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Hi all,
I have the model with 44mm carbs and twin pipes and rebuilt it this past summer after a crank bearing meltdown, the motor got bored .020 over and minimal case matching but I think I used too thick of a base gasket, I used the .040 gasket and did not shave the head...I was told by a friend I needed to change the gasket to a .030 and shave the head .030 Is this right? Right now the squish measures from .080 to .085 .
I am kind of wondering which gasket to use and how much to shave the head, The sled runs great but just doesnt seem the be what it was before...the idle used to be pretty stout...good sounding almost popping sound and now it sounds anemic and low end power is not there, more like a low end bog then at 4000-4500 it goes like a rocket!! Could I have put the rotary valve in a couple of degrees off and it's causing this? or a combination of that and the lower compression from the thick gasket? maybe timing?? I've tried everything to get rid of the horrible low end...thorough cleaning of the carbs, checked both carb boots for cracks etc.. sync'd the carbs and air screws are at 1.5-2 turns out, cleaned primary and secondary drives and replaced the belt, replaced plug boots .
This weekend I'm going to tear into the motor to change the base gasket and if I have to shave the head and retime the rotary valve with the degree wheel, at rebuild I just put the mag side at tdc and lined the valve up with the factory scribe so we'll see!! anyone have any base gasket suggestions or just suggestions as to what may be causing this anemic low end...Like I said carbs were thoroughly torn apart and cleaned and made no difference so I'm at a loss!!

Thanks,
Brian
 

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allrighty...heres how i see it . i think with the pipes your gonna want to run a thick base gasket, at least what ya got. your at .085 now , take .020 off the head and youll be at .065...or put a .050 gasket in and take .030 off and be at .065. i personnally wouldnt run less than .065 on the 670 on the trail...their piston eatin machines....now if your just 500 footin it then .050.
 
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