Motorcycle Burning Oil?

My 2003 Nighthawk 750 with 7,000 miles on the odometer appears to be burning oil at a rate of one quart per 1,000 miles. At least I think it is burning oil. I can’t find any leaks. It is an air/oil-cooled inline four cylinder engine with hydraulic lifters, so I doubt the valves are the issue, but I am open to ideas.

I just bought the bike four months ago “as is.” So warranty help is out of the question. I was thinking about trying another viscosity and/or switching to a synthetic motorcycle oil. I currently use Castrol 10W-40 motorcycle oil, but the shop manual says I can go up to 20W-50.

Do you have any suggestions? Is this normal with air-cooled engines?

I’m a motorcycle guy but not a Honda one at all. Serviced a couple of Nighthawks and Shadows but that’s about it. Expert I’m not.

To me, oil useage sounds a bit high although an air-cooled engine may have a tendency to use more than a liquid cooled.

What I would do is run a compression test. Write down the readings. They should all be about the same and probably in the 170 PSI range. If lower then squirt a dab of oil into the cylinders (one at a time) and retest the compression. If it takes a jump upwards then you know there is a piston ring problem.

Buying used also means you have no idea how the original owner trested the bike as to break-in procedures, maintenance, and how hard and often the throttle was being twisted.
The only way I would want to run 20/50 oil would be in warm weather and if most of your riding is on extended trips; say 40-100 miles, etc. Oil in the 20/50 weight is pretty thick for short hop and cold weather use.

My old Harleys use straight 60 weight but that’s the nature of those beasts and what is recommended for them. They also use a different oiling and bearing system as compared to just about everything else.

It’s not normal from my experience having had a number of air cooled bike engines. The testing OK4450 suggests would certainly establish any mechanical defect causing the excessive consumption.

I had a puzzling oil loss issue last summer with my '01 Intruder 1400. I was running conventional 10W-40 (motorcycle/heavy duty) oil as recommended but also experiencing a common complaint of gear box noise and clutch grabbiness. So I switched to synthetic as recommended by a number of enthusiasts. Big difference. Noise gone, clutch much smoother. But, it burned that oil up at an alarming rate. I thought I had developed an oil consumption problem and was adding oil as necessary.

At one point, I decided to switch back to conventional oil and lo and behold, the oil consumption problem disappeared entirely. This bike appears to be quite sensitive to viscosity so perhaps a change will work for you too.

I’d be hesitant to go to too thick where I live unless it was in the middle of summer but it would be a good experiment to try. As it is now, I get some clatter after exiting the expressway if I’ve been running 85-90 for miles (here come the flames!). It quits as soon as the oil has had a chance to cool down a bit. So I’ve been considering a bump in viscosity for mid summer driving.

I’ve owned several bikes, all Hondas. 4 CX 500 Turbo’s, 1 SuperHawk V Twin, a standard CX 500, and a 2001 750 Nighthawk. Some of the bikes used more oil than others, 1000 miles per quart doesn’t seem too bad. The burn off rate with oils is more significant from my experience with my bikes. Remember the clutch and transmission are also lubricated by the same oil as the motor. I think the clutch action sheers the oils molecules faster than cars. The air cooled motor on the Nighthawk runs hotter, my other bikes were all water cooled. This also is tougher on the oil. I’m not sure about moving to 20W-50 until you get into the hot summer months if you live in the north. I ran 5W-30 in the winter and I’d ride as much as possible into the fall and early in the spring. Once the nighttime temps were above freezing I’d go to 10W, if I was taking a long trip in the middle of summer I’d go to 20W.

Your bike has very few miles, and really is not much more than broken in. If you are going to put more miles on it than the previous owner, consider that you are still breaking it in. Change the oil a bit more frequently than called for and perhaps your burn off will be less later on in the summer.

Since this my first air cooled engine of any type, I was thinking of using Mobil 1 10W-40 synthetic. Shouldn’t it hold up to the heat better than a conventional motorcycle oil? I changed the oil as soon as I brought it home and I plan to change it every 3,000 miles. I am just a little worried because my other bike, a 2005 750 Shadow Aero with 28,000 miles doesn’t burn a drop of oil, although it has a liquid-cooled engine and I bought it new. I guess I was wrong to expect the same from a used six year old air/oil cooled bike.

So, UncleTurbo, do you think I should continue to break it in with a conventional motorcycle oil or go ahead and make the switch to synthetic?

You may want to determine the oil leak first. Synthetic tend to leak easier than conventional oils, and this could get expensive if the oil usage actually goes up with oil that is much more expensive. If it is being burned at this rate, there should be evidence on the plugs.

Motorcycle oils are blended differently from car oils primarily because of the clutch being exposed to crankcase oil. The action of the clutch can determine which oil works best in your bike. Some synthetics are so good at reducing friction the clutch on the bike can slip. I believe I heard stories about Mobil 1 doing just that because it is the best stuff out there. I used Castol GTX of different weights depending on the time of year. Since I live in PA I’d do a pre winter change, then go to a higher weight at pre-summer change. I didn’t change out oil because of mileage.

You are not going to rack up lots of miles on your bike and changing the oil is very easy so I’d just use a good quality conventional oil since you are likely going to change it out before you ever get to 4,000 to 5,000 miles. If you live in a year round riding climate perhaps you can go to synthetic and change it at 7,000. Most guys like to fiddle with their bikes anyway so I’d stay with more frequent changes.

I didn’t change the filter every time I’d change oil, I changed the filter once a year on frequently ridden bikes and every other year on others. I rode about 24,000 per year but used several bikes.

Unless you see some oil leaking from a gasket or seal, the oil is probably going out the tailpipe. If you have any leaks get them sealed up for safety reasons. Oil on a back tire is not good at all.

The 750 Nighthawk is a nice smooth running bike and easy to maintain due to the hydralic lifters (no valve adjustments is unique in the world of motorcycles). Change the plugs now and again, change the oil, keep it clean and just enjoy it. When I traveled I took a small container (I used a left over fuel additive bottle) of oil to top off the bike. 1 quart per 1000 isn’t great, but not to worry either. I think with trial and error you’ll find an oil and weight that will work out just fine for you.

As an aside, I sold off the bikes and got a Ford Thunderbird as the best way to capture the open air experience of riding. Is is not the same but I hit a deer (we have way too many of the buggers here in the mountains of PA) and did the whole helicopter ride, trama unit thing. Enjoy, but be careful out there.

Thanks UT. I will stick with the conventional 10W-40 and 3,000 mile changes.

I live in northeast Florida, so there are only a few days each year that are too cold to ride. My personal cut-off point is 50 degrees (F).

Actually, I plan to rack up a lot of miles on the Nighthawk. My plan is to customize it to make it a touring machine. The first upgrades will be to replace the seat with a Corbin seat and install a National Cycle windshield. Next will be a pair of Aerostich saddle bags.

Thanks for easing my mind. I will check the plugs and confirm again that no oil is leaking from the engine.

A qt. every 1000 miles is considered normal. When I tried 20-50 in a Kawasaki Z-1 (air-cooled 4) there was a noticeable power loss due to viscosity drag. I doubt your bike has hydraulic lifters. Check your book for valve adjustment interval and procedure. Again, a little oil consumption means you are getting proper upper cylinder lubrication.

Thank you for easing my mind.

I doubt your bike has hydraulic lifters.

I am 100% sure it does. This was a unique distinguishing feature of this model.

Caddyman, my Intruder has hydraulic lifters. I was very happy to be rid of that periodic chore…

Whitey- enjoy the bike. I got hooked into need for “more speed” which is easy with motorcycles. Your bike will be great for touring.

I found windscreens were a problem for me, I got awful buffeting on my helmet. Airflow can do strange things, hopefully your windscreen will work for you.

ALWAYS wear a good jacket, gloves, kevlar lined jeans, and boots. I hit my deer at 30 mph while coming home at dusk from a run to KFC for some dinner. There were times I could have hit one going 100+, but even a low speed hit on a mid size bambi did plenty of damage. My helmet was a mess, my jacket shredded, and my gloves saved my hands. Without that stuff no more UTurbo. Riding is great fun, just always ride smart.

Yes, the Nighthawk 750 has hydraulic lifters!

I always wear a full face helmet, crash jacket, over the ankle boots, full finger gloves, and on long trips I even wear Aerostich riding pants. I had that same buffeting problem with my Shadow, but with a Memphis Shades shield and lower air deflectors, it isn’t a problem, especially when I keep control of my speed. The shield I am considering is from National Cycle and it kind of has the lower air deflectors built-in. Here is a picture. I am hoping buffeting won’t be a problem. I really prefer to ride without a windshield, but in cold weather and on long trips I would rather deal with a little buffeting than the back ache I get from leaning into the wind.

I have been reading recently about how ineffective leather is for protection. The road rash protection form leather really isn’t much better than cheap denim. So I have been upgrading my gear appropriately.

I have a 250cc Nighthawk, nice little town tooter that tolerates 2-up riding…Juice lifters will greatly simplify motorcycle maintenance and no doubt prolong engine life at the same time.

Since M/C motor oil must also lube the transmission in most cases, a steel against steel lubrication issue, it must be formulated differently than automotive lubricants. I suspect M/C oil still has a healthy dose of zinc-based extreme pressure additives which have been removed from automotive oils to protect the catalytic converters…

A low mileage engine that uses oil may simply not be broken in yet. A lot of low mileage oil burners are owned by people who break them in too gently.
My current ride is a Kawasaki ZRX1200 with 83,000 miles on it that burns almost no oil whatsoever.
This bike was previously owned by someone who traded it in for a ZX14 because the ZXR1200 wasn’t fast enough for him!!

I will watch out for deer … and wild turkeys too.