Hello. This is my first post on here. I have owned a 1970 XLCH for 3 years. I'm attaching pictures from when I first rolled in on the trailer and the last pictures I took to show the difference.

Before I bought this bike it sat for 23 years. I got it running before the title was even transferred. It has burned oil and smoked since I bought it. Now that I have more time and a little more money I have decided to rebuild the top end.

This last summer I only put about 200 miles on it since I noticed a knocking sound from the front cylinder top end. Currently the motor is on the floor and the heads are on my kitchen table. I have taken the rear rocker cover off and the rocker arm looks great. I haven't taken the valves out to check them out yet.

I just wanted to start a post to get input from experts. The cylinders look to be in great shape still. My plan is to check the valves, seats, springs. Anything else?

All input is appreciated! I'm looking forward to my first top end rebuild.

 

I would pull the cylinders off and have a look at the pistons. Post pics here of the pistons and of the cylinder bores. Use flat/indirect lighting and no flash so the details will show up.

With the cylinders off, and with the primary partially dismantled you can check the rods for play. You will need a couple of large sockets and perhaps an air impact [rattle gun]. The details are in the Factory Service Manual 99484-78.

If you do not have the FSM, and also the Factory Parts Catalog 99451-78B, you should order these as they are your most important tools. Enter the part numbers into the Google and eBay searches or just buy from a local bike shop or HD dealer.

 

I pulled the cylinders off. The pictures are attached. There are no grooves in cylinder walls. Next time I go out to the garage I will take pictures of the pistons.

 

I am not an expert on this so you should get another opinion, but those vertical lines in the cylinders should not be there. They are a sign of the pistons or rings scraping the cylinder walls; could be from overheating or inadequate oiling.

What we should see is the original hone marks which are more cross-hatch/circular and not vertical. My opinion is that these cylinders need to be measured and honed; they may need to be overbored to the next size up.

Best done by a good automotive machine shop - especially a shop that regularly does work on vintage engines, especially cast iron engines. And they need to have the HD FSM in hand and study it before doing the work.

I am anticipating that there will be similar vertical lines on the pistons, again a sign of overheating or inadequate oiling.

The pistons should have a code on the tops, either STD for standard size pistons or a multiple of 10 in the range {010, 020, ..., 170} indicating the overbore size .010" etc.

If no one else chimes in here with more expert opinion i will have more suggestions.

 

I agree, those lines appear to be wear. Your cylinder bore may be "out of round." New iron "settles" from repeated heat/cool cycles over time. The settling causes the round hole punched in new iron to become slightly less than circular. Having them bored (your machinist will know how much) will clear the wear and restore the shape. The bonus is your rebuilt top end will hold up better over the long haul than a new one because the cylinders are more stable.

 

Since you have it down and your going to it RIGHT.. I would do the UNLEADED vale job so you can bune unleaded gas. I would replace the pistons with new ones 10.1. I also would bore out your oil galleys so you have more oil going to the top end of the motor.. One if the things that Harley should of done in the first place.. To much oil at the bottom end instad at the top end.. Just open up the galleys alittle bit.. Hope this helps you a little..

 

+1 on the valve job.

In the almost 10 years of being on these forums and listening to many experts who have worked on IronHeads since the 60s and 70s, including guys who had their own shops etc, i have never before heard this suggestion of opening up the oil galleys. So i would research this idea carefully before giving it serious consideration.

Perhaps ironhead tommy could give us more detail, historical, technical, whatever.

 

them cylinders are wasted. shouldn't be any lines. time for a over bore.

 

It's like a heart with arteries, the smaller the artery less blood flow or in this case less oil. The trick was to open up the oil gallarys slightly so you would have more oil flow through the engine. So the answer of the story is to open up the oil gallarys for more flow. Harley Davidson always had more oil flow at the bottom end of their motors instead of the top end where it should be. We all know oil flows down. That is the reason why iron heads run hot on the top end.

If your having your motor done thru a certified mechanic. Ask him about opening up the oil galleries. The valve job I mentioned is so you can run the unleaded gas that's on the market today. They call it the unleaded valve job. I hope this helps you.
Ironhead Tommy

 

With all due respect, but this sounds more like a personal opinion than accepted technical practice. So my recommendation to people is to not consider having this done.

You might consider posting this idea on the IronHead forum at XLForum.net There are several guys there whom i have known for years, who have been IronHead mechanics for decades. It would be interesting to see what discussion would ensue.