HELP - THIRD TOP-END REBUILD and still BLUE-GREY SMOKE

ANLAF

ANLAF

XS650 Guru
Messages
1,526
Reaction score
7
Points
38
Location
Anglezarke, Lancashire, UK
Yesterday I finished rebuild number 2, this time with new new pistons and piston rings and matching cylinders (at great expense from Heiden). This morning it started easilit enough then billowed blue-grey smoke - a thin haze on idle, then billowing clouds with throttle. It was coming from the left cylinder.

So, I took a deep breath and stripped the top-end again today, lots of oil in the exhaust port area and on the left cylinder on the piston and obvious signs of oil coming in through the exhaust valve. I fitted a new valve guide and lapped the valve again, cleaned up and put the whole lot back together again.

Third rebuild finished and started up first time - then billows of blue-grey smoke.

By the way, with my hand over the end of the exhaust (oil mist coming out) there was hardly and compression from left cylinder.

HELP!

I have everything torqued down to spec, new head gasket, hmmm! Help.

Anlaf
 
Jaydela, the new cylinder, pistons and rings came as a unit. The advertisement on the Heiden website read:

"533 Cylinder (6 bolt tensioner). Precision Bored bead blasted cylinders. Includes fitted pistons, piston pins, clips and matching piston ring sets. No exchange core required. !! PLEASE CHECK THE NUMBER OF YOUR ROD BEFORE ORDERING A CRANK, RODS OR PISTONS!!..."

They arrived, I fitted them. I did not measure the ring-gap. They say 0.25 on the pistons. I expected new stock cylinders, it is a little unsettling that the pistons are 0.25 - unless stock new are indeed 0.25.

Anlaf
 
You say you replaced the valve guide but do you really mean just the valve guide seal? If you haven't replaced the guide (and even if you did) did you check the valve to guide fit? The valve should be a sliding, slip fit in the guide with no side to side "wiggle". If the valve wiggles in the guide, it and/or the guide are worn and need replacing.
 
Thanks, 5twins - I think we are getting somewhere with your answer. I just replaced the guide seal, not the valve guide - which is new territory for me. I looked on my donor engine cylinder head and wondered how the heck that would come out. The only thing that seems to move is the large washer the springs sit on.

So, new cylinders, pistons and rings, so unlikely to be a failure there. New head gasket, and all torqued to spec, so unlikely to be that. The only other source of oil ingress to cause that billowing blue-grey smoke can only be that it is being sucked down the valve guide.

Right then, I will never give in, strip-down number 4 coming up - so, how do I change a valve guide, my friend?

Anlaf
 
How long have you been "running in"... and are you using basic mineral oil ????

Semi or full synthetic is a bad idea as the rings have trouble bedding in!!! If you've only done a few mile (less than a couple hundred) I'd give it a while to settle in.
 
5twins, I am searching the forum and I understand there is a valve guide removal tool - and Sundie says stick the head (of the bike) in the oven and the guides will come out easily.

Sounds like a search for that removal tool.

Anlaf
 
Pigford, I only got to the end of the street. It was the firing on one cylinder that said 'Go home before you stop.'

I understand where you are coming from, but this is indeed a lot of smoke. I recognised a problem that had to be sorted, and would not simply go away. If it had only been a little smoke I would have given it a while - but this was serious, like a First World War bi-plane going down in flames. Thanks for chipping in, Pigford.

Anlaf
 
This is something I've never done but may attempt sometime in the future. The guides are a pressed in interference fit. From what I've read, you can stick the head in an oven for a half hour or so and then gently tap the old guides out. Install is the reverse but freeze the new guides 1st so they shrink a little. There is a special little guide driving tool you use to tap them in and out. It's basically an 8mm diameter shaft that fits into the guide bore with a lip that rests on the top outside of the guide where the seal would sit.

Do some searching on the site here. There should be threads on this. That should give you the needed details like how hot the oven should be, how long to "bake" the head, etc.
 
But before you go through all this, test the guide to valve fit. Does it wiggle in there?
 
5twins, I had some small amount of blue-grey smoke before the rebuilding adventure, now it is billowing like clouds on a summer day.

Would a valve guide fail so suddenly - and would a failed guide produce these dramatic symptoms? (smoke and hardly any pressure of exhaust gases from left exhaust pipe).

Anlaf
 
Go to the Yamaha Service manual .................www.biker.net. Its written up as to how to measure for valve guide wear.

A dial indicator is used to measure the side clearance. Valve is positioned 0.4" from the seat, and the dial indicator at 90 degrees to the valve axis, measures the "wiggle" or side clearance.

Intakes wear limit is 0.004".....................my engine was 0.002"

Exhaust wear limit is 0.005"....................my engine was 0.005"

Even though my exhaust clearances were at the limit, I did not replace them. They have been fine for the last 5 seasons, with no smoke or oil usage.

So get yourself a dial indicator and have at it.
 
I can't say for sure. Parts wear but continue to work as they do. Finally, they reach that wear point that puts them past the serviceable limit and they're done. Maybe that just finally happened to your guides. There's also a chance you did something else like break a ring during the assembly (while sliding the cylinders on) or possibly install one upside down. I guess you won't know for sure until you have a look inside.
 
With new seals I don't think it would smoke as bad as you're saying even with worn out guides. Plus the lack of compression in the left side. Did you stagger the ring gaps? I'm assuming you've decided it isn't just assembly lube burning off. Is the cam timing right?

Do a real compression test on the left side.
 
I'm wondering if there is any chance you installed the oil control rings incorrectly, on the left piston.Expander goes in first, then the 2 oil rings with the gaps 180 degrees apart.

For sure you want to do a direct comparison of the left and right cylinders/pistons/valve guides etc., since the right side does not have a problem.
 
Thanks, fellers, for your help.

I have never done a compression test, and don't have the equipment - and I don''t want to risk a ride to where I can get one done.

What I will do is strip it all down again and start from the obvious with checking I installed the piston rings correctly and for damage! What! do they have to be a certain way up, 5twins?

Then I will check the expander and oil rings, Retiredgentleman

I was careful to fit them with gaps in the correct positions, xjwmx, but who knows what I will find.

Fingers crossed.

Anlaf
 
Ummmm ..... yes they do, lol. There's usually a mark of some sort, either a number or letter stamped on one side of the ring, sometimes just a dot. The mark faces up. This is for the top two rings, the oil rails don't have an up or down side.
 
5twins, many thanks. In case you might not have picked up my question, I started a new thread - then I found the manual and discovered what you have described. So, the oil scraper is likely to be upside down - hence oil. If the compression ring is upside down too, would that account for loss of compression?

Anlaf
 

Similar threads

cbertels
Oil and smoke in right-side exhaust
Replies
18
Views
631
Grimly
Grimly
Roy
Top end rebuild
Replies
3
Views
163
Vincenthdfan
Vincenthdfan
Duck749
78 Special - Top End
Replies
7
Views
361
XSTime
XSTime
C
Excessive oil loss through breather, '75
Replies
8
Views
548
cra-z1
cra-z1
K
Running hot after BBK and total top end rebuild.
Replies
7
Views
727
kwhy3000
K
Back
Top