harleyKmodel

Hello,

This is my first post to see if I might get the benefit of the collective wisdom here while in the process of topping a KHK. I'm retired from the aviation business and now spend much of my time fussing with old bikes in my friend's shop. He also is retired from the AvBiz and tinkers with vintage bikes and cars. I've mostly owned and worked on Guzzi, Ducati (Bevel), Triumph and a smattering of other sundry bikes, but this is the first Harley that's come across the transom. In ages past I worked at a Harley shop north of Atlanta where Clete Borchert was the service manager if he's familiar to some here as the "Old Dude" in Old Dude Motorcycles.

Anyway, I pulled the top end apart for smoking and plug fowling problems and found that the rings are shot and the pistons (.070: O.S.), though in reasonable shape, had a bore clearance of about .005" which I take to be rather over limits per the manual that the bike owner provided. I noticed that the cylinders had aluminum spacers that you can see below leading me to wonder if they are actually K Model cylinders spaced up to the appropriate KHK height. Common practice?

I see that at least one parts supplier has .080" pistons for 750cc flatheads ( http://www.45restoration.com/ ) so hope is to bore for a set of those to clean it up and get back to an appropriate bore clearance. 45restoration in their catalog recommends .003 - .004" rather than the .001 - .0015" that the manual I have recommends for the early Sportster. Thoughts?

Also, this bike has 18mm spark plugs which from what I can find on the internet is not correct for a KHK. It has Champion K-12G fine wire plugs installed, but thinking of replacing with NGK A6 or Champion D16 which it appears are appropriate for earlier flatheads. Again - thoughts?

George
Vancouver BC

Quick way to tell is look at the base of the cylinder - you will see either a -52 (K model), or -54 (KH/KHK model)...

Those are some thick stroker plates - what do your flywheels look like? Any markings?

Simon wrote:Quick way to tell is look at the base of the cylinder - you will see either a -52 (K model), or -54 (KH/KHK model)...

Those are some thick stroker plates - what do your flywheels look like? Any markings?

I haven't looked, but will tomorrow. Will check the barrel numbers too.

G

Stroker plates on a KH using K cylinders are 5/16" thick. Pistons for a 45ci WL H-D do not work in a K model, K deck height is different. All 45 pistons are a -29 part number, K are -52. Piston pin location differs and 45 pistons won't reach the top of the cylinder.

Piston clearance is usually supplied by the manufacturer. It will depend on whether they are cast or forged. Different piston materials expand different amounts. The more silicon content the less expansion.

Make sure the piston oiling circuits are there. I run Std K pistons in the KHKs bored and fitted to .001" to .0015" With easy break in. 10 to 15 heat cycles before ripping up the road. If sleeved some folks don't drill oil feed. The long stroke requires this oiliing to live even more than the 45".

OK, got to the shop. Measured the stroker plates and they are 3/8 "/ .375" rather than the 5/16" mentioned by Rubone. I can only surmise that this is because they have been made to seal with o-rings in machined grooves you can see in the bottom photo on both sides rather than gaskets on either side. When the heads came off it was apparent that the pistons extended about 1/8" above the upper edge of the cylinder bore. Apparently, this is normal from what a photocopy of a section of what I take to be a service manual that was with the bike says.

The cylinders have a cast in number that ends in -52 so I take it that they are K model.

Simon: I looked through the timing hole and on the outside of the crank flywheels and besides the timing marks on the side, the only other marks visible is a "B" stamped into both flywheel halves adjacent to each other.

I got a reply from Old Dude and they don't have any .080" O.S. pistons or the exhaust valves, so I guess the hunt for those will continue. Any suggestions for the next place to inquire about those?

The oiling holes are there and the stroker plates have corresponding holes that are even counterbored to allow for o-rings.

Nothing on the 18mm spark plugs?

G

KH flywheels in a sportster . plates are usually 3/8 ".

Well, if you're going to shell out for new pistons - or sleeving - you could always shell out a little more and get some -54 cylinders. They won't be getting any cheaper moving forward. .080 and I would think the bore is getting pretty close to the valve seats?

Looks like the work done on those stroker plates was thoughtful.

What sort of cams do you have?

Simon wrote:Well, if you're going to shell out for new pistons - or sleeving - you could always shell out a little more and get some -54 cylinders. They won't be getting any cheaper moving forward. .080 and I would think the bore is getting pretty close to the valve seats?

Looks like the work done on those stroker plates was thoughtful.

What sort of cams do you have?

Since this is an "outside" job, it's only getting the repair work the owner authorizes, so no plan to pull the timing cover and see what's in there. The replacement barrels sounds like it might be a good way to go if they're not already at .070" over like these are though a set of -54 barrels is probably serious unicorn shit. Another possibility is to get them Nikasil coated by Millenium and use the pistons that are in it with new compatible rings.

Oddly, the pistons both had 2 top compression rings in place of the normal single ring. I assume (have not spoken to former owner Dan about this) might be because he couldn't find the stock or other correct size ring or maybe the land was worn and this was a way to shade-tree it back to running order. It worked apparently. I haven't been able to come up with service info that has K-Model specs for this sort of thing.

Who, beside Old Dude are the main sources you guys are having luck with for parts?

As an aside, the guy that the present owner bought this bike from apparently did an overhaul on the engine before doing a fair amount of riding on it. He also has built from scratch a number of amazing machines:

I imagine that Dan may well have made the stroker plates.

http://velobanjogent.blogspot.com/2014/ ... th-in.html

http://www.motorcycleclassics.com/class ... v4-replica

Dan is currently building a Vincent to be installed in a Featherbed frame with SV650 front end. When I say building, I mean casting his own cases, cylinders, heads and making his own crank. He already has the molds from a Vincent he built before. I feel like a real loser when I visit his shop.

Here's a picture of the bike when Dan still had it:



Part of Dan's garage:



BTW, I was talking to John, the owner of Moto Parts in Edmonton AB about some Triumph back ordered parts and was describing the KHK. He mentioned that he has one of the seats like this one that's been hanging on the shop wall for ever if anybody's interested. http://www.motopartsinc.com/