Trials Australia Forums

chippy wrote:Hello everyone,
David very interesting and I remember watching Peter Paice when I competed a lot in NSW in the late 70's and watching him ride was really inspiring and some of his bikes did seem 'trick' in the day.

Also I have just weighed the Ossa Mar 350 magneto flywheel and it is 4.7kg. Also weighed the 350 crackshaft and it is 3.3kg as against the Ossa Mar 250 is 2.5kg.

I was especially interested in the weight of the magneto flywheel as I'll let you know why later....

Chippy

I just weighed a couple of magneto flywheels that were easy to access

Kawasaki KT250 3.07 kg
OSSA 250 Explorer 3.75 kg, and it does look amazingly like as if it is cast from lead but I'm having trouble believing it

Here's some Bultaco weights that I have weighed
M49 magneto Femsa VAR 41-9 , 2.375 kg, primary counter-weight 2.5 kg
M125 magneto Femsa VAR 41-52 , 2.8 kg, primary counter-weight 2.8 kg [ rounded off when I wrote them down]
M183 magneto Femsa VAR 41-52 , 2.836 kg, primary counter-weight 2.819 kg
M198 magneto Femsa VAR 41-51, 1.7 kg, haven't weighed the primary side yet

Hi Everyone,

chippy wrote:
Greg, I said you could borrow my Mar 250 that is running, but I didn't necessarily say that it was in one piece....but I'm sure you will be able to sort it out.

Chippy, Now you have me curious, just how many pieces and will I run out of fingers and toes? Sounds like you have been picking on one of the heaviest flywheels?

David, have I got this right, we need the lightest frame and the heaviest flywheel?

Memory tells me there was a prototype bike (maybe in the Eighties) that ran a really big flywheel that balanced the bike with a gyroscopic effect similar to wheels when you go fast. The rider would keep it revving to increase balance in tight spots until it was banned by the powers that be.

Brownie, thanks for the ride on your beautifully prepared BULTACO.

Well Donna and I have been camping at the Granite Gorge this week, I was particularly keen this year to go and find Colflat Rock. Apparently there were no tyre marks on it yet, a Virgin! We managed to track down a well known local identity, used the usual throat and tongue lubrication around the campfire on a dark and stormy night, miraculously he agreed to take us there. Just sharing some photos, can you work out which bike I took away this year?

JC1, you might have to sit this one out as I think you know?

can't see any motorbike in those photos - nice rock - I hope you rode up and down it

Greg I am going to go out on a limb here and say it was probably a bike with two wheels and a motor in it. Would this be correct? Graham.

The Alpina is going back together and this photo is to illustrate the longer swingarm on the Alpina compared with the Sherpa T swingarm.
If you look at a Sherpa T swingarm of similar design, before the time of the rear engine mount being supported by the swingarm axle, you should see that the gap in front of the leading edge of the tyre is somewhat less than this Alpina has. To be a truer comparison, I might take a photo later on when I have fitted a rear trials tyre instead of this knobby, which may have a slightly lower profile than a trials tyre.

Hi David - only longer on that model. Getting the extensions from Hughs for my M116 swing arm. Makes a notable difference.
What gear ratio are you running David?

David Lahey wrote:can't see any motorbike in those photos - nice rock - I hope you rode up and down it

Hi Everyone,

Realising that finding my bike in those photos is about as easy as guessing the weight of Colflat Rock, here is a photo with some zoom to put things in perspective.

Graham, you are closer than I think you realise as it is under a limb.

Chippy, I have weighed a couple of my heaviest flywheels for you:

Alpina 350 Motoplat Semidino = 2.976 kg

Montesa 349 Motoplat Dinosaurio (got to love the name) = 3.6 kg

Oh and David, I followed Brownie up the far end of Colflat Rock and I have given myself 12 months to think about riding the main face as it is a little daunting. After parking my bike under a limb, I borrowed the Totally Loved Machine and rode to the far end for photos. It is fair to say that I skirted along the bottom like a big Girls Blouse on the return trip!

BOGWHEEL wrote:Hi David - only longer on that model. Getting the extensions from Hughs for my M116 swing arm. Makes a notable difference.
What gear ratio are you running David?

I just went and counted sprocket teeth and ran out of fingers and toes well before the whole way around - then tried another technology and came up with 11/47. Those sprockets are just what came with it when I got it. I've only ridden it at home in my practice sections and up to fourth gear on an open bit of mown grass, and that was probably fast enough for me for trail riding. At the other end of the speed scale, first gear is probably a bit slow to use when trail riding on anything except jumping over big logs. It is slow enough in first to ride the practice sections without having to resort to any clutch stuff. I think if I was going to road register it, it would probably need higher gearing to be comfortable. Pretty sure my old 325 Alpina from when I was 17 had a rear sprocket a fair bit smaller on it when I rode it on the road.

OK Greg I'll have a stab at the bike under the limb. I reckon it's that M49 you rode at Conondale, because it's the only one I can think of that has a black front guard