Piston rings

I used Hepolite Apex rings on my 850 when fitting new rings in the 80's. They had a 3 piece oil control ring. The Wassell Hepolite piston's are moving over to a similar ring made by Goetze. They may supply the rings seperately. The 850 burns no oil to this day.

Holger, it would be good to see more pics of your seized piston to be certain, but from the clues in the pic you have posted that was most likely a 4 corner seizure which is from an overheated piston. Unless you have fixed what caused the piston to get hot then its liable to happen again. Four corner seizures are not related to rings.

See http://www.marshland.co.nz/ftp/2Strokes/PISTON%2520SEIZURES.pdf

Four corner seizure: Both sides of the piston will show heavy scoring and seizure marks on each side of the wrist pin hole. The pattern of these four seizure points often appears to be a perfect square, hence the slang term "four corner". The scoring takes place in this pattern because those areas of the piston casting are the thickest.

In an air cooled engine the most likely cause is insufficient piston clearance, hopefully you had the bore re-honed and this will have opened up the clearance.

When I rebuilt my Electra with 20,000 miles in 2004 I put in new rings without a rebore. Same pistons. Honed bore. One piece oil control ring. Used about a pint every 500 miles. Replaced rings 7000 miles later, when main roller replaced. Did not hone bore. One piece oil control rings never seemed to bed in.

Now at 36,000 miles. Still on original bores and pistons. Ring set with 3 part oil control rings recently fitted and no fall in oil tank level after a 700 mile trip to Hampshire 10 days ago.

These are the same rings as identified as Twiflex above. If you can find them, they really seem better in my limited experience.

Peter

Taylor Mattersons when they were open sold an oil control ring, made by Wellworthy. They were part of the AE Associated Engineering Ltd.They were called Duaflex oil control rings. They are of a three piece design, and are 68 x 5/32 x.117 chrome. I have used them in my Dominator engines. I bought many of them back then and i still have some left. 

Are your bores worn? How many miles have they done since the last rebore or is it still on its original bore? Just using a flexy hone or the three sprung leg type of hone will only put a fancy surface on the bore. They are more correctly called glaze busters. It wont correct a tapered/oval bore and that is what needs correcting first. Get the bore measured and then decide what needs doing. A proper cylinder hone is one made by Delapena, Not cheap and the use of it will require the bore getting measured with a comparitor (bore gauge)      

Speaking only of singles experience here: In a model 50 with a +30 piston and a bore within tolerance; I bought a NOS set of rings from RGM made by Cords of London. These took up the slack and restored a lovely quiet engine. (No re-bore and piston required to achieve the same) 

By the same token, there used to be a top ring called the ridge dodger, or words to that effect.

All I'm saying is that an expensive re-bore isn't always necessary and a step towards a re-sleeve.

Sounds like you fixed the root cause. Happy riding.

Honing for cast iron rings is done with 150 to 180 grit, the 3 piece oil control will be a steel ring  but top and middle will be cast iron. So 240 would still be too fine. 

OEM supplier to Ford, Jaguar, Land Rover and Vauxhall.  A quality supplier of motor industry  components.  I have used their products in many rebuilds with great reliability.

J

I do the following.

1. Hone for cast iron

2. Wash the bores repeatably until a white cloth rubbed in the bore comes out spotless.

3. Dry piston assembly with a couple of spots of oil on the front and back of the piston well below the rings.

4. Get the bike started, if timing needs doing then get it over very quickly and do not let the engine idle for any length of time.

5. Get out on the road and vary the throttle with shot bursts of full throttle and no lugging at low revs. This creates the highest combustion pressures which get behind the top two rings to force them out to bed in against the hone.

If all that has been done is new rings then after 100 miles of the above you should be bedded in.

The honing and the rings wear against each other, so lots of debris, so change the oil often. I do the first at 50 miles.

Castor oil would not be my choice for a running in oil but the strip down to move from breaking in oil or a cheap supermarket oil to castor does not give you options other than go for castor 30 wt during running in before going to castor 50 wt. Why use Castor on a road bike ?