Trials Australia Forums

Hi everyone,
Nice work David on the KT Greg, I havent had a chance to get more photos of the TY trio.

I also hear on the grape vine that Bully Fanatic has had to purchase his first ever Trials boots from his traditional Gum Boots. The end of an era!!!!!

Furthermore Greg, I think that KT exhaust flange is very familiar and will save some weight.., maybe 50 grams??

I also have some photos of another basket case I have had for some time.. Not sure if I will get around to doing anything with it for some time.



Chippy

Further on the Whining, the Cota 247 i'm working on has Helical gears on the primary.




In the books I have read on the subject of gears the Helical gears allow for constant meshing of the gears but increase the friction due to the sliding contact of the angle and the axial thrust caused by the angle.
With the straight cut gears the gears are not meshing at all for very short periods of time causing small impacts between each gear tooth and hence the whine sound.

A question on the 247 clutch - What is the function of the springs to preload the plates onto the clutch basket?

It's so nice to see all those primary drives and hear all the technical stuff about gears.
It just so happens that today after work I was preparing my 1968 for a trial on the weekend and it involved taking the primary drive cover off but sorry - no gears!

The photo is mainly to provide photographic evidence of five Barnett friction plates fitting comfortably into the basket.
By fitting this clutch with Barnett friction plates and Surflex driven plates, it has the best action I can get with off-the-shelf parts and most importantly, Bully Fanatic will be happy.
I had a brief test ride before it got too dark and am impressed with the clutch action. Light lever pull, very low drag, smooth action and smooth engagement over a fairly short amount of lever travel. Will be good to give it a full tryout on Sunday.

Kurt that 247 primary drive looks a lot like a 348 primary drive, except that there is a higher/bigger ratio with the 348 gears. I remember mentioning this feature/improvement when the 348 came out as by doing it, they were able to run a tiny rear wheel sprocket (33 teeth) which was done to improve the clearance between the chain and passing rocks.
As for your question about the strange ass-backwards 247 clutch design, apart from the three-legged spider and tiny brass button, it is basically the same layout as a KT250 clutch and your question applies equally well.

Chippy did you know that's the first time I've ever seen your 348 and it looks great. What on earth are you waiting for? I hope you get it going before I'm too old for us to have a 348 get-together ride.

Thank heavens you showed a real primary drive David. I thought I was watching a horror movie there for a moment. Looks like the M49s have a lot more room on the primary side too David. I tried to put 5 Barnett plates in my M151 engine in my B motor and I had to chop all the clutch nuts in half to make it turn over without the nuts grinding on the primary case. I ended up only using 4 on all of mine. M159, M199 and the M151 engine in my M199B. So

Graham

You could have done with one of these clutch-cover spacers:
https://ajrmotocicletas.es/epages/c3bd3 ... /B23140432

Or maybe one of these to covert the chain primary to geared to remind you of your Mk10 Pursang wine:
https://ajrmotocicletas.es/epages/c3bd3 ... /AJ5000061

New clutch included for a mere 1250 euros

I'll find a pic of one installed

JC1 wrote:Graham

You could have done with one of these:
https://ajrmotocicletas.es/epages/c3bd3 ... /B23140432

Or maybe one of these to covert the chain primary to geared to remind you of your Mk10 Pursang wine:
https://ajrmotocicletas.es/epages/c3bd3 ... /AJ5000061

New clutch included for a mere 1250 euros

I'll find a pic of one installed

Looks amazing but there's a strong weakness in that geared design for trials motors (apart from the cost)

Yeah. No extra flywheel weight on the primary drive
And too much gear-wine to enable you to concentrate!
(Note the third gear in the pic on the link above, needed to keep the clutch spinning the same direction as the crank as with chain drive it replaces)

It's a fantastic idea and looks to be well-made. I would absolutely love the racket from the gear train

Steve Stuart rode this newly-built Lobito converted for trials in its first trial today and it went well. It's a pretty cool looking thing so I thought it would be good to include a photo.
It fits nicely in this Basket Cases forum because it was an unwanted basket case before he started working on it.

Very nice Lobito David. John, I have to wonder at that geared primary drive kit for a Bultaco. All the stuff I have read over the years says that the reason Maico, Bultaco and many other European makers used a primary chain was the chain was quieter and let more horsepower through. All of mine work well with 4 Barnett drive plates in them.