questions about 72 Commando

Status
Not open for further replies.
After all the money you own is thrown at it ,,,,,,,,,, it's still just a painted up Norton. 8)


have fun !


Tim_S
 
After all the money you own is thrown at it ,,,,,,,,,, it's still just a painted up Norton. 8)


Yeah, your right but it sure is a cool norton probably won't paint it. Just want to make sure the norton is in good running condition. For long trips
 
stevesbsa said:
The other question I have is about the rear mounted breather vent on the back of the crank case. Is it really necessary to mod or change the location of the breather if your not racing the bike.
Click to expand...

Steve I do not like the way old britts does this mod. I prefer to NOT remove all that material as it acts as a baffle to the rear breather. I just relocate the oil pick up to the rear and the best thing to do now is the CNW breather reed valve at the original lower rear place instead of the 850 style.
 
bill said:
stevesbsa said:
The other question I have is about the rear mounted breather vent on the back of the crank case. Is it really necessary to mod or change the location of the breather if your not racing the bike.
Click to expand...

Steve I do not like the way old britts does this mod. I prefer to NOT remove all that material as it acts as a baffle to the rear breather. I just relocate the oil pick up to the rear and the best thing to do now is the CNW breather reed valve at the original lower rear place instead of the 850 style.
Click to expand...

Bill,
This is interesting to me (partly because I have '72 cases that have never been modified). What you are saying is to redrill the pick up, plug the old one, but not to remove the material from the case? I have noted on several occasions that I have to hold my throttle above 4.5 to 5k for extended bursts to see no oil return to my tank. For obvious reasons I have never held the throttle there to see if this condition will persist (as I assume it will). Since I don't cruise at RPMs in that range I don't worry about it. Instead, I plan to deal with it when the day comes to break the cases apart for a complete over haul.

Russ
 
I have run one Combat into the hi rpm wet sump regularly, which mean holding into 6000's for more than a minute. Here's how I did mine just drilling the baffle.
I used hi temp JBWeld to plug front drain and its held up fine. PCV completes the oil containing then must deal with old fasteners rusting at barrel base. Attached the external baffle to the old magneto face and put the PCV valve up high on the breather hose run horizontal into oil tank port. Definitely an intimate mod to make ya feel like a real Nortoneer.

questions about 72 Commando
 
Steve I do not like the way old britts does this mod. I prefer to NOT remove all that material as it acts as a baffle to the rear breather. I just relocate the oil pick up to the rear and the best thing to do now is the CNW breather reed valve at the original lower rear place instead of the 850 style.

Bill , wish i would have seen your comments yesterday. A friend of mined worked all day to make a set up to mod the case like old britts. From what i got off of this site is most everyone mods their 72 cases like old britt recommends. Has anybody experienced any problems after doing oll britts mod ? Is it still possible to use CNW breather reed valve after mod. the case
 
I have run one Combat into the hi rpm wet sump regularly, which mean holding into 6000's for more than a minute. Here's how I did mine just drilling the baffle.
I used hi temp JBWeld to plug front drain and its held up fine. PCV completes the oil containing then must deal with old fasteners rusting at barrel base. Attached the external baffle to the old magneto face and put the PCV valve up high on the breather hose run horizontal into oil tank port. Definitely an intimate mod to make ya feel like a real Nortoneer.

Make's good sense by not removing the baffle just drilling it. I would think since that high rpm the oil is being slung counter clock wise the baffle would act as catch for a more positive feed to the pump. If my thinking is correct.
 
stevesbsa said:
Bill , wish i would have seen your comments yesterday. A friend of mined worked all day to make a set up to mod the case like old britts. From what i got off of this site is most everyone mods their 72 cases like old britt recommends. Has anybody experienced any problems after doing oll britts mod ? Is it still possible to use CNW breather reed valve after mod. the case
Click to expand...

here is how I do them

questions about 72 Commando


questions about 72 Commando


all the holes are .109 so it act's as a sort of strainer and the pick up hole at the front is plugged off. I would think you can still use the CNW breather with all the baffle removed it just makes it a little easier to get oil in the breather. there is more mod's to the CNW system to the timing case side also.
 
There is a LOT of oil coming out of the rear CNW style breather at low RPM so keeping a bit of that baffle could help reduce the quantity being pushed out along with air from the crankcase. I don't know if it is good or bad to reduce the oil coming out with the air, but it would be something to try.

Jean
 
Jeandr said:
There is a LOT of oil coming out of the rear CNW style breather at low RPM so keeping a bit of that baffle could help reduce the quantity being pushed out along with air from the crankcase. I don't know if it is good or bad to reduce the oil coming out with the air, but it would be something to try.

Jean
Click to expand...

my thought's are air moves easier than oil so less crank case pressure. I also don''t see ANY reason to drill the baffle ala hobot as the timing side leaves it open anyway.
 
Steve I do not like the way old britts does this mod. I prefer to NOT remove all that material as it acts as a baffle to the rear breather. I just relocate the oil pick up to the rear and the best thing to do now is the CNW breather reed valve at the original lower rear place instead of the 850 style.



Well I bought the reed style valve from CNW,and the case is modified like the way old britt does it . That mod seem like it will be ok their is a lot of meat there. The funny thing is,I since talk with a few guys that work on norton engines, and they were unaware of this scavange problem with norton engines. I do like your idea of drilling the hoses in the oil passage way. Do you think i should drill more holes in the passage way, after doing old britts mod. I don't see the reason for blocking the forward oil passage way, what I'm i missing here.
 
Hi rpm oil get slung to rear by crank and also the bike acceleration, so tends to pile up in back and not go down the front drain. Baffle don't seem to do much even in factory combat, holes just help oil get past and down the drain. There should be a screen over the drain as about anything that breaks off end up beat up enough to enter and ether jam the drain and or the pump ports as I've seen more than once ugh. A few smaller holes in the bottom are head smacking double solution, ugh.
 
stevesbsa said:
Well I bought the reed style valve from CNW,and the case is modified like the way old britt does it . That mod seem like it will be ok their is a lot of meat there. The funny thing is,I since talk with a few guys that work on norton engines, and they were unaware of this scavange problem with norton engines. I do like your idea of drilling the hoses in the oil passage way. Do you think i should drill more holes in the passage way, after doing old britts mod. I don't see the reason for blocking the forward oil passage way, what I'm i missing here.
Click to expand...

the problem is only on the 72-73 750 case's. there is no need to drill any more holes the way old britts mod is done and yes you need to plug the front pick up hole to force it to pick up as much oil at the rear as possible and crank rotation push's it there anyway.
 
The case is mod for the oil scavenge problem and the hole is plugged. The new super blend bearing is installed and the reed valve from cnw is purchased. Thanks everyone for the advice. Moving on to the crank, Is it necessary to split the crank to check the sludge trap? I pumped oil through the crank and it came out the journal nice and clean. The journals are standard size, very nice and still in spec. I know I'm right there but the bolts and nuts are staked hate to disturb them if not total necessary.
 
stevesbsa, I know, I know, it is a pain to split the crank. Remember how old these bikes are though, has the crank ever been apart ??? As big a PITA as it is ... I would bite the bullet, split the crank, and clean it. Everyone I've done, I was glad I did. There is no way of knowing how bad (or good :eek: ) it is otherwise. Think of it as "insurance" .
 
Yeah, I guess your right, Just hated to brake those nicely staked bolts loose. I guess the bolts and nuts should be replaced and Locktite and re staked. Thanks
 
Old Brit bikes are all a test of will power to go the length it takes for peace of mind. A motto I learned off NOC and BI list, "Clean The Sludge Trap". I never ever expected to see the inside of one crank let alone 3 now but each time was worth while to remove sludge surrounding the rod oil holes to go another 3-4 decades of full flow. After seeing how loose crank bolts get after a while I nip em up tight as possible w/o busting them or the wrench, ok I've broken wrench jaws on them, then loctite, lock tab or stake em. Real Norton mechanics all know crank insides.

Not sure about re-using the crank fasteners, not much pull apart loads, until rpm get near top so crank flexes to pull its sections apart. Worth while to have checked for run out and corrected. I found good cheap place if needed.
 
Has anyone ever opened up the sludge trap on an oil filtered bike and found anything there? I seem to remember someone looking and found nothing to clean.

I suspect all of the problems with sludge traps was from unflitered engines like, well, Triumph and BSA and the rest.
 
swooshdave said:
Has anyone ever opened up the sludge trap on an oil filtered bike and found anything there? I seem to remember someone looking and found nothing to clean.

I suspect all of the problems with sludge traps was from unflitered engines like, well, Triumph and BSA and the rest.
Click to expand...

The Beast had 32,000 miles showing when I got it. I think that is pretty accurate because the speedo gearbox called it quits about 1000 miles after that. It is a filtered, very late model 1972, 750 (kind of Combat without the "C" head) and yes the crank had crap in it. This is not to say that the PO changed the oil at anything like regular intervals and it was nothing like the packed up poop you normally pull out of a Triumph T140 but it was pretty dirty. That said we used to see a regular stream of Triumph twins through the shop with left hand rods tied up due to packed up cranks. Then we got to see quite a few oil in frame Triumph twins actually blow up due to plugged up screen filters in the frame sump. I tell you this because I never saw a Norton bottom end problem that was related to a packed up crank in my time at the shop. I think the oil filter helps a lot. Frequent oil changes are even better.
 
Has anyone ever opened up the sludge trap on an oil filtered bike and found anything there? I seem to remember someone looking and found nothing to clean.
Click to expand...

OH UGH-, I'd read reports on NOC and BI list that cranks inspected 10'000's miles after oil filter and best oils showed pristine clean, YET, when I opened new Ms Peel's crank after 7000 miles, with oil filter installed and best oil changed 1000 to 2000 mile intervals, I found about 1/2 as much as first time in 30+Kmiles w/o oil filter and ordinary off the shelf oils who knows how regularly changed. 1st time I found ~one tablespoon/3/16" layer, 2nd time half that much, Ugh. Not really an issue either time as oil holes still clear and nil effect on BF. I suspect that the sling of crank will keep oil holes clear and flowing with particles too small to bother the rod shell clearance. For sure none of the sludge layer is going to bust off and plug a hole as the sludge takes physical removal, solvents just lighten up color but leave the mass attached.

On my 2nd Combat Trixie, also about 30K miles indicated but with oil filter added long before me, I found about same as Peel, ~1table spoon/3/16" max layer but not blocking flow.

Going by what I've found, maybe the Always Clean Sludge Trap motto really only applies to Turnips and not Nortons.
 
Status
Not open for further replies.
Back
Top