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Post Info TOPIC: Overboring


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Overboring
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I bored out my cylinder to 58mm.Do i need to bore the head also or there is no problem?



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Guru

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depends on if its to high on compression, but should be ok



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i did have a clearance issue and had to widen the squish band a little on one of my heads but that was for a 58.9mm piston. also the head gasket is too small for the larger oversizes, what i did was scribed around the inside with my vernier caliper set to the measurement i  wanted and then used a dremel to just take off the edge to the line i marked.  for the head measure the crown of the piston and then measure the width of the squish to see if you will have a clearance problem or not.  Also because your also going over a mm oversize on the piston you will have to check clearance on the powervalve roller and grind some off to suit (much easier to do and adjust wile the barrel is off)



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how do you make gifs
1988 DT125R


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Once i get my piston i 'll check.I have already grind my valve about 1mm.

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power valve? there was a topic on this issue

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I GO TO WORK I FIX BIKES, I GO HOME I WORK ON BIKES, I GO TO SLEEP I DREAM BIKES! HEELLLPPPP :)



Guru

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iv had a question on my mind a while about overbores ,,, does it make the bike perform better or not i have a +1.50 and i have a complety standard top end im sure is quicker with the +1.50 top end fitted on it

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well its will be higher on compression but only slightly

mines +1 mm which is 133cc

more CC= more powerbiggrin



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DTR Respected Member

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yeah 'no replacement for displacement', lost count of how many old boys said that to me over the years, 1mm overbore is 129.4 cc its a 2mm over bore that gets you 133cc (got me double checking my math there as i'd bothered declaring the size on the v5 lols)



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how do you make gifs
1988 DT125R
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