Resurrecting a '51 Pan-Shovel
#171
#172
While there seems to a bunch of extolling of the CV carb's ability to handle changes in elevation, it's not as good as some think. I've run both a Super G and CV51 on a bike from 200 feet below sea level to 6600 feet with a wide band afr sniffer. In both cases the motors picked up about the same richness based on the gauge. Both idle up to about 1/8 throttle and WOT function the same on the 2 carbs. The big issue on butterfly only carbs (SnS super) is the crossover between low speed and high speed jetting. The SnS carb cam have quite a bit of fluctuation of AFR on the transition. The CV (or slide/needle) car will not. The fluctuation becomes exacerbated with altitude at times enough to cause a hesitation.
I would guess that you could try installing an adjustable air bleed to help with the transition like on the Tjet kit.. They are external and easy to change..
I would guess that you could try installing an adjustable air bleed to help with the transition like on the Tjet kit.. They are external and easy to change..
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NM Pan-shovel (06-08-2022)
#173
#174
But they are sexy, would be unique in this application, and engineering challenges are just plain fun, IMHO. I'll likely run the Super E once dialed in for high desert riding for the near-term future, then snag a 40mm CV setup when I get ready to do some interstate touring.
Question: which (CV vs. Super E) would be easier to swap jets (or needles) on the road as needed if the tour dropped closer to sea level?
#175
You know, I vaguely remember Ron (the outlaw biker--real, not a poser) from whom I bought the flathead describing the Mikuni he'd fitted as a smoothbore. This was in the late '70s, so would that be more likely back then? It was a single carb, though. I'm positive about that.
#176
Decided to rebuild the shift lever bushing, as there's too much slop and I'd like it to shift perfectly. Was out in the garage when the dog alerted just around the corner in the entryway courtyard from his perch inside the French doors. This is what had him a bit perturbed...
It wasn't huge, only about three feet or a bit longer, but the thing must've cruised right by where I was tinkering away, slithered down the path and into the courtyard. Luckily, the wife had hung out the laundry and went back inside...
It wasn't huge, only about three feet or a bit longer, but the thing must've cruised right by where I was tinkering away, slithered down the path and into the courtyard. Luckily, the wife had hung out the laundry and went back inside...
#177
#178
#179
Yeah, the wife wouldn't let me dispatch it, as they keep the pack rats and mice down to a dull roar. But this is the second time in two successive summers I've had 'visits' from these guys. Last time, I had a car up on the Quick Jacks to do some work, and a 4-footer came into the garage, glided past my steel toe boot (I was trapped between the scissors and couldn't get away), checked out each corner of the space, then went on its way.
Here's a photo of a non-venomous visitor I found one morning during the build last summer.
Never a dull moment here in the high desert...
Here's a photo of a non-venomous visitor I found one morning during the build last summer.
Never a dull moment here in the high desert...
#180
So, these S&S cylinder head castings are great--triple valve springs, high quality valves, large and clean ports, etc. However, the bike suddenly lost power and, after limping home, I determined that the intermittent miss I had early on, and which I'd initially attributed to a slightly lean mixture, had blossomed into the rear cylinder barely firing at all.
I did a leak down test and sure enough, the exhaust valve was leaking. I knew it hadn't burned because the AFR is a touch on the rich side at this altitude with the standard Super E recommended jetting (even with the shotgun pipes and shorty Sportster mufflers).
I then pulled and disassembled the head, and it looks like the valve and seat were physically damaged during assembly. Perhaps by a metal chip or keeper or something else getting clamped in there by those powerful springs. It must've either been expelled by the tech--who then did not do a sealing test on the bench--or by the exhaust pulse when I fired up the bike. No way I would've heard something that small clink out through the pipe with these loud mufflers.
Anyway, I've asked PowerSports Superstore (least expensive retailer of these heads that I could find) how they want to resolve the issue. I can't recall the S&S warranty terms, but I hope they or the retailer will do the right thing. We'll see...
BTW - check out the lousy work done on the sealing surfaces, probably with a worn, gouged cutter. Compare to the fourth pic, which is my typical hand-cut seats...
Dent or chip out of valve tulip
Corresponding dent in seat--which I have to say has lousy sealing surfaces in general
Compare with a burned exhaust valve from a racing engine that had a cracked intake manifold
I did a leak down test and sure enough, the exhaust valve was leaking. I knew it hadn't burned because the AFR is a touch on the rich side at this altitude with the standard Super E recommended jetting (even with the shotgun pipes and shorty Sportster mufflers).
I then pulled and disassembled the head, and it looks like the valve and seat were physically damaged during assembly. Perhaps by a metal chip or keeper or something else getting clamped in there by those powerful springs. It must've either been expelled by the tech--who then did not do a sealing test on the bench--or by the exhaust pulse when I fired up the bike. No way I would've heard something that small clink out through the pipe with these loud mufflers.
Anyway, I've asked PowerSports Superstore (least expensive retailer of these heads that I could find) how they want to resolve the issue. I can't recall the S&S warranty terms, but I hope they or the retailer will do the right thing. We'll see...
BTW - check out the lousy work done on the sealing surfaces, probably with a worn, gouged cutter. Compare to the fourth pic, which is my typical hand-cut seats...
Dent or chip out of valve tulip
Corresponding dent in seat--which I have to say has lousy sealing surfaces in general
Compare with a burned exhaust valve from a racing engine that had a cracked intake manifold