Robin EX-27 What size threads are these?

[i6pwr]

Mounting a pump bracket to these 4 holes, I can't tell if they are M10x1.5 or 3/8-16. All the holes have debris in them, I have cleaned them and carefully tried a few bolts, but the 3/8 seems to thread easier. So before I use a chaser, I want to verify since both are too close to call.

Japanese engine, my thoughts are metric, but doesn't seem to be the case.

 

[Chris142]

Very unlikely to Be sae.

 

[SC Maintenance]

3/8 is 9.5mm. Likely why it seems to go in easier.

I can't imagine anything Japanese being SAE.

Can you order OEM bolts? Might be worth it rather than stripping out something.

 

[i6pwr]

I tried these smaller holes, definitely 5/16-18. So I'm perplexed unless PTO mounts are imperial.

 

[SC Maintenance]

I tried these smaller holes, definitely 5/16-18. So I'm perplexed unless PTO mounts are imperial.

View attachment 331403

You sure those are not 8mm?

Could be though. If it was OEM to mount to someone's pump they might have spec'd SAE.

 

[i6pwr]

You sure those are not 8mm

Yeah...the 1.25 pitch was too fine. The 5/16 was a perfect fit...fully threaded down.

 

[Trav]

Something like this may help. Nut and bolt checker

 

[martinq]

Is this a "new" engine or has it been used before? I'm wondering if someone used the wrong bolts previously.

"Japanese" doesn't tell us much. Make & model?

 

[i6pwr]

Is this a "new" engine or has it been used before? I'm wondering if someone used the wrong bolts previously.

"Japanese" doesn't tell us much. Make & model?

It was used, but I bought it with minimal use over 5 years ago, just needed to now use the mounting holes for a different pump bracket.

In the title.."Robin EX-27"...it's a Subaru/Robin 9HP. Sadly Fuji stopped production of most of their small engines so getting hard to find parts. Was a sad day as these engines just purr.

 

[martinq]

It was used, but I bought it with minimal use over 5 years ago, just needed to now use the mounting holes for a different pump bracket.

In the title.."Robin EX-27"...it's a Subaru/Robin 9HP. Sadly Fuji stopped production of most of their small engines so getting hard to find parts. Was a sad day as these engines just purr.

Thank you, yes I remember Robin / Subaru now. Thanks for the info, I would expect metric threads but they could have been left blank and let the OEM tap them per their application.

 

[i6pwr]

I would expect metric threads but they could have been left blank and let the OEM tap them per their application

Same, I think they are metric but hard to tell for sure. They are definitely threaded.

 

[Exhaustgases]

What size is the output shaft end ? If its imperial then likely the pto bolt holes are as well.
I'm sure there is manufacture specs on what they are.