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compression and squish
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Author:  Wolf [ Sun Nov 06, 2016 1:55 pm ]
Post subject:  compression and squish
Dear community,

i'm preparing a 750cc motor for my TT2. currently i deal with the compression ratio which is way over the 10.3:1 which is my goal. I'm using pistal pistons, heads with the bathtup-geometry. Since the crankshaft is already balanced (the other way around might have been favorable) I don't want to remove too much material from the pistons...anyway, is there a rule of thumb how thin the piston dome might become?

an easy way to get rid of the compression, is to use a thicker gasket - how large may the squish become?

Any comments are welcome!

Cheers

Wolf

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Author:  Carlo [ Sun Nov 06, 2016 4:42 pm ]
Post subject:  Re: compression and squish
Hello, you make one squishy 1.2 mm, and the compression ratio is just so, for my humble opinion :)
Author:  sports [ Sun Nov 06, 2016 6:42 pm ]
Post subject:  Re: compression and squish
As Carlo says, 1.2mm is OK for squishy. I find 1mm is still OK but 1.2 is a good starting point.

If the pistons are up to 10 grams out either way on a 50% balance factor it isn't worth the effort of getting closer and risk loosing the desired compression - In my own humble opinion.
Author:  Eldert [ Mon Nov 07, 2016 5:17 am ]
Post subject:  Re: compression and squish
Hi Wolf

another option would be tulliping the valves .

Eldert
Author:  Wolf [ Mon Nov 07, 2016 7:29 am ]
Post subject:  Re: compression and squish
Thank you so far!

Eldert, this is an interesting idea with the tulliping of the valves

is there any experience how thin the piston dome may be?

I think this is my bottle neck....

Wolf

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Author:  Eldert [ Mon Nov 07, 2016 10:32 am ]
Post subject:  Re: compression and squish
Lacey Ducati has some fitting notes for pistons on his website . see if the link works

http://www.laceyducati.co.uk/news/?page_id=75

Eldert
Author:  Wolf [ Mon Nov 07, 2016 10:40 am ]
Post subject:  Re: compression and squish
Eldert,

this is helpfull, thanks a lot!

Wolf
Author:  Carlo [ Mon Nov 07, 2016 6:07 pm ]
Post subject:  Re: compression and squish
Hello friends, the problem does not present 'ever, if the motor shaft is more' heavy of a possible balance. If the crankshaft is heavy, it never vibrates instead if the crankshaft is more 'light of the rod weight calculation + half of the connecting rod, more' calculating the remaining oil inside the crank pin, then the motor will vibrate.

If you leave the original drive shaft and mounted lightweight pistons, the engine does not vibrate. The problems come if the crankshaft is lightened too.
Author:  brad black [ Wed Nov 16, 2016 7:29 am ]
Post subject:  Re: compression and squish
when i fitted the high comp ferracci pistons to my otherwise factory 750 engine, they were 50 grams lighter (same as an 800 piston btw) than the originals and there was no change in engine vibration that i could feel.

i wouldn't open the squish. that can lower the comp, but also make it more likely to detonate.
Author:  Wolf [ Wed Nov 16, 2016 1:46 pm ]
Post subject:  Re: compression and squish
Brad,

this is good news for me - I estimate that each piston have a lesser weight of 18g - this should not matter than

Wolf
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