I bought a ty 250 mono today and am trying to work out what year it is, and someone has been modifying the cylinder i'll post a few pics let me know whats been done and why??

At a guess, 91 pink yam, the inlet was shortened to make it run better

Was a standard mod along with a 270cc conversion.

May have an earlier rear wheel on it, WES silencer

Chain has dropped off the chain tensioner !

Edited May 19, 201214 yr by shedco

Before I write anythng else - do you realise the chain is wng side of the tensioner roller, it should be above it.

I have seen a couple of these Yams with the modified inlect tract in about 1990 - 91. I don't know who did the mod or if the capacity was inceased. I can't remember the names of the riders but they were decent / occasional win at centre level riders in the North Yorks / Richmond area. The bikes pulled and gripped really well. They seemed able to pull 3rd gear where a standard Pinky could only use second and found grip a lot easier on the clay / limestone sections common in that area.

Cheers

I only bought it about 5pm today and had just got home with it and got it off the trailer and took a few pics.. how do i tell if its a 270cc??

take the head off and measure the cylinder?? what would the bore measurement be if it's a 250 or 270??

The front rim is stamped 90 and the rear 87 so i thought the rear wheel must have been replaced at some point.

how much of a differance does it make with the shorter intake?

Edited May 19, 201214 yr by hop blip and a jump

If it's a 270 it needs to be done right, they are more responsive, if wrong they pink badly and power is all wrong. There is hardly any difference between the 250 and 270 bore sizes, I had them side by side before now. I think a Yam IT piston is used. Google IT / TY bore sizes ??

Hello I had one done by Mick Andrews in 1989 on a white framed ty250r. He also put on a hand built silencer and altered the porting. The capacity wasn't altered on my bike as it wasn't very old when I had it done. I've seen similar silencers on eBay since. They were sealed unitis made of alloy that you'd have to cut open to repack. At the time all the ones that he converted had these silencers added

Edited May 20, 201214 yr by robb7610

I had one which the original and previous owner had had sorted by Nigek Birkett and carried what sounds like the same silencer. I don't know if it was ported or just carefully jetted, but was still a 250, it had no alteration to the inlet but it found grip where other Yams didn't. I sold it just before a class for these things became common - a mistake.

I gave the beast a wash, what do you think??

Looks genuine enough and a good basis to start building on. They are a great bike. Wish i had kept my old one which Mick modified to 270 ported and shortened inlet tract, custom silencer etc and she pulled like a train. Enjoy

It looks like its pre -pinky version... OK the engine cases may have been changed but pinky's had grey cases. and as Shedco says the back wheel is different (well it maybe the original ...).. pink trimmed ones had grey hubs.

Not that there is much difference. Other than the front brake set up of course( which may have been added later on this bike)... some late white ones had disc mounts on the forks even with the drum brake on!

Wes silencers don't seem too good on these bikes

270 over 250 is hardly any difference it's all in the porting and shortened inlet.

Edited May 24, 201214 yr by Rosey

Well spotted Rosey,

So to sum up, it may be a 1988 Ty 250 r model.

With a 1991 front end fitted & a pinky seat added.

I should have spotted it first as it is similar conversion i did to my

first mono!

Was a good bike rode better than the genuine pinky I bought after it!

I have a barrel like that that was apparently modified by John Shirt. It is also a 270. It rattles like hell when cold, but quietens up a bit when warmed up. I probably need to whip the top off and measure things to make sure all is well. I too would be interested to know what piston/rings to use if/when I need to replace them.

Pinky will have engine and frame number prefix 4AJ.

Earlier 250R is 3BA (i think)

A sad story here. The lad posting has bought my stolen Pinky. The engine had been sprayed black at some point and had my spare rear wheel fitted hance the doubt about the age. Its looks to have had a hard time over the past weeks since stolen and was far nicer when with me last. I dont think anyone would knowingly post a known hot bike, but £275 is rather cheap for a pinky.

I am collecting it tomorrow from its "new " owner as HS+J had sold it on.

A Gas Gas TX250(270 actually) and a Beta tr34 260 were also stolen amongst other things, but it looks like some progress can now be made.