Excessive oil consumption question.

After lurking through the forums for the last several months the time has finally come to register and post a few questions.

I got my FJ600 back in July. It's bone stock w/ no mods that I'm aware of. I don't know the exact milage (clock reads 15k) because the title read "exempt" and bike has had at least 4 PO's.

The bike starts up instantly and warms-up quicky with excellent accelleration except for a slight stumble/ flatspot in the lower gears around 8.5-9K when I gun it. I seem to be getting less than stellar fuel economy as I'm averaging only in the low 30's MPG.

Having said this I've got a definite oil consumption issue. If I top out the oil when I fill-up (approx 5 gal tank) by the time I've gone 130-150 miles enough oil will be gone to cause the oil light will come at low RPMS. This has happened to me three times in the past couple of months during return trips from visiting my Mom (approx 150 miles round trip) and my Bro (approx 130 round trip).

On each occassion when the light came on I needed 4-6 onces of oil then the light went off. Now I have some slight seapage from around the valve cover gasket and from a few of the rubber washers under the valve cover holddown bolts, but nothing close to accounting for this amount of lost oil. The seapage is so slight that I never leave any drips when I park.

The plugs don't appear to be oil fouling and other than the above mentioned stumble the engine runs smooth as silk with lots of power. I'm looking for advice to try and solve this problem any help would be appretiated. TIA

Ciao,
Rob

 

You might be "Eating" oil. The mixture might be so lean as to use the sheen of oil wiped on the cylinders as fuel.

The plugs would not foul. The "Flat-spot" you mentions is A-symptomatic and the engine usually runs hotter as a result.

Get yourself "ColorTuned" ... there's a good chance that's all it is.

Your miles per gallon isn't all that far-off. The way you ride the bike determines economy. If I had a 600 ... I'd probably be showing it the whip ... and be very low in the mile per gallon department.

 

One thing I will warn you about is that the seepage you mention may be the cause even though you say it isn't enough to account for the amount of oil lost. Much of the oil will fly off into the slipstream of the bike. Therefore you will not be able to account for it. The valve cover rubber washers can eb bought new from partsnmore.com and some RTV on the valve cover will answer that leak pronto.

 

>I'm averaging only in the low 30's MPG.
If you have a needle valve that leaks slightly, float valves are set too high or some past owner has increased the size of the jets or put washers under the tapered needles in a misguided attempt to get more power it will hurt your fuel mileage a lot.
You should check the carbs and make sure all the jets are the right size, floats are set properly, needle valves are not leaking and tapered needles are set properly.

 

Thanks for the feedback guys, you've definately given me much food for thought. I now think that my problem is a combo of the several mentioned.

I went riding down to the beach this past weekend and got stuck in traffic under extremely hot conditions (lane splitting is illegal in FL). While there I noticed an obvious sign of a vacuum leak, as my idle abrubtly began to race up to about 2k (it was about 90 degrees outside). When I parked it I noticed some cracks around the outer intake boots. So perhaps this is a contributer to the lean conditions I'm experiencing.

I was planning on taking it in to have the valves checked and adjusted anyway so I'll just replace the leaking gaskets then.

I guess now I'll have to add a set of intake boots to my shopping list and install them. While I have the carbs off I'll tear them down and thouroughly inspect them. Then I'll try fooling around with the jetting.

Which brings me to my follow-up questions. Years ago I owned an FJ600 new, and prior to that an XJ550. Both were set extremely lean from the factory and ran very hot here in the extreme heat and humidity of South Florida. I fixed them both by going to K&N filter with Dynojet stage 1kits. After a little tweaking setting the needles I got them to run flawlessly until I sold them.

I've searched around the forums but haven't found much info regarding the Dynojet/K&N combo here. Instead most of the talk seems to center around the trial and error method and rejetting with larger size stock jets and needles. I don't have a lot of time to be fiddling with my carbs as I'd rather be riding. Other than the cost, is there another benefit to rejetting from scratch? Am I missing something?

And finally, if I'm going to be tearing the carbs down perhaps I should go ahead and get rebuild kits. What is included in them? Do I need to purchase float valves additionally or ar they included in the kit? Are new needles provided? Anything else I may need (besides the kits) if I'm going to rebuild them completely? TIA

Ciao,
Rob

 

If a K&N filter with Dynojet stage 1 kits give you the size of jets you need that's great but I've got several sets of Dynojets and never found any jets in the set that I could use so I always say to just buy the size you need and not a whole set of useless ones. The set seems to be aimed at bike owners who are either unwilling or unable to check the mixture to see if it's right and adjust it properly and just want a plug n play solution they can install and forget. If that works for you it's great but since I have to pass emissions every year I can't use it.

 

Don't do any Kit until you get the bike on-the-money and see how it performs -- tuned-up right.

Then, you can opt to install a kit and begin the endless tweaks and frustrating re-jetting search for Idle, Low-end and Power.

Seems like most kits only let you pick two!