The attached pictures are of heads from a 95 evo with larger valves and a W shape to accomidate the vales. The bike has severe detonation issue's and I am wondering if the combustion chamber shape could be the cause. The motor is bored +10 with dome pistons that have been reduced .030 on the dome, heads decked .030 and a ev23 cam static compression is 160 front and 150 rear.heads-machined.[attach id=110702]heads-machined.jpgheads-machined.jpg
Curious what bore and stroke combination is used to make a 95" evo?
They look like they were done by a car guy that modeled them after the heads on his car.
I'd get a different set if it was me.
You definitely lost a large percentage of the squish area. Less squish area means less chamber turbulence and that aggravates detonation.
Quote from: turboprop on July 25, 2022, 04:45:14 AMCurious what bore and stroke combination is used to make a 95" evo?
I'm guessing 1995 Evo?
Yes 1995 evo motor would machining them so they are hemi- spherical help or hurt ? Or cut out the center point and create a straight edge ?
looking for suggestions to solve the problem, new heads not in the owners budget.
Give those heads to someone that you don't really like.
Someone set those heads up for a race bike. WFO and good fuel, not pump gas and normal driving. They actually look like they would make good power WFO on alky.
Not really worth the effort of fixing them, but should be easy enough to trade for a set of unmolested heads.
To fix them would require a lot of TIG time or cutting that partition out and running a shovel type piston. The low budget repair path would be to cc them, then cut the piston dome to get them down in the 8-8.5:1 compression range. But it won't be a head turner set up like that.
Thank you Thermodyne you are correct on all points the bike is a road king and needs to run on street and pump fuel.
Quote from: turboprop on July 25, 2022, 04:45:14 AMCurious what bore and stroke combination is used to make a 95" evo?
IIRC Axtell had 3 13/16" Iron cylinders for stock stroke EVO's to make 95"
Quote from: xlfan on July 25, 2022, 05:36:20 PMQuote from: turboprop on July 25, 2022, 04:45:14 AMCurious what bore and stroke combination is used to make a 95" evo?
IIRC Axtell had 3 13/16" Iron cylinders for stock stroke EVO's to make 95"
Nope.
3-13/16" x 4-¼" = 97"
3-⅝" x 4-⅝" = 96"
I know of no, common, off-the-shelf bore/stroke combination that equals 95".
For the street, hard to beat flat top pistons and the double D S&S heads...
-JW