Author Topic: Engine (Still) Buring alot of oil (Read 4721 times)

Leanier · « **on:** May 30, 2011, 09:26:57 PM »

Ok, so, I have been chasing this engine burning oil issue for two top end jobs now, probably due to my cheap nature. Anyway, used to burn about 1 quart every 100 miles of highway riding. So got new in spec cyls and new rings. Put her all back together, runs great now. has 160psi compression all around. But still seems to be burning a significant amount of oil. So far have done full rings, hone job, all gaskets. And new valve seals. Only smokes once its warmed up fully. And then only usually alot under heavy acceleration. (but it smokes a ton then). The only thing left I can think of is valve guides, but dont see why, the bike only has 17000 miles on it. And they didn't seem to have alot of slop on the last rebuild. Anyone confirm that this sounds like the guides?
And yes I'm pretty sure that the rings are installed upright and properly.

(Also, it doesnt like to start when it's been sitting for a few days, takes a few cranks over, but that I believe to be unrelated fueling issues, as no smoke comes out on startup.)

Thanks guys!

Greggo · « **Reply #1 on:** May 31, 2011, 12:40:15 AM »

Dude, how sure are you you've put the rings in correctly?

Leanier · « **Reply #2 on:** May 31, 2011, 12:47:16 AM »

Well I checked them twice, but then again I'm pretty prone to making minor errors like that. Perhaps I mixed them up entirely. Any Idea which ring goes on top? I had chrome edged and not chrome edged rings, (one of each per piston)

Greggo · « **Reply #3 on:** May 31, 2011, 01:19:40 AM »

Did it get worse after the last rebuild? Did you ever do a leak down test on the head?

Leanier · « **Reply #4 on:** May 31, 2011, 04:50:21 AM »

Staggered the gaps yes, 3 piece oil thing are installed correctly. Haven't done a leakdown test. But yes it did seem to get worse after a few hundred on the rebuild.

MCRider · « **Reply #5 on:** May 31, 2011, 06:40:06 AM »

Quote from: Leanier on May 31, 2011, 12:47:16 AM

Well I checked them twice, but then again I'm pretty prone to making minor errors like that. Perhaps I mixed them up entirely. Any Idea which ring goes on top? I had chrome edged and not chrome edged rings, (one of each per piston)

The chrome edge is top, (compression) black (iron)(scraper) is middle. Printed side up. Staggering ring gaps is not material to oil consumption as rings rotate during operation, and the gaps get mixed up arbitrarily. Truth be known staggering them upon install is bunk as well. IMO I do it anyway just to feel good, but I know its bunk.

http://www.diagnosticengineers.org/journal_%20articles/Ring%20Gaps%20vs%20Knowledge%20Gaps.php

There's really only two ways you blow oil out the tailpipe. Rings and guides. Any part not replaced is suspect. Even though your guides were low mileage, if they weren't replaced or objectively checked, they are suspect. Loose guides can allow the valve stems (also suspect) to wobble inside an even new seal, causing it to leak.

Leanier · « **Reply #6 on:** May 31, 2011, 06:48:06 AM »

Thanks for confirming MC. Now to dump more money into this bike I suppose haha. And I did put the chrome ones on top (a complete guess on my part haha. Any price estimate on new guides? Would I need new valves as well then?

MCRider · « **Reply #7 on:** May 31, 2011, 06:51:24 AM »

Quote from: Leanier on May 31, 2011, 06:48:06 AM

Thanks for confirming MC. Now to dump more money into this bike I suppose haha. And I did put the chrome ones on top (a complete guess on my part haha. Any price estimate on new guides? Would I need new valves as well then?

Did you do new guide seals as well? Didn't see that in your posts. They definitely wear with age (get hard) regardless of mileage.

Anyway, valves should be checked, mic the stem diameter, or have head machinist do it. Don't know about price.

Leanier · « **Reply #8 on:** May 31, 2011, 07:03:56 AM »

Yep did new seals, was trying to get the oil leak solved as cheaply as possible, But that never works anyway, always might as well do it all at once.

MCRider · « **Reply #9 on:** May 31, 2011, 10:42:57 AM »

Did you have a chance to read that article? I think clearly they do. And here's an example where they actually cut away a xyxlinder so they could watch them rotate. Roughly 1 rpm per 1000 rpms of engine operation.

http://www.sacskyranch.com/piston_ring_rotation.htm

The fact that so many service manuals say to space the gaps on install, simply shows the lengths to which humans will cling to a falsehood. (That includes me, but I do try) The earth used to be flat, some still say it is.

The footnote is dated 1946!

MCRider · « **Reply #10 on:** May 31, 2011, 10:57:02 AM »

The second article makes the point why do 2 stroke engines peg their gap? To keep them from rotating and hanging up in a port. Sort of proves the point. And i can remember seeing 2 stroke pistons when i was a lad 50 years ago that had a peg, so rotation is nothing new.

neverendingproject · « **Reply #11 on:** May 31, 2011, 01:06:41 PM »

You can lead a horse to water...but sometimes the only thing that works is

http://article.nuclear.or.kr/jknsfile/v31/A04803285773.pdf

MCRider · « **Reply #12 on:** May 31, 2011, 04:08:46 PM »

Thank you for that neverend. From this we can conclude that piston rings do in fact rotate, often in different direction, unpredictably. And that when the gaps line up oil consumption increases (duh) but so what? its negligible and within a few moments the ring gaps will again become misaligned and so on and so forth.

And I have absolutely no problem accepting that every four stroke service manual is wrong about any implication that staging ring gaps has any importance at all.

It can't hurt anything, but it is worthless effort. Once one manula puts it in, who's going to be the first to leave it out? Gutless editors.

Rings rotate. The comments about 2 stroke ring pegging does not refute but rather supports the fact that they do rotate. If one was going to peg rings in place they would definitley do so the gaps were not aligned. That doesn't refute the idea that they would rotate if they were not pegged.

I'm done.

Leanier · « **Reply #13 on:** May 31, 2011, 04:12:23 PM »

Perhaps there aligned like that when first put together to aid in compression when you first start the engine, before anything is seated properly, making it easier to start the first time?

Ernest T · « **Reply #14 on:** May 31, 2011, 07:54:54 PM »

Did you measure your valve clearances when you replaced the seals? The specs are pretty tight, if you can feel them wiggle they are probably worn. Usually when you have a machine shop do a valve job they will measure the clearances and advise you to replace them if they are worn.

Leanier · « **Reply #15 on:** May 31, 2011, 08:30:51 PM »

No I didnt measure. They had a tiny bit of wiggle, on the exhaust side only. I'm sure thats the problem. Would it damage anything if I were to take it on a long trip? I have a 8 hour round trip planned in two weeks that I'd rather not have to skip..
Other than that, what do I need to do the guides myself? just a driver? or do I need hones and valve seat cutters etc? Anybody have a good source for guides? I havent found any good sites.

Leanier · « **Reply #16 on:** June 01, 2011, 02:22:48 PM »

Does anyone think this would do any harm? I figure it'd only fill the exhaust with oil, which will burn off anyway.

MCRider · « **Reply #17 on:** June 01, 2011, 05:17:55 PM »

Quote from: Leanier on June 01, 2011, 02:22:48 PM

Does anyone think this would do any harm? I figure it'd only fill the exhaust with oil, which will burn off anyway.

Is this your 73Cb750? Wouldn't happen to be an F2?

I'd ride it. Use some Seafoam and change oil before leaving. Watch the level doesn't get too low. That's just me. It could make whatever is bad worse. Likely. All's gonna be replaced anyway, eh?

DIY valve/guide job not recommended by me. A competent non-motorcycle small car engine shop can do it. Guides should be readily availble. Or send it to APE or MRieck.

Leanier · « **Reply #18 on:** June 01, 2011, 10:54:05 PM »

It's my 73 K3. Been burning it since I got it, cause I didnt want to pay the cash to have the guides done..

bryanj · « **Reply #19 on:** June 01, 2011, 11:10:14 PM »

Guides HAVE to be reamed after fitting and Honda use a none standard size.

Valve seats need re-cutting 99% of the time.

Save up and send it to Mike(or purchase a used head and send him that) for him to work his maguc on, you will not be disapointed

ben.cb500 · « **Reply #20 on:** September 07, 2011, 06:12:27 AM »

I have exact symptoms, rebuilt in june, head ,rings seals.

Assumed was exhaust guides, either stem seal or oring.

BUT consider the pattern of carbon left on pistons, mine were clean around edges with carbon depositedin rhe middle suggesting rings were allowing oil.

$60 ebay set, not honda,installed correctly, showing proper wear on oil ring.

So i aim stuck between it being rings (machinist opinion) or guide issue. Im leaning towards rings being inferior.

ekpent · « **Reply #21 on:** September 07, 2011, 06:43:54 AM »

Long time ago before I got the knack I installed the scraper rings upside down in an RC836 ring renew. That thing was a super big smoker,embarrassed to drive it .Tore it down with advice from a builder,did it right and no smoke.

camelman · « **Reply #22 on:** September 07, 2011, 07:28:07 AM »

I ran across an issue with my valve guides that seems to be causing some serious smoke. My valves aren't loose, and I have new seals on them (350F). However, I still burn a lot of smoke even with a new bore and correctly installed rings. I believe my issue comes from scratches inside the valve guides. The retainers on my valves slightly marred the ends of the valves. When I pulled a couple of the valves out, there was a bit of resistance. I saw very visible scratches on one guide, and believe that is why I am burning oil right now. Did you remove the valves in your head? Notice any burrs?

I also noticed some relatively minor oil leaks a while back that ended up being the major cause of my oil consumption (roughly one quart per 100 miles). After fixing those leaks, my oil consumption has dropped dramatically, and the only issue now seems to be a slightly stinky cloud coming out of my exhaust.

Camelman

jessezm · « **Reply #23 on:** September 07, 2011, 07:43:39 AM »

Yeah I just broke down and bought new bronze guides, o-rings, and seals to address the exact same symptoms on my 466cc-kitted bike. Hopefully that will take care of the smoking, and give me a chance to get the leaky head gasket right this time (third time's a charm, right?)

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Author Topic: Engine (Still) Buring alot of oil (Read 4721 times)