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How you gonna change the CC of yer head???? The Piston will dictate how much you can shave the head/jug interface....
Bust out the Welder??
thanks, but I'm simply asking, what is the average size of the combustion chamber on a completely stock evo? Is it 85cc 83cc ?
Once I know the ball park estimate of what my stock heads are, size wise, will determine whether I take them to the machine shop to get milled / cc'd or whether I just bolt them back on.
hope this makes sense now.
Cheers
thanks, but I'm simply asking, what is the average size of the combustion chamber on a completely stock evo? Is it 85cc 83cc ?
Once I know the ball park estimate of what my stock heads are, size wise, will determine whether I take them to the machine shop to get milled / cc'd or whether I just bolt them back on.
hope this makes sense now.
Cheers
thanks Texas, that's what I've seen on the BB calculator..... just heard from other people who build motors that they are often a bit larger? Sometimes around 85cc .... that's why I asked.
But if there's a good chance mine are 83cc then that saves me a trip to the machine ship and an extra cost.
Cheers.
OT. I also have a '92 with breathing heads, but I'm using the bottom breather.
Is it possible that it also have the rockerboxes for a head breather then?
If so, should I close the vents off, because right now it has hollow bolts holding the air cleaner?
Top breather heads have the same casting number as non-breather. However, breather heads have a drilled port - on the top of the pushtube side forward of the rockerbox mounting threads closest to the intake port. That drilling continues the port thru the side of the head where the air filter backing plate mounts.
Generally, the mounting threads for the air cleaner are larger on breather heads, but easiest way, if looking at a photo - look for an extra hole near the 5/16" tapped hole on the intake end. Breather type heads also require a different rockerbox for those ports, but they can be used on older engines, either with the later rockerboxes or without plugging the outlet on the engine case. The earlier rocker boxes will simply cover the port on top.
In '92 1/2 they did away with the fitting on the right case, under and behind the oil pump where the breather was located and began allowing the crankcase to breath thru the top and back into the intake... for EPA I reckon. Though I have seen a few 92's with breather heads AND the case fitting for a breather. Mid-year changes - ya gotta luv em
Will a top breather rocker box spacer(some folks call em D Rings) work for a bottom breather?
Actually on my 80 inch, dual plug EVO, I run a case breather and head breathers.
I run a reed valve on the case breather and that motor never dripped anything.
It's in the garage put away and made room for a 127 in my FLSTF.
Someday I'll throw together and old time scoot and use her again.
Last edited by Construct; Apr 20, 2021 at 10:20 PM.
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