feetupfun

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?

Here are the basics for setting up forks of the twinshock era: Spring preload Fork spring preload should be set ideally to give static sag of 40% to 60% of travel with you standing on the bike pegs with no weight on the bars. It is adjusted by adding or removing spacers above the springs. TY175 standard has a tubular steel spacer about 70mm long. If you add too much preload, the springs will coil-bind (which limits travel and may kink the springs) Oil level Fork oil level should be approx 125mm from top of tubes with springs removed and forks fully bottomed. The resistance to bottoming can be increased by using a higher level of oil. Too much oil volume and you will limit the travel. Too little oil and the damping holes will be exposed to air at the top of the stroke. Oil viscosity Start with 15wt oil. Heavier oil will increase resistance to bottoming out on sudden impacts but will be of little benefit during sustained heavy braking (on a steep descent). Heavier oil also produces a more dead feeling front end which makes hopping the front harder work than it normally is on a twinshock bike. With a bike the age of your TY175, it is entirely possible that there have been modifications made which are causing your forks to feel weird. I have tried many modifications to TY175 forks (wide range of oil type, different springs, air caps, a great range of preload adjustment) over the years and finally ended up with them completely standard as being the best performance. The next change was to fit TY250 forks which made it just how I wanted it all along. If you are in doubt about what trials bike forks should feel like to ride with and even just to push down on, try someone elses similar bike for comparison. If still in doubt, compare what your forks look like disassembled with a set you know to be standard.

Brushing epoxy works perfectly. It is thin enough to get it to coat everywhere inside and it takes hours to set so you can leave the tank to drain out and only a thin coating remains. It sticks great to old fibreglass if you clean out the premix properly. I cleaned my tanks out with turps, then thinners, then acetone and left them to dry fully overnight before the epoxy. Choose a bright day so you can see inside easily to see that you have coated everything. I put plasticene where I dont want the epoxy to stick ie like the cap thread. Brushing epoxy protects the fibreglass from the ethanol that is in some car fuels too. You should be able to buy it from boat shops and model aircraft shops. It cost me $40 for 500ml which is enough to do an M138 Alpina and an M49 Sherpa. If you do them all with the one mix, that would probably be enough to do three tanks. Only about 75ml stays inside the tank but you need to put about 250ml inside to start with to make sure everything gets coated.

The steering angle on the standard Ty175 is not as steep as most bikes from the same era. If you raise the rear with stiffer springs, more preload or longer shockies, the steering angle improves towards the ideal. If you then slide the forks down in the clamps, the steering angle will move back towards standard, but will improve the ground clearance. A negative with sliding the forks lower is that it makes the front end even more flexy in rocks. Going the other way (lowering the front), there is a limit created by the clearance between the front mudguard and the lower fork clamp. This limit is just a bit past when 20mm of tube protrudes above the top clamp. If you are serious about improving the front end, consider fitting the forks and clamps from a Ty250 twinshock. It is a bolt in job and improves the front end quite a bit, especially if you ride big obstacles or are over 80kg. In that case, the tubes are fitted flush with the top clamp and this puts the bike height at the front the same as with the TY175 forks with 20mm protruding. With either set of forks, you really need to set it up to suit yourself. I have found that it is far more important on TYs to get the oil level set exactly right than what oil weight I use. They have seriously poor damping if the level is even slightly too low. I find 10, 15 and 20 wt all work OK with the correct level.

JayLael You knew someone was going to ask if you would post a picture of the modified KT, didn't you? Please do if you can. Thanks David

The leverage ratio on twinshock type suspension never stays exactly the same throughout the travel. The mount locations on standard bikes are usually well chosen to minimise the variation in leverage ratio throughout the travel. When people modify only one mount location on a standard bike, the new arrangement can produce the desired increase in wheel travel but becomes less ideal as far as leverage variation is concerned. Laying down shockies by moving only the top mount forwards (or similarly by moving only the bottom mount forwards) usually causes the opposite of rising rate ie the leverage ratio on the shockies increases as the swingarm moves upwards.