Topic: Piston Orientation

[Ellz10]

So I asked awhile back and never got an answer about this. This 836 kit came from Ken at Cycle X and he labeled them as such. 1-4, 2 L's and 2 R's.

Now I thought they were to be installed in numerical order, however, after thinking about it and looking at the bottom of the valves, the Pistons themselves and the way the 2 Lefts are the same and opposite that of the 2 Rights, I believe I'm correct in assuming that the 2 Lefts should be installed on the first 2 on the left when looking at the cylinder from the cam chain tensioner point of view. So in reality it's 1, 3, 2, 4. 

Correct?

[scottly]

1 2 3 4

[PeWe]

Pistons with valve pockets like these must match the head.

Check that spark plugs have clearance to pistons. Some high compression pistons need double washers under plugs.

You might need a test assembly anyway.

You'll see when looking at the head and how valves are located.

From dynoman's piston
tech page.
http://dynoman.net/tech-sheets.html


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The entire pdf show ring gaps with orientation too.
This for 890cc forged pistons.
http://cloud.tapatalk.com/s/6236ca79d98ff/67mmSOHC%20%286%29.pdf

[david 750f]

You guys have me confused now... Is this only for the Cycle X kit? I hope this doesn't apply to the Wiseco 836 kit. I installed them with the factory arrow pointed towards the exhaust (As per the instructions). Haven't had any issues.

[PeWe]

This is for ALL pistons with valve pockets like this.

2 type of pistons  in each kit, pockets are milled where valves are. 
The larger cut out for IN valve. But they must be installed right, as the picture shows which is how it look like when looking at the cylinder 1,2,3,4 like head but mirrored.

That is obvious when looking at the pistons.
I have early cast RC836 (65mm), modern forged JE890 (67mm), JE970 (70mm) and JE1005cc (71.25mm) where the valve cut out look like this and must be placed in right cylinder.

Each piston match 2 cylinders.
The modern pistons  of today seems to have same size and weight so less need to verify which of 2 bores it match best for balance.
Like 1 match 2, 3 match 4 and 1+4 match 2+3 weightwise.

See how chambers look like, valves to get more space into pistons.



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3 different 836 pistons
Early cast RC (marked to fit 1,3), later forged RC, cast Action Fours.
The left one must sit in correct cylinder. Kit of 4 has 2 types.
The other, all 4 pistons look the same in a kit, only thing is correct orientation. IN side has larger cut out.

Some pistons have wristpin displaced a little. How it will act at TDC.

[Ellz10]

I'm more confused now than I was before. I think I'll just give Ken a call and see what's going on with placement.

Oh and to clarify, they are Wiseco Pistons 65mm.

[PeWe]

You will know when looking at the piston crowns.

Like the photo I added about 3  836 pistons side by side.
Piston can have an arrow pointing to exhaust (front).

If you cannot see this difference there are more that can go wrong if you assemble the engine. Better you get help to do it.

This thread started with a kit where there are 2 different pistons that must be placed in right cylinder.

[HondaMan]

You guys have me confused now... Is this only for the Cycle X kit? I hope this doesn't apply to the Wiseco 836 kit. I installed them with the factory arrow pointed towards the exhaust (As per the instructions). Haven't had any issues.

Yours are correct.

[craz1]

Pretty obvious by looking at the valve configuration. if you take a look at his marking for piston 1-2 there is a right and left for that side. Piston 1 is on the left and piston two is on the right for that side. So piston 3 would be on the left and piston 4 would be on the right for that side of the bike. Just install 1-2-3-4 starting on the left and you will be good.

[Ellz10]

Ashamed to admit, but I did take a look and I was wrong all the way around. The orientation was indeed 1-4 in order, however I wasn't looking at the head in the correct position. Suffice it to say, all is well, last night I installed them correctly and the cylinder is now on.

Side question if anyone cares to share some insight:   When spinning the crank slowly after installing the pistons in the cylinder on the crankcase, is it normal to hear a noise from the pistons moving up and down in the cylinders? Like a quiet scratching is the best way I'd describe it. Or should it be completely silent when spinning the crank with a socket?

[bryanj]

You can get a noise from the scraper rings

[PeWe]

Scratching sound normal with new pistons in fresh bores.

I rotate the crank to see how all pistons move up and down  looking for scratches in bores after rings.
There is a risk that a ring has sharp burrs or other errors.

Easy to see the oil film in bores when pistons are at lowest position. 1;4 vs 2:3

[Ellz10]

You can get a noise from the scraper rings

Great, thank you!

Scratching sound normal with new pistons in fresh bores.

I rotate the crank to see how all pistons move up and down  looking for scratches in bores after rings.
There is a risk that a ring has sharp burrs or other errors.

Easy to see the oil film in bores when pistons are at lowest position. 1;4 vs 2:3

Ohh thats a good idea, I didn't think of that! Thank you for this, I will be checking tonight!!

If there were to be a burr or some other abnormality with any of the rings, would it present itself as a scratch on the cylinder wall or in another way?

[PeWe]

Probably seen as scratches. The marks in oil film after ring gaps the only thing I have seen sofar. 

I have pistons with paper thin oil rails (XA rings) , too easy to pinch one. 
It hooked into the expander and could not compress enough and came outside the groove.
 I noticed it direct, no damage in bore but I ordered new ring set when I did not trust a slightly bent oil rail.

I filed the inner corners of the oil rails end gaps rounded so it could not hook into the expander for easier assembly.

I gave another set same treatment just for sure, thicker rings, XC.

Sharp ring ends seen, felt by finger, in time so they could be rounded off with grit 400 paper.

All ring gaps checked in bores before assemble them on pistons?
0.25mm on all work fine. This is often the gap when measure. 

Measure with feeler gauge when ring is pushed into the bore by piston to make it to sit right.
This to make sure that no ring is too tight.