ty 250 mono aftermarket parts

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Jon V8
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Re: ty 250 mono aftermarket parts

Postby Jon V8 » Thu Feb 02, 2012 11:38 pm

Ferretflasher wrote:Spoken to a local scooter racing guy other day and he thinks that because I have increased the volume of fuel/air within the crank case then there is more fuel/air to be scavenged into the transfer ports and hence more into cylinder. With the standard flywheel, there was not much free space left in there, most of the volume was contained in the 2 halves where the rod is located, it really is a snug fit in there as standard.
Its either going to go 1-of-2 ways .... it will be either totally rubbish or will rev like a good 'un !! Time will tell !!!
Bought a clutch of eBay other day and it contains dimpled steel plates .... never seen a TY with dimpled plates before ...... its a trick often used with Mont 315R plates as these are same as CR250 'Sureflex' MX clutches. Dimples hold oil and prevent drag when faffing with gears etc stops the steel plates sticking to the friction plates.

I think your scooter bloke is talking cr-p, I think it will be gutless.



Ferretflasher
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Re: ty 250 mono aftermarket parts

Postby Ferretflasher » Fri Feb 03, 2012 1:02 am

Gents .......I don't know WHAT to expect !!!! But you cannot deny that there will be more fuel/air in that crankcase ...... at a lower pressure admittedly. NOBODY can tell me about what mods were done on works motors, not really of any interest to mainstream riders today and those who did know have virtually left the scene. But if anyone does know, enlighten me !

Maybe someone could give the definitive answer based on experience rather than supposition. I am just making it up as I go along ... so .... how else could I make a short stroke motor ??? Don't want to even think about asking someone to machine the original flywheel for me to 64mm stroke, would cost a fortune ..... !!! Sorting out timing is just reposition stator backplate at 4 oclock position and keep adjusting until it works.

My costs so far are crank US $ 25, flywheel US $ 30, shims about $2 while biggest cost will be a 70mm piston, maybe $150 ???? Everything else is just heaped up in the chicken shed. So assuming it is really pants then I have a good motor that just needs a standard crank refitting ........ do it in about 5 hours if its not -10 C in the garage. Barrel will need to be mated up to a 70mm IT or DT piston (because it will be 4 mm shorter) but again I end up with a fully sorted motor.

Better to have tried and failed than failed to try !!



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Re: ty 250 mono aftermarket parts

Postby Bully fanatic » Fri Feb 03, 2012 11:44 pm

Hello Ferretflasher, Good luck and I hope it works. Remember the old saying. If at first you don`t succeed try try again. Graham.



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Re: ty 250 mono aftermarket parts

Postby FM350 » Sat Feb 04, 2012 1:11 pm

The effect of reduced crankcase compression mean will mean less mixture in the cases and greatly reduced transfer port velocity, and this is almost certainly going to result in a lot less power at all engine speeds. Reducing crankcase compression on a 2T motor is not the same thing as reducing compression on a 4T motor, and messing with the case compression on a 2T has no advantage whatsoever.

Many years ago I tried a bike which had been fitted with a crank about 2mm smaller in diameter than the original part, and it was completely gutless, running more like a worn out 125 than the 250 it actually was.

I would advise you very strongly to forget the nonsense you have been told by your scooter "racing" mate! If you are seriously interested in improving your bike, then buy a few books and get an accurate idea of how a 2T motor actually works, rather than spending time and money on alterations which are almost certainly going to make it run worse.



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Re: ty 250 mono aftermarket parts

Postby Ferretflasher » Fri Mar 16, 2012 1:37 am

Thanks for the advice but I'm nearly there now ....... biggest prob has been the flywheel. The Taper on the IT crank is smaller than the TY taper so it has meant finding an IT / DT / YZ flywheel that will fit, I have now got that sorted with a DT400 flywheel, it just needs the keyway widening to take a 5mm key. The coil trigger point is all wrong but that simply means I have to reposition the stator back plate about 120 deg back on itself, using existing slots, so Yamaha must have used a parts bin special somewhere along the line !!! This flywheel has no extra weight so shall keep things simple and get it running first.

Next job is the most expensive and that is to buy a YZ piston from Birketts and shorten the barrel. Cost so far is crank US $55 and flywheel US $45, everything else just recycled !!

Unfortunately work gets in the way and I now shall be working in Darwin for a few weeks .... and its not in Lancashire regrettably .... this means the Normandale round at Darlington is off and so too might the Mansfield round...?? Chris Koch spanked everyone at Bootle Fell with just 2 dabs and indeed the C class entry topped 22 riders. That being the case I failed to score any points and even Pete Roscoe (2011 C class Champion) only score 1 point such was the wealth of talent in this years C class. Many riders appear to have dropped B class and chosen to ride C class this year, whereas there were typically 5-6 riders now there are 22, so its appeal is now obvious. This probably explains why Yam TY mono's have gone up is price as everyone saw / remembers a good machine once sorted......there were 13 Yams that day at Bootle !!

PowerWater is my home for next few weeks/months ..... Gaa'da !!!



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Re: ty 250 mono aftermarket parts

Postby FM350 » Fri Mar 16, 2012 6:16 am

I thought Chris was riding his 125 Scorpa this year? Not much go, but handling and brakes much better than any other air cooled mono, so seems a good choice for that class?



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Re: ty 250 mono aftermarket parts

Postby Ferretflasher » Fri Mar 16, 2012 10:43 pm

Its a Scorpa alright .... but its a 175 at least ??? That's what the tank logo said ...? Don't know whats happened to the Cotswold we shall see next trial.
It is a very good choice .... but put an expert on any bike and they can do things normal wobblers cant !! I watched him through section 6, 7 & 8 and he was inch perfect.



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Re: ty 250 mono aftermarket parts

Postby FM350 » Sat Mar 17, 2012 5:00 am

Not sure Chris is riding the TS class in Normandales this year? I think he is doing air cooled mono this year?



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Re: ty 250 mono aftermarket parts

Postby Ferretflasher » Sat Mar 31, 2012 2:37 pm

Now working in Darwin for 6 weeks .... and its a horrible climate to someone used to Yorkshire !! Not much evidence (well non actually) of any off road activity, seen a small MX track at Palmerston but thats all, certainly not trials weather here in NT Aus !!! Wet season just about to finish and begin of dry season. When it rains here, gosh it dont half rain, never seen owt like it!! It hurts out there if you get out of car , like been jetwashed all over, floods of water river down streets etc !!! :mrgreen:

Still should be back for SSDT nice gentle rain up there not like this stuff!! Only 28 days to go and then up to the Fort !!! =D>



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Re: ty 250 mono aftermarket parts

Postby pop » Sat Mar 31, 2012 3:56 pm

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