TY 250 Improvements

Need help finding information or parts for that old machine in your shed? Someone in here will know!

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David Lahey
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Postby David Lahey » Tue Jul 31, 2007 6:56 pm

The thing that holds the TY250 in gear is a spring loaded plunger that screws in from the bottom of the gearbox case. If it had old gummy oil lubricating the plunger in its guide, then having the engine warm (and the oil then a bit more slippery) might make a difference in how well it indexes and holds a gear. If it is that, then it is an easy fix by taking it out and cleaning it next time you change the gearbox oil. You may find the spring that pushes the plunger is a bit sagged as well which may be contributing.
TY250s are sometimes a bit dodgy on changing gears. One of mine sometimes gets a neutral when changing from second to third if I'm not paying close attention.
I use one of those clear conical shape in-line filters with a sintered element on each bike. The screens on Yamaha TY fuel taps are quite coarse and easily holed. It is amazing how much gunk the in-line filter catches that would otherwise cause havoc in the carby. Sometimes water can get in past the throttle cable ferrule too.



Stanm
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Postby Stanm » Mon Aug 06, 2007 9:07 pm

Thanks, I will take out the detent device out and check the spring next oil change

I decided to try increasing the falcon preload springs. I found one of the shafts bent. so i found the high and low spot with the spring off the shock. Gave it one mild hit on the high spot and to my suprise the shaft moved full stroke freely. Luck or Skill??

David have you got you boyesen reed yet? I am interested in your comments on their performance.

I have shifted my pegs up to the original position and believe it is better as i dont have so much peg scraping.

Also my petrol tap leaks and I have added a inline mower tap. With an in line filter it will get a bit crowded. Any hints on repairing the fuel tap . Or can you buy replacements.

Cheers



David Lahey
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Postby David Lahey » Mon Aug 06, 2007 10:19 pm

I've only just replaced the LH crank seal on the TY250 motor that is getting the Boyesen reeds and am expecting to go for a test ride tomorrow to see what difference it makes. It had been leaking a bit of air due to the inner lip being folded under for about 1/2 the circle of the seal. The motor was rebuilt at a bike shop donkey's years ago when a friend owned it and that is the second thing I have found that was dodgy from that rebuild. The other dodgy thing was the cylinder holding down nuts were all loose. I found that when the cylinder base gasket started leaking last year.
I will be fitting the Boyesen reeds after a local club trial this weekend as I suspect they will stuff up the jetting and I won't have time to get it right again before the trial.
You can buy new Yamaha TY250 twinshock fuel taps from John Cane in the UK. I haven't tried at the local Yamaha shop as I reckon the KT250 fuel taps are better anyway so have fitted them to my TY twinshocks.
Another option is to make a F/F adaptor to fit the fuel tank stub and a standard aftermarket bike fuel tap. They work well and don't cost much. The tap I am thinking of has a male thread and is made to fit all the Spanish 1970s bikes. They are advertised on eBay coming from the UK. I've bought a few of them so far for my Spanish bikes and Majesty and they have all gone well. Still prefer the KT taps for the TY twinshocks though as I don't have to make adaptors that way. If you want a picture of the aftermarket tap I'm talking about let me know.
Another option is to make a loop in the fuel line so it goes down from the tap to near the top of the gearbox and then loops up towards the tank and then back down to the carby connection. My TY250B is like that because the KT tap outlet points down so the loop makes it easier to fit the inline filter.
You did well fixing your Falcon shockie like that. I've seen it done with the standard thin shaft jap shockies that come on TYs but you must have just the right touch to do it with a Falcon. I had a Falcon with a bend in the shaft and took ages to work out why the bike felt so bad in rocks and had such poor lift on obstacles. It wasn't obvious just pushing down on the bike. It wasn't till I took it off the bike and took the spring off that I could feel the tight spot.
About the footpegs it is good that you retained the standard footpeg mounts so you could switch back to test the difference. I compare the TY250B which has the lowered luxurious HEBO pegs in my photos with my TY250A which has the standard tiny pegs. I'm not sure that the increased stability I'm feeling with the TY250B is a result of the pegs being that bit lower or because they are so much wider ie left to right width giving more leverage for my feet for controlling the bike???



Stanm
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Postby Stanm » Wed Aug 08, 2007 4:37 pm

Look forward to your feedback on the reeds.
Yeh the A foot pegs are tiny and I could not ride without widening them.
Thanks for the info on the fuel tap and pictures would be appreciated.
With the Falcons should the gas charge force the shock in the extended position or is the gas charge balanced on both sides of the piston?

Regards

Stan



David Lahey
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Postby David Lahey » Wed Aug 08, 2007 5:24 pm

The gas pressure acts on both sides of the piston. The gas and oil are not separated by anything. The rod pushes out because the pressure inside the shockie is higher than the pressure outside the shockie.

I'll get a photo of one of those fuel taps tonight



David Lahey
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Postby David Lahey » Wed Aug 08, 2007 5:48 pm

Photos of
KT250 fuel tap fitted to TY250B
Aftermarket tap for Spanish tanks fitted to Majesty
Aftermarket tap for Spanish tanks fitted to Bultaco Alpina

Click on photo for full resolution

Regards
David
Attachments
fuel tap photos 004.jpg
TY250B
fuel tap photos 001.jpg
Majesty
fuel tap photos 002.jpg
Alpina



David Lahey
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Postby David Lahey » Wed Aug 08, 2007 6:02 pm

Here is what the aftermarket fuel tap looks like. Photo from current eBay listing.
Attachments
58db_1_b.jpg



Stanm
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Postby Stanm » Fri Aug 10, 2007 6:15 pm

Thanks for the fuel tap photos. I got a fuel filter and aftermarket fuel tap tonight. When i tried to fit the tap it didnt fit as i expected. So i took off the F/F adapter on the TY original and it fit the aftermarket one. Easy. So the tap i got was a MCS - FT3A.( $15) Can supply a photo if required.

Ok next thing that I would like to do is fix the rubber hose from the carby to air box that has shrunk and it's fit is dodgy. Any ideas?

cheers
Stan



David Lahey
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Postby David Lahey » Fri Aug 10, 2007 6:51 pm

Yes the A model carby to airbox hose goes hard in time. Later model TY250 hoses fits the 250A model. That's what is on my A model. I bought a second hand hose from a bike wrecker for not many $$$. As far as I know they are not available new from Yamaha. It is possible to have replicas made using an original as a pattern but I haven't heard of any being made yet. A new old stock Yamaha hose sold on Australian eBay recently for about $80.
An alternative idea would be to fabricate a steel exhaust-pipe bend to fit the spigot on the airbox and use a straight piece of hose to connect to the carby.
I've seen people use a clamp-on pod filter but they would be a bit vulnerable to water ingress.
There are so many derelict TY250s in Australia you will probably be able to buy one from a wrecker without too many hassles.



yamaly
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tricking your bike

Postby yamaly » Sat Aug 11, 2007 4:07 am

Hi folks,

You can do a hell of alot with the old ty's believe me!!

Stanm

A simple trick is to drop your front forks through the yokes 15mm gives better handling and doesn't stress the frame so much if your a big fella.

you seem you've done quite a bit!! I personally don't rate the reeds if you get a good set up (carb and timing)
You can really start throwing money at a bike when all you really need is a good set up.
If you elongate your holes on your timing plate you can set your points exactly and then by moving the timing plate you can advance * your timing to your liking.

Chop of all unnesassary lugs remove autolube saves around 2kg

Take a look at my 175 unfortunately have to sell it because i'm moving downunder in october and I'll probabley see some of you guys around

Cheers yamaly
Attachments
My Yamy.jpg
Just finished rebuild was a basket case




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