feetupfun

My Dad was a road bike rider from his teens, only having a rest from bikes when he had to build a house so he and my Mum could raise kids. When my sister and I were old enough (in about 1968) his bike passion took over again and he started fixing up old bikes for himself and us to ride. There was a 100cc MANET scooter, a 125cc CZ road bike, a 16H Norton with sidecar, a Tiger Cub and an early Yamaha 80cc road bike (G1FD). I became hooked in a flash and by 1974 I had a TS185 which I then modified for Trials so I could ride with a kid from school who had a proper trials bike (RL250). I soon learned that the TS185 was hard work in sections so bought a M85 Alpina, which was only a bit less hard work. Practice was a daily thing after school at the local bush and that place was also used by the state trials champ of the time for practice so I had a pretty good guide to what was possible to do on a proper trials bike. This led to buying a TY175B second hand in 1976 which was like a breath of fresh air to ride compared with the Alpina. I rode that TY175 till 1980 when the girlfriend thing became too much of a distraction. Then it became a wife thing and it wasn't till 1988 that I rode trials again. The Ty175 was still quite competitive at that time but it was getting very worn out and I kept hitting brick walls trying to buy parts or even parts from wrecks to fix it. Long distance Trail rides and Enduro competition took over until about 1994 when I learned of the VMX and Twinshock Trials movement and I got very interested in trials again. I bought the first going twinshock trials bike I could find (a TY250A) and rode a state titles event and loved it - riding against other old bikes. Things then sort of spiralled upwards out of control as over the next 10 or so years I bought every Twinshock trials bike I had wanted as a kid (most of them not going) and brought them back to life. The arrival of the internet in the late 1990s made it incredibly easy to get old bike parts and it keeps getting easier. By 2006 I had gathered all the twinshock trials bikes I wanted except a 250 Yamaha Majesty (they are very rare in Australia) and had contacted people all over the world trying to get one and tried to borrow an original to make replica Godden Majesty frames locally. Later that year I got THE phone call from a guy in Western Australia who was ready to sell his unused Godden 250 Majesty frame kit. At the time I had made plans to make a replica of the first Majesty 250 (the one that is made from a TY 250 frame) and was very close to starting. Soon after getting my Godden Majesty going new replica Majesty frames became available which is just another example of how things have improved as far as being able to buy parts for the old bikes. I keep most of my twinshock trials bikes close to standard for the purpose of being able to compare what they would have been like to ride in their prime ie not moving footpegs, shockie mounts, fitting different forks, doing frame chops or swingarm extensions. One exception is a TY175 that I like to try all sorts of mods on and has become a bit of a beast. It is great to be ride the bikes back to back and compare what I feel to what the magazines of the day said about them and to hear other twinshock riders opinions about how they compare. Riding twinshock trials has become quite popular here but is still nowhere near the fanatical level seen in Spain - here it is mainly riders who started their trials riding on twinshocks in their youth and still love riding them.

If the problem started all of a sudden, it could be an ignition stator problem. The symptoms you describe are what mine was like to ride when the stator failed.

Look on the bright side - at least the clutch plates aren't stuck together.

I had to take that gear off my 348 and I'm assuming your 247 has the same sort of taper. I found that a gear puller with fingers couldn't put enough force on so I made a tubular puller that has a full circle shoulder that goes behind the gear. It is made in two halves so it can be fitted over the gear, then the two halves are held together for the pull. It worked. I think that sort of puller is available from Montesa specialist Jared Bates or can be made with a welder and lathe.

Tony there are other Ty175 models than the 525 prefix models. There is also a Ty175 model that has a frame like the Ty125 and has prefix 1N4. Not sure where else they were sold but they were popular here in Australia as they came fully set up for road registration while the 525 models only had basic lights and a (relatively) noisy exhaust. I guess the LH sidestand was for road registration requirements in some countries. david

One way to be certain is to measure the diameter of the bore. If it is 66-68mm, it is a 175. If you are tricky enough you might be able to make this measurement through the exhaust port with the pipe off. If it has the original barrell, you should be able to tell what capacity it is from the engine number prefix. I can't remember what a TY125 prefix is but the most common TY175 prefix is 525 and the road-going TY175s here are prefix 1N4.

Yes the front hubs on TY175 and TY250 twinshock are the same. Rims are different widths - don't know why.

TY250 forks do have a better action than TY175 forks for people over a certain weight (damping and springing) and using them will preserve the existing steering geometry (being in-line axle and can be set to provide the same ride height). They are 34mm diameter though so would be too small for your bored out triple clamps. TY mono forks have a better damping action than TY250 twinshock forks but being leading axle will reduce the steering trail. A better bet would be to use TY mono triple clamps too but this requires work to get the steering stops right. Both the TY250 twinshock and TY mono forks are heavier than TY175 forks. I wouldn't complain about someone using TY mono forks on a Majesty because they are comparable in performance with the forks seen on late model twinshock bikes. We have a manufacturing cutoff date of 1987 here for twinshock bike technology so there would probably be no issues. I've seen TY mono forks and front wheel working quite well on a heavily modified RL250 too.

It may have been fitted with a different wheel to what came new on the bike. The "honda" pattern front wheel on 1980s Cotas is notorious for the spoke flange failing and people usually fit a different wheel to get around the problem (and because the same thing has already happened to all the bikes being used for spare parts). I've seen Honda CT110 wheels and earlier model Cota wheels used in Cota 200s and 349s.

The shims fit between the seal housings and the main bearings ie outside the bearings. If you have split the cases (new gasket), fitted a new conrod kit or even new main bearings, you will need to determine what thickness shims are needed. A common mistake made when assembling that motor is to bend the crankshaft by squeezing(bending) the crank when fitting the seal housings.

Here is what it looks like with the Explorer tank.

The Explorer is an easy conversion unless you want the same wheelbase as the Mk1 MAR. The Explorer is based on the Mk2 MAR which has a longer swingarm than the Mk1 MAR so if you want the short wheelbase you will need to shorten the Explorer arm or get a MK 1 swingarm. If you fit a shorter swingarm to the Explorer, the bottom mudguard mount needs to me modified to provide rear tyre clearance. My OSSA trials bike is based on an Explorer and has been fitted with a redecorated MAR tank, MAR seat and a MK1 MAR swingarm. It is great to ride. The photo was taken yesterday at a trial.

This model Alpina can be made into a very nice trials bike, very much like the M199 Sherpa T but how good depends on how far you want to go with the conversion. Yes the tank and seat are obvious. The airbox and sidecovers arrangement on that Alpina is much wider than the Sherpa T. Replica M198 Sherpa T airboxes and sidecovers are available. An early model Sherpa T or Alpina funnel type air filter would also work but would be a lot louder (induction noise) The wheel hubs on that model Alpina are Pursang/Frontera type and as such are lots stronger/heavier than Sherpa T hubs. The triple clamps are Pursang type (to provide more trail in the steering geometry) so to get the trail down to the same as Sherpa T, you will need Sherpa T triple clamps. The M213 frame has good geometry for trials, but has extra bits that could be cut off to save weight like the rear grab rail. The motor setup should be fine for trials as it is, but you will need a very big rear sprocket to get first gear slow enough, because the lower gears are taller in the Alpina than on the Sherpa T while 5th is about the same. If it still has the original Betor shocks, the springs will be a much higher rate than ideal for trials. Regards David

The bit I'm a bit lost with is that you are mentioning the relative cost of things that priceless. Since when does the cost of your hobby/dreams/memories come into the equation? Yes my twinshocks have cost lots of $$$ and I've spent thousands of hours in my workshop but riding those bikes is still probably the best value for money fun I have ever had in my life. I suspect that my lukewarm feelings about TY monos are because I eased up on riding trials in about 1980 and it was 1994 before I became fully obsessed again. The years of riding from 1973 to 1980 are burned forever into my psyche. I suspect that you have a connection with TY monos for a similar reason.

If Oliver's Dad looks at this forum or of someone else knows, please tell if Oliver is using the rear brake to help with balance or is it all throttle control? Thanks David (yes my kid rides an OSET 16)

What election?

Did you mean to type "sold" or "solid"? If you meant "sold", then I think you need to think again. Maybe you are a bit young to have witnessed what happened in the 1970s but Bultaco Sherpa Ts and Yamaha twinshock trials bikes would both have outsold air-cooled Yamaha monos by a ratio of at least 10 to 1, and are also well loved by the riders of their era. I do think a class for air cooled monos would be good for the people who like riding them.

I can't see much of the fork caps in that photo but the caps look like they are of modern manufacture to me rather than made by Montesa. Schrader valves are simply the type of valves that are used on car and bike tyre tubes and act as a non-return valve to hold the gas in and you push a litle pin in the end to let the gas pressure out. A different type of gas valve was used in the fork caps of a few old trials bikes like Bultaco Sherpa Ts and Kawasaki KTs. These are called vented caps.

An Alpina sold in 1975 might be a M115(250)/116(350) or a M137(250)/138(350). The M137/138 is the type of Alpina that is furthest removed in design concept from the Sherpa T of the same year. I'm not sure about the M116/117 as the ones I have came with triple clamps removed and mixed up in a box. After the M137/138 Alpinas came Alpina models (M212/213) that went back to being very similar in geometry and design to the 1978 M198 Sherpa T. The M137/138 has the Pursang triple clamps as Woody mentioned and a long swingarm - I have a restored M138 Alpina and I can tell you it would make a poor trials bike compared with one of the Alpina models that are very similar to Sherpa Ts. The first Alpinas were the M85 (250) and M99 (325) and it is these models that are most like the Sherpa Ts of the same era, differing mainly in the internal gearbox ratios and the seat/tank. If you can advise the model (the M number is the first part of the engine and frame numbers) of your Alpina or post a photo it would help identify it.

If it runs with the choke on, then there is fuel getting to the float bowl. If it stops when you turn the choke off, then either the pilot jet or the main jet or both jets are blocked. You haven't given enough info to differentiate/diagnose further.

Yes there is no friction at the spring/tube surface if you have no springs, but the friction at the fork seals goes up dramatically with increasing air pressure which is why very few manufacturers used air springing on its own. Most had air and steel springs together. Any bike with sealed fork caps is making use of the air inside as a spring, whether the caps have the facility to adjust the pressure (schrader valves) or not. Jaan, you can buy new springs for the Cota 348/349 but most people just add a bit more preload to the spring. When the springs get so sagged that to get the preload right, you have to put in enough spacers that the coils touch each other before the forks bottom, it is time for new springs. Sagged single-rate springs have the same spring rate as new springs, they are just shorter overall when relaxed - hence needing longer spacers to achieve the same preload force. In the case of my 1976 348, I have about 10mm more spacer length than standard, and ride with the pressure set at atmospheric pressure with the forks topped out. Be careful when comparing settings from one 348 with another 348 because some came with higher rate springs than others. If you have the low rate springs, as Peter says, you will need to run some air pressure in them.

If it is a standard 348 kickstart lever, it will bend OK cold but it will be much easier to bend if you heat it up. A standard lever will not shatter. Either way you will be wrecking the plating finish. It must have taken quite a hit to bend it out of shape as they are very strong - as you will find if you try and bend it cold.

Yes it should move a wee bit. Its called a floating disc and helps the disc stay nice and flat when it gets hot, and ensures that the disc can move to align with the pad surfaces when braking if there is any slight difference in alignment without flexing the disc.

Yes it is a matter of opinion and I didn't want yours to be the only one.

I have to disagree about sliding TY175 forks down flush. Whatever shockie length, footpeg location or handlebar rise, sliding the forks tubes down flush with the top clamp might improve the ground clearance but it makes the steering in sections worse, not better.