feetupfun

Sounds like you are pretty keen to pull that Z motor apart. From memory, the puller for the magneto flywheel is the same as for the TY175/TY250.

Unless you are made of money, don't pull anything apart till you know what is wrong with your Z. You need a much better diagnosis. I'll try and help. First off you need to describe the symptoms much more clearly. Why do you think it is "oiling up the cylinder" and what do you mean by killing spark plugs? There are many reasons for losing spark and changing the crank seals is probably the last on the suspect list and the most expensive to do. If your crank seal on the clutch side has failed, gearbox oil will be getting sucked into the engine so you can easily diagnose this by the gearbox oil level going down with use and the exhaust gas being very smoky and smelling unusual. Your spark problems may be something much easier to fix so how about some better information about what is happening with the bike.

The frame kits that Craig is now selling are made on the jig used for the last of the 250/320 Majesty frames. These frames differ in many ways from the TY250 frame. The wheelbase is longer, the motor is higher, the swingarm is longer, the footpegs are much lower relative to the motor and the shockies are mounted to provide about 6.5 inches of rear travel. The overall effect is a bike that has much better ground clearance, much better rear suspension action, better balance, better stability, more room between the pegs and handlebars and very similar steering. The only thing that is not quite as good as the TY250 framed bike is the front wheel takes a slightly wider line in tight turns due to the longer wheelbase. The other frame you are talking about I'm not sure if you are looking at a mini-Majesty framed bike or a Majesty framed bike. The Majesty 200 frame is the same as the 250/320 except for the differences needed to mount the 175 motor. The Mini-Majesty is a completely different frame that is much smaller and uses the Ty175 swingarm. The mini-Majesty suits riders of small stature and is very light. Newly made full-sized Majesty frame kits to suit TY175 running gear are available through France Trial Classic. NOS Mini Majesty frames are available through Craig Mawlem.

Thanks Woody. I'm happy that you have debunked my conspiracy theory. I'm now trying to work out if all that work on the frame would be worth it.

If the float arms are close to horizontal when you hold the carby upside down you are pretty close. You may also want to check if either of the floats has a hole (and full of fuel). The most common cause of what you describe is a worn float needle/seat. If the fuel height is too high of course it will run rich. I would be amazed if fuel came out the float bowl vent while the carby is up the right way. More likely to be the float bowl overflow line (the one that comes out the bottom of the bowl). I've just looked at the owners manual and the text says the fuel level should be 4~6mm below the joint between the main body of the carby and the float bowl. The diagram shows the measurement as 2~4mm below the joint. To check the fuel height the way the book says requires a special fitting that replaces the float bowl drain plug with a clear hose on it. If you want to see the page from the manual, send me an email and I will send a scan of the page.

If the float arms are close to horizontal when you hold the carby upside down you are pretty close. You may also want to check if either of the floats has a hole (and full of fuel). The most common cause of what you describe is a worn float needle/seat. If the fuel height is too high of course it will run rich. I would be amazed if fuel came out the float bowl vent while the carby is up the right way. More likely to be the float bowl overflow line (the one that comes out the bottom of the bowl).

I'd like to explain my conspiracy theory about the early Majesty frames based on the TY250 frame. I have studied photos of Majestys of the type that use the modified Yamaha TY250 frame till I'm blue in the face and am not convinced that the motor mounts were moved in the frame. Yes I know that is what is said in the famous magazine test "In The Rough" when these early Majestys were publicised but I reckon it is bunkum. Yes the motor is higher from the ground than in a TY250 fame but it is done with two simple modifications: One is that the swingarm is set at a steeper angle down at full droop. This lifts the rear. The other is that the main frame loop has had about 25mm added to the length of the top tube. This is where the modifications to the toolbox section come in. They are just a result of the work to add the extra bit of frame tube. This lifts the front of the bike (and steepens the steering angle) because it causes the front section of the frame to pivot forward around the front motor mount bolt. Maybe the top tube is lowered too. I don't know because I've not seen a detail photo of one with the fuel tank off. The reason I started thinking about this was that I had a few spare TY250 frames and wanted to build a Majesty replica but if you have a close look at the TY250 frame, the technical difficulty of raising the motor even one inch is quite extreme while achieving the same result using the method I have described is quite simple. If someone can debunk my conspiracy theory I would be very pleased. Good close up photos of the top frame tube modifications and of the rear engine mounts would be quite sufficient. David

Similarly soul searching is the issue about whether to allow the Yamaha MX400B in Post-Classic motocross events. Here in OZ, Post Classic MX is for pre-75 bikes and the MX400B came out in late 1974 so should be eligible, but like the OW10, is also a (cantilever) monoshock bike. I reckon that if we were lucky enough for someone to turn up on the OW10 at a Twinshock trials event, we should welcome them with open arms to have such an interesting bike to watch. The more competition oriented riders can be assured that such a bike would not provide any technical advantage over late model Twinshock trials bikes. There are good reasons why trials bike design did not follow along the lines of the OW10.

Perhaps the numbers would be different if the riders had their choice of riding two or four stroke. Being factory riders means that they usually don't get to choose.

The concept of protecting the tank by putting it within the confines of a perimeter frame might be an advantage depending on whether you put a higher value on the frame or the fuel tank. I personally think it is easier to fix or replace the tank than to fix or replace the frame in the event of that part of the bike being hit hard enough to damage it.

Its probably dry bearings or brushes and may be able to be fixed with correct lubrication which may entail pulling the fan apart. Is it possible that water has entered the fan motor from a high pressure water blaster? It seems that every trials bike I know that has had the cooling fan motor fail has an owner who cleans the bike with a high pressure cleaner.

My Majesty 250 is finally ready to ride. Was put together over the past few months from a NOS 1981 frame kit. As fas as I can tell there are now three 250/320 Majestys in Australia. Photos on the Trials Australia website. http://www.trials.com.au/BB2/viewtopic.php?t=2420 David

I had the older treatment for short sightedness (radial keratotomy - radial cuts partial thickness of the cornea) in 1995 at age 36 after wearing minus 3 glasses for 23 years. I had tried all the types of soft contacts available at the time but my eyes were too dry for them to work for more than a few minutes. The radial keratotomy RK technique is now about 45 years old and was developed in the USSR. As with LASIK the results were astoundingly good for activities like Trials riding, swimming and snow skiing (yes we have snow in Australia). It is now 12 years later and my vision for driving and riding is still fantastic but I am 48 and old-age vision has crept up to the point where I need reading glasses for close work. LASIK was available at the time but was relatively new then so I chose the time proven RK method. Time has since proven the LASIK method as also being successful long term. I would have paid lots more than what it cost to get the results I got but don't tell the eye surgeons that.

Of the covers made by Yamaha, the 1975 B model and later models had a flat cover with a bump in the middle and covered the sprocket and are made from magnesium and painted silver The 1973/74 A model has a domed cover that is aluminium with a polished finish and also covers the sprocket. There are also covers made by specialist UK trials suppliers which are flat with a bump in the middle, don't cover the sprocket and are of much stronger (thicker) construction than the magnesium and aluminium Yamaha covers. If you want photos of the three types, send me a PM.

If you explain what pilling is and in what way the clutch isn't working I will have a go at helping you. It would also be good to know: How long have you had it? Did you work on the hydraulics or just on the clutch assembly? Did it work OK for the previous owner?

The usual reasons for a failed big end in a two-stroke: Corrosion due to being stored with only fully synthetic premix oil for protection. Corrosion due to motor being filled with water by accident and not immediately dried out. Pre-ignition and/or detonation over an extended period. Poor air filter maintenance practices (usually affects the bore and piston/rings first). Its pretty hard to read your message without any punctuation but it sounds like either your mate only just bought the bike last weekend or you only rode it for the first time last weekend. Any other clues about the bike ie how did it run prior to the failure and what sort of riding does the bike see?

B&J Racing in Tennessee sells the footpeg kits for the TY250 twinshock. Yes they appear to be based on the Universal footpeg kits sold by Sammy Miller. To fit them you will need to cut off the existing peg mounts and drill and tap a thread into each stub for the upper fixing. Your model TY250 should have threaded holes for the lower fixing already.

If the 4.10 tyre you are thinking of is a MITAS, it will fit a standard MAR but will have very little side clearance to the chain guard. Diameter wise it is a better tyre than a 4.00 competition tyre for an MAR because the large OD of the 4.00 tyre causes OD clearance problems with the wheel at the forward end of the adjusting slots. The MITAS 4.10 is about 20mm smaller outside diameter than a Michelin XII 4.00

Yes the pinion is much wider than the driven gear gear on TY175. The TY175 primary drive gearsets are not made in matched pairs as far as I know so any TY175 pinion should work OK with any driven gear. If in doubt, put it together and test for excess or too little clearance using plastigage.

Why does it have to be silicone? What's wrong with aluminium? You could support it from the existing muffler if you make it light enough.

Yes inserts are available and they are made of aluminium and are intended to be welded into the barrell. There may be other places to get the inserts but I just bought one for my MAR from Keith Lynas in the US. There is a link to Keiths website on the fantastically informative OSSA site run by Mats Nyberg. They usually strip because the nut works loose and the threads rub together due to engine vibration. Prevention in the form of tie wiring the nut will prevent it happening again.

If you truly are selling because of lack of space, you will certainly regret doing it later on. I reckon keep at least one OSSA even if it means getting a bigger storage area or leaving it at someone else's place till you can fit it in. I'm with Big John on this. There is no way I would sell a twinshock trials bike that has some meaning to me. It would be like selling your family videos and photos. There is no way to put a price on those either. For the mercenary people though that are thinking along the money lines, remember that we are probably the only people sufficiently interested in our treasured twinshock bikes to restore and enjoy them. Once our generation is gone, there will be very little interest in them hence demand (and prices) will eventually drop.

The Scorpa SY250 motor eventually suffers from both shiny plates and grooves in the basket fingers. The shiny plates mean there is no way for the air to get in between the plates when the clamping pressure is released. Roughening the plates provides a path for the air. I successfully filed the fingers smooth on my TY250Z (which has the same motor as the Scorpa SY250). Baskets are very expensive so it is worth filing them a few times before replacement. It needs to be done very carefully to prevent bending the fingers and keeping the engagement surfaces on the fingers flat and square. From how you describe your riding style it sounds like once you fix your clutch it will stay good for a while. Have a look at what the top level riders do with their clutches when jumping up big obstacles from a standing start and you will see that they cop lots of hard use ie full throttle, peak RPM, drop clutch in third gear. I've heard that the clutch in your Scorpa SY250 shares a clutch with an early 1990s Yamaha YZ125 so it is designed for a bit of abuse.

Pumping the clutch lever does nothing but build arm muscles. Leaving the clutch lever pulled in when you are not riding it sags the clutch springs. To free the clutch, there are two easy options: Option 1 Without starting the motor, change into 6th gear, hold the clutch lever in and rock the bike. Option 2 (if you have the riding space available) Start the motor in neutral. When you are ready to go, push off with one leg and select first or second gear while it is still moving. Change up gears until you are in a high gear and then pull the clutch lever in and ride around a bit like that till it breaks free. You can fix the problem by: Roughening the steel clutch plates (bead blast or coarse abrasive paper both work fine) and removing any wear grooves from the fibre plate tangs against the basket fingers. Both fixes are temporary if you are hard on the clutch (probably the same as you've seen with MX bike clutches). What people have told you is right. It is a common problem with trials bikes. Most people don't bother to service their clutches because once the clutch is freed it works fine till next time.

DT175s from 1978 onwards have a different stud layout than the TY175. So some DT175 barrels are interchangable with TY175 barrels and some are not. The TY175 motor is based on the 1974 DT175A so the A, B C and D model DT175 barrels should fit. I know the question was about the TY125 but I've never worked on one of them. Why would you want to fit a DT barrel to a TY motor anyway? Is the DT barrel better in some way than a TY175 barrel?