to make them from a piece of 1/8"x1" strap iron and a skateboard wheel.
Just use an ordinary tension spring onto swing arm.
Jubilee clip works to hold spring in correct place, pivot it off frame and its 'automatic' as suspension moves

 

[Erskine]

Re: CG125 Decaf - trials mock-up

We used to make them from a piece of 1/8"x1" strap iron and a skateboard wheel.
Just use an ordinary tension spring onto swing arm.
Jubilee clip works to hold spring in correct place, pivot it off frame and its 'automatic' as suspension moves

Now I've got the trucks squirreled away from the deck I used for the seat ...... I knew they would come in handy.
I think I can safely extend the spindle slot a smidgen. Every 1/4" helps.
The reality is I could actually do with an extra 2" on the swinging arm, I'm not sure about stretching it because I want to keep the mounting points in the same place. On another site, an XL one, I saw an extension done by cutting the rear mount plate and welding it back together with a bit of plate in between. I'm not sure how strong that would be, how ever it was done on a competition bike so it must have been quite strong, but I don't think I'll be going down that route.

 

[crazypj]

Re: CG125 Decaf - trials mock-up

I did that on my XL185.
4" extension on the axle plate is too much and flexes.
2" extension was fine though..
With a sidecar,(even a real light one) I would brace swing arm as much as possible, you'll be amazed how far swing arm will bend and twist
Check for tyre marks on shocks after a few weeks ;D

 

[Erskine]

Re: CG125 Decaf - trials mock-up

I'm glad you mentioned a brace PJ......... it's the right timing forme to be thinking about that, as it will affect where I can mount the tensioner pivot. I have some shaped tubing (squirrelled away lol) that should do the trick. I can't believe how much stuff I've started hoarding already since the move! All I bought with me was that length of angle iron and an off cut of sheet ally.
The extension on the axle plate? So that is a viable option?

 

[crazypj]

Re: CG125 Decaf - trials mock-up

I would look into some box section and possibly sleeve the entire left side of swing arm.
Take a look at CB 350 frame brace from center tube to side tube above swing arm pivot.
I would also make a bolt in piece from swing arm pivot to top shock mount, it's adding weight but strengthening frame
The Bantam had a stronger heavier, wider frame than CG.
You will twist frame, just depends how bad ;D
I still think it's totally worth it though, you won't believe how much fun sidecars are, plus, 'people' ( ) don't get 'scared' by them and will ride in chair when they wouldn't ride on back of bike
With Christmas approaching, you will do dumb shit on it and you will be overloading it 8)
There's just something about sidecars that 'forces' you to do these things ;D ;D ;D ;D ;D ;D
The more I think about it, the more I want to build one for my XS :

 

[Erskine]

Re: CG125 Decaf - trials mock-up

PJ you fry my sweede.
Any other suggestions to throw into the mix?
In the long run would I be better off looking at adapting something like a box section 'pro-link' swinging arm and sticking on twin shock mounts?
I'm picking the chair up this weekend .... can't wait, although I know it will take a bit of work to get it fitted.

 

[crazypj]

Re: CG125 Decaf - trials mock-up

I wouldn't worry too much, I'm basing things on how I would drive it ;D
Eventually you will start 'leaning' on it so strengthening various parts should be a good idea.
I wouldn't bother with a Pro-Link swing arm, being longer it will probably put too much stress into frame.
Don't forget to 'toe in sidecar wheel.
Do you know how much 'lead' it has?
There are various instructions online, and a couple of international sidecar clubs, you can find any help you need

 

[Erskine]

Re: CG125 Decaf - trials mock-up

This is the info the seller gave me:

Toe in about 2"
Lead about 6-9"
Lean out 0-small degrees.

I drive like a gripper. Even the feds take the piss out of the speed I drive at. They said they never have to put my registration through the data base to see if I'm taxed, they just read the disk as I go past.

 

[Erskine]

Re: CG125 Decaf - trials mock-up

Have travelled down to the coast to collect the chair - it's soooo dinky! weighs only about 25 kg / 50lb and is well made. Just the mounting points need attention, but they would any way to adapt to fit the CG. Can't wait to put it along side and see what's what

 

[Erskine]

Re: CG125 Decaf - sidecar questions?

I've got the chair home and broken out the old yard stick to get some measurements. Here's a picture of the frame so y'all can relate to the questions.

I've been specced 6" - 9" of lead ( the chair spindle forward of the rear wheel spindle - on a full size bike it's about 10")
See the two holes at the bottom of the rear engine cradle ..... if I mount the middle of the chair in line with the front hole It will give me 8" of lead so its a good zone with useable options.
Now the big question. The chair shock is either seized or collapsed or both. it is 11" long as is and gives a platform height that is pretty much the same height as those cradle holes. However this is about 4" lower than the swinging arm pivot.
Are you still with me?
I'm going to have to replace that shock, looks like a C50/70/90 item (I think it was called a 'Cub' in the Land of the Brave)
If I source a longer shock this will of course raise the determined platform height towards the height of the swinging arm
pivot.
Still paying attention?
So is it more beneficial to have the platform height closer to the S/A pivot height or the rearwheel spindle height or does it not make any difference?
And another thing .......... Should I be looking for a chair shock that matches the spring weight of the bike shocks, or is lighter or heavier?
Remember this is not a speed machine so I'm not worried about tank slappers at a ton, but don't want passenger to get compactures of the spine nor do I want it to be flipping over like a catholic girl as soon as the going gets interesting.

Answers on a postcard please.

 

[crazypj]

Re: CG125 Decaf - sidecar questions?

Using a single shock on chair means it will need to be a bit heavier than twin shock but should be close to same rate as pair on rear if your carrying any weight.
If it's going to be running empty, a real light shock would probably be a good idea. (although running empty won't be a good idea while your 'learning')
Platform slightly higher than bottom of sump will probably be best for you, lower the better unless you expect to do actual trials?
Using center stand mount should be OK,maybe a lit low if you go off road?
Just make sure you brace from one side to the other, it's pretty thin there
Run another mount to rear shock position, get things triangulated as much as possible
As well as toe in, you also need the bike to lean in or lean out slightly so it will be level when your riding
I forget which way affects left/right turns, It changes with sidecar suspension.
Viewed from rear, you use sidecar wheel as pivot point, right handers 'load' sidecar suspension, left handers unload it.
Sidecars are seen as 'safe' so used to get 40% insurance discount, you may have to check around though
I can't tell from the pics but is there a mounting point on chair at front where panel fits?
(lower 'corner')
That would be 4th point to lower front engine mount

 

[Erskine]

Re: CG125 Decaf - sidecar questions?

Thanks PJ, All taken on board.
I shan't be competing this outfit so not over concerned about getting radical ground clearance, I'll try it with one of the 12" Forsa Midi shocks from the previous incarnation.
The chair has four mounting points:
1. Front lower to the engine mount - I'll be making a new one from 3mm box section carved up. (I think I'll weld on the bash plate to this and bolt it somehow to the rear cradle which will add more strength)
2. Front upper to the top of the main down tube.
3. Mid platform to rear engine mount.
4. Back of platform to rear shock mount area.
And yup, I will brace the rear cradle internally to withstand the new load.

 

[crazypj]

Re: CG125 Decaf - sidecar questions?

Sounds like your good to go
Can't wait to see it up and running

 

[Erskine]

Re: CG125 Decaf - sidecar questions?

I've had a bit of a busy week so did some catching up on the bike.
As well as fitting a captive nut for the tank, drilling and tapping steering stops and adjusting the front mudguard stays, I brought the chair over for a first look at the fit.
I think this will have to go over 2 posts because there's more than 4 pictures:

 

[Erskine]

Re: CG125 Decaf - sidecar questions?

The track (width) is looking awfully narrow, around 650 mm
ACU specify 850 mm minimum for competition.
PJ/TJ any thoughts?
I visited the local auto parts dude and he's looking out some old track rods and track rod ends ..... any other ideas on how I can redo the attachment method?

 

[beachcomber]

Re: CG125 Decaf - sidecar questions?

My 4 penarth would be DEFINITELY widen the track. Without be a sidecarist - logic is screaming at you that it is likely to "fall over" if travelling in a lively manner !!!!!!!

I've been monitoring your thread, but you seem to be getting excellent advice without me chiming in.

On the platform height, the lower the better compatible with the terrain you are likely to be covering.

Just another observation - in teh lower pic there is a lug with a nut/bolt through it. Where does the missing link go to ? I'd be tempted to triangulate it with either the rear strut or forward to meet the front strut. There's currently nothing to stop the mountings "lozenging". Any triangulation you can introduce will reduce stress on the mounting points to the frame and thus the frame itself.

I'm now officially seriously envious !!!!!!!!!!!!!!!!!!!

 

[crazypj]

Re: CG125 Decaf - sidecar questions?

At 650mm it would be an 'expert' outfit ;D
Even at 850mm it will probably be bit of a handful with high center of gravity
You need to make it wider, probably want the wheel centers (track) at least a meter then extend platform towards bike
Mild steel tube will be easiest to work with, old track rods would work well if your bolting them in, not sure if they would get brittle if you welded them?

 

[Erskine]

Re: CG125 Decaf - sidecar questions?

Thanks Guys!
Tj - That lug in the middle - I think that was bodged to bolt on to a bantam footrest bar. I'll be removing that and extending the central floor tube to connect somehow to the rear engine cradle.
Thanks for the confirmation regarding the width ......... I'll start looking at how to get it out to a meter.
Pj - I'll be looking at bolting track rod ends, even using sections of steering rack, I'd prefer to use mechanical fixings and gaining the ability to fully adjust.

And another thing, I watched a chair setting up video on you tube which said to lash the bike and chair suspension compressed before adjusting the lean and toe in ......... ?

I think I'll start by lengthening the new centre bottom mount and attaching and work the rest out from there.

 

[crazypj]

Re: CG125 Decaf - sidecar questions?

I wouldn't have suspension fully compressed, just where it will be in normal riding.
Load a bag of sand or similar in chair then add some weight to bike (about 10~15lbs more than you weigh)
Then set up toe in and lean