feetupfun

Here is a rather more complete 198 for sale http://cgi.ebay.co.uk/ws/eBayISAPI.dll?Vie...A:IT&ih=003

You have just got the exhaust system hot enough to start cleaning itself out. Thats what makes the smoke. You can't "blow" rings on a 2 stroke. You can sieze 2 stroke rings or wear them out but neither causes smoking. You probably need to do a few more fast runs on you bike to clean it out fully or have the engine and exhaust decoked. Anything that requires the throttle well open for a minute or so will usually do the trick. Very long steep climbs are what I use. The strange uneven running could be anything from using old fuel to running out of fuel to a crankcase air leak to a partially blocked pilot jet. More info on the "backfiring" needed. Very rare for such a bike to backfire in use. I think you need a better description of what it does and how you are riding when it happens. It's not uncommon for 2 stroke trials bikes to only fire every 5 to 10 strokes on throttle-closed overrun if the revs are up a bit. Is that what you are getting?

Acetone addition not recommended for fibreglass fuel tanks

Hi YamaDan Pardon my ignorance of world place names but where is The Oc and is there good weather for trials riding?

I'd have to agree with Majestyman340 on that if you want to ride it in competition the Bultaco is the go or maybe the very last model Cota 349 (which are as rare as hen's teeth). If you only want to look at it then it's a very personal thing. Of those you have listed I only find the Bultaco attractive-looking. The others have styling that looks too modern (or too weird in the case of the OSSA Gripper).

Pirelli (I think model is MT43) are similar to your old Barums. Barum is called MITAS nowadays. MITAS also make trials tyres that wear slower than the Michelin/Dunlop/IRC competition-only tyres but probably not as long wearing as the Pirellis.

The IRC tube type rear is great for twinshock use. The only difference in performance from Michelin tube rear is the IRC needs a slightly higher pressure than a Michelin to feel the same ie it is a bit more flexible in the carcass. The IRC is especially good because it is the only tube type rear that is easy to get a hold of here.

OSSA MAR handlebar clamp screws are M7 x 1.0 x 55 long (from end of screw to underside of head) and the thread is 20mm long Dave This OSSA person is the same person who fixed up their M49 at about the same time as you did yours. David Lahey

The first model Majesty made for the TY175 motor did use a modified Yamaha TY175 frame. The only frame mod though was to relocate the top shockie mount. The frame tubes under the motor were left untouched. Later Majestys with purpose built frames made for the TY175 motor had no frame tubes under the motor.

Dave, OSSA MAR handlebar clamp screws are M7 x 1.0 hex socket head. I will check later tonight re the length. David

Further to the posting by MichaelMoore regarding the use of Reynolds 531 to make replica frames, I seem to remember reading that the standard OSSA MAR frame is made of chrome moly tubing. Whatever it is, it seems to work just fine to me.

Maybe the 600 UK pound Majesty frames are someone modifying TY250 frames to be replicas of the first model Majesty? I have wondered for a while why no-one is doing this as a business as there are so many TY250 frames around. If someone was making new Majesty replica frames and selling them for 600 UK pounds, they would be losing money on each one.

Here are the photos of how I did it for future reference

Its possible that the standpipe for the fuel tap has fallen off or split. You would need to take the tap out and have a look at it to know for sure.

I think you need to be a Site Supporter to post photos in a forum

They are quiet and well tucked in but if you want performance get the two piece WES.

Dan Yes the lower co-efficient of friction of the steel inserts is one reason for the special treatment for the basket finger/fibre plate interface, but it also greatly reduces the rate of formation of grooves in the basket finger slots ie because steel is more wear resistant than aluminium. David

Why not use a smaller bore master cylinder or a larger bore slave cylinder?

How could making a fibreglass tank be as easy as welding up a steel tank?? Welding will take an hour at the most while making a fibreglass tank would probably take 10 to 20 hours. Yes you need to purge the tank of air before welding it. Nitrogen, Argon or Carbon Dioxide will all work. I've even seen a tank purged with exhaust gas from a car prior to welding (but I don't rcommend it) Washing out with detergent and then drying before the inert gas purge prevents fuel residue causing problems with the heat.

CaptainFur The TR77 is a very nice twinshock bike, but not many were sold in Australia. That one on eBay at present is the only one I have seen in Australia for many years. At the time they were available new, the popular bikes for trials were the Montesa 348, Yamaha TY250 and Bultaco Sherpa T. Parts for all OSSA dirt bikes are readily available but the main suppliers are in the US, UK and Spain. Many of the TR77 parts (wheels, forks, engine parts) are interchangable with other popular (in Australia) OSSA models like the Explorer and MAR but parts specific to that model (ie the exhaust) would not be easy to source second hand locally. It would be fine to use for trials and mountainous trail riding. David Lahey

Welding the existing tank would be much easier or find a second hand tank from something else that will fit. Making a tank that looks any good from fibreglass will take lots of labour and they are easily damaged. I would love to have a steel or aluminium tank for each of my bikes that have fibreglass tanks.

I don't have a Cota 200 but here is somewhere you can get a manual from: http://www.southwestmontesa.com/montesa/manual.html You may get a better response if you post in the Twinshock forum next time

Thanks guys. Yes I see that will work well - thanks Woody. I'll post some photos for future reference.

I'm doing some renovations to my MAR and want to run the ignition wiring differently to where I found it (getting squashed between the bashplate and the engine cases) It seems obvious to run the wiring forwards and up the RH front downtube as I see was done to the MARs I see in photos with Mick Andrews riding. My query is how to route the wiring to the downtube. If I use the exsiting grommet slot directly underneath the flywheel but run the wiring forwards rather than backwards, I suspect it will get just as squashed as it did going backwards from that hole. If I make a new slot for the slide-in grommet at the 4 o'clock position, I fear that I will be weakening the crankcases in a critical spot (under the RH front engine mount lug). Another option is to cut a grommet slot in the magneto cover, but I think this might look a bit strange. Ideas, suggestions, comments please

More info needed for diagnosis over the internet