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Effects of mis-matched heads

Started by Greaser Greg, May 23, 2021, 09:30:18 AM

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Greaser Greg

  I don't remember if I put the polished and cc'd heads on this bike I'm working on, or the other one, and a plug hole has stripped while cleaning and checking plugs.  The stripped head looks like some other spares I have in that there are small casting imperfections and the dome is not very shiny.
  What have people noticed about running a set of heads on an R5 where one head of a matched set needs a repair, and is replaced with one that is unchanged from its factory condition?   Stuff like how it runs and if stuff will go wrong?
I get that the compression and squish bands will be different.  Will there be required jetting variance?  What else?   
If the volume is close to the same, is that ok?  How much difference in volume is acceptable?

Basically, I'm hoping for some insight into what can happen if an engine is run, and bike is ridden with two heads that are of different internal volume and combustion characteristics.  Asking for  a friend. :whistle:
Not a race bike, but I will flog it 
Every day above ground is a good one.
'71 R5B "Rusty"  '71 R5B "Decaf"   '99 KZ 250
'97 XL1200S "The Vibrator"   '08 XL1200N  "Greenie" (totalled)
'78 CB750F "The Skunk"   '74 CB550 "Blackie"    '78 Honda Hobbit

m in sc

get a time sert and repair the worked head.

usually no that big of a deal unless a LOT of work has been done, but change them as a set.

Greaser Greg

I get that and will. 
Anybody care to elaborate with the details of why?  Will it just run crappy i.e. not balanced, because of the different squish bands and compression?  (I'm lonely and don't watch tv.)
Every day above ground is a good one.
'71 R5B "Rusty"  '71 R5B "Decaf"   '99 KZ 250
'97 XL1200S "The Vibrator"   '08 XL1200N  "Greenie" (totalled)
'78 CB750F "The Skunk"   '74 CB550 "Blackie"    '78 Honda Hobbit

m in sc

depends whats been done but you want both sides to run as even as possible. hard on crank if they dont.  you have to view an rd, triple, etc, as 2 identical motors linked to each other.

Greaser Greg

Pulled the other head to compare; both stock I think because of the rough texture and steep squish angle.  Also look the same as two other heads I have. 
Two heads in a box on their way to Ed Toomey Designs today! :nana: Might as well get fancy while they're off. :whoop: :celebrate: :bacon:
Every day above ground is a good one.
'71 R5B "Rusty"  '71 R5B "Decaf"   '99 KZ 250
'97 XL1200S "The Vibrator"   '08 XL1200N  "Greenie" (totalled)
'78 CB750F "The Skunk"   '74 CB550 "Blackie"    '78 Honda Hobbit