HI TO ALL.

CAN ANYONE PLEASE TELL ME WHAT PISTON I CAN USE TO MAKE THE TY 175B INTO A 200. I NEED SOME MORE POWER AND WITH A REBUILD NOW DUE I THINK 200 WOULD BE THE WAY TO GO.

Edited January 20, 201016 yr by suzukirm500

You might be interested in this thread

http://www.trialscentral.com/forums/index....=ty175+big+bore

Regards

David Lahey

The work required for the extra 20-odd cc really isn't worth it as the gain is barely noticeable. You'd be better off finding another ignition flywheel and skimming some weight off it which will quicken the throttle response (use a spare so that you have the original to go back to if need be)

There are two possible ways to go on this one.

As Woody has said you can take weight off the flywheel and the engine will pick up faster.

The standard Yam porting is very conservative, the squish gap is way too wide and the 22mm carb and reed block are good for low end power. The airbox is also restrictive.

With a standard engine I would, cut back the airbox lid and drill other holes to allow air in.

Use the thinest air filter I could find.

Open up the reed stops.

The squish gap needs to be reduced to 0.9mm and barrel lapped to cylinder, for example my 175 had a squish gap of 2.15mm as standard!

The rear tailbox needs replacing with a WES or similar.

Or more radically you could port your barrel and retain the standard flywheel weight along with the above mods.

The theory is to have a high powered engine calmed down by a heavier flywheel with more inertia. this is better for finding grip or at the top of bigger steps.

This is effectively the route taken by the 200 fantic which was very succesful after the Yam.

For the porting a good starting point is to raise the four transfer ports by just 1mm. also widen the smaller rear transfer port as much as possible without overlapping the end of the rings.

I allow 3mm from the piston pin to port vertical side.

Finally I also add the reed cage and airbox boot from a TY 250 with a 5mm reed spacer and use a NEW!!! DT175 24mm carb or OKO 24mm flatslide.

Most old carbs are worn out and need replacing.

This needs about 3mm removing from each vertical side of the reed entry on the cylinder.

Finally I then take a load of aluminium from the roof of the inlet side to allow much more gas to flow directly up the boost port.

The exhaust port remains standard.

I also use a DT175 piston as this has larger windows in the rear for improved gas entry.

You can go even more radical on the boost port and rear transfers so that they open earlier but try the first mod first.

I have a bike that both lugs reasonably well down to low rpm and then will really rev out almost like a modern 125.

It needs to be ridden more like a small bore modern bike on and off the clutch. Happily the clutch will stand the abuse.

It is great fun to ride on easier events.

The easiest solution-

Buy a Fantic 200 !