Wednesday in perfect weather a friend and I rode off into previously uncharted territory and found ourselves on all types of roads, including a few miles of unpaved road covered with thick oil and sand. I was into it before I had a chance to stop, and I didn't dare put my foot down in that gunk and attempt to turn around, so we forged on.

It was really bad, with oil and sand getting on everything, and it was a two-hour ordeal getting it all off the bike. What I still have is a heavy caked-on combination of oil and sand under my wheel wells and I'm not sure what to do about it. I will be changing my rear tire in the next six months and can clean it out at that time, but there are no plans to remove the front wheel anytime soon.

I'm not sure whether to deal with this now or wait, maybe even doing nothing and hoping in time the gunk will fall out on its own, or wash itself out while riding in the rain. I don't want to pressure-wash it with the wheel installed, as then it would get all over everything again, including the tires. It is caked up under the wheel well as much as ½" in places.

I'd like to know if anyone else has ever experienced this and how they dealt with it.

 

Not oil/sand but I did get tar/oil up inside the fenders once. You might want to try S100, simple green, or dish soap first. I ended up using engine Degreaser (don't remember which brand) and hosed it out. A little drastic but it worked pretty well.
I tried to only spray the areas that really needed it, didn't leave it sit too long and rinsed it very well.

 

Since I own a detail shop and several bikes let me recommend that if its that bad then you need to disassemble the front and rear fenders. Go to a local auto paint supply store and purchase something along the lines of a wax and silicone remover, perhaps 1gallon of XL 910 Wax and Grease Remover may get you started and should not kill the paint. Spray bottle it because your going to have to saturate until it runs off, otherwise you may just grind in the sand.

Last time I did a bike like that it took me about 10hrs...but it was perfect!

 

Sounds like road oil they use to put on dirt roads. Back in the day when I use to haul asphalt and concrete treated base rock we always were able to get it off with diesel fuel. I would try that before putting chemicals on your paint. Oh yeah take the wheel off first, I wouldnt wait too long as that stuff will cure over time. The fuel will soften it up, may take a couple of soakings if its thick and use a plastic scraper to get it off

 

I used Simple Green on the surfaces I could access--like the lowers, wheels, and forks--but it didn't dissolve this stuff as well as I thought it would. Only naphtha got the stains off the bare-alloy part of the wheels, and I used this on everything except painted surfaces.

At present the majority of the caked-on gunk can be removed by hand, but my hand and arm go up into an installed fender only so far. I think I'll wait 'til my tire change to do the rear, but may remove the front wheel and do it sooner. I'm not sure leaving it would hurt anything except add a bit of extra weight.

I've also used turpentine and water on car paint before to remove tar, but I don't currently have any turpentine. It never seemed to harm the paint.

 

I use WD-40 to remove tar. Let it soak then wash with soap and water what you can get to and spray with a direct stream of water from hose that that you can't reach.

 

Take it to the carwash and blast out the fenders with the high pressure sprayer and be done with it.

 

Any of the Citrus cleaners.I used to work in the Road Dept of a city govt. and were always dealing with dumb azzs driving through our fresh pavement in their cages so we started using the citrus cleaners. It will disolve the oil and won't hurt the paint.