37 replies to this topic

[elgringo]

Hello all,

Been having a nosey round this awesome corner of the forum for some inspiration and advice.

As a direct result of my mate Petorius' purchase of a Tiger Cub project i am now the proud owner of a Bantam project.

I'm not new to the world of bikes (i'm on 6 and counting) and projects but i am somewhat new to the world of trials and in particular pre 65.

The sorry looking pile of parts currently consists of a D3 1956 swingarm frame, a 1959 D7 engine, a chrome tank, and not a lot else.

One thing i have found is a casting on the underside of the head "GT100B", i was led to believe that the engine had a Todd centre plug head, i was wondering if this casting corresponds? Are these heads rare?

The aim of the project is to build something i can have a bit of fun on without getting bogged down in historically accurate details and mega bucks parts.

I have a lot of questions but i was wondering does anyone have some basic guidelines to get me going?

I've looked at a few posts around the swingarm width and modifications, using a 4.00 x 18 tyre etc.

I think it will probably be a "modern" front end, TS50 or the like. What sort of shock length would i be looking for?

Please forgive all my questions, i'm really looking forward to falling off very soon!

Cheers

Chris

[andy m]

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[andy m]

Hi Ref Todd heads fins are thicker than std heads and there were 2 castings made part number on underside of head...
GT 100 A for short reach plugs (1/2")
GT 100 B for long reach plugs (3/4")

The compression may be too high for trials use, you will need to run it to find out. They sell well on ebay if it's no use.

[smelling123]

Andy M, on 30 January 2012 - 11:22 PM, said:

Hi Ref Todd heads fins are thicker than std heads and there were 2 castings made part number on underside of head...
GT 100 A for short reach plugs (1/2")
GT 100 B for long reach plugs (3/4")

The compression may be too high for trials use, you will need to run it to find out. They sell well on ebay if it's no use.

I use the Todd GT100B on my bantam they have more finning than standard so the cooling is better - important on a trials bike as you dont get much air flow due to the low speed (and can be covered in mud). Also Bantams run hot because the barrel is quite small - again not as much fin are.
I run it at about 11:1 (geometric) compression ratio with 1mm squish gap. Be careful if you 'big bore' it (to 185) - you will need to re-machine the squish band to suit the new bore size. The engines very smooth and has plenty power so I think these settings are about right - although it may stand more compression - I think the later Fantics ran about 12.5:1.

[charlie prescott]

Hi Guy's
Hi ElGringo.
What you have said in your piece, makes me think, that what a friend and I have been thinking, is probably one way forward to get more riders into the sport.CHEAPLY.
What we were considering was a "Trick-Shock" class, where the only stipulation for the bike being built would be. "A"] to use and air cooled engine of any origin. "B"] drum brakes, and "C"] two shocks on the back, any thing else would be what you have to hand or find kicking around.
Example. I have a New Chinese 230 engine sat in the back kitchen price £160, OKO carb £50. a CoTTOn
1967 trials frame which came with an engine, cost nothing, even has a good tank seat and rear shocks, a pair of wheels that I was give in the IOM. and a pair of MP forks that are not brilliant but were £30. £20 for a pair of plastic guards, a new chain and rear sprocket, and a bit of work, and you could be out for a grand mornings sport, for not a lot of dosh.
So "Trick-shock" what do you think???
Regards Charlie.

[old trials fanatic]

charlie prescott, on 31 January 2012 - 01:04 PM, said:

Hi Guy's
Hi ElGringo.
What you have said in your piece, makes me think, that what a friend and I have been thinking, is probably one way forward to get more riders into the sport.CHEAPLY.
What we were considering was a "Trick-Shock" class, where the only stipulation for the bike being built would be. "A"] to use and air cooled engine of any origin. "B"] drum brakes, and "C"] two shocks on the back, any thing else would be what you have to hand or find kicking around.
Example. I have a New Chinese 230 engine sat in the back kitchen price £160, OKO carb £50. a CoTTOn
1967 trials frame which came with an engine, cost nothing, even has a good tank seat and rear shocks, a pair of wheels that I was give in the IOM. and a pair of MP forks that are not brilliant but were £30. £20 for a pair of plastic guards, a new chain and rear sprocket, and a bit of work, and you could be out for a grand mornings sport, for not a lot of dosh.
So "Trick-shock" what do you think???
Regards Charlie.

Already have a class for Trickshox in our calender for this coming year. www.peakclassic.co.uk

Edited by Old trials fanatic, 31 January 2012 - 02:09 PM.

[andy m]

Re the cooling,some are using a modified Fantic 200 head, I have one for my build. like this...

[jimmitchell]

Andy M, on 31 January 2012 - 04:55 PM, said:

Re the cooling,some are using a modified Fantic 200 head, I have one for my build. like this...

Is the mod easy DIY or of the machine shop type?

[andy m]

I bought mine already done. I believe it is fairly simple, a template needs to be made of the shape of a Bantam head, mark the Fantic head and cut it using a jigsaw with the correct blade. It will then need tidying as required with file or emery, and either painting or blasting. Not sure about the squish / combustion chamber. Also some work is req'd to make adapters so as the cylinder studs can be tightened. If you want dimensions or pics pm me. Fantic heads are about, around £25 .

[bashplate]

very neat indeed

[old trials fanatic]

Andy M, on 31 January 2012 - 04:55 PM, said:

Re the cooling,some are using a modified Fantic 200 head, I have one for my build. like this...

Like it but is it Scottish Pre65 legal and do we care

[wetfeet]

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[wetfeet]

here are a couple to look at for the guys who are building bantams

[martin 305]

wetfeet, on 03 February 2012 - 05:58 PM, said:

here are a couple to look at for the guys who are building bantams
Great pics thanks for them Martin

[old trials fanatic]

wetfeet, on 03 February 2012 - 05:58 PM, said:

here are a couple to look at for the guys who are building bantams

Which all goes to prove why it's so important not to be obsessed about the Scottish pre65. There ARE 51 other weekends in the year after all

[andy m]

Judging by the money changing hands for frames and parts at Wrightys show there will be a few more about soon........

They were like kids in a sweet shop at one point on one stand..

[old trials fanatic]

Andy M, on 05 February 2012 - 01:50 PM, said:

Judging by the money changing hands for frames and parts at Wrightys show there will be a few more about soon........

They were like kids in a sweet shop at one point on one stand..

Looks like the doom merchants saying pre65 is dead in the water were more than a bit premature then ??