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Re: ty 250 mono aftermarket parts

Posted: Sun Jun 01, 2008 5:15 pm
by Stork955
Needle position? Usually 3rd groove down. 48 sounds OK for the slow jet, early TY's are 50.
Also, when checking the float level you should tilt the carb slightly so the full weight of the float doesnt compress the spring and give a false reading (this would make the float too high and give a rich mixture). After all that it doesnt sound carb if it still runs with the slow screw right out. Is there freeplay in the throttle cable?


Re: ty 250 mono aftermarket parts

Posted: Sun Jun 01, 2008 8:54 pm
by dad
I checked that the cable has enough freeplay as it shuts the slide right down after screwing the idle adjustment screw right out.

Needle was in middle position now in top slot in an attempt to lean it out.

I'll try resetting the float again and set it too low to see if the carb leans out.

I don't think that I mentioned that this is a Teikei carb.

If I can't fix it soon I'll try to source a mikuni to suit it.

I'll let you know how I get on



Re: ty 250 mono aftermarket parts

Posted: Thu Aug 21, 2008 10:56 am
by OKOAustralia
Hi Dad,

We have successfully fit the OKO 3030B flatslide to the TY250R without any modification. The results are very noticeable. Flatslide cleans up the engine response considerably compared to the Teikei and/or Mikuni.

OKO Australia

Re: ty 250 mono aftermarket parts

Posted: Thu Oct 15, 2009 5:16 am
by Ferretflasher
Hi there from Blighty,
I know this is an old thread but I have started my own project 'Pinky' and I too intend to fit a Kehien or an OKO 28mm carb to the TY Mono. I believe the old OEM JK carb to be sub-standard and it was common practice here in the UK to fit Mikuni's all those many years ago.

The inlet manifold mod was also done for many top lads by Mick Andrews, he took the standard barrel and shortened the whole thing, machined back the fins and welded the reed block back in as in attachment. The barrel was also bored out to 270cc and it generally made the whole thing a bit more responsive and torquey. This was around 1987>1991 to my knowledge and needed a good carb set up and run on old 4-star high octane petrol. The ports were also modified to put a bit more air/fuel into the back of the barrel and so prevent the pinking experienced by Ty's and similarly on 315R's that were not ported. Additionally the barrel was skimmed top and bottom ever-so-slightly to give more crankcase/scavenge compression and piston compression. Unfortunately with the advent of unleaded fuel it all went wrong and they pinked even worse until super-unleaded came along. Now we can use Shell V-Power or BP Ultimate/Ultra to fuel the Yams. Even so they were and are a proper modified engine and a bit rare these days.

I now have an ex-Mick Andrews 270 motor and a good frame, so I can begin to assemble a good Pinky for next years use.
How do you folks in Aus manage to get hold of those Z spokes, they are very rare here in Blighty and only Birketts appear to have a small stock. Any known suppliers over there???

Re: ty 250 mono aftermarket parts

Posted: Fri Jun 10, 2011 6:56 pm
by Ferretflasher
Old thread time TY mono is alive and kicking, has been for last 18 month, use it in UK ACU C class rounds (air cooled mono class) and its still an effective tool in the right hands......! not always mine I hasten to add. Nigel Birkett is still the place to get stuff and TYTRIALS in Manchester plus JK Hirst as a 3rd resort.

I have been playing with the inlet manifolds and find that the shortening process is not too hard, just need the right equipment. Firstly, find a good barrel that has a near standard bore (then it could be rebored at a later date) and assemble a hacksaw with 18tpi blade, large coarse (bastard cut in english - that's its name) file and a medium smooth file. Objective is to take out approx 12 mm of inlet, so mark it out and cut hand as below.
Start sawing here.

Finish cutting with these 3 pieces.
Discard centre piece.

File weld prep onto edges as shown

The welder needs to be skilled obviously .... the top of inlet is welded from the inside, the other 3 sides are welded from outside. So long as it has plenty of prep (chamfer) then the joints will fill-in nicely and the whole inlet must be sealed with no gaps. Just make sure your welder is sober and good at his craft.
More later.

Re: ty 250 mono aftermarket parts

Posted: Sat Jun 11, 2011 8:21 am
by FM350
Not sure that even a highly modified TY Mono is likely to be comparable to a stock 245 or 305 Fantic, and always seems a bit strange that people put so much effort into modifying the TY Mono, when a bog standard Fantic is so much better?

Flat-slide carb is a big improvement though, but the TY intake hose is a little short, and on an OKO or Keihin its a good idea to relocate the air screw and throttle stop on the opposite side, as they are hard to get to otherwise.

Re: ty 250 mono aftermarket parts

Posted: Sat Jun 11, 2011 5:31 pm
by Ferretflasher
Hi FM350, in answer to that I would say first and foremost.....that TY parts are so much easier to obtain ..... ebay is generally awash with them and secondly ..... the Fantic is a wide beast compared to a Yam Mono .....take that tank & seat combo .... you have to admit its a bit on the bulky side !!
Secondly the way the Yams were built makes them better IMHO than a Fantic ... I have had both and the Yam quality wins every time .... in my time I have come across 2 Fantic's that needed new big end's fitting ............ I have NEVER come across a Yam that need a new big end !!
Dont get me wrong, yes the Fantic's are good but I would argue the Yam's are better to ride, maintain and keep on going.

Next area to concentrate on is that TY intake hose ..... its all wrong ...... too long & narrow ..... too restrictive .... air box volume too small etc etc.............

ps cost of that barrel so far;
buy 15 GBP
modify 0 GBP
weld 10 GBP

job done for total 25 GBP ..... and the liner is perfect ..... no expensive chrome - nikasil plating required here !!!

Re: ty 250 mono aftermarket parts

Posted: Sun Jun 12, 2011 10:45 am
by FM350
The TY Yam is probably a good choice for easy club trials with air-cooled mono class, but its a dead duck for more serious competition! M8 of mine has won the air-cooled mono class in the UK classic championship a couple of times, riding a highly modified Yam Mono.............but when he changed to a 300 Fantic TS, he felt the TS bike was an awful lot more capable in every way.

Re: ty 250 mono aftermarket parts

Posted: Sun Jun 12, 2011 6:35 pm
by Ferretflasher
I don't deny the 300 TS Fantic is a capable weapon but I could never really get on with a TS machine simply because of those rear shock top mounts being in the way ..... I simply dont know how people manage to ride a TS without developing a bad case of Rickets ! I rode a 240 PRO for a few trials and a Honda 250 TLR for a year but both gave me back ache and a pair of sore knees. In the end I had to abandon TS and went back to mono's, rest is history !

The recent 300 Fantic's I have seen at UK Classic Champs are very very trick indeed bristling with handmade exhausts, titanium parts and modern forks, not much change out of 3000 GBP at the very least. Anyway don't underestimate the Yam Mono, UK national champ Dan Thorpe still rides his dad's old Hamilton Yam Mono and will blitz anyone on anything on any section !
But as you rightly say for clubmen they are perfect but I don't agree they are a dead duck for anything serious, part of the appeal of old bikes is that you can still better your mates riding modern machinery on an old shed .... and they DONT like it up 'em when I beat them !! \:D/ \:D/ \:D/

Re: ty 250 mono aftermarket parts

Posted: Sun Jun 12, 2011 7:44 pm
by FM350
Dave Pye didnt seem to have many problems riding his 300 Fantic TS in the SSDT this year...............cant remember his exact finishing position, but I think he beat half the entry all of whom were on modern bikes! A lot of people fit TS bikes with poorly designed shocks, which simply dont work very well and this is something that will certainly compromise performance.

Phil Wiffen who last year won the Normandale twin-shock championship on his 300 Fantic, and didnt have any special Ti or magnesium parts fitted, and neither does Dave Pye. Many so called "P65" bikes do have these type of parts fitted though, which means a competitive bike costs around £10k to build currently.

The only person in the UK who has had any sort of success with the TY250 mono in recent years is Chris Koch, who has a heavily modified Mono motor fitted into a special monoque TS frame made by Jon Bliss. The main reason Chris has done well on this though is down to the fact that he is a very good rider, as the Yam motor is certainly lacking when compared to Fantic power.