Running Piston Rings In

[Yorks Lamby]

I've always some may say gone to the extreme on running new rings in going to 450 mile, anyone else say otherwise, the cylinder was run in a long time ago so maybe a lot less than 450 miles is needed, i know some say 100 mile is enough...any thoughts?

Thanks

[Toddy]

I've always some may say gone to the extreme on running new rings in going to 450 mile, anyone else say otherwise, the cylinder was run in a long time ago so maybe a lot less than 450 miles is needed, i know some say 100 mile is enough...any thoughts?

Thanks

Cast or a modern cylinder ?

[Warkton Tornado No.1]

I’d done a detailed response then lost it all when ‘tinternet fell over

Bedding in depends upon what the rings are made of & whether the bore is as OEM (cast iron) or plated….

[Yorks Lamby]

Thanks for replies, cast iron original Innocenti cylinder also put a new piston in, it is not a 'rebore' just new piston & rings...

New Meteor piston & rings i.e. current ones

[Warkton Tornado No.1]

I hope this helps. I lifted this from t’internet & edited it a bit. I think it is excellent advice & would stress that a fan cooled engine needs revs to avoid overheating.

IMO this following procedure applies to the majority of Lambretta top ends but ‘hard’ rings with a ‘hard’ bore will require more bedding in*



Bedding in Lambretta Meteor steel piston rings (often 1mm ‘racing’ type) requires a careful, heat-cycle-driven approach to ensure the rings seat properly against the cylinder wall, maximizing compression and longevity. Meteor rings, specifically those often used in 175cc/200cc kits, are high-quality and sometimes chrome-plated, needing a specific break-in process to prevent glazing*

Recommended Bedding-In Process

Initial Startup & Heat Cycles:

Start the engine and let it idle until the cylinder head is warm to the touch, then shut it down and let it cool completely. Repeat this 2-3 times.

The First 50–100 Miles:

Vary Speeds: Avoid constant throttle positions. Use the full throttle range, but avoid wide-open throttle (WOT) for extended periods.

Gentle Load: Ride in a hilly area if possible, as the alternating load/deceleration helps seat the rings.

Keep RPM Moderate: Do not exceed roughly 75% of your max RPM, but don't lug the engine.

Oil Choice: Use a high-quality 2-stroke oil. Avoid fully synthetic oils for the first few hundred miles as they can prevent the rings from bedding in **



* Although it may be obvious, the harder materials used in chrome rings & plated bores will need a longer period for bedding in, but the trade-off should be that the finished result should last far longer than OEM type piston rings & bore.

**There’s more to consider - besides the rings & bore - particularly the lubrication of the big-end & whether the engine is piston port or reed valve, so if the oil normally used is ‘proven’ - whether synthetic or not - it may be best to stick with it.

Don’t make the common ‘schoolboy error’ of adding more oil during bedding in. This will not only hinder the process, a richer oil mix means a leaner fuel/air ratio.

[Yorks Lamby]

I hope this helps. I lifted this from t’internet & edited it a bit. I think it is excellent advice & would stress that a fan cooled engine needs revs to avoid overheating.

IMO this following procedure applies to the majority of Lambretta top ends but ‘hard’ rings with a ‘hard’ bore will require more bedding in*



Bedding in Lambretta Meteor steel piston rings (often 1mm ‘racing’ type) requires a careful, heat-cycle-driven approach to ensure the rings seat properly against the cylinder wall, maximizing compression and longevity. Meteor rings, specifically those often used in 175cc/200cc kits, are high-quality and sometimes chrome-plated, needing a specific break-in process to prevent glazing*

Recommended Bedding-In Process

Initial Startup & Heat Cycles:

Start the engine and let it idle until the cylinder head is warm to the touch, then shut it down and let it cool completely. Repeat this 2-3 times.

The First 50–100 Miles:

Vary Speeds: Avoid constant throttle positions. Use the full throttle range, but avoid wide-open throttle (WOT) for extended periods.

Gentle Load: Ride in a hilly area if possible, as the alternating load/deceleration helps seat the rings.

Keep RPM Moderate: Do not exceed roughly 75% of your max RPM, but don't lug the engine.

Oil Choice: Use a high-quality 2-stroke oil. Avoid fully synthetic oils for the first few hundred miles as they can prevent the rings from bedding in **



* Although it may be obvious, the harder materials used in chrome rings & plated bores will need a longer period for bedding in, but the trade-off should be that the finished result should last far longer than OEM type piston rings & bore.

**There’s more to consider - besides the rings & bore - particularly the lubrication of the big-end & whether the engine is piston port or reed valve, so if the oil normally used is ‘proven’ - whether synthetic or not - it may be best to stick with it.

Don’t make the common ‘schoolboy error’ of adding more oil during bedding in. This will not only hinder the process, a richer oil mix means a leaner fuel/air ratio.

Thanks, i think first 100 mile is likely enough (others have said 100 mile is sufficient), probably take it steady for another 150 miles to be on the safe side as the cylinder is worn in.

Had a few nips which i've put down to fuel starvation & the piston that was in it you could clearly see that hence changing it & the rings, no major scores on the cylinder but you can see where it has nipped.

[hullygully]

cast iron re-bore & piston, castrol for first full tank, 1000 miles, 30, 35, 40 etc.........
piston & rings only, 500 miles

new alloy kit, 500 miles.
new piston & rings, a very carefull 250 miles

[Yorks Lamby]

cast iron re-bore & piston, castrol for first full tank, 1000 miles, 30, 35, 40 etc.........
piston & rings only, 500 miles

new alloy kit, 500 miles.
new piston & rings, a very carefull 250 miles

Thanks, i've previously run new rings in upto 450 miles probably too much, piston is exactly the same piston (Meteor) as was in previoulsy would have thought a few hundred tops but asking as some have other opinions on this usually head on side of caution but off away soon so doubt i'd get more than 300 mile in by then on her.

[Warkton Tornado No.1]

One further piece of information I would suggest to be of use is that a honing tool is a very worthwhile addition to anybody that rebuilds their own engines that utilise a cast iron/steel bore. TBH there have been occasions when I have carefully ran a honing tool up a plated bore due to some kind of edge or damage existing, but I realise such a practice is contrary to normal recommendations

The three legged, sprung type can be used to good effect, but I think it worth emphasising certain conditions to achieve good results. They can be bought for far less than the price of a pattern piston & will cover a range of bores. Honing legs in various grades are available to allow for working through from course to fine.

The honing legs should be as long as can be obtained. IMO 4” is the minimum & if anybody knows of any reasonably priced longer - say 6” - legs available, I’d be interested. The longer legs tend to allow for the transition of the legs over the ports without snagging or tipping.

The sprung pressure should be adjusted so that it is as light as possible & only gradually increased.

The rotational speed needs to be very slow & it should not be presumed that all electric/battery drills will allow for such control whilst having enough torque for the task. For example, of all the power tools I own - which include B&D, Bosch, Hitachi & Makita - the Milwaukee M18 is the best as far as trigger finger control.

A cutting fluid in copious quantity is necessary. Paraffin, white spirit, turps, proprietary cutting fluid, GT85 or WD40 will all work but the emphasis is upon allow the honing stones to cut, not lubricate it as many oils will.

A really good cross-hatch finish can be achieved with care which is ideal for rings to run in. Don’t forget to thoroughly debut port edges & wash out the barrel of all debris prior to use