feetupfun

From my experience those pressed steel caps are only fitted to the outsides of the crankwheels so they are not actually "stuffers" as such because they don't reduce the volume of the crankcase. Did yours have them on the inside ends of the holes as well as the outside ends? If you want there is no law against using stuffers in a TY250 so yes you can use cork or balsa stuffers. The usual sealant however is epoxy resin rather than varnish. I find the standard motor runs amazingly well without stuffers and some people even space the reed cage outwards to increase the crankcase volume so it may not be a good move to fit stuffers if you are not wanting to go out on a limb. Those steel caps may be there to provide some sort of streamlining of the crankshaft to reduce aerodynamic drag at high RPM. I would say that their presence or lack of presence is not something important for performance. Their presence is definitely a liability for the risk they pose should they come loose

MITAS are as bad as MT43

Sounds like they changed the cylinder casting and fork sliders at some point after 006798. There was also a change to a plastic base for the seat pad instead of steel at some point

Nigel this is what the Peter Paice TY250 frame sidecar looks like. If you are seeking current design philosophy for trials sidecars rather than what people used in the 1970s, Justin Gough would be a good local to talk to

From memory there is a set of dimensioned basic drawings in the MA M.O.M.S that show the size requirements for competition trials sidecars in Australia. Also pretty sure that Ron Chadwick (Brisbane) has a sidecar on a TY250 twinshock that you could probably arrange to measure up. Another one for a TY250 twinshock (further away though) is owned by Peter Paice (Newcastle NSW). Peter's TY250 that the sidecar fits is currently at my place in Gladstone so if it helps I could send photos of the attachment points on the bike.

That plastic bit should be inside the tube behind the snap ring. The right side tube in your photo is the correct setup

My OSSA also has the top mount larger than the bottom and it doesn't have an old sleeve still there

The drain holes on the fork sliders on that bike are at the side. Later sliders have the drain holes at the rear.

That is not very early but early enough to have the fork sliders they started production off with. Another thing that changed during production of the 434 model is the cylinder casting. The earliest production bikes have an un-finned section above the exhaust port. I've heard that production TY250A numbering started at 434-000101. Sorry I have no idea about title or MSO in your country.

Here are the footpeg and tank re-shape photos of the mrmikkelsen XL185s trials bike

PM sent

Medium silver metallic. There looks to be plenty of original paint there to do a match at a paint shop if you want it to be exact. The wheel hubs are the same colour as the frame. How early is the frame/engine number? I see it has the early type fork sliders.

I seem to remember he said he pushed out the inner steel bushes

I don't know what it is but it is a beautiful design and well-made

To have so little flaking after all these years, you have got a good one. One of mine on a 1975 bike is still perfect while another on a 1978 bike was terrible and had to have a liner fitted. From memory your bike is a 115 or 116 which may have the type of rear hub that came with a ferrous liner from new.

Before you ride it you will need to fit the frame braces that are missing in your photos. They connect the outside swingarm pivots to the lug on the rear edge of the cylinder head

Yes

New piston kits are available. They are usually in the manufacturer's catalogue as YZ250 or DT250 or MX250 rather than TY250. Wossner make a good quality piston kit for them. You may need to source a little end bearing different to the one in the kit depending on what conrod is in your motor.

Yes you can get parts

Yes, the 320 conversion requires a sleeve with a bigger OD.

I would think that using a ball hone in a 2 stroke cylinder would pretty much guarantee an uneven honing pattern, so there would be an unusual visual effect from the rings on the hone marks. New 2 stroke rings usually take 10-20 minutes of gentle operation to bed in, spread over 4-6 heat cycles. Unless you are seeing darkening of the bore surface due to ring blow-by, I wouldn't do anything except ride it.

Shedworks in the UK advertise that sort of tank for other bikes

fordigas, your NZ Yamaha 200 creation looks like it will be great fun and I can imagine it was great fun making it. Well done

No it won't arc across between kill switch contacts. It is low voltage and a proper kill switch is designed to do it's job. I've never measured any but I would expect it would be less than 30 volts. First off you need to test if the kill switch is actually working or not. I suggest you measure the resistance through it with both wires disconnected from everything else.

We have to use lanyard killswitches for trials competition here and popular lanyard kill switches are made by Leonelli and Jitsie and have a magnetic action https://www.google.com/search?q=leonelli+magnetic+lanyard+kill+switch&rlz=1C1GCEB_enAU911AU911&oq=leonelli+kill&aqs=chrome.3.0j69i57j0i22i30l3.11568j0j7&sourceid=chrome&ie=UTF-8&safe=active&ssui=on All my bikes require the killswitch to earth out the LT circuit of the HT coil to stop the motor. These kill switches I mentioned have two wires and either of them can be used to connect to an earth point. It's best to run the earth wire from the kill switch to an earth point on the main frame of the bike, to avoid sending current through the steering bearings, which could otherwise damage the bearings. Most people connect the kill switch earth wire to where the HT coil connects to the frame. Most people connect the other wire from the killswitch to the LT wire near where it connects to the HT coil.