Starting to smoke from the rear cylinder

[Fast Ed 53]

In a earlier thread you talked about a leaking head gasket sucking oil into the cyl. to create a smoking cyl. I'm starting to smoke from the rear cyl. when I roll off the throttle. Could this be the problem ? Thank's, Ed

[Cotten]

That's a real hard one to diagnose without disassembly.

Oil gets into the combustion chamber:
Past worn rings
Past worn guides
Around the outside of improperly installed guides
Or past the headgasket adjacent to the head drain gallery.

Can anyone think of other possibilities?

[weezeo]

Always thought that when backing off on throttle and it starts to smoke it was the guides.

[sleeper]

Cotten, I think you hit all the possibilities.
Weez, I'm thinking guides also. And............
If it were my Bike, I would do a compression test. With the motor fully warmed-up & throttle WFO & test both barrels & record readings.
Then I would add a tablespoon of motor oil thru the plug hole. 1 spoonful for each & re-test compression.
If your readings are only slightly higher, then the heads/& or gasket is ready for repair.
If however, your readings are much higher then you can start thinking about re-ringing it. & likely bore & new pistons. Both cylinders should be close to 10% of the other.
If you do a Comp. test Post your readings.

[Fast Ed 53]

Thank's Guy's, I was leaning toward guides but I saw that thread about head gasket leaking, Thought I'd ask. I'll leak down the cyl. this afternoon and see what it show's me. Thank's, Ed

Update on compression, Right at 95# comp. on both cyl,s. When this started I was on a 50 mile run at about 65 mph, oil pressure was about 35#. Could I have pump to much oil up to top end and flooded the guide's ? Thank's , Ed

[Cotten]

Ed!

Please remind us with CRS what vintage motor, heads, and pump you are running.
Flooding heads is an occasional problem with overhead oilers, particularly when highvolumeoverkill pumps are added.

[Fast Ed 53]

O.K. I've not had the eng. apart but here's what I know it's a 53 engine with 53 cyl's. the only marking's on the underside of the head's were marked xxxx-50 I assume they are 50 head's. The guy I got the bike from, and I believe he told me the truth said that he had a shop in wisc. install new 7-1 piston's in 2002. I've installed solid lifter converter's and a later shovel pump. I've matched the pump to block opening's for a smoother flow of oil. I believe the cam is stock. I warmed the motor up then took the test on both cyl. The bike start's super easy every time but it dosn't have much comp. The bike start's with about 45# of oil pressure and drops to about 35# at cruising speed and warmed up. Idle's at 7-10#.
Cotten, I know from our conv. you told me to stay close to stock but I had to get the pressure up a little. Do you think I've gone overboard?
Billy, I did not do the second check with oil in the cyl. I can try It if you think I can get a more reliable reading.
Thank's again, Ed
P.S. I've been running 70 wt. oil in this heat.

[Cotten]

The -50 casting number was used until '55, I think, although there were variations over the years.
I'm not a fan of aluminum pumps.
Please remember that our motors require moderate oil flow, not much pressure.
In fact, you can have enormous pressure if something is blocked! Or you can have plenty of flow without even bumping the gauge.
And I would save the 70wt for only the most tired and loose-as-a-goose warhorses; Unless you are doing desert duty, your motor could actually starve for lube at critical interfaces, or worse yet, rollers can "skate", or fail to roll and get flat spots.
Heavy oil is denser, and actually holds heat.

But that's not what your symptom indicates,...yet.

The higher volume pump may be flooding the heads, or something may prevent their adequate drainage (like too heavy of oil.)
But we may be jumping to a conclusion that it is even oil smoke.
Is the rear plug oily? (If so, let it sit under a heatlamp for a minute or to see if it dries, indicating fuel and not oil.)

[sleeper]

Ed, just see what Cotten says, I don't want to confuse your issue...

My mention of doing the oil in the cylinder is very effective in determining if there is a "head/ gasket" problem, or the rings. Top or bottom.
That is it's sole purpose.
But too many cooks in the kitchen is, No good.
This is Cotten's by your request..

[Fast Ed 53]

Thank's Billy,

Cotten I'll warm it up this evening and pull the plug's and put them under a lamp to see what they do. I'll let you know this evening.
Thank's, Ed

[Cotten]

Then do the compression test as Billy suggested!

[Fast Ed 53]

Cotten, This evening I Installed new plug's started and warmed up the engine, then pulled them out and did a comp. check with a better gage. Not Good ! The new plug's came out with oil on the electrode and the tip of the thread's. Compression was 85# on the front cyl. and 83# on the back cyl. Then I forgot to pour the oil in and try it again. Will it help to do the oil test again or do you think the ring's are shot. Thank's, Ed

Just Reread Billy's post and I under stand the importance of this test I'm headed for the shop. Sorry, Ed

[Fast Ed 53]

O.K. Here's what I got front cyl. 87# dry then 110# with oil in it. Back cyl. 90# dry and 110# with oil. Thank's, Ed

[sleeper]

OK, now you have removed "ALL" doubt that it's not just your heads. Better to know, than not. Or just do headwork & wonder why it's no-better..
This test showed that your LOW compression was increased Significantly, by adding a spoon-ful of oil, to each plug-hole. The oil makes the rings seal better, How much the increase is, shows what shape your pistons & rings are in..
Yours were a MAJOR increase !!
You know what this means. Rings, more likely Bore & pistons/rings. & your heads 'may' be not far behind. But they should be thoroughly checked out to see. "Thoroughly"......
If or when you do this, & your rods are hanging out. Give the rod main bearings between the wheels & rods some healthy squirts of 'mineral spirits'/or similar, to wash off the oil on the crank-pin & bearings.
& then check the rod clearances & see if they have ANY up & down play, or too much side play, etc...
This may be a good winter time project. I'm sure you get snow where you're at. I would keep running it till your season is over, since there is "No Harm" involved,
that I'm aware of.......~ But it's up to you~........
My '63 only had about 56-62 psi when I rebuilt her.
You could start it with one hand on the kicker.
She was very-tired! But when she was re-born.. She was a fire breathing 88" stroker & hauled ass!! ;D

[Fast Ed 53]

Thank's for the info Billy, She fired up and ran so good last nite with those new plug's I've got to keep riding her this summer. I was Planning on tearing the motor down this winter when the snow's on. Not quite old enought to spend the winter's down there someplace. Ed