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Thread Like Summary
Denis J, gavin eisler, pushrod tom, Stuart Kirk
Total Likes: 8
Original Post (Thread Starter)
by Denis J
Denis J
Seems feesable... An off road spec'd unit twin under 300lbs using the later OIF frames and choice light parts. Only what's needed.

Anyone tried this yet? Any ideas or specifications?

The thought came to mind as I compared torque output to wet weight of the new 1200XE and others like the 450 Motocrossers and 650 Big Red Pig
They all float in the 6.2lbs per 1 ft lb of torque range.

That maths out to a 283lb 750cc 45ft lb TRI rig (developed engine of course)

Seat of the pants this "should" be a wheelie machine that'll leave you with smiles and shot nerves.
Liked Replies
by Hillbilly bike
Hillbilly bike
My land speed racer weighs 335 pounds as you see it...No charging system,6 A/H battery.
Attached Images
4 members like this
by Mark Parker
Mark Parker
My 883 A65 makes 73ftlb @ the engine converting from rear wheel not running at its best. You only need hp and rpm to find torque. You can convert rwhp to engine hp, as used by factories, by multiplying by 1.134.

The BSA factory had a 770 making 78hp @7000 that's 58.5lbft at that rpm. It's torque peak would be at lower rpm. My friends A65 750 long stroke works out at 63ftlb at 5000, 62.8 @ 5,500, [email protected] 6000 and 68hp, but there it ran out of breathing and power fell at higher rpm. So 45ftlb isn't very realistic for a tuned 750 A65.

Even if you were based off rear wheel hp torque can be 55ftlb + for an A65 based 750. Though spread and hp are important.

So a 300lb A65 750 could be floating easily around 4.76lb per ftlb. But it needs hp across a big range to get the best out of it and a big flat torque curve.
1 member likes this
by Allan G
Allan G
Not weighed all the tinware but a stock oif A65 is about 100lb. There’s a lot of tinware on there which could be removed, light alloy tank track master style. Aluminium barrel. Simplified cdi ignition removing the heavy alternator setup, wiring, switches, lighting etc etc.

You could also fit a SLS front brake off the b25/B50 with its matching right hand fork leg. Again much smaller and lighter and for off road you don’t want a well braked front wheel. Alloy rims.

High level or TT Exhaust without silencers. Fit the louvered inserts if you want some form of silencing.

If you do all that you’ll probably get below the 300lb mark. I think the engine weighs about 160lb in standard form, much lighter still with the previously mentioned aluminium barrel.
1 member likes this
by gunner
gunner
Some further thoughts on weight saving:-
- swap out the primary drive chain and clutch, and use belt drive with alloy clutch got to be a good weight saving
- remove alternator rotor and stator and fit an interspan ignition, these have a built in battery and will run for several hours before needing recharging depending on the type of riding see This Link, you would need A65 specific trigger plates etc. see accessories page. Weighs 700g and can be recharged from a car battery or mains.
- if its an OIF frame with conical hubs, the hubs can have large holes drilled to save weight and the brake plates can be drilled, see This Link the conical hub is shown about 3/4 of the way down.
1 member likes this
by Stuart Kirk
Stuart Kirk
Originally Posted by JakeH
......... For comparison Our DBD race bike weighs 309lbs ..........
This bike is 320 lbs dry.
[Linked Image from i.postimg.cc]
Yamaha WR400 wheels and brakes helped a lot.
An aluminum oil tank and rear fender would take a bit more off too.
(And the stupidly heavy side stand.)
1 member likes this
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