Asked this in the DR350 thread, but nobody knew and/or the question got buried before anyone saw it as is often the case, so.....
They're not structural, so trimming one down isn't going to weaken the engine. All you're doing is slightly reducing the surface area from which the engine heat is dissipated into the air. Grinding a little off to make room won't make very much difference at all.
I had two DR350SEs, both with the Raptor petcock. I trimmed the offending fin, on both bike's cylinder heads. I had no issues at all. You will do no damage to the engine.
The dremel idea is the best way. I say go for it...........a DR could probably run forever with no fins! Cheers
Every single 2t Enduro that came with an up pipe all did far more than trimming ONE fin, you'll be fine. Some shaved half the length of the fins off on one side corner of the cyl and head!
Okay, surgery complete. No big deal with a cut-off wheel on an angle grinder. Interestingly, the fins are shaped kind of like an airplane wing.
Yeah, that fin is the main inlet cam cooling fin!!! Now you will have to make another fin out of JB weld.
Too late to reverse course now captain. A sixteen hour dirt ride including major mountain passes is slated in stone for tomorrow. http://advrider.com/forums/showthread.php?t=864387
Post ride report....Everything worked great, but only 15 hours. No telling what could happen to the main inlet cam if I ever push it further. You can see my photos here: http://advrider.com/forums/showpost.php?p=21760211&postcount=401 Rest of the group posted photos and videos starting about here: http://advrider.com/forums/showthread.php?t=864387&page=28
