feetupfun

The Wiseco DT250 pistons are slightly different-loooking to Yamaha TY pistons, but the skirt is the right length, the pin to crown distance is right, the window holes in the rear skirt are the right shape and in the right place. The rings are standard Wiseco (two thin rings that are flat top and bottom) and piston kits are reasonably priced. Bought through SERCO (Brisbane, Australia) While the Wiseco DT250 pistons work well in the TY250 twinshock, for the TY175 I prefer using PRO-X, which are made using the same alloy and manufacturing process (and look the same as) original Yamaha TY175 pistons and are also reasonably priced.

I've used Wiseco DT250 piston kits in the last two TY250 twinshocks I've had rebored (5 years ago and 1 years ago) and they have both been been fine since - they haven't rattled and everything fitted perfectly

They stop the bearing from moving out of position

Yes the exhaust comes off without having to move the motor but it is a bit of a trick Yes a removable hatch is a good idea if you are going to ride the bike for a few years. Please ask your friend what benefit come from using steel wool compared with mineral fibre. I'm just about to repack my 348 exhaust too and might give it a go.

I couldn't see any model ID on either of my KT carbies. They do have the Mikuni symbol (MIC) on the side of the slide casing. The Owner's manual calls the KT carby a VM26SC

If you can post a picture the carby may be recognisable to someone. If it is from a KT250 Kawasaki, it will be a snap to identify! I'll have a look tonight to see if there are any ID numbers on my KT carby.

Yes the Rev 3 carby is leaned forwards lots and a front down attitude makes it worse. If you do a search on the Beta Forum you should find hundreds of postings on this issue with many suggestions for how to avoid losing petrol out the overflows. It might even be a pinned topic. What is "1 1/2 to 2 1/4 air bleed"?

I have seen this problem in my friends 2001 Rev 3 and his problem was piston ring blow-by. Fixed with new rings. Hard to diagnose yours via forum postings though - yours may be stator failure. The stator problem can cause an effect very much like rich mixture above a certain RPM because the ignition cuts above a certain RPM, causing misfire. Standard carby settings are fine. Most people go through hours of changing things on the carby, only to find that it was not the problem. There was a good reason the float height was set low and you will find out why when you ride the bike more. Set the idle mixture screw to suit your bike. The standard setting or anyone elses setting is only a guide. You didn't list the pilot jet size and that is the thing that people commonly change.

Alan DT forks are not old enough to be eligible for pre-65 in the UK

Provenance is an important component of pricing old bikes for many people

I can suggest trying somewhere that sells parts for Chinese dirt bikes because I recently needed a fuel tank cap for my PW50 Yamaha and the local Yamaha shop told me the cap for the Chinese copy of the PW50 would fit, and it did, and it was very cheap, and from memory the cap for the TY250/350 monos is very much like the PW50 cap.

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).