What to do with a P11 engine rebuild

Hello all, My name is Adam and wanted to introduce myself as well as ask some suggestions about an engine rebuild I have to do on my P11.

To start, my Norton is a P11 titled as a 1968 but has a vin number in the 67 year (frame and engine both 122948). I have owned the bike since 2006. I have ran the bike periodically since then. Short trips here and there but have been reluctant to run long trips due to not knowing the history of the bike prior to me owning it. I have had burning oil issues since I bought the bike and it has progressively gotten worse. Reluctantly (because I want to ride it), I removed the cylinder head to address the problem. This was probably a good thing because the old girl has seen better days.

Upon inspection, the head gasket has been leaking due to loose nuts. The bronze valve guides are extremely wore out, the valve seats are pitted and worn (surprised they even seated), the exhaust threads are starting to gall, and the left side spark plug tap is partially stripped (due to me using a cheap compression checker). Only good thing was that the rockers weren't sticking.





Figured I'd pull the cylinders while I was there too. Lotta leaking down at the split and some significant witness marks in the walls sparking me to probably bore the cylinders.




So this brings me to my questions/suggestions. Since I am in there, and my bike is far from stock, what would you guys suggest I do to the engine while I am rebuilding. I will only be street riding this so I want it to be reliable yet have a little bit of gusto.

Some thoughts I am leaning towards;
-JS Motorsports Beehives and valves (do I go bigger on valves, or leave them the stock size?)
-Mild head work (port and polish)
-JS Motorsports .020" over forged flat top pistons
-JS Motorsports connecting rods and pins
-Honed and silicon carbide impregnated cylinders
-New crankshaft bearings (not sure which ones)
-New gaskets throughout
-Balanced components

This all might be overkill for a street tuned Norton, but I want longevity and reliability and JS Motorsports tells a pretty convincing story about their products.

The cam looks ok, but would like to maybe change that out if I am in there. Don't really know which one would be good though. I've built automotive engines before but never a motorcycle engine. Any benefit to changing head and cylinder studs to ARP (if available) or the like? I just am looking for thoughts and comments on what I should do while I am in there.

Appreciate any feedback/comments, and look forward to adding what I can to the forum.

Thanks,
Adam

kiddcaprix said:

This all might be overkill for a street tuned Norton,

Click to expand...

When it all gets down to the nitty gritty, have you priced all this out ?
For street riding, do you want to spend that ??

Ya gotta watch these racing folks, when price is no object.
You know the saying - Speed costs $$$, how $$$-fast-$$$ do you want to go.

For most of us, sprucing up the old girl with stock new pistons and valves and bearings will see it into another life time of riding.

Jist one point of view.... ?

P.S. Can't tell from those pix if the valve seats need anything doing to them other than a light cleanup with valve paste.
How thin are the valve edges ?
A careful cleanup of the carbon on the combustion chamber will show it better, and if the seats are too pocketed - don't use anything sharp, that will scratch. Looks quite good at this stage though.
Its common to need the spark plugs to be helicoiled.
Much easier to do it with the head off = now !

Hopethishelps.

Thanks Rohan for the reply. Appreciate the insight. I have priced the parts out and am definitely on edge about the cost. Kinda why I posted on here, hopefully to gain some perspective on the parts mentioned. If the price is worth it for longevity and reliability or if those parts mentioned are really for the racer crowd. I assumed the "stock" parts would probably be sufficient for my riding. Just wanted to see if the higher end race parts add any longevity to the Norton. Probably normal maintainence and upkeep will keep it going for years (the bike sat for some 25 years).

To your question on the valves. The intakes seem pretty close to the edge. By the time I get the pits out of them they might be knife edges. So it might require at least valves. I need to clean the head tonight so i will see how bad the seats are. I was wondering if the valves pitted so because of the fuel differences from 68 to present (no lead). If that really had any play in degradation! I have only run premium in it since I got it. I'll take some pics and post later hopefully.

Thanks again, I am really new to the bike engine building scene so I apologize for any noob questions. I'm trying to research as much as I can.

One thing I don't understand and hope somebody can enlighten me on is the "name" of the engine. Because this bike was an early P11, is the engine considered an Atlas, Dominator, or Commando? Where does a "Combat" engine come into play. Or is it just a P11? Don't really know if its relevant or not for searching for parts. Seems like 750 is all I really need to know. Or am I missing something?

Again, thanks.

Regards,
Adam

Robust OEM spec wear parts (basic list of gaskets, bearings, bushings, seals, chains, vales, guides, pistons & rings) should be your MINIMUM budget if you already have the engine apart. THEN weigh the additional cost for performance parts against the remainder of your stack of available cash.

Pay for it once, and forget it for a good long while (as long as you maintain it and don't thrash it mercilessly)

Welcome to the forum.

A P11 is "just" a P11. It is essentially an Atlas engine, but obviously has it's own prefix stamp. BillT and a couple of others will know the actual difference in specs (if any). Commando power unit is mounted on a slant, not vertical. Combat was not till '72.

the production P11, beginning with P11/121007 and ending with P11/129145, uses a standard Atlas motor, and coincides with the change from Amal monobloc carbs and Lucas magneto to Amal concentrics and Lucas distributor and coil ignition.

The spec is the same for any Atlas, N15/G15/33, and P11 built in this period.

Standard pistons were 7.5/1 dished top

Balance factor was around 72%

Commando motors are a bit different, using flat top pistons and a balance factor around 52%



I couldn't find dished pistons, so used .020 over flat top Hepolite, which give about 9/1 CR. Used Black Diamond valves, bronze guides, OEM-spec seals and bearings (I went with a Superblend in place of the roller bearing on the drive side), and had the engine balanced to 82%. I did my own assembly.

Made the mistake of using a Renold chain for the primary drive - absolute junk which flew apart at about 300 miles (nowhere near the master link) and went through my primary. Had the primary repaired and replaced the Renold with a D.I.D. 428 Gold chain, which is rated about 50% stronger and costs a bit less, and have done around 4000 miles since.

Thank you gentlemen for the replies, I appreciate all the info. I will probably go the simple route this time and hold off on all the higher end parts until I gain some funding. It looks as though Colorado Norton Works has a complete head service that covers all the issues i stated earlier broken link removed. I might call them up tomorrow and see what the price would be for that. I could do all of the work, but am expecting my second child in about a month. Not much free time if you catch my drift. I really want to do the work myself though. Really depends on the funds.

I went out to the garage tonight to try and break down the rest of the head so I can clean it, and realized the rocker spindles are in there pretty good. I know a tool is available, but has anybody gotten them out by other means (maybe a homemade slide hammer)? If so, I read that I may need to heat the head up to aid in the removal. Is that true, if so, whats a good temp for that?

Thanks again for the info, I can't thank you guys enough. Seems like a wealth of knowledge on this forum and I'm diggin' it. Can't believe I didn't find this earlier.

Regards,
Adam

For removing rocker spindles, you need to first clean everything as well as possible.

I use crankshaft studs, a sleeve slightly larger ID than the rocker OD, and some washers as a puller tool; I believe there are actual spindle pullers on the market. As long as you match the spindle's inner thread, any long bolt will work. Localized heat with a blow drier or propane torch held at least a few inches from the head for a few minutes will serve to heat it up, or you can pop it in the oven at 250 for 15 minutes or so.

Thanks grandpaul, I'll give that a try. Looks like I might need to get a craigslist oven out in the barn. Is Kerosene a good cleaner for the components? Can I get a bin and put all my parts in there with Kerosene and let it all sit for a night before I start really cleaning these? Or will that have adverse affects?

Was there a reasoning for Norton to switch the oil feed holes on the P11 (pseudo Atlas) from the top to the sides between the rocker spindle covers on the Commando engines? Seems like they may have used the top holes for a head steady on the Commandos and just moved them down to the side (only speculating from pictures). Any benefits to the side verse top locations? I've wanted to put an oil gauge on the bike for a while and have seen people do it on the spindle covers. Seems like this would not be very accurate due to only pulling from one of the lines (say if the other side was hindered in some way, i.e. clogged). Could and inline gauge be placed and be more accurate? Or if there is a spot, maybe on the side where the Commando ports in at?

Thanks,
Adam

Someone in this forum should say something about the vibration problem with Atlas motors in solid frames and the weak upper ends of the Atlas rods that can break (redesigned to be stronger for Commandos).

Adam, If you have already taken it down this far and the previous history is unknown I would consider splitting the cases and examining the bottom end as well as separating the crank sections an cleaning out the sludge trap. Do mark the crank cheeks right and left before dissasembly as they can go back together either way but the wrong way will throw the balance out.

Regarding tuning, a sports camshaft like a 4S grind is a lot of bang for your buck, but they work best in conjunction with a slightly higher compression ratio.

All the best with your project.

I don't think you can mix up the crank cheeks (different threads and profile on the shaft ends), but you can reverse the rotation of the flywheel. I always stamp mine with an arrow pointing in the direction of travel.

Thanks guys for the input. I was planning to break the case apart and check everything. I wanted to paint the cases and the frame while I have it out. Since the whole thing that started this endeavor was the valve guides, is there a guide I can use in the P11 that has accommodations for a valve stem seal? I see Steadfast has some simple ones. Has anyone used valve stem seals in the P11s? I see Norvil has some with grooves. How do the Steadfast guides compare to the Norvil guides?

Would you guys recommend having new seats put in the head to accommodate for unleaded fuels? Norvil shows a seat for "unleaded". Are the stock valve seats sufficient? Looking at my seats last night, I should be able to lap them back in with new valves. Just didn't know if seat replacement is a common thing to do for unleaded fuels?

Trying to do this right so I apologize if these questions are redundant to the forum. If any threads answer my questions, don't hesitate to send me to them. Thanks gents, appreciate the time and input.

-Adam

Paul, since the crank cheeks are only bolted to the flywheel if you have reversed the direction of the flywheel you have indeed Mixed up the crank cheeks left to right, unless of course you mixed them up with something else like a pair of handlebars or a chicken vindaloo!

Since one crank cheek has a sprocket bolted to it, and the other has a timing gear,
it is obviously not possible to swap side with crank cheeks.
It is possible to reverse the central flywheel weight though, so absolutely best if its marked so it goes back in the same way...

Nortons have had hardened valve seats for alloy heads since before cavemen walked the earth,
so unless its deeply pocketed they are quite good to go.

Not heard of anyone fitting seals to Atlas valve guides.
If it wasn't fitted originally, I wouldn't alter them.
Provided they are correct clearances they don't burn oil.
And you wouldn't want them running dry...

hopethiselps.