Fuel Requirement??

N

northernSRX

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Joined
Dec 2, 2010
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Age
46
Location
north sask
I have a 2000 mountain max 700 with thin thin head gasket mod, air box mod, power inc triples. Fresh top end rebuild and never really rode it. Check the compression yesterday and all 3 are at 175 psi. Wondering if premium (91 Octane) would be safe to run? Thanks
 
that cpmression is kinda high.Check with another gauge.I could see it maybe being around 135 to 145 normal,but that is after the motor has been broken in..If it has 175,then after you ride it and break it in..it will climb even higher..FULL RACE FULL THEN!!! Compression really should not be in that range unless you are full out running a race setup...but I am not an expert on that..lol
 
I had a sx/mm conversion with the same mods. Compression was 153, no problems with 91 untill I got a bad batch.
 
checked compression again was the same with same 175 on all 3 with the same brand of gauge but was up to 200 psi on a different gauge (Equis) brand. Now im am wondering if the 600 cylinder head on the 700 would cause it to be so high. 700 head was warped leaking coolant so used the 600 head
 
northernSRX said:
checked compression again was the same with same 175 on all 3 with the same brand of gauge but was up to 200 psi on a different gauge (Equis) brand. Now im am wondering if the 600 cylinder head on the 700 would cause it to be so high. 700 head was warped leaking coolant so used the 600 head
Click to expand...

OH YAH that would do it! DON'T RUN IT LIKE THAT!

You need to find a 700 cylinder head for your 700. The pistons could contact the underside of the head gasket surface as the diameter of the outer edge of squish band is too small among other things such as too small of combustion chambers ect.

Bob
 
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