feetupfun

Thanks Tony yes the toolbox is completely gone. I started out with the Majesty idea of making the notch for the sparkplug, but to be authentic to the original, I later removed the toolbox completely. The standard airbox was too tall to fit after the frame mods so I made one from 2.5mm aluminium sheet. Another thing is that the original bike retained the standard botom shock mountings, which means that the shocks have to be the same length as the original Yamaha shocks. If I was to fit shocks of 340mm, the swingarm would go down too far, and modern 340mm shocks have so much shaft travel, that the tyre would hit the rear frame loop. If I was to ride this bike in competition, I would probably have 320mm shocks made and fit a spacer so they didn't compress too far. The photos in VMX magazine have the bike fitted with NOS TY175 shockies borrowed from a friend. Alternatively I could have made new shock mounts further back on the swingarm and fitted 340mm shocks, but then it wouldn't be a copy of the 1976 Peter Paice bike. Peter used standard TY250B shockies on the original.

This is the finished bike being shown to Peter Paice.

magazine photo of original bike that this copy was built to celebrate. Photo taken at Aussie Titles 1976. Rider Aussie Champ Peter Paice.

photo of finished bike except for shockies

Frame painted, motor fitted, assembly in progress

Showing the making of the exhaust. Main chamber reshaped at front end to miss cylinder head, dent on inner side reshaped to clear the middle downtube. Rear end of chamber shortened to clear the gusset avove the shock mount. The routing of the section of tube above the head is critical. This one ended up with 3mm clearance to the head fins and 3mm clearance to the fuel tank. It would have been easier if I had used smaller diameter exhaust tubing.

photo showing a test fit-up with suspension in place

Photo showing new mount for exhaust chamber, new lower mount for inner rear guard, new shockie mount and new frame gusset above shockie mount. Inner guard shown is fibreglass Majesty item made in early 1980s. Shockie mount pin goes right through downtube and is welded both ends. It is tapered from standard pin size on outer end to 4mm diameter on inner end.

Backbone end shortened to make room for air intake hose

toolbox brace completely removed!

Mods to toolbox brace

Rear downtubes tacked into position. Mid downtubes bent inwards and forwards ready for welding

Rear downtubes ready to be welded, and mid downtubes shortened and with ends shaped ready for bending inwards and forwards

Then cut the mid and rear downtubes and fit a set of dummy cases so the rear downtubes can be shortened and welded. For those who didn't get to read the article about this bike in VMX Magazine, this bike is NOT meant to be a copy of a Majesty frame. It is a copy of a bike built in 1976 in Australia by Peter Paice, who used the original bike to win the 1976 Aussie titles. It was a TY250B frame that was used. In my copy made in the late 2000s in these photos, the frame used was a TY250A. If I was going to copy a Majesty frame, I would have cut the rear downtubes off at their top ends.

Then bend the front downtubes rearwards to put the front mount in the right spot in the horizontal plane. Frame-holding jig was made so the the seat rails are horizontal with the original frame, and they are retained horizontal throughout the frame changes (to preserve the original steering head angle).

Step 1 was move the front motor mount 36mm along the front downtubes

Will do. Had forgotten this promise. Did anyone see the article in VMX Magazine?

Yamaha TYs are easily ridden in a modern stop/go fashion and they also work well when ridden in the style of the time they were new (smooth continuous motion). Montesa twinshocks are not as flexible regarding preferred riding techniques, but are quite good at the smooth continuous motion style. This is one reason why Yamahas and TLR Hondas are more appealing (more expensive) to many riders in 2012. If you are conditioned to ride in the modern style, you will find riding a twinshock Montesa an interesting experience. Another reason for the relatively popularity of Yamahas is that the availability of new and second hand parts for Yamahas is much better than for Montesas. As has been said previously, some parts for some Montesa models can be hard to replace. If you are hell-bent on getting a Montesa twinshock, I suggest you get a 348 Cota because they are good to ride and there are plenty of them around (to get parts from) compared with later model Montesas. The other big seller was the 247 Cota, but it is not as good to ride as the 348. Not all twinshock trials riders are interested in riding the ultimate bike for competition and you will find that Montesas have considerable appeal away from the competition scene. There is a Facebook page for Cota 348 owners which you might find interesting. Very little talk of competition riding on there. Where I live, even though events are usually run as stop-allowed, virtually all Twinshock competition sections are made to be ridden in a flowing style, so there is no disadvantage in riding a Montesa, or a Bultaco for that matter. It is interesting to hear that you see Yamahas as being twice the price of Montesas because the pricing here seems to put Yamahas at the cheap end. It may be due to the immense number of Yamahas sold over here compared with modest numbers of Spanish bikes. https://www.facebook...ps/57549537568/ I've re-read your postings and realise that you are probably asking which Montesa is the best to ride? In my opinion the Montesa that comes closest to the wonderful Fantic 240 is the Cota 242. Unfortunately the Cota 242 is a Montesa that is very hard to find second hand parts for, has inherent weaknesses in the kickstart drive train, and very few aftermarket parts are available.

you can verify a primary drive side crank seal failure by draining out the gearbox oil and measuring the oil quantity compared to what went in. I would say from your symptoms there is little doubt that it is the drive side crank seal failed. A motor mechanic would take about 30 minutes to an hour to change that seal. Parts required are the seal and a clutch cover gasket. If you don't know the bikes history I would buy the crank seal for the other side too while you are at it.

The tool that is labelled as crap is perfect for setting the motor to TDC, and this is useful because a timing mark can be applied to the flywheel rim using a measured distance from the TDC mark. Once you have the timing mark in place, the points can be set on future occasions without needing any tools in the sparkplug hole. The circumferential distance between the TDC mark and the timing mark can be derived from the geometry of the motor components, or by using a dial indicator. The timing mark can be used to check the timing while the motor is running, using a timing light, which is the ideal way to test for correct timing.

I use 340mm Falcon Trial Classic shocks with standard damping and 50 pound springs on my TY250 twinshocks and have found them to have a fantastic action. 350mm shocks will fit OK, but if you want to fit 360mm shocks, you will need to do some work to prevent the swingarm hitting the brake pedal return stop. I haven't compared Falcons with NJB Experts for action because it seems that everyone that I ride with use either Falcon or Betor shocks. I find the steering is perfect with 340mm shocks so have not pursued using anything longer.

I couldn't understand the rule about eligibility of exhausts (or the need for a rule) so I think I am missing something in the translation. Same for the section on brakes - increased leverage on the brake camshaft maybe??

wow thanks greeves. Does appear to be quite strict. I'm going to do a machine translation into english and have a read

No thread. Its on a taper and they are typically hard to get off. Make a puller that spreads the load over the whole circumference of the gear and you can really go to town loading it up. Loading+heat+a sharp tap on the end of the puller got mine off

I didn't see anybody say this yet but on a 2 stroke, yes you should always kick with the throttle at least part open - except when it is cold and you have the enriching circuit on. If you open the throttle, the enriching circuit does not work.