JS Motorsport parts in the mail for my P11

JSM 2-degree stepped cam key, JSM ARP head bolts for Molnar barrels, and JSM D-port exhaust inserts.

More to follow as things unfold. (Contents of this post will not be suitable for P11 restorers, or possibly anyone.)

that rules. congrats. I'm fired up about that stepped key. makes me wanna do a rebuild.

Keep on adding all that great stuff Schwany.

seanalex said:

that rules. congrats. I'm fired up about that stepped key. makes me wanna do a rebuild.

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I may have to do another rebuild if I keep screwing around with this engine.

I'm only going to add 2 degrees of advance. I've read about cam timing theory, but no clue what it will do in real use other than make me have to do some carburetor tuning, especially after I install the D-port exhaust inserts. Those might just come right back out and get used next year.

Point is to go over what it is like to install a stepped cam key without taking the head off and only backing off the valve adjusters to reduce the cam moving. I expect there will be some cussing at myself involved, and I may end up taking the head off anyway. Will know by end of day tomorrow. Unfortunately, I won't get to ride it until the weather clears up in May. I dislike riding in the wet.

Chris said:

Keep on adding all that great stuff Schwany.

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A man has to have his enthusiasms.

With pistons at TDC and all the timing marks aligned the cam doesn't move at all when the timing chain and sprockets are removed and the tappet adjusters are left adjusted. You guys that were laughing when I thought the cam might move can stop laughing now, or at least until I say something else ridiculous. Changing out the stock cam key for a JSM stepped cam key is a piece of cake. At least it seems to be with the JS02 cam so far. I don't have the stepped key yet, but the sprockets are off and nothing is moving.

Thought I'd mention it for anyone sitting on the fence about installing the JSM stepped cam key. The mechanical install part is easy.

You have to be a bit careful changing cam timing especially when combining different parts, cams, barrels, pistons etc to ensure you have clearance between the valves and piston crown.

Have you checked with a degree disc and dial guage what your standard sprocket is giving you ? Very normal to find the machining tolerance of the keyway in the sprocket is up to 3 degrees plus anyway.

When I did the cam timing on my race bike I went through a box of second hand sprockets at British spares and found several which gave a good range without need for a stepped key.

johnm said:

You have to be a bit careful changing cam timing especially when combining different parts, cams, barrels, pistons etc to ensure you have clearance between the valves and piston crown.

Have you checked with a degree disc and dial guage what your standard sprocket is giving you ? Very normal to find the machining tolerance of the keyway in the sprocket is up to 3 degrees plus anyway.

When I did the cam timing on my race bike I went through a box of second hand sprockets at British spares and found several which gave a good range without need for a stepped key.

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I agree that Norton parts are crude. I'll be sure it all works before firing it up. Thanks for the thoughts.

I had a minor setback. The stepped cam key doesn't want to go into the JS02 key slot. The stepped cam key is very hard unlike the stock cam keys which can be filed to finger press fit size easily. I do not have a machine shop, so I get to slowly reduce the thickness with emory cloth. Probably going to take 3 hours. lol

D-Port exhaust inserts in an early Commando 750 head. These fit perfectly flush to the port floor. Zero work on a stock head. Race bike owners may want to do some additional simple port work on the roof and to the sides of the guides. Jim provides instruction for what needs to be done.



The JSM ARP head bolts for pre-2025 Molnar barrels are very pretty.

Schwany said:

The JSM ARP head bolts for pre-2025 Molnar barrels are very pretty.

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Pretty indeed, Let us know how you rate the thread fit. I wasn't please with Molnar's bolts and female threads on cylinder barrels produced 2022-23, as they deviated substantially from the norm.
Molnar's tooling must have been very worn. The latest barrel produced 2024 provided tighter bolt tolerances, but there is still a deviation to the norm on both male and female threads.
Given this situation, it's difficult to get male and female threads to match.

Personally, I am skeptical to using head bolts with threads cut on a lathe. I will therefore install inserts and use ARP bolts with rolled threads,

- Knut

mdt-son said:

Pretty indeed, Let us know how you rate the thread fit. I wasn't please with Molnar's bolts and female threads on cylinder barrels produced 2022-23, as they deviated substantially from the norm.
Molnar's tooling must have been very worn. The latest barrel produced 2024 provided tighter bolt tolerances, but there is still a deviation to the norm on both male and female threads.
Given this situation, it's difficult to get male and female threads to match.

Personally, I am skeptical to using head bolts with threads cut on a lathe. I will therefore install inserts and use ARP bolts with rolled threads,

- Knut

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I'm surprised Molnar didn't put inserts in the barrels from the get go.

The bolts are the last thing I'll do. And since I can't/won't ride in the wet it'll be a while before I put any time on the engine with the new head bolts. I will know if they feel tighter on installation and pass it on.

Well, hell yeah!! I'm looking forward to some sunny days now. That little .5mm offset cam key set for 2 little degrees of cam advance is one heck of a transformation. Seriously was not expecting the results I got from that little part. I hope the throttle response in the garage translates well to the street. Engine idles better, starts easier, and sounds like it belongs on a mile dirt oval. What I don't know because I have not ridden it is if it'll run out of beans a little earlier. In theory it might. Won't matter though. 100mph is fast enough these days.

I did not install the D-port exhaust inserts. I probably won't for a while, because it sounds perfect as is. Also did not measure a single thing. Once I got the stepped cam key in and timing gear tightened up by (not going to say) I used the kick start to turn the engine over by hand a few times and the pistons didn't stop suddenly, so I knew it was time to kick the oil back up into the head, through the return pipe, and light the fire.

Engine parts list:

Stock P11 cases modified to support Commando cams
Molnar crank
Molnar iron sleeve alloy barrels std 750 bore
MAP 750 std bore long rod pistons and MAP long rods
JSM JS02 cam, JSM Triumph lifters, JSM pushrods, beehive springs, and valves
Fred Barlow ported P11 head. 31.5mm intake entrances, exhaust port matched to the 1.5" headers
35mm Keihin FCRs
SMS modified Commando intake manifolds for use on straight up motor
BUB 2 into 1 exhaust with 1.5" headers, 2" collector, and SMS 1.5" open baffle in 26.5" BUB megaphone
TriSpark ignition
Denso Iridium plugs
3rd Party 3ohm Harley style dual coil
TriSpark MOSFET reg/rect
Lucas 2 wire Alternator
Antigravity 8 cell Lithium battery
Other stuff

Not sure if the stepped cam key would make any difference with a stock cam, but it should make some difference. Might be risky with flat top pistons without valve cutouts. I don't know. My engine was built for crazy by crazy, so it all works. It really likes that stepped cam key and the rest of my mad max parts.

Installation was no big deal. Like changing a timing chain, I guess. However, I'd never changed a timing chain without rebuilding the engine before, so wasn't sure what I was in for with the barrels and head on.

Forgot to mention first kick with the ignition on made one hell of a loud backfire, but it didn't blow out the fire and kept running.

I did not do anything to the carburetion before starting the engine after installing the stepped cam key. It just worked. Because it ran so well cold, it is probably running a little richer with the valves starting to open a little sooner.

I don't think I heard the FCR slides do the clicky clack thing at idle with the small change to the cam timing. Could have been wishful thinking and I will need to verify that next time I start it up. Also possible I changed the ignition timing some. I made marks on the timing cover for where the rotor and stator should remount, but did not verify the timing with a strobe.

Next thing I'll do is the head bolt swap. Still contemplating the D-port inserts.

Big thanks to Jim Schmidt for his continued performance parts support for vintage Nortons.

The D-port exhaust inserts don't actually fit well in my P11 head. I had to reshape the outer diameter of the insert along the top outside of the radius to get one in. The rear of the floor in the P11 head is too high and tilts the insert forward at the top. When tightening the adapter for my exhaust up against the insert the top of the insert radius hits the threads and won't go in without what seems like excessive force. Maybe that is by design, but there's no documentation mentioning it. The exhaust ports in the P11 head already have some of the suggested cobra head work done in the roof. Not sure if I did that or Barlow did. I probably won't be having a lot of fun trying to get the inserts out if/when I remove them. It's sort of a jam it in fit. Insert crybaby emoji here.

Will be starting it up later today.

It runs with the d-port inserts in. It doesn't sound as strong at about 1/3rd throttle sitting still, but I have not ridden it to see how it is between stop lights. Maybe tomorrow if the weather holds.

Oh and the excitement over the 2 degrees of advance at the cam with the stepped cam key was actually excessive ignition advance. Ignition was closer to 38 degrees all in. Sounded awesome and responded really quick to throttle, but with the correct ignition advance it sounds about like it did before I installed the stepped cam key.

The JSM bolts for older Molnar barrels saga. Tight they are, so tight after using Molnar's head bolts in Molnar's older barrels, I decided to put the bolts in the spares drawer until I have the engine apart again, should I live that long. The JSM bolts although the same thread would not start in the barrel threads by hand more than half a turn. I'd rather have the head off so I could see if they are going to be chewing up the threads or not. Molnar's head bolts were really in there solid at 30 ft lbs. They may or may not have done something to the threads that would cause the JSM bolts to be very difficult to remove once torqued down. I'd rather find out I need inserts with the head off. I usually run headlong into the fight and do stupid stuff, but not with threads I can't see in aluminum.

Still considering going for a ride, but lack of interest may win out today. Weather is right on the money. If I could just get all the frigging cars to vanish, I'd be suiting up.

go for a ride... I did twice today to shake down my rebuild... I had issues with a float on one side sticking and got it fixed on the second time out and the bike stopped popping and farting. Also one of my stands is dropping and dragging on fast tight left hand sweepers. I recently made a custom side stand to replace the stock side stand and I wasn't sure which stand was dragging... On my second ride today I zip tied the center stand so it can't drop and I think it's actually the center stand that is dropping and scraping the ground which should be easier to fix.

The double shake down run helped a lot. I trimmed and dehorned my floats and the bike is running smoother after that service, and I'm working on my dragging stand issue and I might have it in hand

I didn't go for a ride. Ended up pulling weeds instead.

In order to scrape anything on my P11 I'd have to be in a decreasing radius off camber turn riding way over my 74 year old head. Crashing low side also scrapes parts.

A short test ride would tell me if I have to spend time carburetor tuning for the D-port exhaust inserts or just take them out and carry on. There still could be some benefit I have yet to discover with the D-port exhaust inserts. But like I said at the start my experience is all kind of irrelevant for most Norton owners. Too many modifications stacked on top of one another.

Yes the exhaust port shoes are supposed to tilt in and press down on the tip when installed.

jseng1 said:

Yes the exhaust port shoes are supposed to tilt in and press down on the tip when installed.

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OK, that would definitely hold them in there. I removed some material from the top of the OD of the ring flange to help clear the threads. They are still getting pressed in, but not as much as they would have if I'd left them alone. Getting them out would have been near impossible if I'd left them as is. I don't think I'll be removing them though, so all is good.