67 N15CS Build

Chris Johnson said:

Good catch, I was hoping nobody would notice. It was hanging a bit on closing throttle, a quarter turn in on the pilot screws has cleaned it up for the most part. You definitely need to run these from new long enough to make sure they aren’t spewing fluids then get the rings moving.

I didn’t intend to coordinate but a guy needs to accessorize and it kinda works.

Chris

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Yeah I should get some Red Vans shoes to complete my look in the garage.

Have fun roosting with that engine build on your hot rod desert sled. It does sound healthy.

A few first impressions after two rides over to the next community, about 6 miles each:

Still working on the carbs. The problem was slides open too far and pilot circuit excessively rich. I was suspicious of the #30 pilots that came in the carbs but tried anyway. It’s now tuned better but loads up on overrun… smaller pilots coming and I need to check float height.

The suspension is surprisingly close to correct. I really had my doubts about fork spring rates after seeing standard was so much higher than what I’m running in my BSA & Triumph. Considering I’m bigger than the target rider, I opted for one step higher than standard and it works well. I don’t have any complaints with the lightest oil in the forks and shocks at this point.

This bike makes my little Jack Pine T100 seem like an entry level ride. The Norton is much larger, heavier and far more powerful.

My 5 weeks to tune needs to be amended to 5 weeks to strengthen my legs & arms, and to lose a few pounds.

Chris

I’m finally pretty dialed in on carb tuning. I was surprised to see how much the UNI filters change the tuning compared to open carbs. I had to step down to #20 pilots and dropped the needles one notch from center. The 400 mains seem OK for now.

I got out for about 90 minutes today, riding in the local OHV park. Rear suspension seems right on. Front springs might be a little soft, bottoming out a few times (but feel great). I might give the .85 or .90 springs a shot.

The bike liked to get hot and start pinking, particularly in sand. I completely overlooked the fact that I bumped up compression quite a bit and should have set ignition according to Commando specs. Hopefully that will take the edge off.

I only lost one carb nut and almost melted through my fuel line. Not bad for the first real ride.

Chris

Chris Johnson said:

I’m finally pretty dialed in on carb tuning. I was surprised to see how much the UNI filters change the tuning compared to open carbs. I had to step down to #20 pilots and dropped the needles one notch from center. The 400 mains seem OK for now.

I got out for about 90 minutes today, riding in the local OHV park. Rear suspension seems right on. Front springs might be a little soft, bottoming out a few times (but feel great). I might give the .85 or .90 springs a shot.

The bike liked to get hot and start pinking, particularly in sand. I completely overlooked the fact that I bumped up compression quite a bit and should have set ignition according to Commando specs. Hopefully that will take the edge off.

I only lost one carb nut and almost melted through my fuel line. Not bad for the first real ride.

Chris

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Yeah the old 32 degrees of advance spec is a bunch and can cause some detonation.

You can say "pinging" in the USA.

Did you do any hill climbs?

Pinking is easier to say; the double ing is weird to me.

Getting into it this morning I found the crankshaft oil feed seal blown out so I need to pull a shim from the pressure relief valve.

There was more sludge in the primary than I expected for having maybe 50 miles on it, hopefully just new friction plates seating in.

0.90 kg fork springs ordered today… I’ll do it all again next weekend.

No hill climbs this weekend.

Chris

I got about 90 minutes of riding on Saturday and half an hour of tuning runs in today while taking my daughter riding.

As I’m getting more comfortable on it, I’m able to ride faster and can confirm the fork springs are too soft. The .90kg springs are back ordered but scheduled to be in by Friday. This Norton really is fun to ride and I fit so much better than on my T100.

I made an honest effort to tune out the pinking:
-Timed back to 28 degrees, no good.
-New AAU springs, no good.
-Raised needles one notch, no good.
-One step colder plugs, no good.
I finally relented and mixed up a gallon of special sauce: 91 octane + a few ounces of VP octane improver (raises octane by up to 8 points!!) and I think I can ride this thing safely in the desert, in the sand.

I consider this engine to be similar to a mildly tuned Commando so I’ve been looking there for tips. From what I read, even a stone stock Commando doesn’t like the 91 octane I can get here so I’ll probably leave it at that. The last thing I haven’t tried is strobing it to see at what rpm full advance comes in - I had surprising results doing that to my B44 that used to eat pistons.

Chris

More thoughts after another weekend of tuning:

I’ve stepped up to an effective fork spring rate of 0.9kg with the option of 1.0kg if necessary. Right now I’m in line with Racetech’s suggested spring rate. With that, I was still bottoming hard on small jumps & square edge bumps. Last night I plugged & relocated the oil ports in the damper tubes, which gave a good 1/2”-3/4” of rapid compression damping at the end of fork travel. Today I only bottomed hard once off a fast, small jump. I’m calling the suspension done at this point. I can certainly ride faster than what’s safe for me.

Pinking is still a concern, mostly under load at low revs after the engine gets good & hot. I just now noticed it wants more fuel at idle; AI says octane booster may require richer settings. I may also raise the needles another notch to see if that cools things down a bit. Spark plugs show reasonably clean, no real clues there. I’ll probably spice up the fuel mix for next weekend and see how it responds.

The gearbox likes to overshoot to false neutral on the downshifts if I’m not careful.

The carbs like to boil if I shut the bike off hot. I’m learning to work with that…

First low speed get-off today in the sand. I finally got that out of the way.

Chris

AI is relying on information it scrubs out of multiple possibly accurate information sources. There is still plenty of misinformation out there.

If anything it is probably your JS cam and that exhaust that requires more fuel from those old Amals.

A false neutral on a downshift would be no fun climbing a hill.

Getting off in the sand means the honeymoon is over and it is time to start beating on it. Enjoy the roost.

Chris Johnson said:

Last night I plugged & relocated the oil ports in the damper tubes, which gave a good 1/2”-3/4” of rapid compression damping at the end of fork travel. Today I only bottomed hard once off a fast, small jump.

The carbs like to boil if I shut the bike off hot. I’m learning to work with that…

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Chris,
A few questions, please.
* Which recipe did you use when you modified your damper tubes?
* Coil binding may be a problem when altering internal fork springs. Did you check non-binding for the desired travel when using springs with a 0.9 kp/mm spring rate?
(If they don't bind, did Racetech increase OD of these springs vs. the stock springs?)
* What kind of heat shielding did you install for your carbs?

- Knut

I plugged the 4 holes with 5/16 UNF x 1/4” set screws, locktited & staked then drilled (2) 1/4” holes just above the taper on the damper.

For all their 2341 series of springs (23.5 OD x 410 long), racetech gives a minimum travel of 170mm, about 2” more than I measured with springs removed. What I did notice is the coil count is the same between their 0.80kg and 1.00kg springs; wire diameter increased by about 0.010” (from memory, don’t quote me), ID reduced to accommodate. I’ve not seen stock springs in real life - my bike had 64-65 teledraulics on when I started all this.

Standard thin spacers on the carbs. What I’m reading is the octane boosters containing MMT do like slightly more fuel. Also I’m suspicious that the air filters have lost some of the oil, giving a bit lower vacuum signal, resulting in a weak mixture. Strange that both cylinders needed about one turn in on the pilots after riding this weekend. My last trick will be a few pulls to check the various carb circuits, waiting on a #3 slide for the 389 & a pair of 420 jets to be prepared.

Chris

I surrendered my VIP status and this is the easiest way to share pics:

Forks

Chris Johnson said:

Standard thin spacers on the carbs. What I’m reading is the octane boosters containing MMT do like slightly more fuel. Also I’m suspicious that the air filters have lost some of the oil, giving a bit lower vacuum signal, resulting in a weak mixture. Strange that both cylinders needed about one turn in on the pilots after riding this weekend. My last trick will be a few pulls to check the various carb circuits, waiting on a #3 slide for the 389 & a pair of 420 jets to be prepared.

Chris

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Good luck in the off road event coming up in April and with the carburetor tuning before you get out there. I remember doing rushed final tuning in the parking area the evening before starting 250 mile High Sierra District 36 dual sport rides. Good times were had by all.

My final, rambling stream of consciousness as I finish this project at the last minute:

In my head this is a really long story so I’ll trim it to the basics. After remembering that I installed used pilot jets, then swapping to new ones, the pilot circuit tuned in nicely. The only other change I made was to raise the needles one notch (richer slide & main jets were both bad moves).

The more I think about it, I believe the detonation is caused by other things and I might try to wean it off the good gas after this weekend. I did make the leap to running VP110 diluted down to 95+.

During tuning this weekend, I found both carbs loose, probably happened while riding the weekend prior. This isn’t new to me as I tend to be cautious about warping the carbs so I end up under tightening them; now properly torqued and loctited.

Toward the end of tuning I found a new oil leak under the magneto - lower mag screw came loose. On repairing this I found the mag chain tension sloppy & all fasteners loose, which I think could advance the timing a few degrees. In this case I used a very soft gasket under the mag that tends to extrude & relax over time, relieving tension on the fasteners. Again, torqued & loctited & timing reset to 28 degrees.

Then as a last FU, the threads at the rocker oil feed connection gave up and I had to repair that with a helicoil.

Do or die, I’m out of time

Instagram link

Chris

Bringing this full circle:

I met my goal of finishing this bike in time to race Biltwell100 a few weeks back. I entered the expert desert sled class to get two laps (vs one lap for novice) & realized pretty quick I had no place in expert class. This year I finished 11th and my lap times stayed pretty consistent now 3 years in a row.

The Norton is a monster in the sand, I can ride as fast as courage allows - easily 45-50 mph at one point when there was nobody wallowing around in the course ahead of me. It’s a dog in the whoops, due equally to my technique and the reality of trying to skip a 400lb 60 year old bike across sometimes 2’ deep whoop-de-doos.

On the first lap I chose the ‘hard way’ to shortcut about a mile of the course. On approach, about half the riders in all classes were heading back. The hard way was a steep rocky hill climb, maybe 3 riders stalled & struggling on the hill, more had bounced off into the rough on either side. Pride had me committed so I made an attempt and had a good go for the first 3/4 of the hill, then also bouncing off into the rough, then finding I had burned up my clutch pretty good on the climb. I was able to adjust some lift back into the clutch, got the bike started & finished the climb. Next lap I took the easy route.

I have an obnoxious misfire at low rpm’s under load that I was able to work around by slipping the clutch. The fork bottoming really didnt go away, either.

Overall a great success with only a few low speed tip overs when maneuvering in deep sand. My kid also really took to her Honda 70 on this trip. I brought my T100 & Gold Star too, for more casual riding before & after the race.

Race Day

Playing around

The aftermath:

Almost right away, I ordered Lansdowne fork dampers & Turcite bushings. I wasn’t interested in trial and error trying to get compression damping just right so these externally adjustable units met my needs. We went riding yesterday and I’m able to dial out the bottoming on the same fast, small jumps that I was testing on before.

I hoped the misfire was a rich condition on transfer. Today I tested the next leaner slides with no improvement. I noticed no misfire when the engine hadn’t fully warmed up but once hot it was back. I need to find someone to remagnetize the magneto.

And maybe most disappointing - on wiping down the bike today I noticed almost all the front spokes were loose. I lifted the front to spin the wheel - it’s no longer round; looks like Fred flintstone built the rim. All that bottoming wrecked that nice alloy rim… good thing it’s a dirt bike. I torqued the spokes and won’t look back.

Chris

Chris Johnson said:

The aftermath:

Almost right away, I ordered Lansdowne fork dampers & Turcite bushings. I wasn’t interested in trial and error trying to get compression damping just right so these externally adjustable units met my needs. We went riding yesterday and I’m able to dial out the bottoming on the same fast, small jumps that I was testing on before.

I hoped the misfire was a rich condition on transfer. Today I tested the next leaner slides with no improvement. I noticed no misfire when the engine hadn’t fully warmed up but once hot it was back. I need to find someone to remagnetize the magneto.

And maybe most disappointing - on wiping down the bike today I noticed almost all the front spokes were loose. I lifted the front to spin the wheel - it’s no longer round; looks like Fred flintstone built the rim. All that bottoming wrecked that nice alloy rim… good thing it’s a dirt bike. I torqued the spokes and won’t look back.

Chris

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Honorary member of the District 37 Spoke Bender's club!

Chris Johnson said:

I hoped the misfire was a rich condition on transfer. Today I tested the next leaner slides with no improvement. I noticed no misfire when the engine hadn’t fully warmed up but once hot it was back. I need to find someone to remagnetize the magneto.

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Chris, when mentioning misfire and magneto, do you suspect the magneto not creating a spark at all, causing a late cycle detonation? Indeed, I have heard that rear-mounted magnetos are vulnerable to break-downs due to heat.
If your magneto hasn't been reconditioned, I would opt for a complete overhaul. Switching to EI is another alternative.

- Knut

Chris Johnson said:

The aftermath:

Almost right away, I ordered Lansdowne fork dampers & Turcite bushings. I wasn’t interested in trial and error trying to get compression damping just right so these externally adjustable units met my needs. We went riding yesterday and I’m able to dial out the bottoming on the same fast, small jumps that I was testing on before.

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So, your verdict on the Lansdowne kit is unequivocally positive, despite the fact that damping is one-way at each leg? The alternative is the Cosentino kit. It's pricey though, at $1030 when ordered from the manufacturer. A machinist may be able to replicate it using the appropriate Honda parts ....

- Knut

Knut - the magneto was reconditioned as a requirement of replacing the electrolytic capacitor with solid state Brightspark item. The two things I didn’t do were rewind the armature and charge the magnets. The misfire happens around 1/8 throttle under heavy acceleration, typically when shifting up to the next gear - low magneto rpm/low voltage and very high cylinder pressure which I believe is causing the spark to break down.

The dampers are fantastic. Before the race I put about 20 miles on my T100 and now riding the two bikes same day I was able to identify that the triumph forks (actually B50 forks) were noticeably more firm and this is what I wanted from the Norton. I think it’s reasonably common for the compression & rebound circuits to be split between the forks but admittedly these are now the most adjustable forks I’ve experienced.

Chris

Chris Johnson said:

The misfire happens around 1/8 throttle under heavy acceleration, typically when shifting up to the next gear - low magneto rpm/low voltage and very high cylinder pressure which I believe is causing the spark to break down.

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No fun running that little hiccup down. Too bad you don't have a set of carburetors with an accelerator pump that would only take 5 minutes to install. (fantasy scenario) That way you could eliminate the K2F magneto as the source of the misfire. The alternative fantasy would be a Joe Hunt magneto you could install in 5 minutes to point right at the K2F.

I'm not sure what kind of plugs you can run with the K2F, but you might try a new pair of something different possible with iridium tipped electrodes. Big improvement over standard plugs. Might even get rid of the misfire. One can dream...