ty 250 improvements

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yamaha man
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ty 250 improvements

Postby yamaha man » Mon Aug 27, 2012 10:18 pm

Hi I have just purchased a 1984 ty250 trials bike as a project then to enter in clubman.

I am looking to do some improvements and was wondering about what sort of improvements are doable to improve the bike.

I have heard about moving foot pegs, increasing rear shock length, some throttle mods to change it to a 1/4 throttle along with flywheel mods and big boring with a dt piston.

Are these mods good or bad and what are the measurements if they work well.

Also any other modifications you can think of would be appreciated.

thanks :D



FM350
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Re: ty 250 improvements

Postby FM350 » Tue Aug 28, 2012 6:51 am

Lowering the rests is a good idea, as is a 28mm OKO or Keihin carb. Best piston to use is Wiseco intended for the Yamaha Tri-Z 3 wheeler. Stock exhaust is very poor, but its not that difficult to modify to work much better, and use a modified MX back box.



yamaha man
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Re: ty 250 improvements

Postby yamaha man » Tue Aug 28, 2012 6:41 pm

Cool thanks for those ideas.

Is there any other mods anyone can think of. Especially in the handling department I need all the help I can get.

How would I set the forks and rear shock up as i am unsure i am 6'1 and 65kg

Thanks



yamaha man
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Re: ty 250 improvements

Postby yamaha man » Tue Aug 28, 2012 7:21 pm

Does the tri z piston fit straight in or do parts need to be modified. And does it give any performance boosts.

Also what jetting should be run in those carbies.

Thanks



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Re: ty 250 improvements

Postby FM350 » Tue Aug 28, 2012 8:11 pm

You will need to modify the Tri-Z piston slightly to fit. Steering angle steeper by 2.5 degrees will improve handling, and rebuilding the rear shock will make for much better suspension performance.



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Re: ty 250 improvements

Postby David Lahey » Tue Aug 28, 2012 8:13 pm

FM350 wrote:You will need to modify the Tri-Z piston slightly to fit. Steering angle steeper by 2.5 degrees will improve handling, and rebuilding the rear shock will make for much better suspension performance.

What if the steering geometry has been altered already by a previous owner?

I suggest that yamaha man posts some relevant photos in case the bike has already had (very common) mods done to it


relax, nothing is under control

yamaha man
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Re: ty 250 improvements

Postby yamaha man » Tue Aug 28, 2012 8:42 pm

What sort of modifications need to be done to the piston?

Will this give more power?

The bike is completely stock at the moment.

How difficult is changing the steering angle?

Has anyone heard about shaving weight off the flywheel



David Lahey
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Re: ty 250 improvements

Postby David Lahey » Tue Aug 28, 2012 8:48 pm

yamaha man wrote:What sort of modifications need to be done to the piston? I haven't done it myself, but friends have told me the skirt interferes with something has to be trimmed shorter to miss

Will this give more power? if it is a bigger diameter and is done right, probably yes

The bike is completely stock at the moment.

How difficult is changing the steering angle? by lengthening the shock, or modifying the linkage where the bottom of the shock mounts to it, or doing a frame chop

Has anyone heard about shaving weight off the flywheel - yes it commonly done to that motor so it picks up revs quicker. The steel band on the outside of the flywheel cup is machined smaller or removed, depending on how radical a change you want to make


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yamaha man
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Re: ty 250 improvements

Postby yamaha man » Tue Aug 28, 2012 8:52 pm

How do u modify the length of the rear shock and whats the measurements?

Is the flywheel mods worth doing and if so how much should be taken off.



David Lahey
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Re: ty 250 improvements

Postby David Lahey » Tue Aug 28, 2012 9:01 pm

yamaha man wrote:How do u modify the length of the rear shock and whats the measurements? There is a diagram somewhere on the web that shows the suggested mod to the lower shock mount on the linkage. If you want a longer shock, you could find one the right length from for a different bike, or get the shock modified by a shock specialist. To work out how much longer, you could make an adjustable dummy piece to replace the shock and try different lengths until you achieve the length that will alter the steering angle to what you want. The most common mod in the 80s was to modify the bottom shock mount to lift the bike, as previously mentioned. Nowadays with a plethora of shocks available, and lots of people who are capable of modifying shocks, there are more options available.

Is the flywheel mods worth doing and if so how much should be taken off.This is entirely personal taste, and will depend on what other mods you make, so there is no single correct answer. If it was me I would not touch the flywheel till you are finished fiddling with the rest of the motor


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