Replacing Piston Rings
11-29-2011, 09:18 PM
#2
RE: Replacing Piston Rings
I always get one end up out of the groove with a scribe and just go around the piston and the ring is off and over the top.
To put the new one on - I start one end down the side and more or less thread the ring around the piston and it snaps in place.
You need to clean out the piston ring groove with the old ring before installing the new ring.
There is a pin in the ring groove opposite the exhaust port where the ends of the ring go.
Orient the ring so the tapered end of the groove fits on each side of the pin.
To put the new one on - I start one end down the side and more or less thread the ring around the piston and it snaps in place.
You need to clean out the piston ring groove with the old ring before installing the new ring.
There is a pin in the ring groove opposite the exhaust port where the ends of the ring go.
Orient the ring so the tapered end of the groove fits on each side of the pin.
11-29-2011, 10:05 PM
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RE: Replacing Piston Rings
Further to this discussion, i just replaced the piston, ring and cylinder on my NGH and there is almost no compression.
What should i check? Ring gap? Something else?
What should i check? Ring gap? Something else?
11-29-2011, 10:21 PM
#5
RE: Replacing Piston Rings
like mentioned above work the ring around...try not to expand it... it can break.... i was changing the ring on a st50 glow engine when i didnt know any better and i snapped the ring/// it was brittle
http://www.youtube.com/watch?feature...cHfWlhtM#t=31s
run it up some...the compression ought to improve a bit....
i have an old dl50 with an estimated 15+ gallons through it and it doesnt have a whole lot of compression but it runs like a champ
http://www.youtube.com/watch?feature...cHfWlhtM#t=31s
ORIGINAL: CustomPC
Further to this discussion, i just replaced the piston, ring and cylinder on my NGH and there is almost no compression.
What should i check? Ring gap? Something else?
Further to this discussion, i just replaced the piston, ring and cylinder on my NGH and there is almost no compression.
What should i check? Ring gap? Something else?
run it up some...the compression ought to improve a bit....
i have an old dl50 with an estimated 15+ gallons through it and it doesnt have a whole lot of compression but it runs like a champ
11-29-2011, 10:26 PM
#6
RE: Replacing Piston Rings
This requires going back to the basics
Cylinder finish
Piston to cylinder fit
Ring gap
Spark plug tight
With some Chinese engines, the cylinder wall is "as cast" with the nicosil coating sprayed on. The trueness of the cylinder is not always the best in the world. There is essentially no quality control on a spare part.
Chinese rings are typically very hard and do not conform well to the uneven cylinder.
If the measurements seem to check out, you may have to attempt to run the malfitting parts in with an electric drill or something?
Cylinder finish
Piston to cylinder fit
Ring gap
Spark plug tight
With some Chinese engines, the cylinder wall is "as cast" with the nicosil coating sprayed on. The trueness of the cylinder is not always the best in the world. There is essentially no quality control on a spare part.
Chinese rings are typically very hard and do not conform well to the uneven cylinder.
If the measurements seem to check out, you may have to attempt to run the malfitting parts in with an electric drill or something?
11-30-2011, 08:07 AM
#7
RE: Replacing Piston Rings
Jumkie, Thanks for the video. I thought the guy was serious until he started to twist the ring. Did he use the ring? This is truly a "Do not try this at home" moment.
w8ye, Ernie, Good technique you got there. I am using the Brison(Mahle) cylinders and rings I got from Bill Jensen. I hone the cylinder with 400 grit paper and have good results with plenty of new compression.
Dan.
w8ye, Ernie, Good technique you got there. I am using the Brison(Mahle) cylinders and rings I got from Bill Jensen. I hone the cylinder with 400 grit paper and have good results with plenty of new compression.
Dan.
11-30-2011, 11:32 AM
#8
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RE: Replacing Piston Rings
Here we go again....
Google "careful with that hone Eugene"....
Posted here a few times before....
honing is for iron cylinders and very hard piston rings, neither of which we have in our gassers...Chinese rings are hard, but the same thing applies...
Wonder why Frank Bowman's rings work so well ? Softer material that works better with our chrome of NikaSil cylinders....
Our race engine guru checked on getting about 100 unfinished cylinders rough cast in China, unplated...Cost about $ 10-15 dollars each...Then will get sent to a shop in the USA for finish machining and plating, where the bore size can be correctly plated and finished to OUR specs, round and straight within a few ten thousandths..Probably will use Bowman rings...
We WILL have the best and strongest made in USA 6061 aluminum CNC crankcases with rotary or reed valve racing engines...Look for prototype at the AMA show in January in California at the USRA race booth....
The prototype 180 cc engines are making over 40 HP at 9000 rpm turning 31 pitch props...Might try a carb on one, just to see how it would relate to 3D sport engines...
Gonna be fun
Google "careful with that hone Eugene"....
Posted here a few times before....
honing is for iron cylinders and very hard piston rings, neither of which we have in our gassers...Chinese rings are hard, but the same thing applies...
Wonder why Frank Bowman's rings work so well ? Softer material that works better with our chrome of NikaSil cylinders....
Our race engine guru checked on getting about 100 unfinished cylinders rough cast in China, unplated...Cost about $ 10-15 dollars each...Then will get sent to a shop in the USA for finish machining and plating, where the bore size can be correctly plated and finished to OUR specs, round and straight within a few ten thousandths..Probably will use Bowman rings...
We WILL have the best and strongest made in USA 6061 aluminum CNC crankcases with rotary or reed valve racing engines...Look for prototype at the AMA show in January in California at the USRA race booth....
The prototype 180 cc engines are making over 40 HP at 9000 rpm turning 31 pitch props...Might try a carb on one, just to see how it would relate to 3D sport engines...Gonna be fun
11-30-2011, 07:33 PM
#9
RE: Replacing Piston Rings
ORIGINAL: Antique
Here we go again....
Google ''careful with that hone Eugene''....
Posted here a few times before....
honing is for iron cylinders and very hard piston rings, neither of which we have in our gassers...Chinese rings are hard, but the same thing applies...
Wonder why Frank Bowman's rings work so well ? Softer material that works better with our chrome of NikaSil cylinders....
Our race engine guru checked on getting about 100 unfinished cylinders rough cast in China, unplated...Cost about $ 10-15 dollars each...Then will get sent to a shop in the USA for finish machining and plating, where the bore size can be correctly plated and finished to OUR specs, round and straight within a few ten thousandths..Probably will use Bowman rings...
We WILL have the best and strongest made in USA 6061 aluminum CNC crankcases with rotary or reed valve racing engines...Look for prototype at the AMA show in January in California at the USRA race booth.... The prototype 180 cc engines are making over 40 HP at 9000 rpm turning 31 pitch props...Might try a carb on one, just to see how it would relate to 3D sport engines...
Gonna be fun
Here we go again....
Google ''careful with that hone Eugene''....
Posted here a few times before....
honing is for iron cylinders and very hard piston rings, neither of which we have in our gassers...Chinese rings are hard, but the same thing applies...
Wonder why Frank Bowman's rings work so well ? Softer material that works better with our chrome of NikaSil cylinders....
Our race engine guru checked on getting about 100 unfinished cylinders rough cast in China, unplated...Cost about $ 10-15 dollars each...Then will get sent to a shop in the USA for finish machining and plating, where the bore size can be correctly plated and finished to OUR specs, round and straight within a few ten thousandths..Probably will use Bowman rings...
We WILL have the best and strongest made in USA 6061 aluminum CNC crankcases with rotary or reed valve racing engines...Look for prototype at the AMA show in January in California at the USRA race booth....
The prototype 180 cc engines are making over 40 HP at 9000 rpm turning 31 pitch props...Might try a carb on one, just to see how it would relate to 3D sport engines...Gonna be fun
11-30-2011, 10:07 PM
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RE: Replacing Piston Rings
On the chrome plated cylinders - do we just put in a new ring if needed and no roughing up of the chrome whatsoever then? Or if they get tired, toss the cylinder and piston and start over perhaps?
Thanks,
Ernie Misner
Thanks,
Ernie Misner
11-30-2011, 10:16 PM
#11
RE: Replacing Piston Rings
You do not hone the chromed or nikasil cylinders.
But when reworking one of these engines it is often necessary to buff some grooves with some fine paper.
If you get too aggressive you will go through the hard coating and ruin the cylinder
But when reworking one of these engines it is often necessary to buff some grooves with some fine paper.
If you get too aggressive you will go through the hard coating and ruin the cylinder
12-01-2011, 01:47 AM
#12
RE: Replacing Piston Rings
Frank Bowman recommends a light sanding with 400 to 600 sandpaper when putting one of his new rings in.
I hope nobody is taking that video seriously for our engines. The rings on our engines are brittle and usually cannot be twisted sideways without breaking.
AV8TOR
I hope nobody is taking that video seriously for our engines. The rings on our engines are brittle and usually cannot be twisted sideways without breaking.
AV8TOR
12-01-2011, 05:07 AM
#13
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RE: Replacing Piston Rings
I always bend the ring open by thumb pulling on the ring ends, and index finger pushing inward at the 60° stations. That is about the same way that a mechanical ring expander works.
This makes the ring expand in a circular way, and it slips over the piston easily enough. I never broke a ring this way.
I did manage to damage ring grooves by winding the ring in, so I don't do that again.
This makes the ring expand in a circular way, and it slips over the piston easily enough. I never broke a ring this way.
I did manage to damage ring grooves by winding the ring in, so I don't do that again.
12-01-2011, 05:17 AM
#14
RE: Replacing Piston Rings
A guy set me a ringed Webra that he had got the ring gap caught in the exhaust port. I got a hold of the end of the ring and pulled it off the piston through the exhaust port like I was pulling out a piece of bailing wire. I thought the ring was heat damaged? Maybe it always was like the one in the video?
But I've put them on and taken them off like he shows in the video for 50 years.
But I've put them on and taken them off like he shows in the video for 50 years.
12-01-2011, 08:05 AM
#15
RE: Replacing Piston Rings
w8ye, Should Bowman change his little instruction sheet to take into consideration the cylinders that are lined. I used 400 grit paper on mine. After a couple of flights the compression is very high. I hate to think that I trashed the cylinder. Those things are expensive, and worse, may not be avaiable any more. Dan.
12-01-2011, 08:20 AM
#16
RE: Replacing Piston Rings
I have never broke a new ring on installation. I catch the ring ends with my thumb nails and support it with my index fingers so tension is not in just one spot. I never "wind" rings on with a twist. The only time I broke a ring is on getting a stuck one out of ring grove. A broken ring ground square makes a good tool to help remove carbon in a ring grove...but go easy! Capt,n
12-01-2011, 10:01 AM
#17
RE: Replacing Piston Rings
ORIGINAL: All Day Dan
w8ye, Should Bowman change his little instruction sheet to take into consideration the cylinders that are lined. I used 400 grit paper on mine. After a couple of flights the compression is very high. I hate to think that I trashed the cylinder. Those things are expensive, and worse, may not be avaiable any more. Dan.
w8ye, Should Bowman change his little instruction sheet to take into consideration the cylinders that are lined. I used 400 grit paper on mine. After a couple of flights the compression is very high. I hate to think that I trashed the cylinder. Those things are expensive, and worse, may not be avaiable any more. Dan.
Frank is talking about some 400 W or D in your fingers and just scratch around in there a little to take the glaze off.
I have not been doing anything to the cylinders that were smooth to begin with and the rings usually seat with the first tank.
12-02-2011, 12:27 PM
#20
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RE: Replacing Piston Rings
ORIGINAL: w8ye
Some people want to run a hone in the cylinders and hone them until the cross hatch marks are consistent top to bottom. This is not going to work on our small engine.
Frank is talking about some 400 W or D in your fingers and just scratch around in there a little to take the glaze off.
I have not been doing anything to the cylinders that were smooth to begin with and the rings usually seat with the first tank.
Some people want to run a hone in the cylinders and hone them until the cross hatch marks are consistent top to bottom. This is not going to work on our small engine.
Frank is talking about some 400 W or D in your fingers and just scratch around in there a little to take the glaze off.
I have not been doing anything to the cylinders that were smooth to begin with and the rings usually seat with the first tank.
I usually take a little kerosene and a scotch brite pad and run it around in the nikasil coated cylinders before placing a new ring in.
If the hardness of Nikasil is reported correctly then you would need a diamond hone to cut it any way, that is not counting the chinese flame coatings.
