Installing Pistons in cylinders (2010)

Thanks, I just used an oak "scraper" and a LOT of elbow grease. I used a lot of WD 40 to help the cleaning but it does not do anything at all to dissolve carbon. I shaved an oak stick to different shapes as needed to get into various spots. There must be a better way but I didn't have any serious chemicals available. I used to work in performance car engine rebuilding but we had "guys" who took the old parts and, when we got them, they looked new. I never was directly involved in the process so I don't really know what they used. I know they hot tanked cast iron but you can't do that with AL.

I have made my own ring compressors, too. Two strips of aluminum (about 20 gage) and large hose clamps. I think the pair cost me about $3. I found it a snap to support the pistons on a pair of roughly 3/4" wood dowels and just slide the barrel over the pistons. Unscrew the clamps, remove the clamps, strips and dowels, and let the barrel slide home.

I may be crude but I've done Nortons two ways, I used my fingers to compress the rings when I had nothing around, and once I oiled the rings and just used hose clamps. The block of plywood trick is hard to beat for keep everything steady.

I tried for ages to put the barrels down over the pistons with a set of clamps & got really peed off not being able to do it.
I had put a set of cord rings on the bike which I got from RGM in UK.
Thery are better i'm told for using in worn bores. You have 2 thin rings in each grove instead of just one.
This makes it really hard to get them in without one popping out as the rings are really thin.
I put the pistons in the barrels first & then fitted the barrels on the bike. I managed it 2nd attempt & was really pleased.
You've Just got to remember to have a mate helping you, put the barrel gasket on 1st & put the inner circlips on before fitting the gudgeon pins in place.
Quite easy even for a plonker like me. Best of luck with the job.
Cheers Don

Hi Mike,

I'll post the other view point. Have always assembled pistons to rods then cylinders to pistons. I've been working on Commando engines for 29 years and owned Commandos since my first one in '72. Normal ring compressors are typically too tall to be useful. I use two stainless hose clamps (AKA Jubilee Clips in UK speak) which are just wide enough to engage all three rings. Put something under the piston skirts across the open crankcase such a a piece of wood or I sometimes us my flat tire irons, stabilizes the pistons. Lower the pistons onto the blocks so they don't move around. As the cylinder slides over the pistons the hose clamps are forced downward. Once the rings are in place, unscrew the clamps and remove, take out the blocks and let the cylinder down onto the crankcase studs...done.

Do you guys hone your cylinders when installing new rings, and if so, with a ball hone - what size grit? Thanks

Gday Mike, heres a picture of my Commandos head showing a hole drilled through 3 fins for exrta airflow. I learned this on the forum somewhere in a previous post, apologies to whoever it was but cant remember its creator. Living in Australia it gets pretty hot so thought it worthy a try as every bit helps.


Regards Foxy

That's from Ludwig's bag of tricks. Thanks for posting though, it's great to actually see a photo.

"Do you guys hone your cylinders when installing new rings, and if so, with a ball hone - what size grit? "


The wall finish depends on the ring material - cast iron, chrome faced, moly, etc so you need to know what the ring manufacturer recommends for wall finish. It can vary from 180 to 600 based on the rings.

There is some current thinking that if you are just refreshing the engine and there is no reason to bore the motor, then there should be no honing. In other words, honing is ONLY done if there is boring. If you are just putting in new rings, and did not need the engine bored, you would not hone the bores. Yes, this goes against conventional wisdom re ring seating but there is a LOT of "new" thinking about how all this works and plenty of reported evidence that it works better and that ring seating occurs instantly and no break in is necessary. As I said in another post re ring gaps, I am not recommending this - just pointing out that there is a lot of interesting new information about how engines react that are different than perviously thought. It's worth doing some searching about it just to get an idea. But take it from me, it's difficult to change to something that goes against MANY years of doing it a different way! Dry piston/ring installation is another new concept at several shops I used to work with in car -engine building do that now but I couldn't bring myself to do it on my Commando last week so I compromised by lightly wiping some oil from a cloth onto the rings and piston sides...I guess I call it the "semi-dry" method!

Re ball hones. They work well but I would not use one in a non-bored engine. Because of their design, they will follow any warpage or non-true surface, just putting a nice hone on the non-true area that the piston ring won't touch. The standard 3-stone hone tends to true the surface to some degree. Obviously, any type of hone is not designed to actually true the cylinder wall, that's what boring is for.

Thanks RennieK and of course a bigger thanks to Ludwig! In the photo I posted, it shows up also just how rough the push rod tunnels are!
Also MexicoMike are those standard size valves fitted? Rgds Foxy

Yes, they are standard size (stem and head) Norton 850 valves, "Black Diamond" brand.

Gday Mike, I was interested as they looked large to me, Im putting 41 mm inlets into my 920,s head to help it breath abit better. The ports have been opened up to 33.5 mm aswell. The valves started out as RGM 42 mm but seeing Im leaving the valve angle as standard, I turned them down .5 mm for a liitle extra clearance.DR-HILLIER pm,d me and said he runs 2 Commandos like this with no trouble, he did say he checked clearances first. The valves used are of wasted stem semi tulip type, the wasted stem Im told is for weight saving rather than better air flow.

Rgds Foxy

Sorry for reviving an old thread but...
Is the "cooling" drilling in post #27 above worth doing while you've got the head off?
I see it's attributed to Ludwig.
Any thoughts/experiences?
Cheers
Rob

I did it.

Is it worth doing?

Whether or not it makes any significant difference, I do not know, but it’s a very simple job, and the theory stacks up, and I’m not aware of any down side, so on balance, I’d say it is worth doing.

I have used ring compressors, I have plenty of them. I have also used my fingers; I have never broken a ring using the finger method. I use the Comnoz technique of using 4 deep sockets to support the cylinder with installed pistons/rings, then pin them to the connecting rods. No heavy hands, no mallets. I do check ring end gap prior to mounting on the pistons.

Fast Eddie said:

I did it.

Is it worth doing?

Whether or not it makes any significant difference, I do not know, but it’s a very simple job, and the theory stacks up, and I’m not aware of any down side, so on balance, I’d say it is worth doing.

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Thanks Nigel - I'll do it too then - doesn't appear to be a downside!

Cookie said:

I may be crude but I've done Nortons two ways, I used my fingers to compress the rings when I had nothing around, and once I oiled the rings and just used hose clamps. The block of plywood trick is hard to beat for keep everything steady.

Click to expand...

Same here. Only issue ever was when the machine shop that bored the cylinders forgot to re-bevel the cylinder spigots. Hose clamps work fine. I tighten them up, place the cylinder and then take the tension off a little bit at a time until the cylinder just slips down on it's own.