ty 250 mono aftermarket parts

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dad
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ty 250 mono aftermarket parts

Postby dad » Tue May 27, 2008 7:40 pm

Just wondering if anyone can tell me about ' IHARA ' aftermarket parts.
Been trying to tune my TY250 and just can't get it right.

Then I noticed that the reed 'manifold' has been cut and shut and stamped on the bottom left side of the barrel is 'BS-IHARA .06'

This would tell me that I have to rethink my tuning.

Any thoughts would be appreciated.

Peter.

try these pics

http://i304.photobucket.com/albums/nn17 ... nifold.jpg
http://i304.photobucket.com/albums/nn17 ... barrel.jpg


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David Lahey
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Re: ty 250 mono aftermarket parts

Postby David Lahey » Tue May 27, 2008 8:55 pm

My tuppence worth is that Ihara is a common Japanese name so if your bike is a second hand import from Japan, Ihara may well be the name of a Japanese bike tuner who did the mods.
There were then and still are lots of aftermarket suppliers in Japan of hop-up parts for Japanese bikes.


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dad
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Re: ty 250 mono aftermarket parts

Postby dad » Thu May 29, 2008 7:30 pm

David,

Could you tell me what effect the manifold shortening had on performance?

Thanks
Peter


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Re: ty 250 mono aftermarket parts

Postby Stork955 » Fri May 30, 2008 10:00 am

dad wrote:David,

Could you tell me what effect the manifold shortening had on performance?

Thanks
Peter


It will lift the power band higher in the rev range. What isn't your bike doing properly?

Cheers,

Stork



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Re: ty 250 mono aftermarket parts

Postby David Lahey » Fri May 30, 2008 5:57 pm

dad wrote:David,

Could you tell me what effect the manifold shortening had on performance?

Thanks
Peter

Hi Peter
Sorry to say I haven't been in a position to test the difference that mod makes. I do know that many Yamaha mono motors have been subjected to lots of fiddling and mods by unsatisfied owners. Common mods include the shortening of the inlet tract, reshaping of the combustion chamber, changing the compression ratio, fitment of expansion chamber type exhausts and lightening of the flywheel. Common chassis mods are to lower and move back the footpegs, and mod the shockie linkage to lift the back end a bit (on the first model).
If you do a search on this website and the trialscentral.com website, you will find lots has been written on the subject. I'm not sure they were actually so bad as people make out when standard as I have ridden a completely standard TY250R and while it was sensitive to fuel quality, it ran like a dream (but then I'm used to riding twinshocks). Maybe the Yamaha monos were down on power a bit compared with other brands at the time.
On any two stroke, shortening the inlet tract downstream of the reed valve will increase the crankcase compression ratio. Note that the opposite is done to some other trials motors, by fitting a spacer behind the reed block.


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Re: ty 250 mono aftermarket parts

Postby dad » Fri May 30, 2008 6:28 pm

Firstly thanks for your replies,


Stork,

I think I have a multitude of problems, uneven idle ( I can totally remove the idle mixture screw and the bike still runs) , surging mid range, no top end power, etc.

But the main problem is that the engine has been modified to an unknown extent and I’m going to have to strip it and find out what has been done. Gotta bite the bullet.

David,

The bike has a number of mods already done to it that I can determine, Inlet tract, aftermarket airbox, later model rear shock and whatever has been done internally.

At this point I think I need to examine the ‘internals’ to establish a starting point for carburation tuning
e.g. how far has it been bored, what porting work has been done.


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Re: ty 250 mono aftermarket parts

Postby Stork955 » Sat May 31, 2008 10:09 am

Try cleaning the exhaust system first before doing major work. You may well be surprised at the results. This is something that should be done regularly with all 2 strokes but never is. Hot tank cleaning is easiest and best - take the pipe to your local car engine machining place and they can do it there (it'll need painting afterwards), otherwise go for the caustic dip or burn it out methods. While your at it make sure the airfilter is clean and correctly fitted. In other words - take care of the simple things first.

HTH,

Cheers,

Stork



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Re: ty 250 mono aftermarket parts

Postby dad » Sat May 31, 2008 5:10 pm

Hey Stork,

Already done that, add small amount of petrol, remove 6mm drain bolt, ignite and add compressed air through drain hole and it sounds like an F111 doing a dump and burn.
Loads of black smoke (make sure neighbour hasn't hung out washing) and let cool and have another go.

being an 'S' model I thought that the fitting for the feed from the oil pump had not been blocked. I have 2 'vents' on the top of the Teikei carb and I have tried blocking them in various configurations eg 1 open 1 closed both closed etc to no avail.

had reeds out today and checked that they ok as far as I can see, refitted and sealed.

Can still remove air mixture screw and still ride it?????????????????

Thought about it being an air leak but that doesn't make sense if i can remove air screw and it still runs

Got me buggered.

any ideas anyone

Thanks

Peter


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Stork955
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Re: ty 250 mono aftermarket parts

Postby Stork955 » Sun Jun 01, 2008 8:34 am

Does it start and idle with the mixture screw out? If so it is really rich. All your carb vents should be unblocked and it also sounds like the throttle is partially open for some reason. It should stall when you wind the screw past its run limits, around 1.5 turns out on most carbs. Remember this only affects idle though, it wont make much difference once the throttle is open. I spend a lot of time just resetting carbs to standard and my customers say the bike has never run better. That may be the way to go if all your basics are OK. I think -please correct me if Im wrong - your bike has CDI ignition (no points?) If it does, double check all of that before anything else (point gap, condenser and timing with the backing plate position - it probably wouldnt hurt to have a look at that anyway).

Keep us posted.

Cheers,

Stork



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dad
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Re: ty 250 mono aftermarket parts

Postby dad » Sun Jun 01, 2008 2:56 pm

Stripped and cleaned carby today, blew every orifice out with compressed air, checked float level as per ty 350 manual ( only one I can get hold of ) to 22mm.

Checked main jet size , mine #140 , ty350 #145
pilot jet size , mine #48 , ty350 #37

re-assembled and refitted

same thing happens.

???????????????????????????????

Peter


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