Commando engine into a P11 Hybrid rolling chassis

T

tigcraftboy

Joined
Dec 20, 2008
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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 :twisted:
 
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 said:
I have been told someone here has experience of putting a Commando engine into a P11 chassis.
Click to expand...

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

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 said:
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.
Click to expand...

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.
 
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.
 
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 ...............
 
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.
 
I only came across this forum today,but I put a 1950 Model 7 Norton 500 engine into a Matchless CS frame. With a set of Norton P11 engine plates, it was a very straightforward thing,with almost no problems. Even the stock P11 head steady bolted right up to the 500 engine.
 
L.A.B. has kindly agreed to post a photo of my Matchless rolling chassis, I have also recently bought an oil tank off a G15, so I feel the project is racing ahead, although I still need lots of other parts. I intend to do the bike as a G15 based project and will probably order an alloy tank from The Tank Shop in Scotland. They have a very nice Matchless badged P11 tank on the web site.




Commando engine into a P11 Hybrid rolling chassis
 
I have just received some G15 engine plates and various other bits and pieces bought on ebay and I'm very pleased to say that I loosely assembled a Commando bottom-end into the frame and it looks like it will bolt in with very minimal modification to one lower frame lug. Additionally one of my chums has recently purchased a G80 of the same age as my chassis so I can check the various cycle parts that I need by looking at and measuring his.
 
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