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Engine Oil Consumption. Test From Where


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#16 dotmatrix

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Posted 05 April 2018 - 09:48 PM

 

 

It may appear that there's a lot of clearance between the piston Crown and the bore when cold and I wouldn't at all be concerned about that.
 
It may well need a fresh hone and new rings.
 
How much Oil is it burning?

 
so the running clearance of 0.0025" stated for this piston is in hot conditions? http://www.minispare...-STN100-20.aspx
 
it uses about half a litre every 400 miles.
 
I must say I expected the new pistons and rebore to last about 3-4 times what it has currently done before starting to use oil at this rate.
What was the engine rebored to? Was it checked for bore ovality and any deviation from vertical?

How was the engine initially set up(fuel and timing?)

Half litre to 400 miles is excessive imo, however you say there was also a driveshaft seal leaking, are there any others?

 

 

it was rebored to 998 +20 and it was done by a machine shop I have used many times before and I expect they did what was needed, but don't know.

 

After the rebuild it was setup on a rolling road.

 

to my knowledge no other seals are leaking no so it probably isn't leaking that amount from a driveshaft seal, besides it still smokes on a cold startup.



#17 Spider

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Posted 06 April 2018 - 01:12 AM

The piston to bore clearance is around 0.002" - 0.0025" and that's at room temp. on these, however, that is measured off the piston around 1/2 " from the bottom of the piston skirt. You can't check that from lifting the head. The Piston Crown to Bore Clearance will be around 0.5 mm or more. This is because there's a lot of material in the crown and so the expand a lot when at running temp.

 

1 litre to 800 miles is just outside of normal limits, though, given the mileage, it should use far less. I doubt you'd be be loosing that much from your drive shaft seal, it would leave quite a mess.



#18 dotmatrix

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Posted 06 April 2018 - 06:54 AM

The piston to bore clearance is around 0.002" - 0.0025" and that's at room temp. on these, however, that is measured off the piston around 1/2 " from the bottom of the piston skirt. You can't check that from lifting the head. The Piston Crown to Bore Clearance will be around 0.5 mm or more. This is because there's a lot of material in the crown and so the expand a lot when at running temp.

 

1 litre to 800 miles is just outside of normal limits, though, given the mileage, it should use far less. I doubt you'd be be loosing that much from your drive shaft seal, it would leave quite a mess.

 

Thank you. And those clearances are in total and not on each side of the piston I guess?

 

No I dont think it leaks that amount from the driveshaft seal but it cant hurt to change it, maybe it helps a little and maybe it wears again very quickly :)



#19 Spider

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Posted 06 April 2018 - 07:33 AM

The clearances are total.

 

Replacing the seal would be a good idea for sure. It's possible that the bush(es) in the side plates are also worn in which case, replacing the seal(s) alone won't help with the leak. Best check them too.






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