Piston skirt wear and cylinder condition.
#1
Piston skirt wear and cylinder condition.
Hey guys so I’m in the process of swapping out my crankcases due to a broken motor mount tab. As I removed cylinders and pistons I notice some skirt wear on the rear of both pistons. Is this a normal amount or is this caused by something like flywheel runout or rings improperly installed? And do they look repairable.
Also the intake side of the heads seam to have had some tooling done. Can someone confirm that’s this isn’t how they come stock.
This is my first time tearing down a motor. Any advice is greatly appreciated. Thanks for taking the time to look.
Also the intake side of the heads seam to have had some tooling done. Can someone confirm that’s this isn’t how they come stock.
This is my first time tearing down a motor. Any advice is greatly appreciated. Thanks for taking the time to look.
#3
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#6
Straight wound valve springs indicate pre '05 model and pistons do not look OEM; no coating as typical on OEM pistons. So I am thinking motor work has beed done. Looks like heat, too much timing, poor piston to cylinder fitment and/or sloppy break in; over bore and new pistons for sure. Don't think crank issue is in play but won't hurt to check runout as part of the rebuild process.
The tooling in the intake tells me the heads have been ported to some degree. Post a pic of the chambers/valves. Ported heads would also indicated a possible previous over bore so cylinders may not be reusable. LIke Dan89 says, find a competent machinist familiar with Harleys and he can sort you out on piston/cylinder requirements for the rebuild.
The tooling in the intake tells me the heads have been ported to some degree. Post a pic of the chambers/valves. Ported heads would also indicated a possible previous over bore so cylinders may not be reusable. LIke Dan89 says, find a competent machinist familiar with Harleys and he can sort you out on piston/cylinder requirements for the rebuild.
Last edited by djl; 02-11-2023 at 12:08 PM.
#8
Pistons are not truly round. They are cam turned and that area just below rings is the measure area.
And just looking surprises me you didn't have a very noisy engine from piston slap. Especially when cold, it would sound just like loose lifters.
You need new piston and the cylinders bored true and then cross-honed with a medium coarse hone for finish
Few places have the quality control to do that . Now if you have an outside mic to check piston and a inside mic to adjust to check cylinders.
Then use your outside mic to read your inside mic to see the actual clearance the shop gives you and how straight and round the cylinder are, I would get a set from Harley.
PS. That comment about pistons are not round is only a few .001. And they are round at ring area So before people start bitching, Google it and also how to check pistons and location for wear .
And of course, that's just what I have seen and worked with .
How many miles on it?
And just looking surprises me you didn't have a very noisy engine from piston slap. Especially when cold, it would sound just like loose lifters.
You need new piston and the cylinders bored true and then cross-honed with a medium coarse hone for finish
Few places have the quality control to do that . Now if you have an outside mic to check piston and a inside mic to adjust to check cylinders.
Then use your outside mic to read your inside mic to see the actual clearance the shop gives you and how straight and round the cylinder are, I would get a set from Harley.
PS. That comment about pistons are not round is only a few .001. And they are round at ring area So before people start bitching, Google it and also how to check pistons and location for wear .
And of course, that's just what I have seen and worked with .
How many miles on it?
Last edited by Jackie Paper; 02-11-2023 at 12:23 PM.
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04fxd92 (02-11-2023)
#9
Pistons are not truly round. They are cam turned and that area just below rings is the measure area.
And just looking surprises me you didn't have a very noisy engine from piston slap. Especially when cold, it would sound just like loose lifters.
You need new piston and the cylinders bored true and then cross-honed with a medium coarse hone for finish
Few places have the quality control to do that . Now if you have an outside mic to check piston and a inside mic to adjust to check cylinders.
Then use your outside mic to read your inside mic to see the actual clearance the shop gives you and how straight and round the cylinder are, I would get a set from Harley.
PS. That comment about pistons are not round is only a few .001. And they are round at ring area So before people start bitching, Google it and also how to check pistons and location for wear .
And of course, that's just what I have seen and worked with .
How many miles on it?
And just looking surprises me you didn't have a very noisy engine from piston slap. Especially when cold, it would sound just like loose lifters.
You need new piston and the cylinders bored true and then cross-honed with a medium coarse hone for finish
Few places have the quality control to do that . Now if you have an outside mic to check piston and a inside mic to adjust to check cylinders.
Then use your outside mic to read your inside mic to see the actual clearance the shop gives you and how straight and round the cylinder are, I would get a set from Harley.
PS. That comment about pistons are not round is only a few .001. And they are round at ring area So before people start bitching, Google it and also how to check pistons and location for wear .
And of course, that's just what I have seen and worked with .
How many miles on it?
Thanks for the detailed response.
#10
Straight wound valve springs indicate pre '05 model and pistons do not look OEM; no coating as typical on OEM pistons. So I am thinking motor work has beed done. Looks like heat, too much timing, poor piston to cylinder fitment and/or sloppy break in; over bore and new pistons for sure. Don't think crank issue is in play but won't hurt to check runout as part of the rebuild process.
The tooling in the intake tells me the heads have been ported to some degree. Post a pic of the chambers/valves. Ported heads would also indicated a possible previous over bore so cylinders may not be reusable. LIke Dan89 says, find a competent machinist familiar with Harleys and he can sort you out on piston/cylinder requirements for the rebuild.
The tooling in the intake tells me the heads have been ported to some degree. Post a pic of the chambers/valves. Ported heads would also indicated a possible previous over bore so cylinders may not be reusable. LIke Dan89 says, find a competent machinist familiar with Harleys and he can sort you out on piston/cylinder requirements for the rebuild.
You are correct the bike is an 04 dyna. I plan to have the flywheel checked, trued, and welded. Hopefully I can reuse the cylinders. Luckily I have a shop locally who can do all the machining.