My 91 FXR EVO engine

[railroad bob]

I bought a 91 fxr in 93, stock, 3500 miles on it. Very clean, had one little scratch on the back of the front fender.
Loved it, but always felt under powered. dyno'd at 57 HP stock. Made some changes.
Screaming Eable ignition, Andrews EV46 cam, Thunderheaders, Super E carb. Dyno'd at 72 HP
Very happy.
Rode it that config for a few years.
Developed an oil leak. Very hard to find. Clean the bike, ride it, oil every where.
Rinse, repeat.
Finally, a mechanic serviced it. When he came back from the test ride, he spotted the leak.
I guess I was riding too long before checking.
The right case developed a crack from the rear motor mount wrapping around to the breather.
I did some research, chose Delkron cases for replacement. I decided to use the stock flywheel assembly, increase the bore while it was apart, and bought the largest cylinders that would fit with the stock heads.
Axtell big jugs, 3 & 3/16" bore. This bumped the displacement up to 97 CI. The spigot is 4.0", which fits the bore in the cases.
This made me REALLY happy.

Later, scraped the exhaust in Arizona on Hwy 666 (number has been changed because of complaints from superstitious freaks). Broke an exhaust manifold bolt. Swapped the heads for HD heads modded by Jerry Branch. Polished chambers were like a mirror, beautiful. Even better power, no dyno.
There is no pucker factor quite like having both tires slide sideways in a curve, even at only 30 mph.
I still don't know why I didn't go down. Not riding ability for sure. I was frozen in shock.
Guardian Angel maybe. Once more, on a road miles from nowhere.

Fast forward several years. I've screwed up a couple times, took off on long trips without the extra oil I thought I had, got low, many miles from nowhere, tried to baby it in. got hot, scrubbed the bore. Twice, years apart. You think I would learn.

The second time I replaced it with an Ultima 113, really, really happy now. 120 rear wheel HP.

I have finally gotten around to working on the original evo motor.
3 - 13/16 is 3.8125. 30 over is obviously 3.8425.
My cylinders have been bored out to 3.850 and still have some slight vertical scoring on one.

Axtell has for years recommended only going 0.030 over on the bore.
However, Axtell has, after 20 years of research and use, decided it is OK to go 60 over, and now offer 3.875 piston kits.

This would increase the displacement to 100CI. more

I emailed Axtell several days ago. Made multiple phone calls. No luck. Received a reply today.

Ron Axtell has Covid, hit him hard. A guy named Chaz Cooney has stepped in to help. We spoke today.
He worked at Axtell about 12 years, left 7 yrs ago for a different career. While helping, he is doing the piston sales.

I'm waiting for Chaz to let me know if they have the 3.875 piston kits in stock. Fingers crossed. If not, I'll wait until they have them available.
The alternative is to use a different cylinder/piston kit, and I haven't found anything yet that I like.

The machine shop has miked the cyls, after boring to 3.875, the spigot wall will still be about 0.060, and will be reinforced by the bore of the Delkron cases, and there will be about 0.030 between the bore and the holes for the cyl studs.
Axtell offers multi-layer steel head gaskets by Cometic, 0.040" thick.
I think this will hold compression.

Any thoughts are welcome.

BTW, I'm planning to put this in a Santee hardtail, 2" over springer, 6spd Baker. Have oil bag, harness, controls, saddles, tanks, bars and more parts. I'll start a build log when I get the motor together.

[curt]

i like a good evo build

[railroad bob]

Still waiting to hear about Axtell pistons. No reply yet to my last email.

These are HD heads modded by Jerry Branch, single plug, reshaped combustion chamber, polished, and have a built up area in the intake port that diverts air flow around the valve stem for better flow.
Jerry Branch was a renowned pioneer of modifying Harley heads for better air flow and performance.
I'm thinking about adding compression releases to them, but I need to be cautious.
I don't want to screw up the performance.

Found some on Custom Chrome, printed the catalog blurb.
A friend has Thunder Road here in Fairbanks, an aftermarket shop.
I'll get his advice and talk to the machinist today.

[railroad bob]

Valve seals still haven't arrived yet.
Checked into installing compression releases. I don't think there is enough room to put them in a conventional location.

[railroad bob]

Oh yeah, got an email yesterday from Axtell, they don't have the big bore pistons in stock and don't plan to order anymore because they are so rare. Crap.
I can order custom size pistons, but I've heard (from the ancient archives of mythology and legend) of guys turning down Chevy pistons to use.

I have some standard bore pistons for a Chevy small block, they have a different size wrist pin (larger), and not sure about the piston height.
More research needed for something like that.

Probably much easier to just order new custom pistons with the diameter I need. Hmmm, the cylinders are at 3.850 now, and need a little more taken out.
Originally the bore was 3 13/16", or 3.8125.
30 over would be 3.8425
40 over would be 3.8525
50 over would be 3.8625

I'll call the company I originally got the latest pistons from, see what they can do.

[Dusty-Dave]

If the compression height is the same turning down a piston and making custom wrist pin bushings is doable if ya gots a lathe with a four jaw chuck. Heres a brief post on some custom size Cushman pistons I made.
viewtopic.php?f=30&t=912

[railroad bob]

Dave, I read that thread, good stuff. I have the equipment but no experience with it yet. I'll have to keep that as a possible option, depending mostly on how much time I want to spend learning those skills.
In the meantime, I've been considering the install of compression releases.

These are single plug heads with reshaped combustion chambers. I marked the optimal location inside the chamber.

CR Location Inside.jpg (114.62 KiB) Viewed 4646 times

The next pic shows where I think the release would be located on the top of the head.

marked head.jpg (132.73 KiB) Viewed 4646 times

Next shot shows the center fin that would need to be removed.

Center Fin.jpg (125.81 KiB) Viewed 4646 times

Next is a view of the right side. I think the middle vertical riser could be removed to make room for a mechanical lever.
I'm thinking the lever could have a simple pin hinge mounted on the underside of the bottom head fin. Push it upward to move the release down to actuate it. The lever would extend out from between the pushrod covers.

RT Side.jpg (156.12 KiB) Viewed 4646 times

The lever would have to be fairly long to reach. Heads are at machinists, so I can't measure right now. I might need to rethink the mount point to take advantage of the leverage.

[railroad bob]

Went by the machine shop yesterday. Put my hands on the heads.
In the last photo above showing the side of the head, with the vertical riser marked.
That is actually the same center fin on the top, not a separate riser.
I've ordered compression releases.
The machinist tells me no prob to remove the center fin and drill and thread a new hole for the release.
I'll work out some kind of lever to operate the release. It will be accessible thru the center hole in the rocker covers, but it won't be easy to reach. That hole is beneath the tank and backbone, too hard to reach in.

I think I can mount a hinge pin on the bottom of the finned area, between the pushrods.

Lever Hinge Location.gif (127.59 KiB) Viewed 4638 times

[railroad bob]

I contacted CP Pistons about making custom pistons, they referred me to Terry Stewart, who happens to be the person I dealt with years ago for the previous custom pistons I used.
I left a msg yesterday.

As Ozark Mountain Daredevils sang, you got to keep on churning till the cows come home.

[railroad bob]

Have spoken to Terry Stewart about new pistons. He wants the scoring in cylinders removed and then stop. He will use that measurement to check for best ring size to use, with the goal being to retain as much remaining cyl wall as possible.
No need to take it to something like 40 over or 50 over.
After he finds the proper rings, he will provide a final piston diameter and an estimate for the cost.
The shop will receive the pistons, do a final ring gap and cyl hone.

The manuf requires a minimum order of 4 pistons, and the 2nd set can only be 0.005" over the new size.
The manuf is CP Pistons, and their pistons have a multitude of performance features which attract me like a moth to a flame.
They are associated with Carillo Rods, which has been around forever.
I talked with the machine shop, they will do the bore, and when the releases arrive, they will install them. I gave the valve seals to them a couple days ago. After that, I can start figuring out a way to operate them. Terry Stewart suggested electric comp releases, but I had checked on those, and they run several hundred bucks. OK if this was a racer, but not realistic for a chopper in Alaska. Besides, I like the challenge.

[Dusty-Dave]

Ya can always go my friend Pablo's method. His big inch Iron Head had the kicker arm extended 2" then eventually 3" with the kicker pedal widened enough that he could get both feet on it.
Dusty

[railroad bob]

Ya can always go my friend Pablo's method. His big inch Iron Head had the kicker arm extended 2" then eventually 3" with the kicker pedal widened enough that he could get both feet on it.
Dusty

I once knew a HD mechanic here in Fairbanks with a 103CI. He tuned it for easy starting, and I watched him start it with his hand on the kicker. Pat McCaffrey. He was working at Midnight Sun Cycles at the time.

[railroad bob]

Received the compression releases today, took in to machine shop.
They will modify heads and install.

IMG_7392.jpg (100.02 KiB) Viewed 4601 times

IMG_7390.jpg (133.21 KiB) Viewed 4601 times

Cylinder with most damage was bored clean, currently measures 3.8575. I will give that and an unused CP piston to Terry Stewart.
He said he will use that to find the best ring size, and we will speak about features on the pistons.
CP has added more performance features to their piston line.

Here is a link to the page for piston features.

https://www.cp-carrillo.com/pt-3507-pistons.html

[railroad bob]

Also, the diameter of the CR cap is 0.510, so I'll be looking for a larger cap to fit over that, to use for a lever system to operate the release.

[railroad bob]

Update:
Some slight progress. Piston order completed, sent to engineers at CP. 14-17 week lag time for completion. In the meantime, I've been shopping for cyl base gaskets. I have Delkron cases for 3 5/8 cyls, and the cyls have a 4" spigot at the base, requiring an oversized gasket.
My local independent tried to order from his distributors (Drag Specialties, Custom Chrome, etc) but none have any stock.
Terry Stewart with Shakers and Movers is the dealer placing the piston order with CP, and he has added the gaskets to my order.
I'll see what he can find.
Terry used to compete in All Harley drag races, waa extremely competitive, and should have more resources in the big motor population.
Fingers crossed.
I've been sorting and organizing parts, found an orphaned handlebar lever. Tried it in position for the comp release, and with some massaging, it would work. Probably won't use it, but I know I have options.
Bought a used 5 spd take out for $200. Will probably use it instead of the unused Baker 6 spd, which really wouldn't work well on out crappy roads up here.
Very few places to wind it up in overdrive. Or I could underdrive the sprocket/pulley and have a tree stump pulling 1st gear.