Gapless rings working

acotrel · Nov 3, 2023

concours said:
Because there is no need.

In a 2-stroke, the rings must be positioned so the ends do not coincide with the ports, and snag.

Do you believe the ring gaps might align and leak compression ? That might happen if you ran the motor at 1 RPM.

BERT · Nov 3, 2023

concours said:
Because there is no need.

In a 2-stroke, the rings must be positioned so the ends do not coincide with the ports, and snag.

That makes perfect sense. Thanks.

MCP · Nov 3, 2023

jseng1 said:
The 1st time I rebuilt the small block the Hastings rings had .025" ring gap. I thought this was too much so I called them and they reassured me that .025" gap was fine and it would not result in oil burning. They were wrong. It smoked and puffed at idle. So I tore it down and installed Deves rings with a tighter gap and the problem went away - at least to the point where oil consumption was normal compared to other motors and its didn't puff at idle.

I also built a VW motor for a friend that ran fine for years and suddenly started smoking. He said it would smoke a few days, stop smoking and then start again. When we tore it down everything looked perfect except that the ring gaps on one piston were lined up and pressure was blowing in a straight shot through the gaps (I was carefull to stagger them during the build but they rotated after a few years).

When you install total seal rings the first thing you notice is increased compression. Less pressure is leaking past the rings into the sump. In other words - "blow by" is reduced. You can have more blow by or less blow by - that is your choice.

So a question from a total novice because your descriptions on oil burn sound similar to what I'm experiencing. Using lots of oil.

I have a 74 850 that had new rings, and barrels honed, plus some head work at the same time in Feb. I put on 2500 miles this summer and last week for example, it burned about 1/2 a quart in 70 miles. Sometimes I can ride 70 - 80 miles and it barely uses any, but generally it burns a lot of oil. Tiny bit of smoke at start up, and a bit at deceleration but not often. Once the bike warms up, there is no smoke when you blip the throttle or idle. Bike runs great otherwise.

The other odd thing, not sure if it is linked, the oil is very dirty, and I have changed it twice over the 2500 miles. I compared my oil colour last week to a friend on a combat who has 4000 miles on his oil over the summer. His oil looked like new and he only added a little bit this year. I'm not sure what the next step should be. Any suggestions?

Fast Eddie · Nov 3, 2023

MCP said:
So a question from a total novice because your descriptions on oil burn sound similar to what I'm experiencing. Using lots of oil.

I have a 74 850 that had new rings, and barrels honed, plus some head work at the same time in Feb. I put on 2500 miles this summer and last week for example, it burned about 1/2 a quart in 70 miles. Sometimes I can ride 70 - 80 miles and it barely uses any, but generally it burns a lot of oil. Tiny bit of smoke at start up, and a bit at deceleration but not often. Once the bike warms up, there is no smoke when you blip the throttle or idle. Bike runs great otherwise.

The other odd thing, not sure if it is linked, the oil is very dirty, and I have changed it twice over the 2500 miles. I compared my oil colour last week to a friend on a combat who has 4000 miles on his oil over the summer. His oil looked like new and he only added a little bit this year. I'm not sure what the next step should be. Any suggestions?

That sounds like bad rings to me (bad as in poor quality).

robs ss · Nov 3, 2023

MCP said:
So a question from a total novice because your descriptions on oil burn sound similar to what I'm experiencing. Using lots of oil.

I have a 74 850 that had new rings, and barrels honed, plus some head work at the same time in Feb. I put on 2500 miles this summer and last week for example, it burned about 1/2 a quart in 70 miles. Sometimes I can ride 70 - 80 miles and it barely uses any, but generally it burns a lot of oil. Tiny bit of smoke at start up, and a bit at deceleration but not often. Once the bike warms up, there is no smoke when you blip the throttle or idle. Bike runs great otherwise.

The other odd thing, not sure if it is linked, the oil is very dirty, and I have changed it twice over the 2500 miles. I compared my oil colour last week to a friend on a combat who has 4000 miles on his oil over the summer. His oil looked like new and he only added a little bit this year. I'm not sure what the next step should be. Any suggestions?

Not the same error as FE in this earlier post? Yesterday at 7:41 PM

Mart UK · Nov 4, 2023

MCP said:
So a question from a total novice because your descriptions on oil burn sound similar to what I'm experiencing. Using lots of oil.

I have a 74 850 that had new rings, and barrels honed, plus some head work at the same time in Feb. I put on 2500 miles this summer and last week for example, it burned about 1/2 a quart in 70 miles. Sometimes I can ride 70 - 80 miles and it barely uses any, but generally it burns a lot of oil. Tiny bit of smoke at start up, and a bit at deceleration but not often. Once the bike warms up, there is no smoke when you blip the throttle or idle. Bike runs great otherwise.

The other odd thing, not sure if it is linked, the oil is very dirty, and I have changed it twice over the 2500 miles. I compared my oil colour last week to a friend on a combat who has 4000 miles on his oil over the summer. His oil looked like new and he only added a little bit this year. I'm not sure what the next step should be. Any suggestions?

Oil on deceleration, suggests valve stem seals. Deceleration creates a vacuum in the cylinders,which will draw air and oil in past the oil seals, if they aren't sealing. Likewise, gravity having the same effect on hot thin oil around the rockers, after standing.

Might also be worth checking the oil drain is clear in the head. IIRC, it is at the rear right, easily accessed from the inlet rocker cover. I cleared out old wellseal from mine with a guitar string.

Fast Eddie · Nov 4, 2023

It’s the dirty oil that’s the giveaway for faulty rings IMO.

MexicoMike · Nov 4, 2023

Check to ensure your rocker spindles are correctly installed. If the spindle oil holes are facing 180 out from what they should be, oil consumption will be excessive because oil will pool in the exhaust rocker box faster than it can drain. No valve seals can control oil if they are submerged!

Further - contrary to common belief, oil can be pulled into the combustion chamber via the exhaust valves/seals/guides. I had a new Ducati 900SS some years ago that the factory issued a bulletin adding exhaust seals to the engines for that reason. Sadly, they only did the work if the bike was still in warranty; if not, it was your problem to buy/install the seals.

jseng1 · Nov 4, 2023

I've also noticed that the oil stays cleaner with the gapless rings. There is less contamination leaking from the combustion chamber into the crank case. Good spring loaded valve stem seals also help.

acotrel · Nov 6, 2023

I cannot believe there would be much leakage through the ring gaps at anything above idle revs. The pistons go up and down and the gas probably goes in both directions through the gaps. The highest pressure would be on the down stroke, so you might be right. But the end gap on the rings is only about 12 thou. With the long stroke, the Commando is near the limit where ring flutter can occur, also - the rings can be out of round and not fit the bore properly. When we buy rings, they are sometimes too big for the bore and we adjust the end gaps by filing.
In the end, theories do not matter - it is what works best which matters. Gapless rings probably give a better fit in the bore.

acotrel · Nov 11, 2023

Due to the discussion about valve seals, I have become interested in gapless rings. What is the brand and specification for the gapless rings which can be used in an 850 Commando engine ?
I am not racing these days, however in life I always have a project. My Seeley 850 project is an unfinished one. When I bought the 6 speed TTI gearbox, I knew I was unlikely to race again. however I still bought it. Do think the guy who painted the Mona Lisa was ever satisfied ? I have another project for which I have almost completely lost enthusiasm. It has a modified H1 Kawasaki motor in an Egli frame and needs expansion chambers - I cannot get motivated to finish it - however my Seeley 850 is very different - it is worth completing.

jseng1 · Nov 13, 2023

Back when I was racing - before gapless rings became popular - I read an article from a road racer about tightening the ring gap. He was experimenting with ring gaps that approached zero at racing temp (you don't want them at zero or binding). He claimed an improvement that I can't verify but I did take his advice and found that I was able to run down to .008" clearance cold without any problems even though I was told by an "expert" that .008" clearance would result in destruction. Any leakage through your ring gap is the same as leakage past the circumference of the rings (as in bad rings that don't seal well). The wider the ring gap or the poorer the ring seal - the more leakage you have resulting in more blow by, dirty oil and oil burning.

This was with Hepolite type pistons and he problem I had was with the heavy thick rings pounding out the ring grooves at high RPM. The rings would get loose vertically and eventually break. This problem went away when I switched to Wiseco pistons and thinner rings. Thinner rings also eliminate the problem of ring flutter over 7000 RPM.

lcrken · Nov 13, 2023

jseng1 said:
Back when I was racing - before gapless rings became popular - I read an article from a road racer about tightening the ring gap. He was experimenting with ring gaps that approached zero at racing temp (you don't want them at zero or binding). He claimed an improvement that I can't verify but I did take his advice and found that I was able to run down to .008" clearance cold without any problems even though I was told by an "expert" that .008" clearance would result in destruction. Any leakage through your ring gap is the same as leakage past the circumference of the rings (as in bad rings that don't seal well). The wider the ring gap or the poorer the ring seal - the more leakage you have resulting in more blow by, dirty oil and oil burning.

This was with Hepolite type pistons and he problem I had was with the heavy thick rings pounding out the ring grooves at high RPM. The rings would get loose vertically and eventually break. This problem went away when I switched to Wiseco pistons and thinner rings. Thinner rings also eliminate the problem of ring flutter over 7000 RPM.

Yeah, I had the same problem with the early Hepolite Powermax pistons. In racing use they would eventually pound out the lands. Never had that issue with using them on street bikes.

Ken

worntorn · Nov 13, 2023

Are gapless rings used in some new auto engines?
I looked up one I'm familiar with, the turbocharged 2.5 litre engine in our new Mazda CX30. It is advertised as producing more power than a small block GM V8.
It makes 320 ft lbs of torque starting from a very low rpm. The car has the same acceleration as a mid 60s 427 Corvette, but the Mazda gets 40 mpg Imperial rather than 10 or so of the Corvette.
Mazda used all the latest tricks to make a super efficient engine that also has a 15,000 km oil change interval.
The piston rings have a conventional gap.

There may be other new autos out there that do use gapless rings. If the gapless rings do add power and efficiency it is strange that Mazda did not use them on this highly efficient little engine.

Glen

jseng1 · Nov 14, 2023

Opinions vary about HP diff with gapless rings. Its one company vs the rest qf the industry. But there is no doubt that your oil stays cleaner and less oil is burned. Compression iseems to be improved at low & midrange RPM.

acotrel · Nov 14, 2023

jseng1 said:
Opinions vary about HP diff with gapless rings. Its one company vs the rest qf the industry. But there is no doubt that your oil stays cleaner and less oil is burned. Compression iseems to be improved at low & midrange RPM.

When I read one of your earlier posts, I got the impression that you experienced a performance boost after you fitted the gapless rings. Would you please explain a bit more about the boost ? Was it measured on a dyno, or was it seat of the pants ?- both can be valid methods.
I have always been surprised that my 850 motor performs so well with so little modification. But I do not use the standard gearbox and the Seeley is very light. I probably do not ride like other idiots, I was brought up riding bikes with which I was always at a disadvantage, so my mindset is different.

acotrel · Nov 14, 2023

Some people road-race to win races. I am only ever there for the dog-fight and to improve my motorcycle. My Seeley 850 is only of technical interest to me. If I wanted to win races, there are much better ways of doing it. I do not have a problem riding motorcycles. I just do not want to become compulsive-obsessive about something which does not really matter. When I was a kid, an H2R Kawasaki cost about $3000 - that was not beyond my reach - but why would I do that ? I was far too busy with other things.

acotrel · Nov 14, 2023

I do not use a dyno to measure engine performance. When I make a change, I ride the bike on Winton Raceway - a circuit whichI know very well. It usually takes me about 5 laps to get up to speed. However the mind gets slower, the longer you are away from riding. So things can look faster. The only way I have ever realised I have made an improvement, is I raised the overall gearing and the bike became quicker. The changes which have had the biggest effect, were fitting the close ratio gearbox, increasing the trail on the steering and leaning-off the jetting to nearly the limit.
A boost at low and midrange RPM, would mean better throttle response to me. With a Commando engine, that is always worth having.

Gapless rings working

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