Author Topic: Worth it to machine the head?  (Read 578 times)

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Offline JTknives

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Worth it to machine the head?
« on: December 18, 2019, 09:40:43 PM »
So after a year I am back in the cb500 build. The business really picked up and I had no free time. But my plan is to get it up a running this winter. So I have already rebuilt the carbs and now need to move onto the head. This is where I ended last year because the wife bought me a replacement for Christmas as mine was really hammered. Burnt valve seats and at least one stripped spark plug hole. Also one cylinder looked like someone hammered on it. So after I got the replacement I looked it over and noticed it was bead blasted and it was chuck full of grit inside the intake ports and valve springs. So now I’m guessing I’m it’s going to require a complete strip down and massive cleaning. I noticed while looking it over it has some imperfections in the face of the head. I’m wondering if I should machine it down to clean up. I am a machinist by trade so it’s no big deal to do. Also I scored a 650 cam for $55 which I jumped up as thy are about near impossible to find now a days. So my question is if I’m going this route should I remove more and up my compression. I am not a mechanic so I am not sure which way is best to go. I machine metal for a living so that’s what I’m good at. This is why I am here asking for the expert advise from you guys. Thanks - JT

Offline JTknives

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Re: Worth it to machine the head?
« Reply #1 on: December 18, 2019, 09:43:21 PM »
P.S. I have a surface grinder at my home shop with a 8”x24” chuck that would make quick work of this and give it a perfect finish that’s perfectly flat even more then a mill.

Online dave500

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Re: Worth it to machine the head?
« Reply #2 on: December 19, 2019, 12:48:42 AM »
don't try and up the compression,just skim enough to flatten it if it really needs it,ive never come across one that does.

Offline Bodi

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Re: Worth it to machine the head?
« Reply #3 on: December 19, 2019, 03:46:35 AM »
Minor surface damage won't be a problem. If it is warped then resurfacing is the usual fix, the barrel surface should be checked and also resurfaced as required. Minimum material should be removed to reach flatness. Hold down fixturing is tricky for the head, it can be bent by holddowns and sping back to warped. The barrel section is much stiffer and less trouble.
Aluminum is not friendly to grinding. I've never seen a head or barrels done on a surface grinder. Maybe there are wheels and procedures to do it? The surfaces I have gotten from machine shops after milling were really nice and I don't think a ground surface would improve sealing.

Offline calj737

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Re: Worth it to machine the head?
« Reply #4 on: December 19, 2019, 05:27:21 AM »
Keep track of how much material you remove from the head and cylinders if you do machine them. The locating dowels between the two surfaces must be trimmed in relative height to allow the surfaces to mate flush.
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