crankshaft stroke 50.7mm on 2rh engine

[matoo87]

Hello everyone! I'm new here, I have a TZR 2RH, and the crankshaft is damaged. What I can get in my country is a DT12R crankshaft that has a 50.7mm stroke and my 2RH's stroke is 50mm. My question is, has anyone been able to adapt a 50.7 stroke to a crankcase that holds 50mm? Thanks in advance. Regards.

[tzr-v4]

50.7mm stroke versus 50mm one is only 0.35mm difference at TDC or BDC.
If my maths are fine 

This could be compensated by thicker base gasket to set the top crown piston at the same height.

I think port map will not be significantly modified.

[matoo87]

Thanks for your reply, I'm going to buy that crankshaft and try it out. I'd still have the TZR 4FL stroke, or would it be better to get a 4DL piston? I hope they're the same crankcases and I don't have to modify them.

[tzr-v4]

Check on partlist if same part for :
- Crank Bearing
- Crank Seals

Check also if woodruff key is at the same position otherwise, ignition will be a problem.

For example 200 Blaster crank can not be used in DT200R for this reason.

[matoo87]

I'll look into it. Thanks.

[AndyYam]

Not sure if it helps but the DT125R had 2 different crank/barrel combos.

I think the earlier 3BN cylinders were 56.4mm and the later 3MB were 56mm so the cranks were different strokes.

[matoo87]

If 3BN is the same as tzr 2rh stroke 50 mm, but the one I'm not sure if it can be installed without modifying crankcases is the 3MB stroke 50.7mm, which is the one I can get.

[Toop]

Not sure if it helps but the DT125R had 2 different crank/barrel combos.

I think the earlier 3BN cylinders were 56.4mm and the later 3MB were 56mm so the cranks were different strokes.

You are right !
Update a 3BN with 3MB(no élec starter) is what i have make in the past

[matoo87]

Not sure if it helps but the DT125R had 2 different crank/barrel combos.

I think the earlier 3BN cylinders were 56.4mm and the later 3MB were 56mm so the cranks were different strokes.

You are right !
Update a 3BN with 3MB(no élec starter) is what i have make in the past

Hi Toop! Did you change the crankshaft from 3BN to 3MB, meaning you changed the stroke from 50mm to 50.7mm without making any other modifications?

[Toop]

Yes, just nibble a little on the passage of the connecting rod 

[matoo87]

Yes, just nibble a little on the passage of the connecting rod 

I'm going to buy the 3MB and replace my old 2RH,
Thank you very much!