Oily deposit on air filter-recommendations

[wsunate]

My 97 1500 with 115,000 miles has been suffering worse gas mileage, down to around 30 when I’m historically getting high 30’s (about 175-185 miles before filling the tank).
I’ve read through the forums here on poor mileage and understand the issue of speed and detriment to mileage. Even when I’ve ridden at 75mph, my mileage wasn’t this bad.
I’ve checked the plugs and changed them routinely. They are pretty even in their appearance. I’ve changed the fuel filter. Last summer I pulled off the air cleaner thinking it was time to change and noticed on the side closest to the intake, that there is some oily residue above the left carb. Not on the right. I have since ran about 3 cans of sea foam ( 1/2 can at a time) plus an ounce or so of Startron to see if it might help clean any gunk in the carb. It seems to have helped a little but still not where I think it should be.
I’m considering a carb rebuild, checking vacuum lines before riding season begins in earnest. And I need an alternative to talking about COVID!

The bike is regularly serviced by me, always gets fuel stabilizer for the winter, and I use regular 87 fuel. I usually put an ounce of Startron in the tank at fill ups.

I’m looking to the collective wisdom of this group for ideas, next steps, things to consider before tearing into the carb process.
Thanks so much!

[CrystalPistol]

I have a K&N filter, they like a little oil, they need it actually …

… but if using a paper element filter, they do not like oil. Oil will greatly reduce paper's ability to pass air. A dirty or even slightly oiled paper filter will choke air off and to get same performance or cruise speed will require heavier throttle use. It's a gradual change too. If you are using OEM type air filters, a change is due.

[newday777]

Well lets see....
Have you kept the drain tubes by the alternator emptied when changing the oil? You should also blow out the drain from the air filter box with those caps off to be sure there isn't a blockage.

Is your petcock staining the fuel tray or is dirt collection on the petcock? Those are indicators that the petcock is needing a rebuild and that will effect the fuel mileage.

The other possibility is cracks in the carburator vacuum slide rubbers which will need to be replaced.

Also, the 90 degree bend in the vacuum lines near the spark plugs, under the rubber mat, left side, could be burnt and have a hole in it.

(Be sure to reply back to this post when you fix it what you've found. That will help others that do a search later on and have similar problems)

[newday777]

Have you changed the sub and cruise filters yet? They get crumbly with age and can block components that will effect mileage.
(I've had brand new in package from Honda, that crumbled in the package when squeezed).

There is a 'How To' in the upper left of the main page on changing them.

[wsunate]

Hey thanks for the ideas.
THe rest of the filter (possibly Honda OEM), is pretty clean. It’s only the section above the left carb.

Sub and cruise filters may need changing but they’re not more than 3 years old. I plan to do that so will see if that is an issue.
Yes, I drain the tubes routinely. One collects more than the other so a possible blockage is worth checking into. Good idea.

[wsunate]

Well lets see....
Have you kept the drain tubes by the alternator emptied when changing the oil? You should also blow out the drain from the air filter box with those caps off to be sure there isn't a blockage.

Is your petcock staining the fuel tray or is dirt collection on the petcock? Those are indicators that the petcock is needing a rebuild and that will effect the fuel mileage.

The other possibility is cracks in the carburator vacuum slide rubbers which will need to be replaced.

Also, the 90 degree bend in the vacuum lines near the spark plugs, under the rubber mat, left side, could be burnt and have a hole in it.

(Be sure to reply back to this post when you fix it what you've found. That will help others that do a search later on and have similar problems)

I’m not sure how to check the fuel petcock so will have to look that up. I don’t see the fuel tray being stained although it is dirty but that may be just road dirt. Since I’m planning to do a carb rebuild, it’s a good time to check and rebuild the petcock.
Vacuum lines could definitely be cracked and I plan to replace them. Carb vacuum slide rubbers? I’m not sure where to find those but will look them up and check.
Great ideas, thank you!
Yep, I’ll report back once I find the issues. This is a great forum and I’ve learned a ton from others and found issues I didn’t even know I had!

[newday777]

How to test petcock



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[newday777]

How to rebuild the petcock



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[wsunate]

Newday777, you rock!
Thanks for those great videos

Nate

[newday777]

You are welcome Nate

[newday777]

For the carb rebuild

http://jmartino.me/carb/

[wsunate]

For the carb rebuild

http://jmartino.me/carb/

Thanks. I did stumble across that link and looked through it; super helpful as I gather parts.

[newday777]

Buy either the Honda parts or Randakks has a kit. You only need the rubber parts and maybe float valves(only from Honda). Don't cheap out here.