Nissan NS30 Question

[ric44]

I bought this motor seized due to rusty cylinders but managed to free it up where the starter will spin it . Compression check then revealed low compression as I suspected it would . Pulled the head and the cylinders are pitted some , one more than the other. My question is when I pull it down to hone the cylinders , how much can I clean the cylinders up with the hone and still get by using the stock pistons and replacement ring sets ? I'd rather not rebore if I dont have to . Thanks

 

[Sea Rider]

There's one super size 0.5 mm piston and ring set that comes inmediately after standard ones. How low is compression between cylinders ?

Compression should be 99.6 PSI, should not exceed max 15 % between cylinders.

Happy Boating

 

[TOHATSU GURU]

About .1mm and you can still use the original pistons. Two mm or more and you need to bore both cylinders to the oversize piston size of .5.

 

[ric44]

One was 60-65 the other 80 . Added oil to the cylinders and it bumped them to 100psi or better .

 

[ric44]

Cylinders have pits you can definitely hang a nail in . I'm gonna try to hone them a bit then see where I am . I am doubting .1mm is gonna clean them up though .

 

[Sea Rider]

If you bore to take all those pits from cylinder wall impossible to use a standard piston/ring set again. The piston/ring tolerance is extremely short. Bore it to next 0.5 mm size. It's only + half milimeter compared to original standard piston/ring set. Will have a standard OB again in excellent working order.

Happy Boating