Conkers Swedish Cafe racer Project.

Hi there,

I thought that I would start a thread rather than spreading my build all over the place. If nothing else, easier to follow when I eventually will want to review the project.

I bought the bike (frame number 132728) as a pile of bits, and the seller saw me coming to be honest, but in for a penny in for a pound I love this bike and I want to give it a new lease of life, ride it on the roads and do the occasional classic race or parade lap.

I am not looking for race performance or touring reliability, as I have a Triumph Daytona 955i CE for that sort of thing...

The engine that came with the bike, was suppposed to be 80-90% complete, but it wasn't and most of the parts I inspected were just junk..

After 6 months of searching I found a complete engine, bought unseen and shipped to me, breather on the rear, engine number 203887, I do not have any history of the engine, but it showed no signs of ever being opened or modified.

When I stripped the engine today I have found that the cam is marked SS.

The cam marked SS has more lift on the inlet lobes and more duration, it is on the right in the picture, the one on the left has no markings and came with my junk parts!



What engines were the SS (2S?) cams fitted to? Combat? Does this mean that my engine is a combat engine?

What other differences did the combat engines have?

Mike

Edit: A link to the other threads I have started about my project bike and bits.

boxes-junk-and-unidentified-bits-help-t12768.html

will-this-stator-rotor-work-for-t12746.html

the combat had a 2 S cam, cylinder painted black, head milled .040 to raise compression , 32 MM carb's V 30 MM on a std 750 and the intake manifold's and ports enlarged, porting was usually poorly done.

When I removed the pistons and measured them, they are bang on the STD sizes, no signs of any real wear, cylinders are also bang on the STD sizes, no nasty ring grooves or wear, but sadly some shallow pitting where the engine stood for some 20-30 years.. The ring end gaps are 25 thou (0.025") and the manual says they should be half this, so either they built it sloppy, or the rings are worn. I plan to give it a light hone and fit a new set of rings.

The big end bearings have me stumped, no real signs of any severe wear or damage, but the left BE shells have a groove in them, the right ones do not.
Same bearing numbers on the LH and RH pairs, but the cap and rod bearings have different numbers!
Is this normal...
I supppose it is possible that something has picked up and gone round the bearing, creating a perfect groove, but it really looks to perfect?!!!!

Any ideas?

See pictures:













Ever seen this before?

Mike

bill said:

the combat had a 2 S cam, cylinder painted black, head milled .040 to raise compression , 32 MM carb's V 30 MM on a std 750 and the intake manifold's and ports enlarged, porting was usually poorly done.

Click to expand...

I didn't get carbs or manifolds with the engine, but the cylinder was painted black... I haven't beadblasted the head yet to check the porting, but through the carbon it did look quite smooth, not a cast surface anyway.
I have spent almost 30 years porting heads, so I will clean it up, fit new guides and cut the seats.

Assuming it is a combat engine, would it have superblend bearings?

I spent hours reading the superblend main bearing threads.. and got quite dizzy from it all to be honest..

Here are some pictures of the main bearings:









I want to retain as much of the original motor as possible and keep the costs down for the first build... I'll probably get shot down and persueded to fit new bearings while I have the engine apart though..... ;-)

Mike.

conkers said:

Assuming it is a combat engine, would it have superblend bearings?

Click to expand...

No, not originally.

Those main bearings appear to be the standard pre-Superblend RHP "MRJA30" rollers, as they do not seem to have the "6" Superblend prefix which was etched on (thus: 6 MRJA30)?

Thanks L.A.B....

So do I need to fit superblend bearings.. or will it be ok to run it with these..?

Let the debate begin

Mike.

conkers said:

So do I need to fit superblend bearings.. or will it be ok to run it with these..?

Let the debate begin

Click to expand...

If it was my project....then I would certainly change those bearings.

I was afraid you would say that and I agree with you...

Am I right in understanding (reading babble on the internet) that the combat engine was what gave Norton a bad reputation, until the superblend bearings came.... by which time it was too late..?

I also read somewhere that some combat engines without superblend only lasted 5000miles?

Have you seen my big end bearing pictures further up...? What is your take on the groove on the LH bearing shells?

I'll get everything cleaned up next week and then inspect and order parts..

So far my parts list for the engine is:

Valve guides. (Found a set of new colsibro guides in the boxes of "junk" that came with the project.)

Set of piston rings. To be gapped to 12 thou as the ones I removed were at 25 thou.

Light hone in the cylinders. (current bore clearance is 4 thou LH and 5 thou RH)

New Big End Bearings

Superblend Mains.

Gasket set/seals etc.


I will avoid all types of spit and polish on this build, because I love the patina of the bike and it's racing history.

Mike.

conkers said:

Am I right in understanding (reading babble on the internet) that the combat engine was what gave Norton a bad reputation, until the superblend bearings came.... by which time it was too late..?

I also read somewhere that some combat engines without superblend only lasted 5000miles?

Click to expand...

5000 miles...or less!


Apparently, the problem had become so serious by mid '72 that Combat production had to be halted and all remaining factory stocks of Combat Commandos had their engines rebuilt in detuned form starting from serial 211110. The 6/ MRJA30 "Superblend" bearings were introduced from 211891.

conkers said:

Have you seen my big end bearing pictures further up...? What is your take on the groove on the LH bearing shells?

Click to expand...

Sorry, I can't really offer you any explanation for the groove.

the groove is from some kind of trash going through the oil. I have reused worse but with the other contamination showing in the bearing and the cost V labor is it REALLY worth taking the chance??? also on your parts list add a set of new set of nut's for the con rod bolt's.

I really can't offer any explanation to why there are two different conrod big-end bearings fitted. I concur with you Conkers, that the groove seems too clear and distinctively purposeful to simply be wear from a foreign object in the oil. As far as I can remember, the standard BE bearings were an un-grooved bearing. That would mean that the oil orifice in the conrod which supplies oil to the camshaft lobes would only supply oil when the oil hole in the bearing aligns with the crankshaft oil gallery. By having the grooved machined in the new bearing it would allow a constant supply of oil through the full 360 degrees of crank rotation, not just a sudden burst.

Does anyone know whether the Combat engine had a problem with camshaft and/or cam follower wear due to higher valve-train loading? I suspect that due to the .040 milled from the head and heavier valve springs that higher "follower to cam lobe" loading would be evident. Perhaps the grooved bearing was fitted to fight against this problem, either by a previous owner or by the factory/dealer in an attempt to remove the Combat's explosive stigma.

Kenny

I have an all original combat with 7500 miles on it. Superblends were changed early in it's life by T.C. at sunset motors. He also did a few other things to it. It makes no bad noises and goes like a bat out of hell. Until I tear into it I won't have hard proof, but from all I have read if it has superblends it will usually last quite a while. Mine was street raced pretty hard for all of those miles. T.C.'s hogslayer motors were mostly stock internals, made something over 125 drag strip runs and were never opened up. There is something to be said about a properly assembled Norton motor.

you are ALL wrong on this post. the groove is MOST defiantly from a piece of foreign materiel going through the bearing and more than likely discharged through the oil hole at the top of the rod. next is your statement that the oil hole was for cam lube is also wrong as it was a carry over to lube and cool the pistons to stop piston seizure. just look at where the holes are and you will see they DO NOT face the camshaft. to the best of most people's knowledge the combat did not have cam and follower troubles.

Roadster_Kenny said:

I concur with you Conkers, that the groove seems too clear and distinctively purposeful to simply be wear from a foreign object in the oil. As far as I can remember, the standard BE bearings were an un-grooved bearing. That would mean that the oil orifice in the conrod which supplies oil to the camshaft lobes would only supply oil when the oil hole in the bearing aligns with the crankshaft oil gallery. By having the grooved machined in the new bearing it would allow a constant supply of oil through the full 360 degrees of crank rotation, not just a sudden burst.

Does anyone know whether the Combat engine had a problem with camshaft and/or cam follower wear due to higher valve-train loading? I suspect that due to the .040 milled from the head and heavier valve springs that higher "follower to cam lobe" loading would be evident. Perhaps the grooved bearing was fitted to fight against this problem, either by a previous owner or by the factory/dealer in an attempt to remove the Combat's explosive stigma.

Kenny

Click to expand...

The rod oil jet holes are as useless as remains of horse's toes half way up its leg. Block them off like racers do, they were an initial mistake to correct siezures that turned on to be a bad batch of pistons.

Here's the low down on the Commando Cream of the Crop Combat that essentially spelled the end of Norton but more of em sold and out there than any other. Also introduced the 1st longest ranger Cdo version with the Combat.
http://i283.photobucket.com/albums/kk31 ... ph0003.jpg
http://i283.photobucket.com/albums/kk31 ... ph0004.jpg

Great article Hobot, thanks for sharing.

I see the RGM offer a full bottom end rebuild kit with bearings, rod bolts and nuts, bolts for crank etc.
So I'll do it right...

Under the microscope the bearing groove looks perfect, but without an oil filter it wouldn't take much to machine such a perfect groove at 6000rpm!

What ring end gaps snd piston skirt clearance would you suggest?

Is it worth fitting a thicker head gasket to lower the comp a tad?

Mike

hobot said:

Here's the low down on the Commando Cream of the Crop Combat that essentially spelled the end of Norton but more of em sold and out there than any other. Also introduced the 1st longest ranger Cdo version with the Combat.

Click to expand...

I know hobot likes to think more Combat engined Commandos were sold than any other (Any other what? Model? Year's production?) but that's not really true.

Just my tenpeneth, does the groove in your bearing shell expose a copper like layer or is it white metal? If it has exposed a different layer I reckon debris has done the damage and if so where is the culprit now?

you need to be VERY careful about the rod bolts. first make sure they are genuine andover and that you DON"T remove metal putting in the new ones. My preferd method to lower the compression on a combat is to machine the top's of the pistons .020 - .030 max. look here on the rod bolts http://www.andover-norton.co.uk/Pirate%20Parts.htm

conkers said:

Great article Hobot, thanks for sharing.

I see the RGM offer a full bottom end rebuild kit with bearings, rod bolts and nuts, bolts for crank etc.
So I'll do it right...

Under the microscope the bearing groove looks perfect, but without an oil filter it wouldn't take much to machine such a perfect groove at 6000rpm!

What ring end gaps snd piston skirt clearance would you suggest?

Is it worth fitting a thicker head gasket to lower the comp a tad?

Mike

Click to expand...

Hi Conkers, my opinion:
-dismantle the crank, to clean inside , i do not like the bearing shell groove.
- buy the rod bolts from Andover , or keep yours.
- change the bearings for super blend.
- if not racing , put a plate under the cylinder , to lower compression , a bit , or said above , give your piston the top machined down.
More to come , according to your future inspection.

Oh , yes , show us the camshaft washer, as a 200.000 on engine it should have the bronze washer with two tags , if not there (or looked they were , but had been apart), could be them the culprit of your groove , so check the oil pump (inside), and further on you could play with the Old brits mods , and add an oil filter..........(crankcase breathing too!)