Anyone Reduce Oil Usage Following Engine Rebuild?

ericfreeman · Post by **ericfreeman** » Wed Sep 16, 2009 12:03 am

My '79 has about 39,000 miles on it (I've put on 4k since I bought it) and it uses about a quart every 5-600 miles, give or take. I ride pretty easy too, not many trips high into the rev range unless I'm passing traffic in the mountains. I've heard about old valve seals getting hard and the '79's low-friction piston oil rings contributing to oil usage and was wondering if anyone has done a rebuild that cured the problem. Are the replacement piston rings still the low-friction type or has Honda changed their design?

Lots of folks have suggested that my oil consumption is pretty normal but I've never had a motor use so much so quickly without a problem existing somewhere. I'm curious if this condition has a solution.

Eric

alimey4u2 · Post by **alimey4u2** » Wed Sep 16, 2009 4:44 am

Eric, to put your mind at rest do a compression or leakdown test. My feelings are, a quart every 600 miles is not excessive for an engine of that age... The engine is cursed by its relatively large piston skirt area for capacity but is blessed with even crank case pressure, all due to it's 6 cylinder configuration..

As for rebuilds, it is often the mistake when freshening up a motor, people remove the carbon ring about the outer piston crown, above the rings. My feelings are it's best left where it is...

Poor valve guide seals rear their ugly head during a lot of town use. On open road long runs they don't seem to be that troublesome... Spose that's kinda obvious though...

Didn't answer your question really as mine never has been a heavy user of oil....

Terry · Post by **Terry** » Wed Sep 16, 2009 6:37 pm

I believe oil consumption is directly related to high rpms. My 96,000 mile 82 didn't use a drop on the first nearly 600 mile day of my last tour (at reasonable speeds in the mountains) but on the second day with less mileage but at much higher speeds across the high desert in Oregon it used about a half quart. Is there any other explanation?

Don · Post by **Don** » Wed Sep 16, 2009 9:04 pm

Mine uses a lot more when I thrash it - Keeping it between 5K and 8K in the twisties for a couple hundred miles. Ride around like a sane person and the usage is practically nil . . . . maybe 1/4 quart in 750 to 1000 miles

I really think high RPM's coupled with high cylinder head temps evaporates a bunch of it - No rebuild is going to cure that

Don

ericfreeman · Post by **ericfreeman** » Thu Sep 17, 2009 12:09 am

On my last trip of around 560 miles over the mountains in mild weather, I doubt I ever hit 7,000 RPM once. With my 32 rear sprocket I cruise around 70-80 at 5k or under, with much of my time spent in the 4k range. So, definitely not wringing the snot out of the motor yet still using a full quart in that 560 miles. I definitely think I'll pull the motor this winter and take off the head. I need to do some detailing anyway and I'd like to check the valve clearances as well. Good way to spend some rainy, cold days here in the PNW: working on the CBX motor in a warm, dry workshop.

The wide variety of oil consumption figures among CBX owners has me puzzled though; I'd like to see how many '79's only are having this problem in order to figure out if it was a one-year only situation.

Eric

Terry · Post by **Terry** » Thu Sep 17, 2009 12:19 am

Don wrote:Mine uses a lot more when I thrash it - Keeping it between 5K and 8K in the twisties for a couple hundred miles. Ride around like a sane person and the usage is practically nil . . . . maybe 1/4 quart in 750 to 1000 miles

I really think high RPM's coupled with high cylinder head temps evaporates a bunch of it - No rebuild is going to cure that

Don

Who you callin insane

On my 05 tour I ran the 82 from Cody to Sheridan WY between 6,000 and 7,500+ rpm all the way! Passed a car or truck every 10-15 minutes. Man it was great and the bike didn't mind at all. I'm convinced it was built that way (and) as most of us know, the CBX loves a cold day for riding. I can feel a difference from riding around here in the south bay of silicon valley near Hollister for example (hot) and then as I ride towards the ocean and the cool cool breeze of the Pacific, I can tell the motor is much happier. If my 06 Hayabusa with 30,000 on it starts to use oil I'll be concerned. Just can't get too bothered with oil consumption on 27 and 30 year old air cooled sixes with a combined mileage of 146,000 miles. :)

ericfreeman · Post by **ericfreeman** » Thu Sep 17, 2009 1:14 am

But, I'm an engineer and we can't leave things alone if we suspect something is not right.

I've worked on a wide variety of engines over my career, from single-cylinder small displacement gas jobs to monster ship diesels and this oil usage by the CBX has me puzzled. I'll get to the bottom of it yet!!

Eric