feetupfun

Wasn't there another forum string about this a few weeks ago? Maybe have a look back because your Beta 4T symptoms sound a lot like the other person's. I've just added a link to the string. It started in 2012 but was active again a few weeks ago

Learn how to check the timing. You don't need to accurately measure piston position to check it is in the ballpark. Here's my suggestion: Take the plug out. Take the flywheel cover off. Find top dead centre using a clean object inserted through the plug hole. Make a mark on the flywheel rim in line with one of the holes that the flywheel cover screws go into, with the piston at TDC. Measure around the rim of the flywheel anticlockwise 22mm and make another mark on the rim. Get a torch and look at the points. Find the flywheel position where the points start to open when rotating the flywheel anti clockwise. It should be close to where your second flywheel rim mark is aligned with the screw hole you chose. If the points open within a few mm either side of your second flywheel rim mark then your problem is not your ignition timing.

If you are talking standard bikes, standard TLRs are about 10 years worth of bike development better than standard TLs. Where I ride, twinshock class trials machinery is pretty much carte blanche. With enough effort and know how, you can make a TL125 go just as well as a TLR, and people do. The performance limitations in our twinshock class come from having to have drum brakes, twinshock rear end and a motor that originally came from a twinshock motorbike.

no idea. It's a pain to do it too. I can only remember the number from one of my twinshocks. The rest I have to go looking with a torch. Maybe I should make a list. A friend of mine who also rides multiple bikes confessed last weekend that he just makes up the numbers each time "because no-one ever checks them anyway"

Sorry for not being Guy, but all over the world people remove three of the clutch springs on TY250 twinshocks to lighten the action

Frame and engine numbers on entry forms for trials competitions has been standard practice in Australia for as long as I can remember, but I don't think anything is done with the numbers

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.