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.

 

Plenty of wear on the piston, I'd replace it while I was in there. Probably due to heat. How many miles? Heads have been ported

 

I’m definitely going to replace it. I just need to figure out what piston size I need to match the cylinder because it’s definitely bored over a bit. The bike has 22k

 

You need to get the cylinders honed as well. The shop that does it will tell you what size pistons are needed when they are done.

 

Find a reputable Harley Davidson machinist, he will tell you the size pistons you need, once he has those pistons he will machine the cylinders to the proper clearance.

 

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.

 

When I brought mine in to shop, I had wear on piston and cyliner on rear side, he said it was the load side. It was very noticiable on reverf with 50k, and you could see it a little on stock at 34.

Does it mean something else? Pulled the crank and it looked ok. Did not measure run out.

 

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?

 

I never noticed a noisy engine and the bike ran really well. The bike has 22k. I’ll definitely be taking the cylinders and pistons into the shop to see what I need. I’m really hoping I can keep the cylinders and bore them to accommodate a 95” unless that’s what’s in it already.

Thanks for the detailed response.

 

Thanks for the detailed response.

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.