Casa 185 question

[Adam_Winstone]

Much like the jig that Steve Rowe made for me.... only my little (weak) lathe and poor quality cutting tools don't give me quite such a nice finished product!

[Doom Patrol]

Hang on; before we go off on a I'll show you my jig if you'll show me yours tangent some explanation might be helpful. What are we talking about here? I presume you are machining the head to reduce compression?

[TS1-200]

Problem is, you will enlarge the squish if you machine the head, that is the problem I have at the moment, squish is OK,but I have calculated the C/R at about 11:1, but I suspect its running hot, so really you need to take metal out of the actual combustion chamber,

[dansuper]

Hang on; before we go off on a I'll show you my jig if you'll show me yours tangent some explanation might be helpful. What are we talking about here? I presume you are machining the head to reduce compression?

Correct.

[dansuper]

Problem is, you will enlarge the squish if you machine the head, that is the problem I have at the moment, squish is OK,but I have calculated the C/R at about 11:1, but I suspect its running hot, so really you need to take metal out of the actual combustion chamber,

My squish is spot on, so I don't want that to be affected by the machining. But when the head's on the jig, wouldn't it depend on the tool you're using to remove the metal? I thought you could limit the area so that it would only remove it from the combustion chamber without moving across the squish band?

Having said that, I'm putting this in hands that know a shitload more than I do about this stuff...

[Darrell Taylor]

id be cautious of what your doing as the hard to kick off situation is not a basis to change compression ratio and once material is removed only ally welding/an insert or a new head will get it back
why not test lower compression with an extra head gasket ,i think the casa has a recess but a gasket could be trimmed to fit for evaluation purposes
the hard to kick is more down to the low exhaust duration leading to a longer compression stroke felt on the kickstarter,a common trick on motorcycles was a small drilling above the ex port into the duct that worked as a pressure release but personally id raise the ex port as its extremely low anyway.
on a road going low output motor the squish clearance is not the be all and can be used as a method to obtain lower or higher compression 1mm to 2mm can be used without problem

[Supereibar]

Isn't 11:1 CR a lot for this kit?....

[Darrell Taylor]

the cr is what the manufacturer has decided upon and what everyone who owns one is running without issue i think? ,11-1 im unsure that the head actually is as ive not measured one, most heads i measure have been calculated incorrectly,eden had a head that was sold as 11-1 from memory but actually was 9.8 -1 when i measured it so i take the quoted casa cr as speculation until ive measured a cyl head myself

[Supereibar]

I sit corrected.

Kind regards,

J.

[Darrell Taylor]

not corrected jaimie,was a valid question and 11-1 as you say is fairly high, problems can be caused running it on too lean jetting or std ign timing so if left poorly set up has a greater risk of failure.