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Was at Cahuilla a few months back following a guy on a newer KX450 with a muffler that was bouncing around badly. After I passed him, I waved him off to warn him about it, but he didn't seem to care. Was that you?!
The Shop
When you ridged mount the muffler, the subframe flexes and the tab is being deflected back and forth cyclically. Eventually the tab fatigues and breaks. I've seen welds break, but mine personally broke in the middle of the tab.
I caught it before it totally failed (twice) and there are no tire marks and there is no dent from the caliper contact.
It's not a weld strength issue, and it's not a tab strength issue, it's that the exhaust becomes part of the "suspension" when you don't isolate it. Hence why some pipes are breaking at the header - the pipe is acting like a big lever.
There are 3 things going on. The subframe flexxing while seated, the weight of the muffler being supported on hits and the vibration from the engine travelling through the exhaust. I can see where the flexxing from sitting would be very severe...good point.
Mine broke with the FMF system before i beefed up the tab. I had the extra bracket that FMF gives when mine broke. The bracket kept the muffler from falling off completely and ruining it.
Pit Row
You can adjust them without pulling the cams which is sweet, just pull the finger pivot rod out of the head, grab the finger with a telescoping magnet and swap out the shim.
Also the new valve cover is pretty bulky, so I recommend pulling the plastic harness holders out of the frame and getting as much of the harness loose as you can and fold it up out of the frame. It makes the job much easier.
Exhaust was right in the middle at .16 & .17.
Intake was .14 and .11. Max is .12mm
Guess I will be shimming it. Is there a kit sold?
Safe to run as is for a few more hours?
Eh I wouldn't push it too far. As lash increases the forces on the valve increase drastically.
I personally dont have any issues with twisting bars.
My 2020 I picked up a couple weeks ago.
Did My first ride on the 20 yesterday and the forks did not feel as soft as i remember my 19 did. 2 clicks in on compression and i was very happy with it.
Post a reply to: Let's see/review those 2019 kx450s