IT175 pistoned RD400 motor

[1976RD400C]

I bought a parts lot yesterday and it included a 400 motor with modified cylinders for IT175 pistons. It looks like it has a hot port job, big reeds, 34mm flatslide carbs, and is a 67mm bore. I'm a little bit afraid of it.    Anyone have any knowledge on how well the pistons with a higher pin placement works out?

[Vintagetz]

They work well, they lower the intake port which improves the intake timing.  I built high performance RD350 and  400 motors using IT pistons in the late 70's.  Nothing really to be afraid of other than you have to be careful of which year IT piston you use / purchase.  There are two versions, and only one of them has the ring pin location that is correct for the RD port layout.  I use blaster pistons in my race motor now,  They may have the same pin offset as the IT piston.  I think I have a used blaster piston that I am not going to use, it would let you see if it is an appropriate match for your cylinders.

Looking at your cylinders they appear to be 2VO (Daytoma) this is a good high-performance casting.

[SoCal250]

I'm sure Ed Erlenbach could supply a lot of info here. His parts notes mention the IT piston mod:
"For Racing Bigbore Topends (66mm and up)
1980 IT/DT 175 pistons or Yamaha Blaster Pistons. Either piston is 5-6mm shorter than stock and requires machining the top & bottom of the cylinder to compensate for the height. The blaster pistons also have a 10deg piston dome instead of the RD/RZ/IT/DT 15deg so it does require recutting the cylinder heads (but if you're doing a bigbore you need to recut the cylinder heads anyway)."

You didn't find any name or initials engraved in the parts?

[1976RD400C]

I'm sure Ed Erlenbach could supply a lot of info here. His parts notes mention the IT piston mod:
"For Racing Bigbore Topends (66mm and up)
1980 IT/DT 175 pistons or Yamaha Blaster Pistons. Either piston is 5-6mm shorter than stock and requires machining the top & bottom of the cylinder to compensate for the height. The blaster pistons also have a 10deg piston dome instead of the RD/RZ/IT/DT 15deg so it does require recutting the cylinder heads (but if you're doing a bigbore you need to recut the cylinder heads anyway)."

You didn't find any name or initials engraved in the parts?

Well there you go. Just like you said, decked on the top and bottom. Previous owner said it was a drag bike motor. Also notice the fittings mounted in the crankcase.

[SoCal250]

Tom Turner was the man in 2-stroke tuning, and responsible for creating the TSR software. That's an older build because he's been retired for more than a decade.
http://erlenbachracing.co/tom_turner.htm

[m in sc]

yup, you definitely scored on that one. 

[85RZwade]

Is the fitting in the crankcase for pressure testing?

[1976RD400C]

Is the fitting in the crankcase for pressure testing?

There is one on each side. Maybe NOS injection, but I would think you would just pipe it in the carbs.    Anyway, this thing just needs a check up, seals and new rings. Crank looks real good with polished rods. Sometime this summer switch it out with the motor in my bike and see how it goes.

[m in sc]

you could use that for oil injection. .02

[stresa]

Hi,
I have a bike which has this engine configuration from new. It was a dealer special back in period done by the biggest Yamaha dealer here in Germany back then. They got around 50 overstock european 400E/2R9 models to do with them as the 400 were sold very slowly here as anyone went on the 4stroke waggon.
Beside the engine converted to 424ccm with the modification as written above you had the option of various aftermarket parts. Mine was built with PVM wheels, different fuel tank and seat, Noguchi expansion chamber, clip-ons and Raask rearsets. Some other bikes got full fairings and Lockheed brakes on top.
But I never had the engine open as the engine had only around 16000km when I got the bike around 19 years ago. Only rode the bike for around 100km in that nearly 20 years. But I will restore the bike in the near future and will open the engine of course. I will share my thoughts then.
Bike looks as it left the dealer parts wise beside the missing front mudguard(which I have) and the indicators which were changed by the owner in front of me.


Regards Uwe