feetupfun

The body of the silencer is the same (250 vs 175) but the inlet pipes are different length and shape

My WES end mufflers on TYs are quieter than stock too

Modern internals vs modern forks makes no difference, but fork visuals are important to me. As for the motor, there are potentially important advantages from using a later motor, such as less weight, less width and less length

The last video looks like how a standard Ty250BCDE in good condition responds. The standard motor has a strong flywheel effect that most people didin't like when they were new and the same sentiment applies even more nowadays with grippy tyres and good rear suspension. Lightening the flywheel is a very common mod to these engines. Another beneficial mod to make them more snappy is to fit a good modern ignition.

How about a photo of what you are talking about

Make or find a puller that doesn't damage the gear teeth. The usual two or three arm puller will likely not be able to pull hard enough and will damage the teeth. A suitable puller will pull against the back side of the gear without touching the teeth and it will pull on the whole surface, to spread the load better. I made a tubular puller that is in two halves. There are discussion threads on this forum that cover this job in detail. I can do photos again if the thread has disappeared.

I will be interested to see if you still think it is easy to work on after you get the primary gear off

you've probably sheared the flywheel timing key

I saw the other side via some other photos which were posted on Facebook. I saved the photos and will post them up soon

It's normal for a 4 stroke to have a strong on/off effect with the throttle

My 348 used to have a positive pressure inside the clutch casing. I was never sure that it was a crank seal causing it though because I cleared out the gearbox vent (which was blocked) at the same time that I changed the crank seals.

Despite being Australian, I've successfully interpreted billyt previously and will now have another go: If you ride those three trials with the strange names, the terrain at these trials will suit a trials bike with a fast throttle response

https://www.tyoffroad.co.uk/store/p40/TEMPORARILY_OUT_OF_STOCK.__FOOTREST_LOWERING_KIT_(BOLT-ON)_TO_FIT_HONDA_TLR200._(REF.H025).html

What did the gearbox oil look like?

Not a big deal. A common sight on a trials bike that has ridden a wet trial. I would just fill it with fresh oil. Next time you ride in water it will probably do it again. Sometimes wet oil affects the action of the clutch but if you didn't notice, then I guess yours doesn't get affected.

Easily proven, as I did for myself, by putting a paint marks on the tyre and the rim. Go for a ride starting with a straight valve stem. Look at it after the ride. See valve leaning over and pulled hard against one side of the hole and yet the paint marks are still in alignment. I admit to doubting that this could occur so that's why I did the experiment

Yes the tilting valve stem on a trials wheel is often misdiagnosed as tyre slip. Sometimes fitting a different brand of tube in the same tyre will stop it happening

Sounds like you are thinking of a 5 speed Bultaco engine rather than the Yamaha TY250 motor he is working on.

I love the clutch spring story. It reminded me of when I was working on a TY250 kickstart a couple of years ago. The tiny spring that pushes on the ball went "zing" over my right shoulder at high speed and out the tilta-doorway to somewhere on the rough ground behind my workshop. I looked for about 10 minutes but they are tiny and it would have been coated in dirt so I gave up. A few months later my wife (who knew about the spring incident) gave me a metal detector for my birthday. Well I had a ball finding the most amazing variety of small metal objects out the back of my workshop, but no kickstart spring. I was telling a bloke at work about the spring story and was pleasantly surprised when he later gave me one of those springs that he had ordered along with a swag of other TY parts for a bike he was fixing up. This searching business in a crankcase also reminded me of when I first pulled the cylinder off an OSSA motor. The cylinder studs are usually rusty and if you do it the normal way up there will always be rust particles fall into the crankcase as the cylinder comes free. To avoid this, I hoisted the bike up in the air, upside down, so that when the cylinder moved away from the bottom end, the rust would fall away from the crankcase

I must say I'm impressed with your workmanship, especially the fuel tank. Making stuff yourself is very satisfying. I've wanted to try making an aluminium trials bike tank for a while and seeing yours is motivational. Back on the rules. Over the ditch, we've got a manufacturing date cutoff for "twinshock" bikes (1 Jan 1987) which would be a problem if you wanted to ride that bike competitively over here. Apart from the rules there is always the "pub test". Not sure if this happens in other countries but it definitely is a thing here. Years ago TV reporters doing an opinion piece would posit "what would the man in the street think?" The official legal term is "what would a reasonable person think or do under the circumstances?" But the "pub test" sounds lots better to me because with any luck, she or he will have had a few drinks and be quite prepared to share their thoughts about any topic. I haven't had a drink tonight so I'm probably not the right person to be sprouting off one way or the other.

before you go to the trouble of splitting the cases, try washing the suspected roller out. First degrease the crankcase (so that the steel surfaces aren't sticky) then set up the bottom end with the crankcase mouth facing downwards and with an old bedsheet or something similar suspended loosely underneath and wash the crankcase out with a low pressure water jet (garden hose). If something gets washed out it should get caught by the bedsheet. Spray everything inside the crankcase with WD40 as soon as you are finished to get the water away from the metal. Even easier would be to use a parts washing machine if you have one

Oh yeah - gold rims are fantastic

I posted a photo when I did it years ago but finding that might prove difficult and I'm not ready to pull the tyre off just yet to take another photo. Maybe I can describe it better. If that doesn't work I'll do a sketch. The bike is on a stand with the rear wheel fitted, but with no tyre fitted to the rim and no chain on the sprockets. I cut a circumferential groove in each bead seat with an angle grinder fitted with a 2mm wide cutting disc. I spun the wheel by hand to start it spinning then started cutting and this kept the wheel spinning. I cut one groove about 2mm deep in each of the bead seats. The rubber on the surface of the tyre beads deforms into these grooves once the beads are up on the seats (40psi and WD40 to seat the beads). This keying effect prevents the tyre bead from slipping sideways back off the bead seats when the pressure is let down for riding. Yes there is a tube in there - it is a TY250D tube type rim and a Michelin X11 "tubeless" tyre

A modern Sherco/Scorpa branded as a Yamaha is a quite appealing idea to me. When the Scorpa SY250 came out in about 1999 or 2000 I remember seeing a photo of one in Japan painted up as a Yamaha and went along to the local Yamaha shop with a photo of it and asked when I could buy one of them (I knew what it was). They said you can only buy one from the Scorpa importer and it will be decorated as a Scorpa. I never bought an SY250, despite it having the Yamaha motor. I don't think the trials bike marketing people realize the pulling power of the popular and well-respected brands (like Yamaha) for old blokes like me.