My 91 FXR EVO engine
Posted: Wed Mar 02, 2022 11:32 pm
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.
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.