Why the left?

MikeG

MikeG

VIP MEMBER
Joined
May 31, 2012
Messages
1,327
Country flag
I just changed my valve stem seals. I read up on it a bit before tackling the job and it seemed like a lot of the posters had bad left side seals but the right was OK. I found the same thing, the left side seal was rock hard but the right was still pliable. Just wondering why. And FWIW.....no job is ever as easy as it's written up to be.
 
Maybe the left side does more work, have a look what hangs off the left side of the motor, things hanging off the left crank, primary, chain/belt, rota, clutch and GB, the right side of the motor gets it easy compared to the left side, just my way of thinking but you never know.

Ashley
 
MikeG said:
I just changed my valve stem seals. I read up on it a bit before tackling the job and it seemed like a lot of the posters had bad left side seals but the right was OK. I found the same thing, the left side seal was rock hard but the right was still pliable. Just wondering why. And FWIW.....no job is ever as easy as it's written up to be.
Click to expand...
IMHO: Oil entering on both sides. The right side has the drain, so the left side oil is deeper and hotter. Often, if a seal comes off, it is the left side for the same reason.
 
ashman said:
Maybe the left side does more work, have a look what hangs off the left side of the motor, things hanging off the left crank, primary, chain/belt, rota, clutch and GB, the right side of the motor gets it easy compared to the left side, just my way of thinking but you never know.

Ashley
Click to expand...
There might be more left-hand corners on public roads, which upsets the spark plugs. Does the same seal fail in America or in the UK, regardless of where you are ?
 
marshg246 said:
IMHO: Oil entering on both sides. The right side has the drain, so the left side oil is deeper and hotter. Often, if a seal comes off, it is the left side for the same reason.
Click to expand...

True oil enters on both sides and the drain is on the right, but for some reason Nortons tend to smoke or burn oil on the right side preferentially. There have been many posts on this Forum citing the right cylinder is the smoker.

The most puzzling example of this was related to me first hand by a friend, a professional auto technician. He said he purchased a new P11 which smoked right side only. Back to the dealer who tore the engine down and replaced pistons and rings, afterwhich it still smoked right side only. Having no luck with the dealer after that, he found a guru Norton mechanic who discovered the oil drain gallery dead ended after entering the timing chest!

No oil return from the head, and smoked right side only! Go figure.

Slick
 
texasSlick said:
True oil enters on both sides and the drain is on the right, but for some reason Nortons tend to smoke or burn oil on the right side preferentially. There have been many posts on this Forum citing the right cylinder is the smoker.

The most puzzling example of this was related to me first hand by a friend, a professional auto technician. He said he purchased a new P11 which smoked right side only. Back to the dealer who tore the engine down and replaced pistons and rings, afterwhich it still smoked right side only. Having no luck with the dealer after that, he found a guru Norton mechanic who discovered the oil drain gallery dead ended after entering the timing chest!

No oil return from the head, and smoked right side only! Go figure.

Slick
Click to expand...
Weird! Every post I remember, including my own say smoke on the left. Not saying you're wrong - just that it seems the opposite to me. It seems to me that it's always the left intake seal that comes off or leaks (at least I think so, and that's basically what this thread is about).
 
marshg246 said:
IMHO: Oil entering on both sides. The right side has the drain, so the left side oil is deeper and hotter. Often, if a seal comes off, it is the left side for the same reason.
Click to expand...
Makes sense. I'll admit to not realizing that oil only drains from the right side
 
Well I wonder?.....
Serious here, but it could be due to the lack of torsional stiffness of the crankshaft, with the main load on the left side.
So, it could be that the right side is always going to get it easier - except maybe idling - the right side turns the cam and oil pump.
Much has been made of the lateral lack of stiffness of the crankshaft (Combat, Superblend, Yada yada yada...) but it could be that it is also "too twisty"?

Maybe the right is always going to get it easy while the left works harder and gets hot and bothered - much like.... ;)

(EDIT - just read back and realised what I said is similarish to @ashman in post #2.
 
Last edited:
robs ss said:
Well I wonder?.....
Serious here, but it could be due to the lack of torsional stiffness of the crankshaft, with the main load on the left side.
So, it could be that the right side is always going to get it easier - except maybe idling - the right side turns the cam and oil pump.
Much has been made of the lateral lack of stiffness of the crankshaft (Combat, Superblend, Yada yada yada...) but it could be that it is also "too twisty"?

Maybe the right is always going to get it easy while the left works harder and gets hot and bothered - much like.... ;)

(EDIT - just read back an realised what I said is similarish to @ashman in post #2)
Click to expand...
Nope.
 
Anything to do with the bike leaning away from the drain when on the sidestand?

I had intial smoke on the LH side, which went when I cleared the drain channel, which I think had some wellseal partially blocking it (some small lumps of Wellseal found in the sump filter after clearing the drain). I was guessing the hot, thin oil drained into the combustion chamber that side because it usually sat for a while, to cool down after running, on the sidestand, before wheeling into the garage and onto the centre stand.
 
Last edited:
I recall reading that a tuner (I think in the US) bored the LH cylinder slightly larger than the RH on race motors to address the uneven heat generation.

I wonder if its a function of the distance from the oil pump; i.e., pressure reduces along the crank oil gallery, hence the RH piston gets more oil than the LH.
BSA fitted a drilled LH rod to their nasty A65 monstrosities; presumably to address the issue of them regularly throwing LH rods due to oil starvation (yes it happened to me...)

Easy enough to flip the big end shells on the Norton to blank the RH and leave the LH clear, but I haven't heard of this being 'a thing'
 
I'm guessing that maybe most riders have their wallet in their left pocket
Perhaps we could have a poll ?
Maybe that's the reason I've seen blokes wearing man bags on the right to compensate??
 
Not sure of the reason, but the drive side always runs hotter. I always thought it was due to firing order, i.e. the timing side gets help from the power stroke of the left but gives no help back during it's turn. Left, right, pause, left, right pause.
 
Road Camber?

nah, just kidding. I'm with Mart UK. When the bike is on the side stand maybe oil pools up around the left guide more than the right. Eventually gets past the seal/guide on the intake and the guide on the exhaust. I know old Gold Wings had an issue with the oil seeping past the rings on the left side if left on the side stand, especially after a hard run.
 

Similar threads

Bonzo
Bike pulling to the left...
2
Replies
29
Views
1,387
o0norton0o
o0norton0o
D
What is the length of the sliders inside the Commando front fork ?
Replies
4
Views
373
Stevo
Stevo
WEM
Rough first start for the season
Replies
16
Views
693
trappnman
trappnman
mean gene
The Queen said off with her head!
2 3 4
Replies
66
Views
4,236
Dan1950
Dan1950
Fast Eddie
Why does the 961 vibrate so much ?
2 3 4 5 6
Replies
103
Views
3,621
Bevelheadmhr
B
Back
Top