DR400/SP Stroker Cranks

[SON]

I have disassembled the SP370 with the TT500 Crank installed,
it has been narrowed slightly and several mm turned off the diameter
looks like the Suzuki flywheel goes onto the Yamaha taper but will measure tomorrow
Have photos just have to learn to post from my apple

[ola_martin]

Longer rod = heavier rod so there is a significant trade-off

You can almost always remove material of the crankhalves around the pin to compensate.

[ola_martin]

I have disassembled the SP370 with the TT500 Crank installed,
it has been narrowed slightly and several mm turned off the diameter
looks like the Suzuki flywheel goes onto the Yamaha taper but will measure tomorrow
Have photos just have to learn to post from my apple

Looking forward to it, how big is the spacer used?

[GMC]

Have photos just have to learn to post from my apple

You need to upload them to Photobucket.
You can do this as per Roger's guide (link below)
It has changed a bit since this guide was made but if you choose classic style then it should make more sense

http://ozvmx.com/community/index.php?topic=17785.0

[cloggy]

 I know the 370 and 400 look similar but as I understand it the 400 is beefed up. I'm not sure what is the same and what is not.

[SON]

I will know in a few hours I have a 370 apart on the bench and a 400 engine out of the frame ready to come apart.
the 370 is engine number SP370-100065
I will be at work in 3 hours so I will post then.

[cloggy]

 Looking at the Clymer manual there is mention of a 450 Powroll stroke kit . The picture seems to show a standard rod. Anyone know how a DR piston compares with a XT piston?
I know in standard form they are not interchangeable [disregarding the bore size] as if they were someone would have done it after 30 years, but I would guess that possibly the pin OD might be the same [DR 20mm]. If that is so what is the distance from top of pin to top of piston for a XT piston?

[EML]

If it's any consolation, both SP370 and XT500 pistons are/were used in XS650 hop-ups for sidecar cross.
Wally Wasp might know more.

[oldfart]

XT  TT  SR  500 (87mm) 20mm pin   1mm over = std bore 88mm on the Dr 400     10: 1 comp   
Or go with the 90mm pistons with 11.1 comp  or 12.1  comp.  Piston will need to be modified some what.

[cloggy]

 To get a 450 the stroke has to be 74 which is 9 up the DR's 65.2 so I guess the XT taking 2mm of half that still leaves approx 2.4 mm  for extra compression. I've bent a valve with the standard set up, and that still leaves valve cutaway and  piston skirt as unknowns