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Old 02-11-2013, 05:33 AM   #35
RedRupert OP
Brit in the Soviet Union
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Joined: Jun 2006
Location: Riga, Latvia / Bergerac, France / Colchester, UK
Oddometer: 584
Originally Posted by pdxmotorhead View Post
Yea,, it does not take very long at all to seat rings when everything is right.. 30 weight non detergent oil can be found at marine suppliers sometimes in my country.. as hard and sharp aas nicasil is I'd expect less than 100 miles ot bed the rings, sometimes some mild lugging for 2 or three minutes will help..

On a engine with forged piston and aluminum bore the leakdown needs to be done as soon after stopping as possible, you need the motor warm. The forged pistons loosen way up when cold.. The cosworth I mentioned would go from 30% cold to 5% hot.. :)



Thanks for your advice. I was reluctant to accept it at first, partly because I was annoyed with myself - I did know that synthetic oils are no good for running-in (I've read about the problems Yamaha had a few years ago). I made a half-hearted effort to find a suitable oil, but ended out settling for semi-synthetic.

There is too much soot in the exhaust pipes. The oil is being burnt. The valve-guides and the pistons were in very, very good condition.

Also, as I've said, I led the engine vent pipe into a catch-bottle - rather than into the top of the air-box. Since doing this, the pre-filter has been very black, and so was the front of the OE paper air-filter before the pre-filter was fitted - almost as if there's too much oil in the air around the air-box intake.

I'm going to try using straight 30W oil as you and John have suggested, in order to seat the oil rings.

Please can you give me some advice on:

a) The best oil and how to find/identify it - API standard S? (what suffix if any to go for?)

b) The best way to seat the rings, and what to avoid doing.

Thanks again,


Re the leak-down: I ran the engine 'till the fan cut-in before conducting the test, but was surprised to see that the readings were very close to the ones I'd taken while the engine was cold. I should try it again.
KTM 970 Adventure (2004 with carbed 2008 SD 990)
Yamaha WR 450 F
Honda 650 Dominator (1988)
Kawasaki KLR 650 (1988)
Yamaha RD 350 LC (1984)
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