10 replies to this topic

[corsario]

Hi there! I am converting a street tiger cub into a trials bike. The bike was sittig arround the house for a decade, and never have time to start the project. After seeing a couple of tiger cub trials bike I decided to convert my street cub into a trials.
First of all I want to do a quick mock up and start the engine as it is now (with the street gearbox) After that I will change the gearbox for more low end power and better climbing caracteristics.
I alredy bought a mid 70's front fork from a kawasaki ke 125 and now I want to lace new rims to the existing hubs.
I have a couple of questions for the more experienced here

In first place I want to know if I can use a wm3 rim with the original street swing arm
Second question would like to ask is the better options for front and rear rims and tyres.

Will post pics of what I've got now tonight!

I live in Argentina. Here is very difficult to find parts for vintage bikes, but I plan to order the more important parts (e.g electronic ignition, exhaust and carb) from europe or usa

Take care!

Miguel

[goudrons]

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[goudrons]

The original swinging arm isn't wide or long enough to take a 4 inch trials tyre without fouling, either phyically or with mud once the tyre has picked it up.

There is a kit from Sammy Miller products
http://www.smproduct...rd=swinging arm

You can modify the original one yourself by altering the tubing where the tyre passes the right hand leg, so it's got more clearance, also adding around 30-40mm to the length will help with clearance across the front, it will also help give a better feel to the rear suspension.
To lengthen mine, I cut just in front of the holes for the spindle and added 40mm in there so the lower shock mounts stayed where they should be but the wheel moved back.

[suzuki250]

you heed the arm off a Sports Cub (they are sightly wider for the trials tyre)

See my link

http://www.trialscen...ing-arm-length/

Edited by suzuki250, 20 June 2012 - 02:45 PM.

[corsario]

goudrons, on 20 June 2012 - 10:25 AM, said:

The original swinging arm isn't wide or long enough to take a 4 inch trials tyre without fouling, either phyically or with mud once the tyre has picked it up.

There is a kit from Sammy Miller products
http://www.smproduct...rd=swinging arm

You can modify the original one yourself by altering the tubing where the tyre passes the right hand leg, so it's got more clearance, also adding around 30-40mm to the length will help with clearance across the front, it will also help give a better feel to the rear suspension.
To lengthen mine, I cut just in front of the holes for the spindle and added 40mm in there so the lower shock mounts stayed where they should be but the wheel moved back.

Thank you goudrons, do you have any picture of what you've done? How did you weld it? I allways thought that the tube tend to twist when it get cold

suzuki250, on 20 June 2012 - 02:45 PM, said:

you heed the arm off a Sports Cub (they are sightly wider for the trials tyre)

See my link

http://www.trialscen...ing-arm-length/

Thank you for your reply! How did you weld it (what type welder did you use? It seems stick. And why did you polish the weld? I was told not to grind welds to avoid make them weak. I for sure will try to modify the original swingarm myself. If it doesn't work I will try Sammy Miller's, it looks neat!

Thank you!!!

[suzuki250]

corsario, on 21 June 2012 - 12:35 PM, said:

Its mig welded, I cleaned the weld to make it look neat

I made some bushes to go in the tube to add strength

[corsario]

Great Suzuki250! It does make sense now! I was wondering how did you manage to get those parts aligned during the weld. Another way of adding strenght could have been making a few little holes on the swingarm tube to make a few spot welds to the bushing. As you know I am worried about the strenght of the swingarm. I am big and the litlle cub will have to suffer my weight!!!!
Can you give me the width of the gap between tubes? You told you had a bantam swingarm which I think is wider than a street cub. Do you know the width recommended to run a 4" trial tyre?
Forgive me for all my questions but I am very exited with this project!

Take care

Miguel

Edited by corsario, 22 June 2012 - 01:16 PM.

[suzuki250]

The arm is actually a sports cub (they are wider than the standard cub arm), even though the bike is a bantam!

I will measure it up for you

With the bushes its very strong, I made them a press fit in the tube. Plus don’t forget that most of the load is transmitted though the shocks to the sub-frame, the swing-arm is more for control (like a radius-arm / wishbone on a car)

Edited by suzuki250, 22 June 2012 - 03:43 PM.

[corsario]

thank you Suzuki 250! Are you running a 4" tyre? I've red that using 4" tyres is not a big difference from using 3.5" tyres, but here 3.5" tyres are not as easy to find as 4". I haven't found a complete description of all the modifications need to do to run a 4". I mean cleareance and offset issues.

[suzuki250]

I’ve not go that far yet, I only started this project about a week ago

I was planning to use a 4” tyre

[corsario]

I didn't realise you are a new member! Thank you anyway for all the information and I will be tuned on to your build
Take care!

Miguel

[tony283]

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[tony283]

you might like to read my "blog" on all the modificationsI have recently made to my original SM Trials Cub

Tony