Yamaha 250 piston information.

[firko]

Today I decided to have a look at my 'DT1 from Hell' engine that's been sitting on the shelf since it ate a ring at Condo in about 1997. I thankfully discovered that the engine is in surprisingly fresh condition and will need only a hone, a set of gaskets and a set of rings which brings me to the reason for this post.

The bore is on 71mm using a maximum oversize DT1 twin cast iron ringed piston port piston. Ever since I built the engine the bottom ring has had a bad tendancy to snag the widened exhaust port and get sucked out the exhaust in tiny pieces. To prevent the problem recurring I then started omitting the bottom ring, using only the top ring. Unfortunately these fragile little buggers have a life expectancy in this engine of one, maybe two meetings tops. Now that I've found that the bottom end is in AOK condition  and the bore is usable, I'd like to know if there is a 71mm Wiseco or some other brand piston using a single stainless steel Dykes ring to suit the DT1. Naturally, later reed pistons are unsuitable , it has to be a specific piston for that piston port 250 engine and be 71mm. My stash of 71mm rings is getting pretty low so I'd like to try something different.

[Lozza]

The exhaust port shape and mainly the top radius is to large, next is the profile of the port window. Single exhaust ports can only handle  72% of bore width(51mm across/chordal).
Would need the overall length, pin dia comp height and width across the inlet side of the skirt.

[Iain Cameron]

Firko, I have a old us dirt bike mag on the dt1 they  used a spacer at the base gasket then Suzuki tm piston . I'll look up the mag by using wisco Suzuki pistons you can go over size up to 2mm

[Freakshow]

I have some Dt dykes and normal rings up at 2 mm oversize.  i know what your about to say, but its an option if you want to cut your own rings back down in to what ever size bore your using.  $10 each :O)

[Freakshow]

Also have TM wiseco's if you want to go down that route.  up to 2mm