Trials Australia Forums

Does anybody kbows if a DT crankshaft fit a TY 250 model 493 B model here in Canada

Guy

Guy a DT400B crankshaft will fit in the TY250B bottom end and it has suitable ends to fit TY250BCDE primary gear and flywheel. However I don't know if the if the DT250B crankshaft also has the same ends as the DT400B/TY250BCDE.

It has to be asked David:
Does the DT400B barrel have the same bolting pattern as the TY250?

A TY400 would be a dangerous weapon.

Kurt wrote:It has to be asked David:
Does the DT400B barrel have the same bolting pattern as the TY250?

A TY400 would be a dangerous weapon.

I don't know about DT400B cylinders but the RT3 (360) cylinder (same stroke as DT400B) needs the TY250 rear cylinder hold-down holes moved outwards. The fronts are OK. The 360cc TY250 I rebuilt which has an RT3 cylinder had been seriously calmed down for trials use. Lower compression, much bigger flywheel weight, 26 mm carby.

David, the DT 400 B is listed with a 70mm stroke, if I want to replace the crank in a TY 250 B and keep it standard, what choise do I have ?
We have looked all over the place to find a replcement for that crank, but can't find anyting.
Guy

Guy53 wrote:David, the DT 400 B is listed with a 70mm stroke, if I want to replace the crank in a TY 250 B and keep it standard, what choise do I have ?
We have looked all over the place to find a replcement for that crank, but can't find anyting.
Guy

I'm fairly sure the right hand (drive half) from a DT250B crankshaft will work in a TY250B.
It is quite likely that the left hand (magneto half) from a DT250B crankshaft will fit the TY flywheel taper but I cannot guarantee it.
Are you saying that you can't find a second-hand TY250B crankshaft for sale?

I just thought of another thing Guy.
If it's the left hand end of your TY250B crankshaft that is damaged you can use the left hand end of a TY250A crankshaft and the right hand end of your crankshaft. TY250A crankshafts are easily available but differ from the later TY250 motors in that the primary drive gear sits on a spline. The left end of a TY250A crankshaft is the same as the later TY250 motors.
If it's the right hand end of your crankshaft that is damaged you can use the right hand end of a DT250B crankshaft with the left hand end of your crankshaft.
If you are still stuck after those suggestions, I can sell you a TY250C/D crankshaft (which will fit your TY250B) but the postage cost to Canada would probably be enormous.

I have a couple of A model crankshaft here so we will have a look at the drive side half to see if it is still usable. The bike aparently was droped in a streem and left to rested for a long time, it took a lot of persuation to finaly '' unseize '' and take it appart.
Thank you for the offer to sell me a crankshaft but as you mentionned, I think going to your place and pick it up myself would be cheaper than have it shipped from Australia to Canada. I remember a while back, someone was interested in buying a TY mono piston that I have and It was crasy expensive to ship it ( with cost covering insurance ). I will update the post when we will finaly find a solution.
Guy

P.S. There is a few TY 250 crankshaft on the market but they are all A model.

If I recall correctly, the DT250 cranks have smaller OD than the TY ones. Not an insurmountable problem but you'd lose some crankcase compression and flywheel inertia with a straight swap.

JC1 as the DT piston did not have the bottom of the skirt '' besseld '' as the TY ones, you certainly are right about the early DT but I was thinking about a late ( 1979 here in Canada ) one. Since the crank in question is about 500 miles from our place and not being sure that the seller will give me the real measurement, I would rater ask before order.

Guy