I have been told someone here has experience of putting a Commando engine into a P11 chassis.

I have everything except the engine and was looking for an original atlas motor but think a Commando motopr might be easier to find and see no reason why it would not fit using the same plates

Anyone done this and can give me a steer?

Thx

TigcraftBoy

I intend to do something similar, having just purchased a Matchless G80 rolling chassis. I already have a Commando engine in stock. I believe the main consideration is the crankshaft balance factor. The Commando is balanced at a lower percentage to suit the isolastic system, whereas the Atlas and other 750 motors designed for rigid mounting, have a higher percentage. It is a good idea to have your crankshaft dynamically balanced regardless of the application, it will make a significant difference to the vibration.

I agreee that the balance is the main consideration. If I recall the commando oil pickup is also located for the slant of the engine.
I never had a P11 but I did have a G15CSR and if I recall the engine was upright like an Atlas.
the oil pickup has not been an issue on my current bike since they used the Commando slant to mount it.
I think you would need the short P11 primary case as at least on the G15 there was not much room there.

tigcraftboy wrote:I have been told someone here has experience of putting a Commando engine into a P11 chassis.

Actually I think the person who gave you that information on another forum was under the impression (as indeed I was at the time) that you either intended to put a Commando engine into an Atlas (which has a Featherbed frame) or an Atlas engine into a Commando? As it wasn't entirely clear from the start what your actual intentions were, and you didn't reveal that it was a P11 that you intended to fit the engine into until some while later, so I'm not entirely sure there is anybody here who has done it?

There is a lot more room in a featherbed. That said if he did something about the oil pickup and used the proper primary do you see any other major problems LAB?
When I used most of an Atlas engine in a Commando I just used the Commando case to avoid pick up problems.
I've never heard of anybody doing it but it seems there would not be a lot of problems.
Somebody in the Bay Area just sold a truly ugly G15 engine unit that was still in a frame. I made him an offer for parts but he said it was too low. Anybody here buy it? That would be a bolt in to a P11.

I am gob-smackd that any engine can vibrate more than the Atlas/P11 lump, regardless of its "balance factor". It was typical that a headlight bulb only lasted 5000 miles on an Atlas and it didn't matter whether you ever switched it on. The vibration was bad enough to shake the bulb filament off the posts.

Even the 650SS I used for commuting from Kenilworth to Wolverhampton vibrated bad enough to make fingers and toes numb after that relatively short trip.

I'm not convinced that the oil pickup position is such a critical issue. It seems to have moved around throughout Commando production and although some people recommend modifying the cases on the Combat style cases (I have just done this to a pair myself) to position the pickup at the lowest and most rearward point (this would remain the lowest point with these cases regardless of engine mounting angle, so perhaps this mod is the way to go, I cant recall where the pickup is in the earlier or later cases). equal numbers seem to live happily with the standard set-up, it is after all the oil scavenge pickup and not the feed to the pump and perhaps the result may be a slightly higher oil quantity in the cases during some running conditions). I think Cookie is correct about the primary case needing to be as short as possible and use of this item will probably require modification to the mounting holes at the engine side to accomdate the different angle. I suspect also that the Commando gearbox mounting lugs may be less suitable than the earlier arrangement and an earlier gearbox case, clutch shaft and clutch might also be necessary. I haven't actually made a start on mine yet, as I have just bought two more Commandos, thus relegating my hybrid project to number 6B on the list. My suspicion is that it may be cheaper to buy a P11 restoration project than to build one from bits, even though I already have engine, gearbox and rolling chassis. Things like tanks, side panels and assorted detailed parts seem to command a very high price indeed.

I've not done it on a bike but I have easily moved a few oil pickups. All you do is weld on a bit of tube if necessary. Fords had problems with the sump in the front on hard use. The remedy was simply to use a Bronco oil pan and move the pickup to the rear, that what I did when I put a Ford in my Datsun Z.
As you say the question might be is it necessary? It might depend on how you use it I suppose. P11s were originally gravel road race bikes, and if you have ridden powerful bikes like that in the 90 mph range on dirt, you know that contact with the earth is somewhat tenuous.
Toddling along to the bike meet would require a lot less worry about the oil pickup.

Cookie wrote:That said if he did something about the oil pickup and used the proper primary do you see any other major problems LAB?

I must admit, I cannot talk from experience, but as dave M said, I don't think it would present too much of a problem?

dave M wrote:I think Cookie is correct about the primary case needing to be as short as possible and use of this item will probably require modification to the mounting holes at the engine side to accomdate the different angle. I suspect also that the Commando gearbox mounting lugs may be less suitable than the earlier arrangement and an earlier gearbox case, clutch shaft and clutch might also be necessary.

From what tigcraftboy said elsewhere, he only needs the engine unit, as he has got, quote:- "everything else including gearbox".

The Commando crankshaft is probably longer in the drive side than the Atlas/P11.

It is nice that someone reads these carefully.If he has the primary it should be duck soup since the only other thing I recall that was different was the magneto and he will be using coils.
I'll post that hybrid article again in case it may help in some way.
http://www.motorbyte.com/norton/Report.html

Thanks for the link Cookie, there doesn't seem to be much in the way of printed information on these hybrids, although they do seem to be gaining in popularity and there is one on the front cover of the last Classic Bike Magazine that I bought.

Cookie

Top post - thanks

TigcraftBoy

hi there, the guy who fit a commando engine into G15 frame was Ludwig , and he is posting regulary on the Commando forum, you could find the link in the Hybrid stuff of his bike.
personnaly after fitting a cdo engine into atlas frame , I do not bother with oil pickups , but of course rebalance the crank to 84 % after carefully weighting rods and pistons and putting them within a gram difference thus reducing any possibility of un-balance, but I should admit that at 4500 rpm a slight buzz is present in the handlebars, I had 2/1 primary ratio with belt and 21/43 rear , so at 4500 I am riding at 80 mph.
On the other project I had found a N15 (matchless frame) and fitted an atlas engine , but need definitly the amc/matchless gearbox shell with the different bottom lug, and the specific primary cases, was a bit bothered with the forks as they were the very first (of course 25" stanchions) but external springs , and matchless dampers into "norton sliders", but nobody could tell me the lenght of those springs , so I am fighting with what I could find and either they are too soft , or too hard, still fighting...
I will end with alloy mudguards , trial seat , and small gastank as original ones are hard to find ...............

Hi again , here is the link where Ludwig explain what he has done to his own bike http://motorbyte.com/norton/hybrid/jan_ ... with_a.htm

Wow,

Thanks for that post Marinatlas. Of course that bike is far different than my old G15CSR was but I can still see some similarities. Like him even when I owned the bike no one had ever seen a hybrid, and nobody knew what it was, even I.