Oil Consumption. When to bother with a rebuild?

[Bluesmudge]

My GS is now using at least 1 quart per 1,000 miles. It smokes and smells like gas for the first 30 seconds when I start it up. I assume its burning oil at high RPM as well.

I think its because when I swapped the top end back at 20,000 miles I didn't put in new rings but I did de-glaze the cylinders. I've learned that was a bad idea (should have done both or neither). The bike now has 42,000 miles.

I'm asking because on a trip last weekend I accidentally let the bike's oil get a full quart low. I don't usually put so many miles on at once so I didn't realize the oil consumption was this high.

I have a spare top end sitting in my garage. Should I swap that in with new rings? Should I get the Suzuki oversized piston/rings and get someone to mill the cylinders currently on the bike?
Should I ignore the problem and pay closer attention to the oil level?

I'll ride it as-is for the remainder of the summer but winter project season isn't too far away.

[mr72]

I have no empirical or experience-based knowledge on this topic so I'll offer my completely unqualified opinion

If it were my bike doing that, I'd ignore it for now. For an older air-cooled motorcycle 1qt/1k seems less than excessive. I would check the compression though and if it's low then I'd consider a proper top-end rebuild. But I'm not sure even a good rebuild is going to put a giant dent in that oil consumption.

My GS burned oil on startup even after the top-end rebuild. It leaks oil from the crankshaft seal on the right had side even though I replaced that seal more than once. This is an old-school motorcycle and I think it just is going to do that kind of stuff.

[Watcher]

For what it's worth, 1qt/1000mi is the tolerance that HD accepts, if you respect what the HD engineers have to say.

To me that seems excessive, especially for the riding I typically achieve.  I'd be adding a quart a month.

I don't remember any particular oil consumption when I had my GSs.  Maybe a half quart low come time for an oil change (~4000 miles)?

A quick hone and oversized rings might be worth doing, especially for a winter project, you'll have plenty of time to do it right.

[qcbaker]

For what it's worth, 1qt/1000mi is the tolerance that HD accepts, if you respect what the HD engineers have to say.

A bit off topic, but interesting read: https://www.revzilla.com/common-tread/wtatwta-why-harleys-leak

As far as the topic at hand goes, only thing I'll say is that I haven't noticed any significant oil consumption or leaks. So, to me, 1qt/1Kmi seems quite excessive. What to do about it... My gut says new piston rings but I'm no expert

[IdaSuzi]

If it were me I would leave it be and keep an eye on the level. Try a compression test and then try again but add just a small cap full of oil to the cylinders through the spark plug holes. If the compression raises significantly then you know the rings are bad, if it's the same you have top end/valve/gasket etc problems. I did this on my 89 S10 and found out my rings in two of 6 cylinders must be bad and it consumes about the same 1 qt ever 1,000 miles but I just add a heavy cheap oil and it's getting a 350 I've been rebuilding next spring

Good luck and hope it's not too serious!

[The Buddha]

My 89 with 48K was using a qt of 60 wt in 5-600 miles. If I ran 10W40, it was over 2X, when oil was 66c a qt back in the waning years of the 19's, I was throwing in SF rated Accel 10W40 courtesy wally world. But as that climbed past the $2 mark I went to the more $$$ 60 wt, just so I could put in less often.

No worries, if it run, ride it. I actually sold that bike for the same $$$ I paid for it 10+ yrs earlier, with 8K.

It did run better and look about the same and I told the buyer about oil use.

Cool.
Buddha.

[Joolstacho]

I'm of the 'excessive' opinion. My '89 has never consumed anything like that, even hot, hard running.
The good thing is that you've got a spare top end, lucky lad!
If you like the bike, just run it as is, and in the meantime reco your spare set... O/S pistons and rings if needed, valveguides if needed, etc.
(And personally, I wouldn't dream of comparing oil consumption figures from a Harley tractor with an OHC Suzuki). 

[Oscar_Muffin]

Not meaning to hijack the thread but my 2000 GS500EY seems to use a fair amount of oil. Surprisingly, none of the shaft seals are leaking though. None from the clutch pushrod, output shaft, gear shifter and none behind the cover for the coils on the right side.

However, from looking at the spark plugs, the right plug is quite sooty. I've checked operation of the carbs and it only does it for 5 minutes after startup. So, I'm thinking it's coming from one of the valve seals on the right cylinder.

If I'm doing one I may as well do all of them. Apart from a valve spring compressor do I need any other special tools for the job? I'm planning on replacing the valves, valve guides and valve stem seals.

[Weedy64]

From recent personal experience...rebuild before it runs out of oil and throws a rod.

[sledge]

If I were you I would make sure all 4 header bolts come out without any drama before ANYTHING else 

[The Buddha]

From recent personal experience...rebuild before it runs out of oil and throws a rod.

Yea, you gotta keep it full of oil. But it will never throw a rod, in fact it would never throw nothing, it would like mine did - barely break 80, but as a local city commuter, I would touch 80 by opening the speedometer and touching 80, heck I'll even touch 140.
Cool.
Buddha.

[Bluesmudge]

If I were you I would make sure all 4 header bolts come out without any drama before ANYTHING else 

What does that have to do with anything? I put copper anti-seize on my header bolts every time I have them off. I've never had an issue with header bolts.

So I did a cornering clinic this weekend. Basically a track day but on the first paved road west of the Mississippi. Lots of running at 8k+. I used a half quart of oil in 250 miles!
Luckily I keep an eye on this stuff pretty well. The GS kinda tells you with its vibrations when its getting half a quart low.
Still, seems high to me.

I will get a compression tester and then report back.

[Weedy64]

I cross-drilled and wired mine so they don't need to be  aluminium thread shearing tight.

[sledge]

If I were you I would make sure all 4 header bolts come out without any drama before ANYTHING else 

What does that have to do with anything? I put copper anti-seize on my header bolts every time I have them off. I've never had an issue with header bolts.

Well lucky for you 

Does the fact you have never had an issue mean no one else ever will?

Burning a bit of oil becomes secondary when you have a couple of rounded out bolts to deal with. If they shear it's a game changer

Search the subject, plenty has been said in the past...........you will probably learn something at the same time.

[Bluesmudge]

Thanks for the public service announcement, sledge. Let me know if you have any info or opinion on my oil consumption issue.

If the compression test confirms that its the rings, then I'm leaning towards swapping in the spare head with fresh rings. Am I correct in thinking that is just as likely to solve the problem as re-honing my existing head for oversize pistons and rings? As far as I know, there is nothing wrong with the spare head and it had ~15,000 miles on it.

[The Buddha]

Thanks for the public service announcement, sledge. Let me know if you have any info or opinion on my oil consumption issue.

If the compression test confirms that its the rings, then I'm leaning towards swapping in the spare head with fresh rings. Am I correct in thinking that is just as likely to solve the problem as re-honing my existing head for oversize pistons and rings? As far as I know, there is nothing wrong with the spare head and it had ~15,000 miles on it.

OK I'll tell you the problem with this "fix" - even though I am not sledge.
Standard rings are available by themselves, without pistons. Over sized rings are only available with pistons. Worse yet, 1/2mm is the next step up, you can not put 1/2mm over rings in a standard piston (according to the Society of automotive engineers).

You can put only 1/4mm over, obviously not even manufactured for a GS.

Now, you can go looking high and low for some car crap, get rings that are near about the size you need, hand file and fit em. Really not worth all that effort.

Further - you cant "hone the head" You'd be cutting seats and cutting valves and surfacing the head as well as cleaning the carbon etc etc out of the chamber.
You will be able to hone a cylinder - however you're not gonna hone your way out of the next size up - 1/2 mm - You barely have 1/10th mm of wear on a normal running bike that didn't throw a rod or break a piston or something. You can easily clean up with under 1/4mm, but no, Suzuki wont make and sell you that 1/4mm larger so you can clean up all the crap and run your motor another 40-50K before needing to go 1/2 mm.

Anyway, bore and hone a cyl, service the seats, valves, deck and de-carbon the head etc etc for a full top end rebuild. GS will be ready to take on the next ice age.

If it is the rings, head swap aint gonna do nothing. Bore and hone and new pistons and rings will be needed, you can use your head or that other head, just make sure you move the cam sprockets from your current head, cos it wears to the cam chain, break that pair up and you'd have other problems - likely cam chain wearing out the sprockets too fast or weirdly or something.

Cool.
Buddha.

[qcbaker]

If the compression test confirms that its the rings ...

I could be wrong, but I don't think a compression test would confirm it being the rings that are the problem. All a compression test proves is whether or not you have sufficient compression. Low or no compression could be a valve problem as well, couldn't it?

EDIT: The compression test alone wouldn't tell you whether the rings were the problem, but I guess with all the other surrounding info, bad compression would probably suggest rings...

[Bluesmudge]

Thanks for the public service announcement, sledge. Let me know if you have any info or opinion on my oil consumption issue.

If the compression test confirms that its the rings, then I'm leaning towards swapping in the spare head with fresh rings. Am I correct in thinking that is just as likely to solve the problem as re-honing my existing head for oversize pistons and rings? As far as I know, there is nothing wrong with the spare head and it had ~15,000 miles on it.

OK I'll tell you the problem with this "fix" - even though I am not sledge.
Standard rings are available by themselves, without pistons. Over sized rings are only available with pistons. Worse yet, 1/2mm is the next step up, you can not put 1/2mm over rings in a standard piston (according to the Society of automotive engineers).

You can put only 1/4mm over, obviously not even manufactured for a GS.

Now, you can go looking high and low for some car crap, get rings that are near about the size you need, hand file and fit em. Really not worth all that effort.

Further - you cant "hone the head" You'd be cutting seats and cutting valves and surfacing the head as well as cleaning the carbon etc etc out of the chamber.
You will be able to hone a cylinder - however you're not gonna hone your way out of the next size up - 1/2 mm - You barely have 1/10th mm of wear on a normal running bike that didn't throw a rod or break a piston or something. You can easily clean up with under 1/4mm, but no, Suzuki wont make and sell you that 1/4mm larger so you can clean up all the crap and run your motor another 40-50K before needing to go 1/2 mm.

Anyway, bore and hone a cyl, service the seats, valves, deck and de-carbon the head etc etc for a full top end rebuild. GS will be ready to take on the next ice age.

If it is the rings, head swap aint gonna do nothing. Bore and hone and new pistons and rings will be needed, you can use your head or that other head, just make sure you move the cam sprockets from your current head, cos it wears to the cam chain, break that pair up and you'd have other problems - likely cam chain wearing out the sprockets too fast or weirdly or something.

Cool.
Buddha.

Buddha, sorry I was confusing and mixing up some terminology in my last post. I should have been saying "top end" or "cylinders" when I was saying "head." And I should have said "re-bore" when I said "re-hone."

I have a low mileage top end, including the head and cylinders. I looked back into my PMs and found that its from a bike with only 4,000 miles that ran low on oil and toasted the bottom end.

Will it work out if I just do new standard size rings on the existing pistons and swap in the low mileage cylinders? Keep the same head I have now since the valves are probably fine.

[qcbaker]

Will it work out if I just do new standard size rings on the existing pistons and swap in the low mileage cylinders? Keep the same head I have now since the valves are probably fine.

For what it's worth, that sounds like a solid plan to me.

[mr72]

Will it work out if I just do new standard size rings on the existing pistons and swap in the low mileage cylinders? Keep the same head I have now since the valves are probably fine.

For what it's worth, that sounds like a solid plan to me.

Ditto that. Provided the compression test tells you what you think it will, this sounds like a solid plan.

I see some other posts might disagree, who knows, they say "you are ignoring this user".