KTM Gas Cap Fix : KTM 350 EXC-F

New KTMs come with a fuel tank cap that often won't come off. It's really amazing KTM ships such a great bike with this common problem.
The problem is the button on top of the gas cap doesn't let you remove the cap sometimes. I'd heard this was often a problem, and when I picked up my new bike at the dealer yesterday I tried to remove the cap... and sure enough it didn't come off easily.

First, here are some tips if you get the cap stuck on:

• -There are three prongs that need to lift UP to release the cap. So you aren't helping if you are pushing down on the cap when you try to remove it. You need to pull UP on the cap at the same time as pushing DOWN on the button. If the cap is really stuck get someone else to push the button while you LIFT and turn the cap
• - Also, if you only push on the tab, that might only release the prong on that side of the cap, and if any of the three prongs stay down the cap won't release. Try removing the vent hose and push down on the center where the hose was. Don't use a using a tool to push as it is unlikely to help and will mar the cap. Just push firmly and make sure the button goes down all around, not just the tab on one side.

Summary: Remove the hose. Push down on the center where the hose is attached and watch to see the button is depressed on all sides. Pull UP on the cap while pushing down on the button. Turn the cap counterclockwise to open. Rotating back and forth (clockwise & counterclockwise) may help release the prongs if they are stuck.

Now the fixes:

1. Some people advocate loosening the screws on the bottom of the cap (this was shown in a Tech Tip in Dirt Rider magazine). This might help... but looking how the cap is built I wouldn't recommend it as a particularly effective solution.
2. Some guys have removed the orange three pronged widget from the cap and discarded it. Or just cut the prongs off. This results in a cap that doesn't lock on and makes the button non-functional. It may be unlikely that the cap will come loose in a fall, but I really don't like this solution.
3. Some guys trim the corner that the prong catches on in the tank. This could be a bit scary, as you don't want to drop any bits into the tank or accidentally cut your tank too much. However, it is a really good idea to inspect that corner to make sure a deformation or bit of scarf isn't holding up the release of the prongs.
4. My choice was to modify the prongs on the cap. This should work the same as modifying the tank, and if something goes wrong you have only hurt the gas cap. (Worse case is you just end up with fix #2.) I did the mod by removing the orange widget from the cap, trimming it, and then re-assembling the cap.

Here are some pics of the modified prongs. I did this carefully by removing the widget and shaving it with a sharp exacto knife. This cut corner makes a "ramp" that helps the prong get over the corner it catches on. Done carefully, the cap still latches but the button more easily releases the prongs so the cap can be opened.

Rumor has it KTM has changed the caps for 2014... we will see!

Pine Sol to Clean Carburetors

I have a bunch of carburetor parts to clean and recently read that Pine-Sol did a great job. So I tested it. Looking at the ingredients, I see this stuff is 1.75% glycolic acid. It did go right through my nitrile gloves and I had to switch to some heavy duty ones. And I did wear my safety glasses.
These parts have been soaked about 30 minutes, lightly scrubbed with a toothbrush and wiped off and then soaked for another 30 minutes. Then another light going over with a toothbrush and rinse with cold water. The part on the left is before cleaning, on the right is after.

Wow! Pretty good.

FMF Q4 Mod tested

Somewhere on the web I bumped into a great idea to modify the Q4 spark arrestor to reduce the sound.
So I bought an extra spark arrestor for $35 and tried it out.
The idea is that you cut some slots in the end of the arrestor and bend the tabs over the block the pipe a bit. I used duct tape to mark where I was going to cut:

Here are a few shots of the modified spark arrestor next to an unmodified one:

Results:

FMF Q4 with Spark Arrestor

RPM            Original          Modified

2000             87 dB                87 dB

6000             102 dB               102 dB (whistle sound noticed on modified)

8000             106 dB               106 dB

No improvement! Wow, I really expected this to work.  I guess I could bend the tabs down some more, but I don't want to crudely block the exhaust too much. I guess the lesson is that you need actual baffling, not just some blockage.

Another note is that these measurements with the original spark arrestor are different from the ones in my last post a couple days back. Just shows how variable this testing is.