TY250 silly questions...

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Jools
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TY250 silly questions...

Postby Jools » Mon Oct 23, 2017 2:51 pm

I have a basket case TY250B that I'm building, and I will have plenty of silly questions about it (so I apologise in advance).
Because it's not a 'together' bike It can be tricky working out what's what.
First question (now you'll see why I call it 'silly'):

My rear right hand upper engine mount 'tab' is missing from the frame- I'm making another - that's easy, BUT the crankcase casting for that mount is slightly on an angle, -instead of being parallel with the engine centreline, the casting - face for the bolt/nut is angled slightly in, pointing towards the spark plug. It looks wrong, and I can't see why Yamaha would have done this, but you never know. (There's no damage to the casting to account for this, but I guess it's possible that some other component is bolted in there?)
:?:
Balls! (And I'm not talking the bollocks here...)
Steering head standard ball bearings, 19 balls per race, but what diameter balls are they?

-Jools



Jools
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Re: TY250 silly questions...

Postby Jools » Mon Oct 23, 2017 5:57 pm

Silly answer... I found tytrials.co.uk offering a set of balls:
x19 1/4" balls for the bottom race, and x22 3/16" balls for the top race.
:?: (If that's correct it's good 'cos I have those in stock).
Imperial though obviously...



Rod
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Re: TY250 silly questions...

Postby Rod » Mon Oct 23, 2017 7:31 pm

You're right, they are silly questions. Why are you even bothered about "ball bearings" when you can go tapered bearings?
https://www.inmotiontrials.com/product/ ... -bearings/



David Lahey
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Re: TY250 silly questions...

Postby David Lahey » Mon Oct 23, 2017 7:44 pm

There's no other component fitted to the RH upper rear engine mount.
I've seen a few broken-off engine mounts on TY250 twinshocks.
Having no frame tubes under the engine, the engine mounts on the TY250 twinshock do get a lot of load as you ride so they need to be kept tensioned.
One basket case TY250B I bought had been ridden with loose mounting bolts and the holes in the casings were slots about 2 bolt diameters long.


relax, nothing is under control

Jools
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Re: TY250 silly questions...

Postby Jools » Mon Oct 23, 2017 7:54 pm

Thx David. Yes it's not hard to imagine things going awry with the engine mount setup.

Rod,
(I knew I'd get a silly reply! - as well as my own).
My ball races are in excellent condition and will outlive me by many, many years just with the addition of new balls. If I'd have wanted to go for taper rollers I would have just done it wouldn't I?
I enquired about the ball sizes for the standard races because I want to use the standard bearings. Simple. (Thanks for the advice anyway).



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Re: TY250 silly questions...

Postby Jools » Thu Nov 30, 2017 4:04 pm

So here:
As shovelled out of Dean's ute, the rear sprocket on the rear wheel of the TY250B was a 51T DISHED sprocket (new).
It doesn't line up with the engine GB sprocket. So then I 'trial-fitted' my old worn 51T TY175 FLAT sprocket and that lines up fine.
So I assume either: I have a non-standard rear wheel, OR the dished sprocket is wrong. ??

Second point: Are DT250 Ignition Points the same as TY250?

Third: I have had no response on my wanted ad for TY250B rear suspension units, so it looks like I'll need to buy new aftermarket ones. Opinions on what to get? Obviously I want decent shocks, but I do need to keep the dollars modest.

Ideas?

My fork springs/assembly look nothing like the TY250A parts list illustrations I have. My forks have a simple one-piece spring with a approx 3" tubular spacer. Am I looking at the wrong parts list -did they change the forks from the A to the B model? or are my forks wrong? (mine is a B model remember).

Be good to lose a few kilos off the TY so I've been looking at that as I build it... not many viable options, but one glaring item is the Fibreglass seat unit! -Bluddy'ell talk about overweight that! I'll be making a lighter seat pad for sure. The frame is really light, the engine is heavy, but not a lot could be pared off there even if you start drilling fins, -not much to be gained there, wheels and suspension? Not much there either.

Anyone have alloy handlebars surplus to requirements?



tat ty
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Re: TY250 silly questions...

Postby tat ty » Thu Nov 30, 2017 4:50 pm

Jools.

53 tooth dished sprocket is standard.

A model forks have the bleed screw on the outside. B model to the rear.

Alastair



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Re: TY250 silly questions...

Postby David Lahey » Thu Nov 30, 2017 5:18 pm

Jools wrote:So here:
As shovelled out of Dean's ute, the rear sprocket on the rear wheel of the TY250B was a 51T DISHED sprocket (new).
It doesn't line up with the engine GB sprocket. So then I 'trial-fitted' my old worn 51T TY175 FLAT sprocket and that lines up fine.
So I assume either: I have a non-standard rear wheel, OR the dished sprocket is wrong. ??

or the swingarm is bent or the rim is not central on the hub or the wrong axle spacers have been used


relax, nothing is under control

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Re: TY250 silly questions...

Postby David Lahey » Thu Nov 30, 2017 5:21 pm

Jools wrote:My fork springs/assembly look nothing like the TY250A parts list illustrations I have. My forks have a simple one-piece spring with a approx 3" tubular spacer. Am I looking at the wrong parts list -did they change the forks from the A to the B model? or are my forks wrong? (mine is a B model remember).

B model forks are slightly different to A model forks, but both have a single suspension spring and a single spring spacer. You didn't actually say what looks wrong on yours


relax, nothing is under control

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Re: TY250 silly questions...

Postby Jools » Thu Nov 30, 2017 11:53 pm

David, it was that my forks didn't look quite like the schematic Illustration I have, (Not that there's anything actually wrong with my forks), see CMS schematic below. I haven't completely disassembled mine, just removed the spring and spacer so I don't know what the damper/piston arrangement looks like 'down below', but I'm sure it's ok, I think I was just 'reading' it wrongly initially.

Alignment: I did have to repair one engine mount, but everything seemed to line up very well, nothing apparently bent. Nothing looks suss about the rear hub. -I'll do a more careful 'jig-up' to check.

Image



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Re: TY250 silly questions...

Postby David Lahey » Fri Dec 01, 2017 8:00 am

What might be looking like a second (lower) spring in the forks drawing is the damper rod


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Jools
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Re: TY250 silly questions...

Postby Jools » Sat Dec 02, 2017 1:03 pm

Going back to my rear hub/sprocket, I wonder If I have a wheel off something other than TY.
(My sprockets line up with a FLAT TY175 rear sprocket fitted, not the dished sprocket).

My wheel hub measures approx 128.5mm from the brakeplate outside flange to the face on the other side of the hub where the sprocket fits, (the face on which the inside of the sprocket bolts to the hub).
Distance between my swing arm 'plates' at the wheel spindle position is 205mm (inside of plates).
That all seem right or what?

Interesting that my box of bits came not a 53 tooth dished sprocket but with a 51 tooth dished rear sprocket fitted, (with the dish facing inwards, -not seen that before). Wonder if it came from a DT or something. Hmmm...



outforfun
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Re: TY250 silly questions...

Postby outforfun » Sat Dec 02, 2017 2:52 pm

Hi Jools, I don't have a TY250. However if I did and was going to give advice, I can see I'd be asking about the length of your rear hub spacers as asked before.

Also a picture tells 1000 words.

If you can post a photo of your parts on a bench etc, someone (like David TY Lahey) who have had plenty of experience with the TY250 could say the sprocket you have is wrong, the hub is incorrect or the spacers are wrong size/side/etc.

Does your hub look centre? As in the brake hub stay arm is fitting correctly and not forced to one side to fit.

Standing on the outside imagining what it all looks like, I am thinking that your supplied sprocket may be incorrect. I would also ask my own silly questions
1 Are you looking to restore to concours standard?
2 Are you looking to ride it in a trials event or 3, as any and all trials bikes should be?

If you're looking for a concours standard, I can understand the detailed restoration. If you're looking to ride her? I'd fit a sprocket that suits and enjoy years of pleasure.

Just my 2 cents.



Jools
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Re: TY250 silly questions...

Postby Jools » Mon Dec 04, 2017 1:07 pm

Well one mystery is solved. The reason the PO had mounted the dished rear sprocket facing inwards was so the chain would clear his aftermarket shocks which have fat 63mm (2 1/2") diameter springs that would have interfered with the chain/sprocket. (I don't think he ever ran it like this because there's no wear on the sprockets). Hub and frame are all good. I'll need to get shocks for the bike and am looking at NJB, but I need to check if they will clear the chain, i.e the springs need to be more like 2" diameter at most. The shocks I'm looking at ('NJB Classic Expert') are supposed to be mounted USD which could present a clearance problem with the sprocket.

The bike is not intended to be concourse. It'll be pretty nice, but It's a user for sure.
Dunno about you but I've built about 8 bikes out of boxes parts, and I.D.ing all sorts of odd, strange, mysterious combinations of PO concocted parts is all part of the fun, - sometimes frustrating, but very satisfying when fixed.



Jools
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Re: TY250 silly questions...

Postby Jools » Mon Dec 04, 2017 4:13 pm

Next...
Rear shockers. I want to order these soon. I've seen the options: Falcon, Betor, NJB. I feel NJB might be good as previously mentioned, but I'm just a little wary of the clearance of the shocker to the chain/sprocket. Any clues on this? Experiences?
-Jools
On another subject, I'm a little confused that the TYtrial site are selling 44T rear sprockets for the 250TY when 53T are standard? What gives here?




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