Oil burning on start up

[Nicko]

I hope this is ok that I have started a new thread to see if anyone can help me solve my oil burning problem.

Background
Rebuilt 447 engine last year, worked fine but leaking oil behind the generator.
Had crank realignment done, new con rods and all bearings checked.
Worked great for a few months. Did 1000 mls on it but it Burnt a little oil, no smoke.

2nd rebuild went for a Heiden 750 kit so new pistons and barrels.
Stopped burning oil ran great, but must have been too much valve stem play as oil visible on inlet valves after standing for a few days, so it smokes for a minute on start up, but then cleared.

3rd rebuild, had head reconditioned, new valves & springs seats cut, new seals. I also pulled the new barrels to check if all rings fitted correctly and not broken.
Smoked mainly from no1, but evident on no 2 would not clear, just kept on blowing it out mainly when revved, lost circa 400 mls of oil in 1/2 hour running, I did not bother with a road test.

4th rebuild, new valve guides and head skimmed, smoked a little on no1 start up but cleared and the bike ran brilliantly, I have done 300mls on it now, but the smoke on start up continues, not as bad as before the head was recommissioned.

Compression is no 1 - 160psi no2 - 155psi

I have bought an endoscope, this shows oil on piston crown, (see photos)after plug removed following a ride, no sign of oil on valves even after a few days of standing therefore I believe the head refurbishment has worked.

I contacted Heiden a few days ago to see if this could be related to the 750 kit but as yet no reply. What are your thoughts, could the oil be passing the new pistons/ barrels on start up ( mainly no1 smokes badly a couple of seconds after start up, then clears a little after 1/4 mile, fully clear after a couple of miles) oil is still clean and consumption is not a problem, it has dropped but not by much.

Assuming it is the barrels/ pistons I am hoping not to remove the engine again and that it will bed in eventually, any ideas on a solution would be greatly appreciated

 

[TJZ662]

How many miles have you put on between each rebuild?

 

[Nicko]

1000mls on standard 650 set up
100 mls after 750 update
300 mls since all the work done

 

[Highpower]

If it burns oil when on the throttle, it is rings.

If it burns oil when letting off the throttle, it is the intake guides/seals.

Sometimes if the exhaust is oiled up badly, it will smoke for a while until the oil burns out of the pipes and mufflers.

Another thing to consider is the breather set up. You now have larger pistons pumping up and down and if you have any breather restriction, you could have oil being forced past the rings. There is a reason why nearly all engines from the factory route the crankcase breather into the air intake in one form or the other. Manifold vacuum helps scavenge crankcase pressure. It is for this reason (and several others,) that I absolutely despise pod air filters

If you glaze the bore from burning oil, which you probably already have, the only way to fix it is to hone the cylinders. You may, or may not get by with reusing the rings if there isn't too may miles on it, but with all the work it takes to get to the pistons, it makes little sense not to install new rings.

Sorry to sound like such a downer, but a properly engineered and built motor should go many, many miles before needing another rebuild.

 

[Nicko]

Thanks for the comprehensive reply, I have put another couple of hundred miles on the bike now and the smoke is getting less on start up and still no noticeable loss of oil.

Heiden tuning responded to my email and suggested it could be the 750 kit causing the problem, they gave 3 reasons which have been identified in similar cases
Blasting residue left in the engine after rebuilding, scoring the bores
Scraper rings damaged on assembly, checked ok
Rinds not gapped correctly, checked ok

I have noticed some minor scratches on no1 bores, but if they are the cause why is it only on start up when it smokes, similarly if it were the breather( reed valve breather fitted) would it not smoke constantly.

I may pull the engine again this winter and get the bores checked and honed, plus new rings if it doesn’t settle further

Nicko

 

[Bjorn]

Im following this. Because since my 750 rebuild last year i see some white smoke every now and then during starting.

It is white smoke you are seeing too?

 

[Nicko]

Hello Bjorn,
Yes it is white oily smelling smoke, it appears to be getting a little less as more miles are added and is confined to number one cylinder. Did you get the 750 kit from Heiden and have you asked them for any assistance.
Nicko

Ps love the Nederlands, we have cycle toured there for the last two years and are going again in July

 

[Bjorn]

Hey Nicko,

Yes i got the same 750 set from heiden. Got new rings and pistons to when I did the rebuild. I went from 360° to a 277° crank. They did the valves and valve seals for me. I asked them when I occasionally saw white smoke during starting.

Obviously they asked about the orientation of the piston rings. I paid very close attention during the build.
Secondly they mentioned that having to much oil in the case (more than halfway mark) may cause smoke. Especially when the bike in on the side stands. The crank could spin the oil upwards, at least that's how I understood it.

I tried testing by starting with the bike level. I don't remember if it had a real effect. I found it hard to reproduce the smoke anyway. Sometimes it what there, but not always.

I haven't ridden much this year yet. I will keep an eye out. Let stay in touch.


Yeah cycling is very nice here! Probably better than motorbiking due to the lack of hills haha.

Where are you from?

 

[halfmile]

I have the same problem with my 750 kit. Smokes on the left cyl. I replaced the valve seals and no difference. I used the same head I had on the 650 motor and it had no smoke. 750 kit installed and it smokes??

 

[Nicko]

White smoke isn't oil? White smoke is more likely unburnt fuel?

Looks like there a number of people are experiencing a similar problem especially with the left/ no1 cylinder, I wonder why it is only on start up and emulates a valve guide sealing problem?
My bike definitely smokes less since I put nearly a thousand miles on it, but still way off acceptable, but why does it only do it on start up then clear after about a mile, is it something to do with the oil level? My level is currently about one quarter from the bottom mark upwards, (but started half way)
I have tried level starting and leaning over to the right before starting, no different.
Interesting comment above from it’s been a long time going back in feb,regarding the same 750 problems, I always thought white smoke could be fuel and blue smoke was oil, my smoke is definitely white, I did check at first it wasn’t petrol, but the pet cocks seal perfectly. With the number of 750 kits out there I wonder if anyone has had the problem and sorted it out?

 

[Highpower]

The bike is telling you what the issue is, you just have to listen to what it's saying.

I am convinced it is a product of parking the bike on the side stand. A few seconds of sitting upright isn't going to suddenly alleviate many hours of leaning to the left, allowing oil to pool in the left intake tract. If you still have one, try parking it on the center stand as see if the problem persists

Now, as to exactly why it is doing it, even after replacing the guide seals, I have no idea. It may have everything to do with the oil drains in the big bore cylinders lining up with the drains in the head as it won't properly drain all the oil in the head back into the crankcase. I have no idea if this is a problem with a stock XS engine.

--------------------------------------------------------<Rant mode on:>----------------------------------------------------------------------------------------
This goes back to one of my pet peeves as a former motorcycle mechanic, people that remove the center stand. I know that owners regularly remove them to make their bike more aesthetically pleasing or to make them lighter, or whatever their excuse is, but IMO a center stand is one of the handiest things the manufacturers put on their machines.

They make changing tires easier, as well as lubing or adjusting the chain as well as just doing general maintenance. When I bought my XS, the stand was missing (of course) and I had to buy one off of Ebay to replace it. I won't even get started on removing front fenders, another pet peeve of mine after catching more than a few pieces of road debris during test rides, not to mention water or mud.

Of course, I am at the age where I don't give two poops what someone else thinks about the way my bike looks, I am way more about utility and ease of use over aesthetics.
---------------------------------------------------------<Rant mode off:>-----------------------------------------------------------------------------------

 

[Its been a long time]

@Highpower Cool rant, 100% agree.

 

[dave_a]

Older BMW's would smoke after being on sidestand. Oil down the guides.
Small block Chevy with miles smoke on start up. Oil down the guides.
Ever see a radial aircraft engine start? Oil down guides, past the rings. That's why they hand turn the props to clear the oil and not bend rods.
I'd look for the best, freshest, guide seals i could find if you're stem to guide clearance is correct. Just a guess tho'

 

[Nicko]

Thanks for all the replies, I agree that the centre stand is essential, I had a modern Kawasaki and bmw with no main stand, drove me mad when maintaining and cleaning.

The side stand theory sounds logical, but as I said I always use the main stand so in this case, it’s not the root cause, likewise new guides and seals have been fitted and pressure tested, so it’s not coming from there. The drain issue sounds interesting, because from memory it was a little different, but am I missing something how would oil from the drain get back into the combustion chamber if the cylinder head gasket is good?

 

[Jim]

It may have everything to do with the oil drains in the big bore cylinders lining up with the drains in the head as it won't properly drain all the oil in the head back into the crankcase. I have no idea if this is a problem with a stock XS engine.

but am I missing something how would oil from the drain get back into the combustion chamber if the cylinder head gasket is good?

Oil return (drain) on these engines is through the cam chain tunnel. I know... common wisdom here says the oil drains through the stud holes, but those are essentially blocked off. It doesn't. The valve guide pockets have a return hole cast/machined in (4 of 'em). These feed directly back to the cam chain tunnel.

 

[AUTOMAN]

Fallacies.
I had asked my fellow engineers how wet the seals and guides get from soaking in a bath?
Then I had asked how wet are they when a shower is on them?
Are they just as wet?

5.7L V8 smoking at idle, when on a upwards slope was the problem.(steep driveway/hill)

Lemme see if you guys can figure it out and how to fix.