To remove the liner from an M20 barrel, is there any point in heating it up? As I guess the barrel and liner will expand at the same rate? I can't find a youtube clip other than car/truck engines and ally motorcycle barrels. Ron

email (option): ronpier@talk21.com

37 years ago when I had a new liner in my m20 barrel I watched the engineer stuff a wet towel in the bore and play a flame torch around the cylinder.A mandrel went in the base of the cylinder and a few blows with a lead mallet had it out.

Sounds like a good idea, even put the wet towel in the freezer for a while to get it really chilled.

email (option): tknalder@iinet.net.au

That's interesting information.
If anyone ever tries this, let us know if it works !

Definitely not as simple as that from my experience today. I managed to move the liner in my hydraulic press by the 4mm that sticks out the bottom, but without a precisely made arbor to continue the push, it's impossible. So I spent 15-20 minutes with a new hacksaw blade reversed in my hacksaw and sawed through enough to collapse the liner with a long chisel.

To fit the new liner, I heated the barrel to 250 degrees in my workshop oven whilst the liner sat in the freezer. Me and my press work extremely hard for about 3/4 hour and I still didn't get that last 4mm home. Ainsley will finish it in his big press when I take it over next week for the rebore. Ron

email (option): ronpier@talk21.com

I normally remove them by boring them out until they are wafer thin and then collapsing them.
Cheers, Mick.

email (option): 1963mickholmes@gmail.com

If only I had a boring bar Mick:smile: Ron

email (option): ronpier@talk21.com

Looks good, Ron.
But wasn't it easier to find yourself another cilinder alltogether ?
Or are they becoming hard to find nowadays ?
(can't help noticing that it is rather quiet on the parts offered/wanted front these days)

Well that barrel has been on the bike since I bought it in the 80's and the fins are perfect. The new guides and valves haven't covered all that many miles and I already had the liner in stock from many years ago.

The truth is, I had it bored out 1000 miles ago to accept an 85mm piston to compliment the long stroke M21 crank that I fitted years ago. But I just find the engine too lumpy for my liking. I was more than happy with it in its 600cc state so I've decided to go back to it.

Ron

email (option): ronpier@talk21.com

Did you heat the barrel to 250 F or 250 C?

If 250 F, that is not hot enough. You need to get it up to at least 400 F and the liner will drop in.

The barrel gets hotter than 250 F when the bike is being ridden.

Well it was the 250? on my oven which is as hot as it gets. Ron

email (option): ronpier@talk21.com

They sure do come out and go in hard. I tried to get one out of a 16H barrel once with a 20 ton jack pushing against the main beam of the house, I stopped when I realized the thing wasn't coming out and the house was going to start going up. So I took it to a marine engine shop, they had a press with a piston on it as big around as a 5 gallon bucket, he pushed the old one out and new one in dry, no heat or anything, made it look like you could have done it with one finger. When he got done he said in the thickest downeast Maine accent "Thare ya go mistah! Just as tight as a white bean in a black cats ahss! " Whatever that means, but anyways, the answer is certainly more pressure. :smiley:

email (option): cormiersam@hotmail.com

Pushing it out is the lumberjack way..
As Mick mentioned, the way to do it is to mill it out until it collapses.
And, when the milling is set up correctly it makes the bore at the desired straight angle to the rest of the plot.
As you will be amazed at what 'artistic' angles the old ones sometimes are !
have fun!

Ainsley has a 100 ton press with a nice pressure dial on it. We set it up and took the pressure up to 12 tons for the final 4mm push, but nothing moved until we played a large butane torch around the fins for about 60 seconds. all in now and ready for its rebore for a standard BSA M21 piston. Ron

email (option): ronpier@talk21.com

Rebore completed yesterday. I've washed all the grinding dust off and lapped the valves in. Ron

email (option): ronpier@talk21.com

Very nice, Ron...In a way, I'm quite pleased to hear that the big-bore long stroke way doesn't necessarily make for a nicer motorcycle. Val Page and his colleagues knew what they were doing. :relaxed:

It is all about balance
Changing the bore & stroke alters the engine balance which a lot of people seem to ignore.
Just the same way as altering the compression ratio alters the balance .
Thus things like the "sweet spot" where vibrations cancel out will shift substantially.
Ideally when you go big bore long stroke you should have the entire crank dynamically balanced to around peak torque.
On most side valves this will be between 3000 & 4000 rpm .
Now as we all know dynamic engine balance ex factory was some what random.
I had 3 B40GA's at one time and each one had a different sweet spot to the point one was almost unrideable because of the massive vibrations at 6000 rpm in 3rd which was needed for a smooth change into 4 th

As there is no tacho on our bikes it is easy to ride according to engine sound & vibrations.
Thus when things change it becomes a problem because the sound where we used to have a nice comfortable ride is now in an excessive vibration zone.

When you change the output one should always determine where the sweet spot is then regear the bike so our usual riding will have the engine running in the comfort zone.
And some times this can be done with the countershaft while other times you need to alter the primary .

I could not count the number of times I have transformed some ones unrideable monster to the nicest bike they have ever ridden by altering the gearing

I have also owned bikes that would happily do 5 mph sideways when on the center stand because they were so out of balance at ideling speeds.

The commercial way to remove liners from iron castings, is to run welds down it's length. This way the liner will fall out with no damage to the casting. Just use a low current as you don't want any penetration.

That said let the company doing the finished bore do the whole job, if they can't they are the wrong people.

email (option): pes.sales@btconnect.com

Beware of just 'upping the tonnage' when using a press...Broken barrel base flanges aren't a pretty sight...

An excess of force generally indicates an incorrect method...Ian

email (option): ian@wright52.plus.com

Yes Ian! Ainsley an I were aware of that. But Ainsley has a large selection of large bearing outer races and found one that made a good all-round the bore support. I've just come in from completing 52 running in miles and it's a lot smoother.

The bigger piston was also giving me starting problems. Nothing to do with the higher compression of course, as the valve lifter takes care of that, But whether it was sucking in more fuel or something else....I just don't know, but I spent quite some time kicking on odd occasions and even changing the plug.:thinking_face: Ron

email (option): ronpier@talk21.com

['Very nice, Ron...In a way, I'm quite pleased to hear that the big-bore long stroke way doesn't necessarily make for a nicer motorcycle. Val Page and his colleagues knew what they were doing...']

Val Page is my favourite designer without a doubt and many of his designs are represented amongst the more practical motorcycles..In fact I have his picture on my workshop wall....

However, I would suggest that, by any measure, my oversized M20 is an improvement on the original specification in terms of its performance for long distance touring and for use under modern road conditions, along with the additional bonus of improved fuel consumption due to the increased efficiency of the overall layout bought about by the changes..

Simply enlarging an engine to improve its power without any other consideration of its specifications and how the changes will affect its operation and overall characteristics is an over simplistic approach and one that may, or may not, result in a better machine...It's purely down to chance based on the components used and the subject engines specifications....

As Trevor notes crankshaft balance is key in this situation...I have built 720cc M20s (and other capacities) both with and without rebalanced crankshafts and the former results in a very sweet and smooth engine...In fact it is often the case that the performance of an original standard crank assembly can be much improved by applying modern balancing methods, as original production tolerances and methods were frequently not as accurate...With Royal Enfield twins as a notable exception most companies statically balanced their cranks...Dynamically balancing them is a more accurate method used my most companies offering that service currently...

I appreciate the original designs as much as anyone and also appreciate there is a valid argument for wanting the 'original' experience provided by using a standard specification engine but in reality all designs can be improved upon to suit individual requirements and the only reason some don't do it is simply because they've made the choice not to...Ian

email (option): ian@wright52.plus.com

Ever since I had the A65 balanced @ 4500 rpm it has become SOP on every engine rebuild
BEst $ 200 any one can spend
Now I would not pull a good engine down to get it done but if the crank has to come out then it is a trip to the heat treatters for a carbo nitride then another to the balancer
I killed the A65 by pretending it was an A 10 , gearing it up to get better fuel economy and a longer range.
SO the new build was balanced at 4500 so it is uncomfortable to ride under 3500 and really nice from there to 6000 which has me in license loosing land.
When I eventually get around to fitting Ians nice new big bore pistons I am looking to do a dynamic at around 3000 rpm.
In reality I should build it get it dynoed then balance to just above peak torque but on most long stroke side valves that is somewhere from 2500 to 3500

['Ever since I had the A65 balanced @ 4500 rpm it has become SOP on every engine rebuild
best $200 any one can spend..']

What's SOP..?....Ian

email (option): ian@wright52.plus.com

Standard Operating Procedure :wink: