TOPIC:

i bought 1045 kit (71mm bore) for my mk2 but it has original compression ratio : can i put a small thickness gasket as Copper .010 /.005 to add a little cr ? WHich should i take ?
thank

I don't know the answer to your question, but you may want to consider the fact that bumping up the compression ratio doesn't really push the HP up very much. Either of the links below will let you easily calculate how much power you can gain as you increase the compression ratio. Ed

www.wallaceracing.com/hp-cr-chg.php

www.bgsoflex.com/crchange.html

For a higher compression you need pistons with a higher dome.

stock Piston



Tuning higher cr Piston

There are several ways to raise compression.
First question is why?
What is the cranking compression now?
How do you know the new pistons are the stock ratio?
You will need to know where you are now to know where you are going.


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Use a thinner head gasket if one is available or have the head skimmed.
0.5mm off is roughly equal to a 2cc reduction in combustion chamber volume at this size and a 1 point increase in compression so 9 to 1 would become around 10 to 1.
You really need to cc the head and do the cylinder volume calcs to get an exact figure.
I would also make sure your pistons are set at zero deck height from the start to get the most out of the changes .
If they are below the recommended height you will be starting with less compression that you think and vice versa if above.
Also be wary if your new pistons are cast and not forged as some of these cheap cast kits may not be up to the job of coping with the increased loads.

No eBay APP ID and/or Cert ID defined in Kunena configurationi bought many times ago , i took this one because from usa shipping's cost and duty tax are a lot (for italy)

I would build a torque fun bike and i've just vm29ss , head ported , valve job did , frame braced
what you reccomend ?

You get what you pay for and those IMD pistons are just cast copies of the original OEM ones which were themselves cast..
Not heard anything bad about them so hopefully they should be as good as OEM and should stand a bit of a compression hike via a head skim.
Vm29's will be plenty good enough for what you have and just those with a ported head on a stock motor makes a noticeable improvement.

As others have stated, those are just 2mm over stock pistons. The valve pockets are as stock and it is not safe to machine them deeper, So when you machining the head to raise compression, you are putting the valves that much closer to the piston. Also, surfacing the head retards the cam timing.

But if you already have them, they will probably make a bit more power than stock.