TY 175, shifts not always perfect.

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Takhli44
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TY 175, shifts not always perfect.

Postby Takhli44 » Wed Oct 21, 2015 5:56 am

I have an old 1976 well used TY 175 that shifts OK most of the time but once in a while it is difficult to shift from 2 to 1 or 1 to 2. It happens often enough that I select a good flat spot in the section to shift. I have had other TY 175s that were the same so perhaps I'm being too critical and it's just the nature of these bikes. The shift lever shaft bushing has a bit of play and also has a bit of in and out play. I have centered the adjustment on the clutch side using 2nd gear to do so. Any ideas? Suggestions?


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David Lahey
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Re: TY 175, shifts not always perfect.

Postby David Lahey » Wed Oct 21, 2015 8:27 pm

Even when the bushings and linkage on the left hand side are perfect, and the hooks on the right hand side are set perfectly, the TY175 does not shift as well as many other bikes of the same era.
Yamaha abandoned that strange shift shaft design soon after the TY175B motor was developed. The new design appeared in 1977 in the YZ125D and IT175D, and in the DT175E in 1978, which all shift beautifully.
All the TY175 models have the same design as the original (B) model.
It takes a brave rider to attempt shifting gears in a section on a TY175
It will work a bit better if you get rid of the slop in the mechanism on the left side and keep it lubed well
Something else to check for is that the cover for the linkage mechanism is in position properly. It should have a couple of tiny dowel pins to hold it in position, but they could have been removed, and the bottom frame tubes are known to bend upwards and push against this cover
An important thing when you set the hooks is to make sure the centering spring is able to return the hooks to the same spot reliably. If you have a sticky mechanism the position will vary. It may help to run with the shift lever vertical, or use a lighter shift lever, to minimise the effect of gravity


relax, nothing is under control

Takhli44
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Re: TY 175, shifts not always perfect.

Postby Takhli44 » Thu Oct 22, 2015 2:12 am

Thanks David, I thought you would have the answer. I thought it might be a design flaw but wasn't sure. The frame tubes are bent but not contacting. I'll straighten them and check on the centering spring.
The dowels are in place, I'm running an 11 tooth sprocket which allows me to run a number of sections in 2nd without shifting and gives me a low gear to ride really tight stuff where more momentum is not required. I try not to shift in a section unless there is a really good place to do so.


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paulo
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Re: TY 175, shifts not always perfect.

Postby paulo » Fri Oct 23, 2015 11:11 am

My yz125c uses the same mechanism and as David said it's a pretty average design. I replaced the shaft and linkage mechanism with some nos parts and have shortened the actual shift lever for less play and fewer false neutrals.

There's a trials mob in the uk (sammy miller?) that sell the cover with an extended bronze bush in it to support the shaft a bit more. Doesn't solve the inherent problems with the mechanism, but takes away some of the load on the linkage.



David Lahey
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Re: TY 175, shifts not always perfect.

Postby David Lahey » Fri Oct 23, 2015 1:48 pm

paulo wrote:My yz125c uses the same mechanism and as David said it's a pretty average design. I replaced the shaft and linkage mechanism with some nos parts and have shortened the actual shift lever for less play and fewer false neutrals.

There's a trials mob in the uk (sammy miller?) that sell the cover with an extended bronze bush in it to support the shaft a bit more. Doesn't solve the inherent problems with the mechanism, but takes away some of the load on the linkage.

Here is that repair kit
http://www.tytrials.co.uk/trailandtrial ... TY175.html


relax, nothing is under control

Takhli44
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Re: TY 175, shifts not always perfect.

Postby Takhli44 » Sat Oct 24, 2015 1:54 am

Thanks for the information. I have a spare cover from a parts engine which I pressed out the old bushing.... (Caution here as the factory bushing has divots drilled in it and the cover appears to be cast around the bushing so it takes a lot of pressure to shear the cast into divots and must be well supported close to bushing, I used sockets).... and made a long bushing which I turned from an old handlebar. Haven't tried it yet but if it works I'll post here. I expect it to wear fast and when worn will replace with brass, that is if it works.


Don't let competition get in the way of having fun.

David Lahey
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Re: TY 175, shifts not always perfect.

Postby David Lahey » Sat Oct 24, 2015 11:00 am

As well as the hole in the cover needing bushing, the inner end hole on mine needed rebushing too. I bought a new shaft and fitted bushes in both holes. Can't remember what I used for the bushes but it is still working well and that was about 20 years ago


relax, nothing is under control

Takhli44
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Re: TY 175, shifts not always perfect.

Postby Takhli44 » Thu Nov 05, 2015 8:52 am

Just back from trying the new bushing in the spare shift cover, didn't work. The alignment with the inboard hole was a few thousands of an inch off causing a bit of bind. It would not return to center without giving it a bump. Cleaned and greased the old parts and went out and shifted many times without a single miss.

I can't figure a way to line bore the two holes with the tools at hand. Suppose I could give the bushing a little reaming as it is close but that might defeat the purpose. Think I'll go with what I have.

Folks in trials are a great community, thanks.


Don't let competition get in the way of having fun.


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