Trials Australia Forums

Hang on Rod - the "real" Greg Harding hasn't had a go yet, and I'm pretty sure Tricub knows a few things about OSSAs too

I'm not surprised about the cylinder head. Nothing would surprise me with that bike. It came with square ended forks, the bashplate mounts on backwards and now I find out it's got the wrong head too! Hang on maybe the head is fitted 180 degrees from where it should be?

Some other oddities are that it's got a Yamaha swingarm axle as a rear wheel axle, 20mm spacers under the handlebar clamps, replica KT250 handlebars and a KT250 carby! As well as that it started life as an Explorer. The original OSSA Betor Explorer shocks still work fine but they are fitted to my KT250 where they do a great job.

Mark K wrote:I used to think that bike was invisible till today, but maybe I was just mesmerized. Is post-hypnotic suggestion a real thing?

Hi Everyone,

Mark, after a few trips to Denman this year, we learned the value of front sprocket Covers. This presented a problem when building the Now you see it and Now you don't ( Or was it the other way Round? TLM 11) . After a fair bit of head scratching, I came up with what I call :

THE GRISTY TWISTY!

All was going swimmingly until riding with Donna, I must have been paying TOO much attention to above mentioned jigger and this led to an out of body Experience!

David, can you help Rod out with the elusive oddity that I am having trouble spotting for obvious reasons ?

Chippy????????????

Hmmmmm this sounds like the real Greg now and it sounds like he has given up on the OSSA year model trivia trainspotter thingo

There are probably other things that ID which year an OSSA MAR is from (up to 1976) but here are the things I know about:
The cylinder edge head fin slot that Rod was talking about
The carby-to-cylinder connection - on the first model MAR it is a two-stud flange that Rod mentioned to suit the horrible IRZ carby. On 1974 and 1975 models it is a spigot mount made for slightly less-horrible AMAL carbies. Very fortunately for OSSA riders the spigot mount also suits carbies taken from TM125s and KT250s and probably some of the lovely modern carbies too
The bashplate on Mark Keenan's Mk1 bike is the original fibreglass type that self-destructs almost as fast as the fibreglass bashplate originally fitted to the Japanese rip-off of the OSSA MAR (the TY250A). After the first model MAR they came with a fantastically formed aluminium bashplate that Chippy is chasing to complete a bike.
The wheel rims on the first MAR were originally the rugged AKRONT shouldered (mud-catcher) type. I see Mark's bike still has one of these on the rear and a later front rim. Having the shouldered rims on the first model is merely a function of the bike being made before AKRONT started making their superb lightweight shoulderless trials rims.
The 1973, 74 and 75 MARs all had their exhaust header go straight up from the exhaust port while the 76 model has a longer pipe that sticks out a bit. I suspect that they did this because this model has longer fork tubes (gives the front wheel a bit more clearance to the exhaust), so they could use the longer header pipe for a bit better motor performance.
The 76 model has longer fork tubes and the sliders have strengthening ridges front and rear, like the OSSA Phantom also got at the time. I suspect the 76 forks might also have a bit more travel than the earlier MARs, but the main intention of the different forks was to lift the front end of the bike to match the lift that the rear got
Rear shock mounts on the 76 are lower down the frame upright to lift the rear of the bike and to increase rear wheel travel a bit
Unfortunately the raising of both ends of the bike without changing the frame and triple clamp geometry means that the 76 model has more steering trail than the earlier models, so while it gained some ground clearance over the earlier models, the steering is not quite as good as before, and the centre of gravity is also higher.
Also as Rod mentioned the first MAR came out with a 25mm shorter swingarm than later models. The first model was seen to be a bit short in the wheelbase compared with what people were used to riding with at the time. Fashions have changed over time and many people nowadays would probably prefer the shorter swingarm version. I've heard that you can tell one swingarm from the other by looking where the shockie mounts on, but don't remember what to look for.

My latest Basket Case
This is the "before" photo

I hope that came with more parts than what's in the photo. There seems to be a few bits missing. Maybe I didn't look close enough, but it seems to be missing a clutch cable. Oh, and everything that goes at either end of that and every other cable.

if you OSSA guys started swapping parts about you might get close to an origional bike.

Mark K wrote:I hope that came with more parts than what's in the photo. There seems to be a few bits missing. Maybe I didn't look close enough, but it seems to be missing a clutch cable. Oh, and everything that goes at either end of that and every other cable.

What!!! Can't you see the other parts , they are hidding under the rust and dirt.

He has plenty of Yamaha bits. Maybe he will make a Yamataco or a Bultaha.

M80 David?
Do you have a suitable engine?

Yes John it's a M80. What motor do you think should go in there?

I was just wondering if anyone has had sucess purchasing from Vallmoto as I purchased an order beginning last month and it hasn't been shipped yet. Any one know what their like?