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Dirt Bike Discussions By Brand
Honda MX & Off-Road Dirt Bikes
crf 450 making knocking nosie
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[QUOTE="originaldirt, post: 1403771, member: 18183"] There is an "epidemic" of rod failures in 450's of all brands. Many riders who bought used never saw the factories generally recommend running 97 octane gas. Well you can't buy 97 pump gas so running 92oct or lower you will get "micro" detonation, that is maybe 1 almost undetectable detonation in 4500 to 45,000 rpms. "Micro" detonation rarely leaves a visible mark on the piston unless the whole motor grenades. If you look at the wrist pin with the naked eye it also looks like no damage, but with at least a 10x magnification you can see some discoloration from the rod bronzing de-laminating on the wrist pin. You cannot fix or hide the problem messing with the F.I. program or the E.M box program. You pretty much are just delaying or accelerating the problem. At the recent motor builders (cars, bikes, boats, etc.) conference in Ohio the main topic was detonation and how it is the most common cause of motor problems in all applications (especially in hopped-up J-model F.I. cars). When that happens one of the roller bearings on the big end at t.d.c., you are going to get a damaged roller. That leads quickly to a damaged roller cage and then more damaged rollers. Bingo the crank is toast. This can happen in a new bike with less than 20 hrs. of use. Be safe, run at least 100 octane fuel/gas. Yes you have to pay to play! Honda's and most other J-model fuel injected bikes seem to be more susceptible to this problem. 250's also need at least 97 octane! I have one pro-rider friend who blew three '10 RMZ450 cranks in 7 weeks, before he found that his Dad was trying to save money by mixing VP U4.4 with 92 pump gas. Well, U4.4 is roughly 97 octane, but mixed with 92 it was a time bomb arrangement. You are not alone. The harder you run the bike or the harder the previous owner ran it the less time you'll get on your crank. OriginalDirt [/QUOTE]
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Dirt Bike Discussions By Brand
Honda MX & Off-Road Dirt Bikes
crf 450 making knocking nosie
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