Challenger/BSA Hybrid Woods Machine

[GrumphFighHunnert]

As it sits at the moment. 1968 Challenger frame and forks, Triumph TR25T oil tank, Yamaha wheels and a 1968 BSA B44 engine.Still several things to sort out (rear brake controls, decent shocks, seat, tank mounts, etc, etc) but it is moving forward.

[Gr11mpy]

Challenger/BSA Hybrid

Hi,
Looking real good, keep at it, they're great when done.
Hoping to finish my Griffon/BSA Hybrid this year.....
As ever Oil tanks and Exhaust systems make or break a Special from a 'looks' point of view....
Perhaps we should have a separate section for the BSA engined Greeves like the Triumph-Greeves guys
There must be a few BSA engined specials out there surely?

[greeves246]

white metal big end

looks like a good intersting project i would have a inline oil filter or needle roller conversion big end i beleve dick man did a lot with b25 engine ?

gary

[GrumphFighHunnert]

I'm a big fan of an inline oil filter.

[GrumphFighHunnert]

A photo of the drive chain run from the rear:
and from the drive side.

Fairly satisfied with these results, but I am going
to use a chain guide/tensioner to, hopefully,
prevent the chain rubbing the crossover tube
for the rear brake actuator lever when the shocks aren't loaded.
Also will install a rub pad of high density plastic to the
top of the swingarm for the same reason.

[Brian Catt]

This looks a great project. Is the front brake a home-made conversion or did it get brought-in from something else? Whichever, I'd want to move it to get the cable out of the line of fire of anything that might get caught in it and rip it out!

[GrumphFighHunnert]

Thanks, Brian.
The front brake is a repurposed Yamaha unit and is
not yet sorted. I have to fabricate a method
to secure it from rotating, so at this point
the cable routing is not fixed. Your advice
is duly noted!

[GrumphFighHunnert]

On the ground for some sorting.
Still not sold on this tank and the chain run may prove difficult.
The front end is a tad stout, weight-wise.
Need to source shocks...

[Gr11mpy]

Hi, Whats the issue with the chain run?

[dave higgins]

Hi grumph, i have done a project along the same lines as yours & spent hours trying to gain perfection on the chain alignment, adjusting wheel offset, spacers etc, but the bottom line is that the wheel rim must run to centre line of the frame, & that leaves it very tight.
Choice of tyre is important, i use metzelier mx tyres, which are a bit more forgiving on the side wall, also i will say how surprised i am at how close you can run the chain to the tyre ( 1mm ) without probs, but i do use a light weight tensioner.
If i was to build one again, i think i would look towards moving the engine a few mm to the left, which would help, but its quite an offset barrel/engine as it is & balance & looks are important to.
If you do find a good solution, then please do share it & in the mean time good luck with your build. dave.

[GrumphFighHunnert]

The engine to rear wheel alignment is not the issue.
I did exactly as you as you suggest here and offset the engine to the
left. That worked reasonably well.
The issue I now face is that the chain may end up riding on the swing arm crossmember.
I hope shocks and perhaps a chain guide
will go a long way in remedying the situation as it sits.

[Brian Catt]

Is this a problem of using a smaller rear sprocket than standard? Or is it that you have adjusted the suspension height by fitting over-long units?

[Brian Catt]

Phil, looking at the pics, I think the chain line is OK, it's more a question of getting the chain away from the swing-arm by, as you say, compromise on sprockets and tensioner. I would think most of the problem is the size of the rear sprocket, i.e. somewhat smaller than original, so re-basing the gearing on a bigger sprocket may help. Also trying to get the gb sprocket/sa spindle and rear spindle in line by suspension unit change.
Yet again at the pre-65 MX on Sunday, another BSA Cheney/ Faber etc. threw a chain, simply because they put overlong units on and spoil the natural geometry.

[Gr11mpy]

Specials Compromise...

Hi Phil / Brian.
Absolutely agree with what you are both saying about gearbox sprocket, swing arm spindle and rear wheel spindle being in line etc. when sat on the bike.
Also agree that the best way to create swing arm clearance for chain rub vertically is to play with the sprockets on the rear wheel and gearbox.
Personally I advocate the use of chain tensioners and more often than not a chain guide to help the chain on to the rear sprocket on the specials I build.
Wheels do not have to be aligned central to the frame nor in line with each other for that matter, although it would obviously help if everything else was ideologically correct. BSA, Triumph and Harley Davidson amongst others use wheel offset to balance up 'lop sided engines' on a number of models. Many competition bikes are like this. Including some notable Isle Of Man Hondas...
The problem with fitting a chain tensioner to any special as you know is finding somewhere suitable to mount the damn thing!
I've included pictures of the one I'm working on for my BSA Twin engined MX4. Since the photo's were taken I've changed the roller to a larger diameter type with 'sides' to reduce the chance of it coming off..... Hope this helps.

[Brian Catt]

Phil, I think this is the bike that was featured in "Leading Link". Will need Brave Pills before riding, as it's up around 750cc, I seem to remember!