feetupfun

Yes it sounds like you have answered your own question. It sounds like the pilot circuit is not clear. Pull the carby off the bike and clear out from the air inlet to the air screw hole, from the air screw hole to the pilot jet hole and through the little hole/s where the pilot mixture enters the venturi. They all need to be clear and are easily blocked.

A video record of what happened in your bike storage area can be useful if they do get away with a bike. There are automated systems that just quietly start recording when someone gets in.

I think the suggestion that it might be the condenser is based on the motor (and condenser) cooling while the new plug is being fitted. A test to prove/disprove this theory would be to try one of the old plugs again when the motor was cool.

You didn't mention doing the most important things for good drum brakes. The drum surface has to be free of grooving, and the diameter of the drum has to be matched to the diameter of the shoes. Most old drums need machining and then thicker-than-standard shoes machined down to match the drum diameter, or get the drum resleeved back to standard diameter. Your mate's KT probably has either had this done or is still good from being relatively unworn. The disc will groove up with use too, and when you fit new pads to a grooved disc, they don't work well at all.

Hubs and spokes are the same for all TY175s and TY250 twinshocks. Two different front backing plate types (one with brake wear inspection hole). Two different front brake arms (one steel, one aluminium) and same for rear brake arms. Rims are a different kettle of fish. There are at least two types of TY175 front rim and at least three types of front TY250 rim. Rear rim range similar. Some TY250 rear rims are the same as TY175 rear rims. All have 21"front and 18"rear. The choice of rims by Yamaha reflected in some cases the rim type being used on their MX and Enduro bikes being produced concurrently, and in other cases the rim type was chosen to meet road registration design rules in some countries.

If the TY brakes didn't work then there was something needed fixing. Its just a machine.

You can buy them from people like In Motion or you can make them from a piece of mild steel round bar.

Unless your TY175 has a seriously bent swingarm or an offset rear wheel, yes a modern 4.00 x 18 competition radial rear tyre will clear the swingarm. Make sure you get the tube type IRC tyre - they make both tube type and tubeless type rears.

When you said MH Replica and being stuck out in OZ I wondered if you were near here as I know of one of those for sale locally. Sorry no ideas for a rigid rear AJ trials bike for sale. I like what you are doing with the Serow TY175. It sounds like you are having great fun. David Lahey Gladstone, Queensland

Yes mate. Lots of people continue to ride trials with new knees and new hips

Why would a tubular steel axle need to have solid ends welded on to be threaded?

It sounds like it is self-engaging. If it is, then the cause is usually grooves in the basket fingers which can be removed by filing the edges of the fingers flat again. The grooves form with use and act like little ramps that the plate tabs follow as the torque increases. Unless you are incredibly strong, it is hard to hold the lever in the right position to slip steadily or even engage smoothly. Smoothing the fingers gets rid of the self-engaging but the clutch will always have a wide engagement zone. Those clutches were not designed to be slipped in turns. A better bet with a M199 is to get the motor running very smooth at the bottom and set the idle so the motor will just stop if left alone, and practice riding tight turns using the rear brake and with the clutch fully engaged.

Are you saying 14mm BTDC on the rim of the flywheel or 14mm BTDC of piston travel? Running too far advanced will not cause your exhaust to burn out inside and any heat damage to the fibreglass next to the centre box is quite normal for bikes that have lost the insulation layer from the inside of the fibreglass.

Alan if you change fuels it can cause any existing carbon to come free and it can bridge the plug gap. When we stopped selling leaded car fuel here in Australia it forced almost everyone to using unleaded for their lawnmowers, outboard motors, motorbikes etc and there was an epidemic of fouled plugs that went for a few years - as old carbon deposits came off. If your bridge was carbon you will probably get a few more bridges then it will be fine as the loose carbon will have gone. If it is a metallic looking whisker then it is probably that leaded fuel you are using growing conductive crystals (too rich and/or too cold a heat range spark plug for the concentration of metals in the fuel).

Mk2 1976 (on first Cota 348)

I found that with my 2003 Rev 3 the axle travel available was not enough in all circumstances and at one stage needed to use a one and a half link. Whether or not this is a problem on a particular Rev 3 probably depends on the sprocket size combination in use.

Brochure photos of the TY250C have been provided here http://www.trials.com.au/content/index.php...er&Itemid=6

Brian H tgh30 if you want to ride a beautiful old bike, ride it as it came. MARs are truly great to ride with standard steering geometry. Please test ride a good one before you cut the frame on yours. Lowering the pegs will require removal or relocation of the stand and changes to the rear brake arrangement.

It depends on how serious you are about having good brakes If the drum diameter where the shoes run is different to the diameter of the shoes when they are on the backing plate, the contact area will be small = poor brakes. Standard shoes + worn drum = poor brakes Oversize shoes machined down to worn drum diameter = slightly better brakes Oversize shoes machined to fit + skimmed flat drum surface = great brakes Resleeved drum + shoes that match diameter = great brakes The picture is out of focus so impossible to tell if it is worn too far for skimming or requires a new sleeve.

A similar idea to Dan's was used in the 1980s on off-road bicycles to compensate for the cyclic variation in torque applied to the front sprocket. The sprocket on the pedal crank was made oval shaped and it was called a "biopace gearset". Changing the shape of the sprockets on a trials bike wil not achieve what Dan suggests because he is trying to alter the shape of the motor speed power pulse.

The photos you posted are of Mark Levinge's customised bike that looks quite different to standard. I went to post up some pictures of a standard bike but realised they were subject to copyright so didn't post them. I'm sure you will get good standard photos soon Yes the seat is meant to be black

The spacer between the bearings can usually be moved sideways enough to get a 3/8"steel drift or punch to contact the inner race of the bearing on the far side to where you are. If you warm up the hub the bearing will come out without taking any aluminium with it. The special Yamaha tool does work but an allen key has a radius at its bend that prevents it transmitting enough force to the spacer. You can replicate the Yamaha tool by fitting a piece of 4mm round steel into a cross hole in a piece of 8mm round steel.

The frame and engine numbers are TY250C (1976 model). I am guessing from your spelling of tyre and seeing the snow on the ground that you are from the USA or Canada, so the colour schemes of the bikes sold there may have been different to what they were here, but here in Australia the colour scheme for the TY250C fuel tank and exhaust heat shield was the same as your bike. Yes 21" is standard for the front tyre. Your bike has been fitted with the optional trail-riding footpeg kit that locates the pegs much more forwards than the standard trials footpeg location. It probably had the optional trail-riding seat fitted also and since removed The footbrake lever is home-made. I will go looking for photos of the standard C model

if nothing else is changed, lengthening the swingarm increases the front rear weight bias (heavier at front). Depending on where the new bottom shock mount is, rear suspension travel can be retained or increased.

Being 360mm they are commonly used on those models. They are quite stiff in the damping and so are not considered to be among the best for trials competition, but are reliable and long lasting and the action can be improved with internal mods.