Laser engine, how do you tell what size they are?

[Jon H]

8 minutes ago, Martin Harris - Moderator said:

 

Sorry, what I meant Jon, was would there be any possibility of listing identification clues for the whole range.

 

Ah look see, i try and help one chap id his engine and im back doing a job i no longer have for a company that no longer exists at half 7 on a Monday night. I dont mind helping out here and there but going through the entire range from start to finish would be like writing war and peace. Just the 150 alone has about 6 major versions to cover although many of the versions hardly differ visually.

 

I have given details for the 100 and 120, the 150 is the same as the 120 just 100mm tall not 90. That's going to have to do for now. 

[Martin Harris - Moderator]

Fair enough.  I think we're all grateful for your continuing interest and appreciate that any help is a bonus.

[Paul De Tourtoulon]

It might be worth taking the head off and measuring the swept volume.

[GrumpyGnome]

Or just believe Jon..... he's seen more Lasers than all us forumites put together.....

[Ron Gray]

48 minutes ago, GrumpyGnome said:

Or just believe Jon

That would be a first for Paul 🤣

[Chris Walby]

I must be really missing the point, but as its a pushrod engine if you really want to know, just take the head off and measure it? Its not like you will loose the valve timing.

 

IIRC the valve timing is not that extreme so you could fill the cylinder head with oil (not castor!) at TDC, then turn to BDC, fill and the difference is the swept volume.

 

If you can't be bothered with any of that then put it in a test stand and go through a few selected props, measure the RPM and compare with the Laser engine web site for the recommended prop for each engine (slightly more difficult for the obsolete engines, but do-able). 

 

PS, what did the original have on as a prop MC1 (assuming it was propped correctly)?

[martin collins 1]

Prop was a 15x8 Chris.

[Chris Walby]

Spec for the 100

Additional information

DISPLACEMENT	0.99 cu in (16.21cc)
BORE	27.7mm
STROKE	26.9mm
PRACTICAL RPM RANGE	1800-10000
RECOMMENDED FULL POWER RPM RANGE	7500-9000
RECOMMENDED PROPS	14×7-8 15×6-8 16×6
WEIGHT	810g

 

[Mike T]

If you can remove the backplate, measuring the crank throw will give you your stroke and if you can get calipers on the piston skirt at BDC, that'll give you your bore. 

Pi x (bore/2)² x stroke gives you your swept volume.

[Martin Harris - Moderator]

Not on a Laser - the valve gears and cam followers prevent access to the crankshaft and piston so it’s much easier to remove the head to measure bore/stroke if it can’t be identified by other means. 

[Mike T]

5 hours ago, Martin Harris - Moderator said:

Not on a Laser - the valve gears and cam followers prevent access to the crankshaft and piston so it’s much easier to remove the head to measure bore/stroke if it can’t be identified by other means. 

I don't own a Laser (never will...), that's why I qualified with an 'if' 🙂 

Still, it would be an easier method for most other engines - except that the manufacturers of most other engines sensibly cast or engraved their engines capacities on them...