feetupfun

Mike I will work out what it would cost to buy the same product from Germany because I have not tried before but I suspect it will be more expensive from Germany because: 1 Germany is not near Australia 2 Postage from the USA to Australia is generally much cheaper than postage from the EU 3 I don't pay customs duty or VAT or GST from either the EU or the USA David

the tytrials unit works well and was easy to fit. The only difference I noticed was that there seems to be less variation between the strength of individual power pulses at extreme low RPM. I have not tried the others.

Magura assemblies from resellers in the US for about $70 a pair Suzuki RM80X assemblies for about $50 each from Suzuki shops Both are quite crash resistant. I use the Suzuki levers on my 1970s jap trials bikes because they look right, and AMALs on my Spanish trials bikes. If I had a 1980s trials bike I would use the Maguras.

Full synthetic gives the lesser amount of smoke, lubricates best under extreme conditions (pressure and temperature), causes less carbon build-up in the combustion zone, tends to create less ring gumming issues Semi synthetic is not quite as good as synthetic in all those areas, but protects the steel items inside the motor (conrod bearings especially) from corrosion better than synthetic while the bike is not being ridden.

The right height is whatever you think works best. Moving them up or down changes the steering angle, steering trail, wheelbase, ground clearance and how much they flex around. The standard height from the factory is 20mm protrusion above the top clamp.

Ideal gearing is a difficult subject because it is a personal taste thing. When I started riding my 348, I thought the standard gearing on it was too high, and fitted a rear sprocket with 39 teeth (33 is standard) but the motor was not running very well (AMAL problems). Once I got the motor running well, I found that the bike felt too slow in first gear in sections and second was too fast. I then put a standard rear sprocket on and it is wonderful to ride. The front sprocket was standard size all along. If you buy a Pirelli and use it till it wears out, you will be regretting your decision for a long time. They take an amazingly long time to wear out but are quite stiff in the sidewalls and are scary on wet rocks. Michelin or IRC tube-type rears are really the only decent rear tyres for that rim. For performance the IRC is better but is more sensitive to tyre pressure than the Michelin. Michelin used to sell a very good tube-type rear but the current Michelin tube-type is not as good.

Only the hearts and wallets of many Twinshock riders around the world. Same for the Honda TLR250, which also didn't win any world titles

Mike you can buy them from Don Newell in Brisbane, Queensland (advertises in VMX magazine). I think they (Falcon) only answer the phone after lunch (their time) so it might be good to try early in the morning NZ time.

All of the twinshock TY250 models have interchangable forks ie same travel, length, diameter and mudguard, brake arm and axle attachments. There are minor differences between them but nothing that stops any model forks fitting any model bike.

A TY250 piston can be used to get the motor to about 190cc, but it is not as simple as boring the hole bigger because the gudgeon pins are different diameters and the cylinder requires a bigger OD sleeve

If you can see a gap when holding a straight-edge against the tube, it is bent Whether it can be straightened depends on how badly bent it is and if there are any creases or is it bent into a gentle curve. Another test is to hold the slider still (by carefully clamping it to something solid) and rotate the tube. You will see any run-out as the tube rotates. Are you sure only one is bent? I would be having a close look at the other one while the front end is apart. You should also check for bending/twisting of the triple clamps.

Frame and tank look like Pinky. Pinky did not have a tank cover. No idea what the seat it from

If bogging means the motor dies as the throttle is opened, it may be a blocked or partially blocked pilot jet (lean mixture as throttle opened). dombush's choke test will test this possibility

Only the very first and last models of the Alpina are close in design to the Sherpa T of the same year. Even those Alpina models are not as good as the Sherpa T of the same year to ride in sections. The differences vary from model to model, but the Alpina is generally inferior to the Sherpa T in that the hubs are heavier, the steering trail is too great (most Alpinas use Pursang triple clamps), the wheelbase is too long, the tanks are bulky, some frames are heavier (more frame elements) and the gearbox ratios are too far apart in the lower gears (1,2,3) and too close together (3,4,5). Having said all that, any Alpina is a better bike for trials-type riding than any MX based bike of the same era. In comparison with the Alpina, the OSSA Explorer and Montesa Cota Trail models are much more easily made into capable twinshock trials bikes.

Hi Jon I read your posting on the Aussie trials site. You helped bob1 with your reply and I did not see a question in your posting to answer so didn't reply. There are only a few hundred Twinshock trials riders in Australia and only a few active twinshock trials forum members so don't expect to be knocked over with replies to postings on the subject. For people wanting to buy second-hand TY twinshock parts from Australia, I suggest you look at eBay.com.au because they do come up for sale (it is a different website to eBay.co.uk) The availability of TY250 magneto covers is probably no better here than in the UK, because they suffer internal corrosion and rock damage. Ty250BCDE clutch covers corrode inside the oil pump compartment. I recently bought a TY175 bottom end (with clutch cover) and a TY175 magneto cover via aussie eBay for reasonable $$ and there have been lots of TY250s suitable for parts for sale and also individual TY250 parts for sale. If someone from overseas wants to buy some particular TY parts from OZ, I am happy to help with the logistics if I can. The Yamahas that have the clutch cover without the oil pump compartment that can be used on the TY175 are YZ125ABCXDEF and IT175DEF. DT125 and DT175 clutch covers can be used but look pretty bad and are lots heavier. I don't know of any other Yamaha motor that has a clutch cover that will fit a TY250 but would like to try a DT2 or DT3 clutch cover as I think they might fit.

No it doesn't. That is because the positional relationship between the front frame tubes and front wheel has not been changed, and the exhaust port is now very slightly (approx 1mm) further away from the front wheel than standard. Clearance for the front wheel and guard can be an issue if the steering head angle on a bike is changed by making the cut where the steering head attaches to the frame, but I didn't do it that way.

maybe you are asking which parts are interchangable? Unfortunately for would-be parts swappers, Yamaha made quite a few changes to their 250cc dirt bike engines during the time frame that they were producing the TY250 motor, so your question would have to take into account which DT250/DT2/DT3 motor and which TY250 motor you are referring to. Many parts are interchangable but also many are not. As far as performance-oriented design differences, the TY250 motor has a much heavier magneto flywheel, similar port timing, closer gear ratios for 1,2 and 3 gears, lower compression ratio, smaller carby and very different exhaust pipe design to what was used on the DT2, DT3 and DT250ABCDEFG motors.

Reeds act as a one-way valve between the carburettor and the crankcase and are found in most modern two-stroke motors. Having a one-way valve there means that the volume of air/fuel mixture drawn in can be maximised without limiting the induction timing. Many older two strokes don't have reeds and used the rear bottom edge of the piston to close off the inlet port to prevent the air/fuel mixture going backwards as the piston descends. This makes for a more restrictive flow path than what is possible using a one-way valve (reeds) In your bike the reeds are thin, stiff plastic composite flaps that are fixed only at one end. They flex inwards when open and seal against a flat seat when closed. There is a slight pressure drop through reeds which is why for ultimate high performance in two-strokes, a rotary valve (which does not cause a pressure drop) is often used to control the induction timing instead of reeds.

That ID number puts it as likely being sold in 1976. All 348 TRIALS models (76 77 78) had the same shape tank and all are red fibreglass. The tanks had detail differences though. One is quite plain, having just the M round badges, another also has "Malcolm Rathmell" insignia moulded into the fibreglass below the seat and the third has gold and black slotted stripes from front to rear moulded into the fibreglass. In the UK, 348s were sold with aluminium fuel tanks with a fibreglass cover that looks just like the fibreglass tanks on the non-UK bikes.

Yes TY250B forks and yokes - running with 10mm less fork spring preload than standard for those forks. Regards David

I still haven't made a new brake link but the rain stopped for a while so I took some photos. The yellow TY175 has the modified frame and swingarm. The orange TY175 has a standard frame and is there as a visual reference.

Here are close-up photos of an original Cota 348 clutch lever and perch. The lever mud/dust covers have been removed in this photo because they make it hard to do cable adjustments. My Cota 348 twistgrip in the photo looks the same as the one on the "eye of Fred" Cota 348 so I reckon mine is original Cota 348. It is not on my ride bike because I prefer to use a modern AMAL sidepull twistgrip.

Yes if the front 348 rim has been heat-affected then use the MH349 front rim with the 348 front hub and remove the anodising and polish it. Standard rims are plain polished aluminium alloy - no coating or anodising. You can polish the hubs while the wheels are apart. If you have a bike, you don't need a jig to relace the wheels, you assemble them on a bench and true them on the bike. My 348 came with a black aluminium side-pull twistgrip and will take photos of mine today to show it for other people's opinions. I thought it was the original twistgrip because everything else on the bike was original. Be careful buying AMAL levers. There are cheap replicas available that look right but are brittle and there are also replica AMAL levers that are very good quality (as good as the originals). Cota 348 AMAL levers are black.

Photos coming up soon - yet to make a nice-looking brake stay

The steering frame mod detail: I wanted a steeper steering angle and for the bars to be further forwards but to avoid shortening the wheelbase. I added 25mm length to the top frame tube. To accomodate this, I bent the front downtubes at a point just above the front motor mounts (approximately the same distance from the ground as the front axle). This steepened the steering angle and moved the steering head forwards by approximately 25mm and slightly upwards, but did not move the front axle forwards or aft. Because of the change to the top frame tube, I had to make new front fuel tank mountings and relocate the HT coil. With 340mm shockies in the standard position and TY250 forks fitted with the tops of the tubes flush with the top triple clamp, the steering angle was indentical to a standard TY250 fitted with 340mm shockies. Of course since then the steering has become slightly steeper because I have extended the swingarm which has caused the back end of the bike to be slightly higher.