Squish on stock heads

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biofotis
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Squish on stock heads

Post by biofotis » Thu Mar 10, 2016 11:48 am

Does anyone know what is the stock squish clearance on the bike? I got the engine in parts so I cant check but I would like to machine the heads to 1mm squish before assembly.

dinogt
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Re: Squish on stock heads

Post by dinogt » Thu Feb 07, 2019 5:41 pm

3 years after, I can say you 1.7mm origin squish with 1.23mm thickness top gasket.
Bleu smoke at the horizon

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OZZYSBIKES
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Re: Squish on stock heads

Post by OZZYSBIKES » Sun Feb 17, 2019 6:38 am

HI Dinogt,

A personal thanks (is that merci ? sorry I do not remember much French from my Grammar school days but my excuse is that it was 45 years ago !) to you for contributing to this forum, good information and great website, I have bookmarked your site as help with the NS is now getting thin on the ground,

Back to the subject in hand, I have read that raising compression is a good mod on the NS400 so obviously going from 1.7 to 1 mm would achieve that and improve combustion at the same time due to the better squish,

Can anyone confirm the above ?

Regards Jeff

dinogt
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Re: Squish on stock heads

Post by dinogt » Sun Feb 17, 2019 11:09 am

On each motor with a 56mm diameter (or a little more) need less than 1 mm squish to have good power.
You must call a cat a cat, squish is not compression, squish is a distance and comptession is a mathematical report.
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OZZYSBIKES
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Re: Squish on stock heads

Post by OZZYSBIKES » Fri Mar 15, 2019 8:13 am

I know the difference between squish and compression ratio.
If the squish is reduced then the compression will be raised unless other modifications are carried out,

The question that I asked was a question to any forum members, is it a good idea to raise compression ratio by a small amount ? Does it have any noticeable impact on performance without compromising reliability,

On most production engines the compression ratio is very conservative and can be raised without any negative effect on the engine (I always use quality high octane fuel, Shell usually)

katinas
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Re: Squish on stock heads

Post by katinas » Wed Mar 20, 2019 9:20 am

Hi,

This is just from long testing with NS250/400 engines, but maybe it could help.

All NS400 head modification on stock engine, depends on ignition system.
With the stock ignition and unchanged squish band width, squish height must be no less than 1-1,2 mm, with 13,5-14 cc head volume (with plug hole) on 98 RON, 14-15 cc on 95 RON.
The stock ignition is too much advanced for higher compression and smaller squish gap, with stock, wide squish band. This cut power at higher revs. Just AVGAZ can help.
0,7-0,8 mm squish works only with retarded stock ignition, or narrower ( 4-5 mm) squish band width.

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