Carrillo conrods

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alfonso420

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Hello:
I rebuild a 1973 mk2a Norton Commando Roadster fitting some new parts as Carrillo conrods, big valve conversion (cylinder head) mk3 isolastic mountings, new head steady (from Norvil), reaconditioned oil pump, but I seized left hand side piston october the first, in a sunny and hot saturday morning (30 degrees centigrades), when me and my wife were going up a hill at 4000 rpm. overtaking a car, my bike lost power but not stopped, then I turned to the right hand side of the road and continued riding slowing down, after 20 km. we arraived where we wanted to go. When I started the engine again, I herd a horrible noise :CLA CLA CLA¡¡¡ I managed to ride 25 kilometers to home. I dismanteled cylinder head and cylinders, cylinders were good, not damaged, only left hand side piston was seized. My question is , could be caused for oil pump malfunction?, my news Carrillo conrods does not have oil reservoir on PE nor forced pin oiling as used to have my standar aloy conrods. as much I improve my engine I have more problems. I´m thinking about fitting Megacycle camshaft, but could someone give me some advice about it.
Thank You all.
 
I've run Carrillo steel rods on a variety of race Commando engines, as well as two street Commandos, with no problems at all. I doubt if the rods had anything to do with the piston seizing. The standard rods don't have forced pin oiling, just a spray from a hole in the big end of the rod that isn't necessary. What sort of pistons did you use, and at what clearance?

Ken
 
Carburation / ignition . Fully laden , one fuel tap open ?? Whats the Carburation on it , and ignition .wot spark plugs .

You familiar with plug chops & jetting carbs ?
 
lcrken said:
I've run Carrillo steel rods on a variety of race Commando engines, as well as two street Commandos, with no problems at all. I doubt if the rods had anything to do with the piston seizing. The standard rods don't have forced pin oiling, just a spray from a hole in the big end of the rod that isn't necessary. What sort of pistons did you use, and at what clearance?

Ken
Click to expand...
Hello Ken:
my pistons are 0,40 AE Federal Mogul, 77,6 mm diameter and 0,5 mm clearence (cylinder diameter: 78,1 mm.).
Thank You
Alfonso.
 
rpatton said:
How many miles on the rebuilt motor?
Click to expand...
Hi:
First time we rebuilt engine with standard aloy conrods before second rebuild about 2.500 kilometres. The second with different conrods, Carrillo, and crankshaft ballanced for new conrods, no more than 100 kilometres until seizing.
Thank You.
Alfonso
 
Matt Spencer said:
Carburation / ignition . Fully laden , one fuel tap open ?? Whats the Carburation on it , and ignition .wot spark plugs .

You familiar with plug chops & jetting carbs ?
Click to expand...
Hi Matt:
I have two Amal 30 carburetters, standard for 850 Commando, spark plugs I think are N7Y, electronic ignition, and two taps open, one for each carburetter.
Than You.
Alfonso
 
I am not sure if this is a typo or what you really have on you bike. 850's came with 32 MM carbs. if it has 30MM carbs you need to look at how it is jetted. the standard 850 has a different spray tube and needle from all other setup's 750's have a flat spray tube and the 850 has a notched one, this makes the need for a different needle and CAN NOT be interchanged. can you look at just what size carb, which spray tube and which needle (ring count or other marking's NOT circlip groove ) you have along with main jet size???


alfonso420 said:
I have two Amal 30 carburetters, standard for 850 Commando,
Than You.
Alfonso
Click to expand...
 
ludwig said:
alfonso420 said:
my pistons are 0,40 AE Federal Mogul, 77,6 mm diameter and 0,5 mm clearence (cylinder diameter: 78,1 mm.).
Thank You
Alfonso.
Click to expand...
shurely you mean 0.05 mm ?
Click to expand...

Yes , it is a little bit more than it is consider acceptable (77,90).
Thanks.
Alfonso
 
bill said:
I am not sure if this is a typo or what you really have on you bike. 850's came with 32 MM carbs. if it has 30MM carbs you need to look at how it is jetted. the standard 850 has a different spray tube and needle from all other setup's 750's have a flat spray tube and the 850 has a notched one, this makes the need for a different needle and CAN NOT be interchanged. can you look at just what size carb, which spray tube and which needle (ring count or other marking's NOT circlip groove ) you have along with main jet size???


alfonso420 said:
I have two Amal 30 carburetters, standard for 850 Commando,
Than You.
Alfonso
Click to expand...
Click to expand...
Sorry I want to mean 32 Amals, I´ve been using since a long time ago with no problems, all my problems came with cylinder head big valve conversion, I felt the bike more brave, sounds louder than before.
Thanks.
Alfonso
 
No wonder you hear a horrible CLA CLA CLA when you start your bike with 0,5mm piston clearance! In case you meant 0,05mm clearance this explains your seizure cause it should be around 0,10mm.
 
Alfonso, your piston clearance dimensions are still incorrect, you are ever running to much 0.5mm{0.020''} or to little 0.05mm{0.002'')

the seized piston may have 1/2mm clearance, at 78.1 it shouldn't have seized
 
Big Valve Hemi Head almost a new configureation . The ignition timing and carburator jetting would not be satisfactory as previously .
With Ignition to spec. Full Throttle Runs made , hitting kill switch and declutching after 5 to 10 seconds .

If centre electrode is looseing Sq corners , plugs to hot or ign to advanced . LOOK UP specs for PLUG for P.R.

Centre insulator White to ( preferably ) yellowish tinge .

Outer yellowish to brownish .

The darker shades richer . Preferable , better power , cooler running . sfa mpg differance ( - 5 mpg , maybe . )

Also ' Piston Sizeure ' o.k. The metal goes dry and picks up .
Did the RINGS sieze in the Piston . Did the PISTON Sieze ( Gall ) in the Bore . Did the RINGS sieze in the bore ( pick up / scuff ) photos ?? .

Presume youve the Re Angled intake Valves , as per Dunstall & P.R. whith the full hemisphere chamber and No squishband ? ? Picture ??

so What colour are Int and Ex valves in chamber , ? what colour piston crown . ? blitered beyond white indicates a bit of temperature .
Lean/ airleak / fuel starvation / , erroded indicates premature ignition . Not that ethanol rubbish fuel , pray tell .
 
Hello:
I don´t know how to upload pictures, when I took out cylinder head, valves were covered by a black carbon deposit as pistons head, spark plugs were more or less black coloured as mixture was rich in right hand carburetter and less in the left hand side carbureter (this piston was seized, left hand side.). all piston rings were ok except second beginning from the top that did not move.
Thank You.
 
If the seizure is due to weak mixture or ignition fault, then you should be able to see signs of carbonised oil on the underside of the seized piston crown. Contrary to popular belief its very difficult to get an accurate idea of fuel mixture condition by taking plug colour readings, as these are affected by ethanol bearing fuels, so even though plug colour looks fine, there may well still be issues with the mixture .
 
If I understand your replies correctly, those pistons were run for over 1500mi. I have a hard time believing that a shop would do a bore and hone to
0.5mm[0.020''] or 0.05mm[0.002'']. Maybe you need to mic them.
But on this last assembly it went 50mi and seized on the first time you really leaned on it. Maybe it's about fuel. If it were me, I'd start with the petcocks and work my way down. You said you're using one petcock to each carb? Petcocks are notorious for clogging.
 
All good points but I've run my C-do's up to highway speed to have em die in sputters 1/4 mile later d/t forgetting to open taps after a gas stop so everything full temp, but no seizures. Longer running lean with starving fuel feed is still a possibility to check. Gotta love these critters because we have to get so intimate with them so often. Hope to learn at anothers expense this time so thanks ahead of time.
 
When a piston seizes from a lack of clearance it tends to pick up out towards the gudgeon pin bosses, a lack of lubrication normally shows up on the thrust faces
 
splatt said:
When a piston seizes from a lack of clearance it tends to pick up out towards the gudgeon pin bosses, a lack of lubrication normally shows up on the thrust faces
Click to expand...


I would imagine that as the OP was able to ride his bike 25km after the piston had seized, that lack of oil can probably be ruled out as the cause of his problem?
 
Carbonfibre said:
splatt said:
When a piston seizes from a lack of clearance it tends to pick up out towards the gudgeon pin bosses, a lack of lubrication normally shows up on the thrust faces
Click to expand...


I would imagine that as the OP was able to ride his bike 25km after the piston had seized, that lack of oil can probably be ruled out as the cause of his problem?
Click to expand...

Yes you are probably quite right , but you will notice I said a lack of lubrication not a lack of oil, one of Alfonso first question was if the lack of squirt holes would make any difference, also I'd say he probably rode home very worried.
 
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