R5 vs RD350 Crank

[Czakky]

My R5 project has RD350 crank cases and transmission, with R5 stator/ignition timing.

My question is how do I tell the difference between an RD and R5 cranks?

[m in sc]

i think the r5 crank is slightly heavier on the flywheels (that's hearsay, i never measured), but they are interchangeable.

[Czakky]

So there is no telltale sign? Bummer.

[Brad-Man]

No difference between R5 and Rd cranks 250 or 350.

[SUPERTUNE]

i think the r5 crank is slightly heavier on the flywheels (that's hearsay, i never measured), but they are interchangeable.

Correct.
Thicker and heavier.
I have a special press plate I made to do R5 cranks.
C

[SUPERTUNE]

No difference between R5 and Rd cranks 250 or 350.

Incorrect.
See above...
I'll find one and post measurements of the flywheel thicknesses.
Chuck

[Czakky]

I'm trying to get some parts together to ship to you Chuck.

Do you have the thickness of either flywheel?

I'm trying to decide if I should send you my crank.

[Czakky]

Here's what was inside my bike.

[SUPERTUNE]

After texting back and forth we have detremend Bill has a RD350 bottom end and not a purebred R5 engine.
So he has a RD crank not a R5 crank.
I've tried to find a R5 crank at my shop, but can't fine one to measure.
Chuck

[Yamaha 179]

I think I have a R5 crank in my crankshaft spares box.  I'll check later today and if so, will post the info.
Lyn Garland

[teazer]

From a practical point of view are there any real differences or reasons to prefer one rather than the other?

I couldn't see any differences between the R5C parts book and RD350B list.  Maybe earlier R5s or later RDs had different parts.

[SNice]

You guys (Supertune & Yamaha 179)helped me through this way back when on the old site!  I had the same question!

The R5 cranks are heavier with thicker webs. Critical dimensions are the same - thus they are interchangeable.

The "connecting rod gap" - don't know the formal term- is smaller on the r5 crank (thicker webs) by about 1mm.

The r5 webs are about .5mm thicker. I have 1 of each. The r5 measures 21.4mm (roughly) and the rd is around 21.05 (roughly)

As has been concluded - it appears you have an RD crank.

I guess it comes down to what is the benefit of spinning a lighter crank?

Unfortunately the cranks exceed the limit of my small scale so I can't get a weight difference.
Pics on my phone are too large to upload....

[bhh1989]

Very interested in this - if the heavier R5/DS7 crank makes a difference in performance. I just bought my next project bike (a DS7) and the crank is likely bad from sitting without plugs in the top end. If I go replacing it...

[Czakky]

Chuck (SUPERTUNE) has my core crank. Hit him up.