ty 250 mono aftermarket parts

Got a technical question? Ask it in here.

Moderator: Moderators

Ferretflasher
A grade participant
A grade participant
Posts: 102
Joined: Fri Nov 24, 2006 7:45 am
Location: grimethorpe, UK

Re: ty 250 mono aftermarket parts

Postby Ferretflasher » Thu Jul 21, 2011 7:56 pm

So what model is it? Mr Scarlett insists that the only worthy Yam is a white one .... that makes it the 59N & 3BA types. Mind ... he did get special bits direct from Mitsui ......!! I have a rear shock that is some 20mm longer and this does sit the back end up higher, once I have fitted new piston to engine, I shall be able to see what it does! The DeCarbon rear shock is very difficult to rebuild as we know but looks like someone has done it with mine cos it has a tyre valve on canister and so can pump it up with a MB shock-pump if necessary.
Mine are Pinky's ......... very pink ......... !!! A 3BA in drag and a proper 4AJ ex MA.
Strange one on our UK eBay at present, alludes to be un-used for last 21 years but its a S with steel tank and all those frame lugs etc that clutter the bike up.



FM350
Expert participant
Expert participant
Posts: 488
Joined: Thu Apr 14, 2011 7:04 pm
Bike: Fantic
Club: Otter Vale

Re: ty 250 mono aftermarket parts

Postby FM350 » Fri Jul 22, 2011 3:28 am

Not quite sure if bikes built using very special Japanese works parts can be compared to modified stockers? Think the bike I have is fitted with a more modern shock from another machine, as the stock ones require machining to make them rebuildable and never seemed to perform that great anyway.

Interesting thing that related to the TY is that on the works supported machines, they had much larger capacity air boxes fitted, which I would think really is a must to help increase torque, after the motors have been modified to rev higher. Have seen one of these and it does look quite a bit bigger than the stock part, and I would imagine works very well.



brownie
TA Supporter
TA Supporter
Posts: 146
Joined: Wed Jan 14, 2009 10:46 pm
Bike: Bultaco's
Club: denman
Location: armidale. nsw

Re: ty 250 mono aftermarket parts

Postby brownie » Fri Jul 22, 2011 10:20 am

Here is a photo of the bike that started this topic with its after market airbox
I bought the bike off Peter (dad) and reconditioned it but it never ran any good with the OKO so I went back to the TK which it ran well with.
It was a nice bike to ride after I lowered the footpegs, miles ahead of the TLR200 that I had, I have since sold it mainly because of the brake being on the wrong side compared to my Bullies.
Ross



Ferretflasher
A grade participant
A grade participant
Posts: 102
Joined: Fri Nov 24, 2006 7:45 am
Location: grimethorpe, UK

Re: ty 250 mono aftermarket parts

Postby Ferretflasher » Fri Jul 22, 2011 6:23 pm

It is well known that the stock air box and that silly rubber tube are rubbish and strangle the air flow, in my way I have plans to make mods to the air box but its clear that the tube would be still a limiting factor. I have looked at the modern GG & Beta boxes and these have significant volumes and minimal flow losses. The early Fantics were about as bad as they could ever get and the introduction of reed valves made things worse. When a modern reed valve engine is reving hard the inlet depression takes a massive gulp of air and any impediment will sap its power and ability to rev cleanly. So the Yamaha is well handicapped with the rubber tube.

Anyone care to post a photo of modified box and tube?? Thanks Brownie, given me food-for-thought ...... !!! :wink:



FM350
Expert participant
Expert participant
Posts: 488
Joined: Thu Apr 14, 2011 7:04 pm
Bike: Fantic
Club: Otter Vale

Re: ty 250 mono aftermarket parts

Postby FM350 » Sat Jul 23, 2011 6:59 am

Cant see there is any way to modify the stock TY air box, as there doesnt seem to be much space to make it any bigger? The works type ones were quite different to the stock ones, and utilised every scrap of space available to increase volume. OKO carbs work very well on the TY mono, but they must be carefully set up for each specific bike, and may not work very well if not set up right?

On the TY the very restrictive intake and exhaust systems, compound problems caused by a cylinder which seems to have been designed for mx/enduro use, with very large area transfer and intake port ducts, which result in very sluggish gas flow at lower engine speeds, which is the main reason for lack of throttle response, and any number of weird and wonderful modifications which seem to be intended to give the bikes a little bit more go.

I know someone who has a works type cylinder, which was used on the magnesium crankcase 6 speed twin-shock bikes, and has this fitted to a TY mono bottom end. Totally transforms the bike, and makes it into something that seems very competitive indeed. Port dimensions are a lot smaller than the stocker, even though the capacity is larger, but Yamaha would I imagine have opted for the very low tune stock parts, to make the bikes more reliable and easy to ride for total beginners.



brownie
TA Supporter
TA Supporter
Posts: 146
Joined: Wed Jan 14, 2009 10:46 pm
Bike: Bultaco's
Club: denman
Location: armidale. nsw

Re: ty 250 mono aftermarket parts

Postby brownie » Sat Jul 23, 2011 9:19 am

A bit closer look at the airbox it was made of fibreglass and used a standard filter element, the outlet of the airbox was elliptical with a short offset stepped carby connector, a pretty good low restriction design for the allowable area



FM350
Expert participant
Expert participant
Posts: 488
Joined: Thu Apr 14, 2011 7:04 pm
Bike: Fantic
Club: Otter Vale

Re: ty 250 mono aftermarket parts

Postby FM350 » Sun Jul 24, 2011 7:18 am

That air box looks quite like the works type ones, which are also GRP..........is yours made in Japan I wonder? Lots of special parts for the TY Yam's were made by manufacturers such as Kato, who I think used to work pretty closely with the factory.



brownie
TA Supporter
TA Supporter
Posts: 146
Joined: Wed Jan 14, 2009 10:46 pm
Bike: Bultaco's
Club: denman
Location: armidale. nsw

Re: ty 250 mono aftermarket parts

Postby brownie » Sun Jul 24, 2011 9:17 pm

It was a Jap import and I think all the modifications were done in Japan;the airbox, shortened inlet,later piston?,Kato silencer, head work, weight removed from the flywheel,remote canister shock and maybe more that I didn't notice
I don't think it had been used as a Tokyo commuter.



FM350
Expert participant
Expert participant
Posts: 488
Joined: Thu Apr 14, 2011 7:04 pm
Bike: Fantic
Club: Otter Vale

Re: ty 250 mono aftermarket parts

Postby FM350 » Mon Jul 25, 2011 7:08 am

I get the impression that nearly all the mods carried out in the 80s on TY Yams in UK, simply copied what had already been done in Japan. The Kato silencer for instance looks to be almost exactly the same as those sold in the UK by John Shirt and Mick Andrews. However all these mods are not likely to work that well with the stock air boxes used in the UK, and not sure whether the improved air boxes were ever available in the UK?



Ferretflasher
A grade participant
A grade participant
Posts: 102
Joined: Fri Nov 24, 2006 7:45 am
Location: grimethorpe, UK

Re: ty 250 mono aftermarket parts

Postby Ferretflasher » Tue Jul 26, 2011 4:48 pm

OK I am on with it asking my contact in Japan what he could find out regarding any trick parts still hidden away so we have to wait on that one. The cost to make any would be prohibitive given that less than 10 would be sold ... eventually .... !! To make these would be possible ... if I were any good at making a wooden mold and laying-up fibre-glass etc but I'm not .........!! Now if anyone has an old works air-box in the shed / garage / workshop .... then please find it out and post a detailed photo, it will help to produce the mold I will eventually knock up !!! :mrgreen: :mrgreen:

Anyway what can be done is to modify your engine, fit a new filter and minimal filter support / top piece from the latest 4AJ's , Boyesen reeds (those stainless reeds just kill the intake velocity ) and a new Pro-Monty exhaust & silencer ... and the old mono then does begin to perform. Fit a modern tubeless rim & rear tyre, 4-pot front brake, set the carb up and it then does become an effective tool. Now I'm not a good rider, I can ride like a total tool ... but when I'm in the mood, I can blitz many a rider on a modern bike (only in my class of course) and any 5's are simply due to rider error, not the bike!!

The more I ride the more I enjoy it, but its only good for club trials and a few selected nationals, absolutely no use for championship rounds .... so don't get too excited cos it wont do the technical stuff !!

Keep looking for that works air-box folks ........... its priceless at the moment !!




Return to “Technical help”

Who is online

Users browsing this forum: No registered users and 6 guests