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Yamaha TY175 id help


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Hi folks,

just bought a TY175 at a fair price and I need some help to find out the bike year (roughly) and other info..

It is unregistered but all numbers are there. Couple of strange things about the bike (to my limited TY knowlege)

It has chrome wheels and a different front brake plate to others I see, also a plastic generator case.

The rear sprocket is HUGE with 60 (teeth?) stamped on it, After a quick internet search, the engine seems to be from a 1978 DT175MX , likely thats why it needs that big rear sprocket.

Engine number begins with *2k4-then 6 digits.

Dissapointed that the wrong engine is in the bike, I am positive the previous owner ( a police guy)  didn't realise as he never used the bike after buying from a guy selling up bikes he had stored for over a decade.

Is there any way to save/use this engine by changing internal gearing to get it the same ratios as a TY motor? I think there will be other differences such as ign type and flywheeel weight maybe the cylider ports also?

Seems I have got some of a TY, it has a sammy millar tank/seat top and the frame is in very good condition.





Edited by crankcase
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So it looks like you have a TY175 rolling frame with 1978 DT175E wheels and engine.

If you post photos of the complete bike and at least the first half of the frame number it will allow for an ID of the frame and the other components.

As for the gearing, one of my TY175s had a 1981 DT175G motor (which is very similar to your motor) in it and first gear was fine for trials sections but second gear was like third gear on a TY175. It would be easy to get your first gear to work well for trials by selecting a suitable front sprocket, probably 13T with the 60 rear. I think mine with the DT motor was 12/54. Putting a TY175 gearbox into your engine is a lot of work and expense and if it was mine, I wouldn't bother because I don't use anything but first gear in sections and the DT gearbox makes it much better to ride between sections and trail riding.

That DT175 motor is actually pretty good for trials use. The porting of the DT175 motor is pretty much the same as the TY175. The port timing is the same but the ports in the DT motor are more squared-off in the corners. The DT175 motor has higher compression than the TY175 which is something that some people do to TY175 motors to get more grunt. The standard carby on the DT175 motor works fine for trials. The biggest difference in the motors is that the DT175 flywheel is a fair bit lighter than the TY175 flywheel. Some people lighten the TY175 flywheel and for experienced trials riders the DT175 flywheel would be fine. For novices it would be a bit easier to stall with the DT175 flywheel.

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Thanks feetup,

At least it seems it has potential, I was thinking to contact the seller to return or sell it with the info I know.

I'll contact the seller to ask what he knows or if he has the contact of the person who he bought it from  There is a very very small chance I could find the original motor if all local people.

Not easy to find a TY motor I suppose.

I thought I had found a bike I had been wanting for a long time so quite disappointed today, I knew it needed work and happy to sort jelly suspension and wheels but I never realised it had the wrong motor, so easy to spot with a bit more info :(

The frame number begins 525-221

Can you even buy the internal gearing for these engines?



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From the photos it looks like it's got a mixture of brake backing plates and wheel hubs from various DT175 models and TY250 twinshock forks and triple clamps. All quite suitable for trials use.

The frame number means it is based on a competition TY175 model frame from 1977 onwards.

Maybe take the magneto cover off and see if someone has fitted a TY175 flywheel and ignition. They can be made to fit under those plastic covers with a bit of trimming of the cover and the flywheel weight.

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... remove the rear shocks and move the swing-arm through its entire travel, if the rear brake actuator lever moves (brake applies) when the suspension moves through its travel then the brake needs rework.  Would not be a problem if the rear brake was cable actuated.   

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42 minutes ago, crankcase said:


I appreciate your experience and advice.

Not even TY175 forks? what are the differences? is that a common and good mod or not?

You really know your TY's


I confess to being a twinshock trials bike train-spotter.

TY250 forks have 34mm diameter tubes and TY175 forks have 30mm diameter tubes.

TY250 forks overall are about 20mm shorter than TY175 forks, which is fine on a TY175 because the standard setting on a TY175 has the tubes about 20mm through the top clamps.

The clamps are the same for both apart from the size of the holes for the tubes.

Yes it's a common and good mod.

I don't have vernier caliper eyeballs and it can be hard to measure fork tube diameter using a photo, but I could easily tell with yours because they look to be bigger than 30mm and TY250 fork caps have an internal hex and TY175 caps have an external hex and the sliders are the right type.

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Regarding gearing, after playing with my front sprocket I only use 2nd and 3rd gear for trials on my TY175 (even geared up I still found 1st too short to be useful), so the DT gearing might be better!

Good luck with your bike, it looks like a fun Heinz 57 :)

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