Ty 250 Twinshock Problems?

[marky g]

Right, after musing over converting my 250 mono into a twinshock I've decided not to bother, I want to ride some of the larger twinshock rounds with my mates next year and the converted mono wouldn't do.

My Gas Gas is up for sale and I've decided to look for a TY250 T/S, I've heard lots of negative things about the yam but it's about the only T/S I would like to own within my budget......what are the bikes bad points? what year is best?.

Another + point is the prices of the bike seem quite good, a good base example can be had for as little as

[woody]

Not as bad as they are made out to be. I rode one about 5 years ago and another 3 weeks ago. Both standard examples and I've also owned a standard Yam framed Majesty. Brief impressions of the TY were;

Engine flat as a pancake, same on the 250 Majesty I had, but I would think most of that is down to the flywheel weight. The pickup off idle is really slow so if you need a quick burst of acceleration from nothing to get up a step, bank or whatever, it isn't there. It takes time for the power to come in so you're holding onto the throttle longer. This can in turn mean you're still accelerating when you're past the ideal point to shut off and roll over the crest of whatever it is you're going up. The inertia of the heavy flywheel can also have a negative affect at this point and keep the bike moving instead of it deccelerating quickly enough when you shut off. OK, this is generally on harder sections so isn't much of an issue in most classic events but something to be aware of if you're considering throwing it at harder stuff. The slow response also makes it difficult to pick the front up in flick turns.

I took the flywheel weight off my 250 Majesty and it livened up considerably, along with running the timing at 3mm BTDC. Engine was much more responsive and changed it from being a 1st gear only bike to being able to use 2nd as well as it would pull 2nd off idle. It wouldn't with the weight on. If 2nd was in use and you shut off, no way would it pick up again up a climb, the engine would die. You can of course 320 them but they are a real bugger to get right, especially to make them rev right out. Loads of grunt though and pull any gear. There are 270 kits available using 72mm pistons and this actually makes about 264cc - same size as maximum oversize so not really sure what the difference is and why it's called a 270 kit. Craig at Yamaha-Majesty UK does this conversion but also does some porting work with it for more torque.

Chassis is nicely balanced, it steers well and with the engine livened up feels lightish and flickable, although the engine is actually a heavy lump. Front forks are too soft and are under sprung and under damped, ok if you are light I guess but no good for me as they were standard forks on my Majesty. I could never get them to work 'normally' like my Ossa forks, they bottomed and topped or locked up with too much oil, could never get the happy medium - nightmare. Modifying the damper rods sorts the damping if you know how to do it, I didn't and it wasn't for the lack of trying.... better damping and stronger springs give a better action, I've tried a bike with this mod and they worked very well (one of Craig's Majesties) Decent rear shocks on the back are probably all that is needed. Angling them like a Majesty may improve things, I don't know, there was a whole lot more done to a Majesty back end than just angling the shocks.

Clutches are ok, you shouldn't need to use it much but with the flywheel weight off it pays to cover it just in case it stalls too easily when trying to plonk it. Brakes are no better or worse than other bikes from the same era as they are now 30 plus years old, some will have worn better than others.

So, my feeling was, only a couple of negative points which could be overcome and turn the bike into a reasonably competitive twinshock. Not a Fantic beater obviously but more than able to hold it's own with other bikes from the same era and easily capable of tackling the sections in the Miller and Normandale series.

A genuine twinshock and much better bet than the converted mono route. They really are a nothing bike with no real point to them and would you be happy riding it when you know that everyone else in the queue at the section is thinking just that.

[jon v8]

As Woody said really,except I would add that with a decent rider on they are more capable than many think.You only have to watch Barry Barthorp in action on his VERY well used,standard example,rarely touching the clutch - to see what they can do.They are quite low and the engine is quite wide,they can seem like a bit of a plough in narrow bits.The engine is better than the Beamish as I remember mine,and there is loads you can do to pep them up.As Woody said they pick up quicker with the weight off the flywheel,but I've stalled mine a few times since removing it.Toying with the idea of refitting half of it and see if its a good trade off.

They were very well made and everything is available to keep them going,and they can be made to look very smart with the new tank/seat units and alloy exhausts etc.

Oh yes - they are bloody reliable too.

[marky g]

Cheers for the detailed reply Woody / Jon, sounds like there's a bit of work to do to make them tick then, still should be a good project.

My mates got a well sorted Bulto 250 with a 175 frame, sounds good and he's rides it well but the bikes does nothing for me, Fantic 240's are nice (I've had one years ago) but they seem to hold good money, TLR 250's are lovely but I just can't afford one, so a Yam it's got to be

Just a side note Woody, I'm taking my mono out to 270 (actually 261 I think) apparantly they use a piston out of the 250 T/S!!! don't ask me what all thats about but it's the only route I can go down now as my mono is already 1mm oversize.

Edited February 6, 2010 by Marky G

[andy m]

Re your 270 conversion. I believe they use an IT piston, I had a pinky that had the conversion it also had the shortened inlet conversion that is a common mod with the 270. If you do both be careful who you get to do it as if they aren't done right they ride like a bag of sh*t as mine did. I found a std 250 top end and went back to that.

Edited February 6, 2010 by bo drinker

[jon v8]

Here you go; http://www.trialscentral.com/classifieds/d...php?siteid=7196

[famousamos]

Check this out, story on my TY by Tony Down

http://blackcatvintagetrials.com/2009/10/30/freds-fancy.aspx

Fred