Siebenrock - Nikasil Pistons+Cylinders kits

[goathands]

Hi all,
I have a issue in right cylinder burning oil. I performed a leak down test which was not very positive, and am considering replacing the pistons and cylinders with a new Nikasil coated set.

I wanted some advise on whether to purchase a Siebenrock replacement kit, or piece together the OEM equivalent. Does anyone had experience with these Siebenrock cylinder/piston kits.

Thanks,
James

[Tony Smith]

No experience with Siebenrock, but tens of thousands of R65s and their owners have received satisfactory service from the OEM parts.


There is a trivial difference in the "deck height" between the Pre and Post 1981 pistons, the approximately half a millimetre difference would make a very small difference to compression. I posted photos of the the early and late piston locked together by using the rings to show how small the difference is.

It seems that the bores wear much faster than the pistons, so it is entirely likely that you will have worn iron bores and perfectly good pistons, but the only way to be sure involves the use of a suitably sized micrometer.

If I was doing what you are thinking of doing, and if I wanted to achieve maximum lifespan of the components I would buy new pistons and then send my pistons and my worn iron bores to a place that specializes in spraying the nickasil material, they would bore out the iron liners oversize and then apply the nickasil lining and machine it to the correct size.

If you want to be rid of the iron liners forever then you need to find second hand nickasil barrels. In passing if you happen to find a spare RHS barrel and piston, let me know.

[montmil]

Goat, What year and model Airhead are you referencing?

[goathands]

It is an R100T that was built March of 1980.

[montmil]

Nikasil-plated cylinders are long lasting. The required piston rings are soft iron rather than chrome as found in the iron bore BMWs. Depending on how long you plan to keep the 100T would drive the decision on the upgraded replacement jugs n' slugs.

I recently replaced the cylinder head assemblies and rings in my 1981 R65. Mileage unknown but definitely a veteran of the road. After scrubbing the bores with hot soapy water and a green ScotchBrite pad, the cylinder glaze was gone and the OEM cross hatching was revealed. That Nikasil coating is some tough stuff.

Let us know which route you decide upon.

[goathands]

Thank you for the advise. I'm pretty invested in the bike.
I Will keep you posted how the repairs go... Pic's too.

[Justin B.]

Apparently the early NikaSil attempts were a bit on the iffy side.  My '81 RT had one jug with large "chunks" of the plating missing and that side had about 60 PSI compression.  I replaced with later model jugs and slugs.

1st pic is the R/H side jug with the defective plating and the other is the L/H side jug which was still perfect.  Notice the cross-hatching still there after almost 90k miles.

[goathands]

Interesting, and you only replaced the one side. Good to know.

[Barry]

Nikasil and other similar plating systems are magic when they work and superior in terms of wear compared to cast iron liners.  But there is some history throughout the automotive industry of plating systems failing even on recent engines. VW (as if they are not in enough trouble) and Toyota are two where my son has experienced horrendous oil consumption due to plating failures. It's a known problem and on say a 5 year old car the repair costs are so high it effectively writes the car off.  I've never had a vehicle with plated cylinders myself and always teased him that my 26 year old Merc with mega miles on cast iron liners used almost no oil by comparison.  I've got to say I wasn't too disappointed to find my new 2009 Merc has cast iron liners and at 50,000 miles oil consumption is close to zero.

So plating is great when it works but can be a serious liability when it doesn't. At least on an airhead the fix is relatively cheap.

[Justin B.]

Goat - I replaced both sides as I got a low mileage L/R set off fleabay...