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.
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
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
David Lahey wrote:I just did some calcs using that table that FM350 provided a link for. I'm guessing that FM350 is looking at the unladen weight balance in that table for his theory about front end loading but bikes are not able to ride themselves so I worked out the load on the front wheel with a 180 pound rider aboard for the 2003 GasGas, TY250 mono and TY250 twinshock, using moments about the rear axle for bike weight and rider weight, assuming all the riders weight is applied to the footpegs (just like we are taught to ride).
Gas Gas 0.513x150+180x17/53=134 pounds
TY250 mono 0.468x184+180x14.25/52.25=135 pounds
TY250 TS 0.45x201+180x15.5/52.5=143 pounds
So the oldest design has the most weight on the front end, and the TY250 mono has slightly more than the 2003 Gas Gas
Maybe a different explanation might be required for why modern bikes are easier to ride (rather than front wheel loading).
I think the main contributing factors are improved mass centralisation and reduced weight.
Guy53 wrote:Good lord.
I do not want to start a war but for the second time this friday I attended a class on how to ride a TS and the first point was the riding position to make sure NOT to load the fornt wheel. I certanely won't go to a trial with section made by you FM.
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