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Re: ty 250 mono aftermarket parts

Posted: Sun Oct 07, 2012 7:47 am
by Ferretflasher
OK update on progress. Most work done and only remains to sort timing out, as previously stated the IT crank keyway is at 5 oclock position when piston TDC so that's where coil needs to be. The coil pictured (thats the supply coil, not the trigger at 4.4 ohms) was actually a poor scrap coil with only some 170 ohms impeadence rather than 250 ohm at it should, so this pictured coil was changed. Anyway got it going with no bother ......... and what a difference !!!!!

Certainly revs cleaner and the pick up is instant (well more instant than standard) and there is very little over-run on a closed throttle, the standard motor does take ages to decelerate so response is much much quicker. One point I did fall 'dummy' to was the odd noise the motor was making, I thought was a rough clutch bearing as it would 'whine' quite loudly. Turned out to be lack of barrel fin dampers, those bits of rubber that prevent the alloy fins from 'ringing', fitted 5 new dampers and now super quite. Still need to replace the standard steel reed valve petals with composite type petals to give it more umph!!

Have yet to ride it in a trial but work once again spoils an otherwise promising trials career !!!

Whats it cost ?? Well crank & flywheel from eBay (USA) cost some $80 (USA), new mains, gaskets and consumables cost about $55 (USA) big dollar item was Birkett 70mm Wiseco forged piston this was about $275 (USA) plus the re-bore costs $75 (USA) so actual spend up-front was $485 (USA) so approx 325 GBP! Hidden costs were parts laying about in chicken shed and in cellar plus my lathe work.

Anyway it is possible to make a super smooth short-stroke motor for a Pinky Mono just using an IT250 crank-shaft .... just make sure you buy the flywheel and ignition stator back-plate while you is at it !!
More later when I have ridden it.

Re: ty 250 mono aftermarket parts

Posted: Thu Dec 20, 2012 4:21 pm
by Ferretflasher
Hi there late night stalker .... latest 'blog' offering. For those interested, I rode first trial last weekend but with timing a mile out. Referring back to photo above, I now run with stator back plate in next slot up with trigger coil virtually at 5 oclock position, ie more advanced. It now certainly lives and revs like a modern bike with the power more instant. I added some fibre 2-stage Kevlar reeds to the inlet, those stainless reed petals are pants and kill the intake velocity making for slow response.
So as a tuning method and exercise I can fully recommend the short stroke option to improve your mono. Birketts piston mod was most difficult to overcome with it being necessary to machine head down to put combustion chamber some 8mm further down the bore (giving me back 7mm squish). Second most difficult was to machine barrel base down some 4mm in order to get everything back in place a BDC.
Thereafter it was a case of just making everything fit proper. Extras I do are always personal like the stainless exhaust seen on eBay, use very light gearbox oil (30 grade), fibre reed petals and open up the airbox lid to aide breathing.
Still has all those virtues of the mono, good chassis, Jap quality in engine build quality and 1/2 decent chassis.

Next little project is the 350 lump I have acquired and compared to my usual stuff this thing is huge. Massive flywheel and massive piston all in a chrome bore. Problem I now face is finding a 350 TY mono piston, just dont see them anymore so over to you downunder, any info finding a new 350 piston most welcome.

Re: ty 250 mono aftermarket parts

Posted: Sat Dec 22, 2012 4:16 am
by Guy53
I had a TY 350 a couple years back, but wanted a 250 so I sold it to a guy who told me at the time he had bought 2 piston from a guy in England that made a batch. So i gave im a ring yesterday to check if he remenber the name of the seller, he does not remember but told me he had the info from either TY Trial or trial and trail UK. Hope this will help.


Re: ty 250 mono aftermarket parts

Posted: Sat Nov 30, 2013 2:44 pm
by RiverRight
Ferretflasher wrote:Back to the thread for Lords sake ......

which is "FF's blog with commentary by FM"?
No. Hang on. Its supposed to be about "ty250 Mono Aftermarket parts"
Can anyone refer me to places I might purchase such articles.
And I'm in Australia, south coast NSW, not the midlands, or cotswolds, or bloody dales.

Re: ty 250 mono aftermarket parts

Posted: Sat Nov 30, 2013 4:21 pm
by David Lahey
There are a few aftermarket parts for the TY250 mono, but different parts are made by different people. What parts are you after?

Re: ty 250 mono aftermarket parts

Posted: Sat Dec 07, 2013 5:02 pm
by RiverRight
David Lahey wrote:There are a few aftermarket parts for the TY250 mono, but different parts are made by different people. What parts are you after?

I am renovating a ty250 mono R/S (53y Aus ADR compliant) from paddock basher state to ridable as an explorer/playbike and later registerable as a local commuter.
I have spent considerable time on the fuel system (filthy) and it now starts but wont run for long.
Looking at all/any parts available.
I suppose I have a more current need for:=
. chain roller/guide/guard
. plastic fuel tank (to replace steel POS)
. rear wheel ( or rim & spokes)
but I'll look at anything that fits.

afaiac bike will never be used for competition or show.

Re: ty 250 mono aftermarket parts

Posted: Sat Dec 07, 2013 6:25 pm
by David Lahey
Rear rim would be easy to buy new or second hand. Are they 36 spoke?

Rear (Z) spoke sets here: ... shock.html

The TY mono plastic and steel fuel tanks are a pretty unique size and shape. Haven't seen anything from a different bike fitted to one yet. There are fibreglass covers made to hide an ugly one and new fibreglass tanks are available but expensive: ... -unit.html

maybe if you measured up the rear wheel you might find one from something else fits (for a lot less money than rebuilding your wheel)

chain guide: ... -Mono.html
chain roller: ... -Mono.html

Re: ty 250 mono aftermarket parts

Posted: Sun Dec 08, 2013 9:41 am
by RiverRight
Rear wheel is 32 spoke.
Thanks David. I was onto tytrials, BJ racing and Sammy Miller.

Do you think I'd be able to fit an "OEM" plastic tank to replace my steel one.
Would I have to modify the frame (cut off "C" brackets?, and/or drill hole for new fixing bolt?).
Is there a good, preferably Australian, place for scoring OEM parts on the net, or perhaps on the phone?

Re: ty 250 mono aftermarket parts

Posted: Sun Dec 08, 2013 1:47 pm
by David Lahey
Best Aussie Yamaha OEM supplier I know of is Gladstone Motorcycles
best international Yamaha OEM for old trials bike parts I know of is John Cane TYTRIALSUK
France Trial Classic is pretty good for Yamaha OEM too but more expensive
There are a few Japanese wreckers on the web. Heres one
Pretty sure there are no more new plastic Ty mono tanks in Yamaha's parts inventory
The plastic tank model sold well in the UK so eBay UK would probably be good to watch
No idea about swapping tanks. The only people I know with tin tank TY monos still use the tin tank.

Re: ty 250 mono aftermarket parts

Posted: Sun Dec 08, 2013 1:50 pm
by David Lahey