Hi Guys

Thinking of building a Trials Bantam/ Cub & my first issue is front frame modifications. Before I decide which way to go I thought that there must be members out there who have already been down this road.

Headstock angle

I have a D10 front frame & want to sharpen the headstock angle, been advised to change the front down tube for a C15 tube which is one inch shorter.

What headstock angle are we trying to achieve?

Please suggest how best this can be done

Engine mounts

It's usual to move the engine mounts to the left to aid the chain run with a Cub Engine in a Bantam frame, Does anyone have the details?

Also what other front frame mod's should I be considering?

Cheers - Frank

I can't comment re the cub engine fitment but the way the head angle was changed on my std Bantam frame was by moving the rear top sub frame mount back down the upright tube (if that makes sense) in effect it turns the front main frame loop forward so altering the head angle. I can't quote angles but can measure it if need be.You can make out in this pic where the mounting is.Also had a new sub frame made and wider swingarm, and the bottom tube cut out and replaced with bash plate.

Hi Andy

You have a superb set up & exactly what I want to achieve but with a Cub Engine.

I think I know what you mean - the front upright tube is reduced in length & re-welded thereby drawing the headstock down???

.

Did you make the frame changes yourself & if not who adapted the frame for you?

Thank's Frank

TXR front end ?

Edited January 18, 201313 yr by b40rt

TXT front end ?

Beta stripey I believe. Only temporary until I can fit something more in keeping like a set of Marzocchis in some 3ta bottoms.

Hi Andy

You have a superb set up & exactly what I want to achieve but with a Cub Engine.

I think I know what you mean - the front upright tube is reduced in length & re-welded thereby drawing the headstock down???

.

Did you make the frame changes yourself & if not who adapted the frame for you?

Thank's Frank

No it's a case of moving the rear mounting (below the back of fuel tank) down the tube, the one that is the top subframe mount, this in turn changes the geometry. The front down tube has been cut but it doesn't alter the geometry, just plated on the end for the bash plate mounting.

Hi Guy's.

Hi Andy.

All you are doing by moving the subframe top mount is forcing the swinging arm down by shortning the damper top mounts.

This pushes the back of the bike up giving better ground clearance and by tilting the frame forward makes the steering head angle less, so the steering is quicker. Correct?

Regards Charlie.

Hi Guy's.

Hi Andy.

All you are doing by moving the subframe top mount is forcing the swinging arm down by shortning the damper top mounts.

This pushes the back of the bike up giving better ground clearance and by tilting the frame forward makes the steering head angle less, so the steering is quicker. Correct?

Regards Charlie.

That's right Charlie. Needs to be done with the addition of a new type subframe as the BSA ones are lop sided, and a wider swing arm of course.

I have leading axle forks also which needs to be considered

Edited January 18, 201313 yr by andy m