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General Category => Modifications => Topic started by: ajacstern on June 15, 2021, 09:11:12 PM



Title: Timing Advance and a Rattle
Post by: ajacstern on June 15, 2021, 09:11:12 PM
Hi all,

I recently did the ignition plate advance on my '87 FJ to +4 degrees. I am running 91 US fuel in the FJ as it is the highest octane non-ethanol fuel we have available, not sure if the knock checking was done on these using 91 or 93 and if +4 degrees is safe with 91 octane. I ran through about a tank and a half and the bike felt great, much more response and pulled hard through the entire power band.

However, yesterday I came to a stop and noticed a really loud rattle coming from the bike, I normally can't hear much rattling from the bike with my earplugs in but this sounded really bad. I stopped the bike and started it again and the rattle was really bad at startup and decreased slightly after a few seconds, it increased with RPM but I couldn't hear it over the exhaust above 3kish. I was only a couple minutes from home so I drove back at as low RPM as possible in case it is a cam chain issue. I started it again today when it was cold and there is definitely a rattle / tick there that wasn't there before, though it isn't nearly as loud as it was the day prior. I did the valves and cam chain tensioner about a thousand miles ago so a valve suddenly becoming loose seems odd to me. I checked for header leaks but didn't see any, didn't check very thoroughly though. I can try running the bike until it gets hot and seeing if the really loud rattle comes back and taking a video of that. Running 15w-40. No idea if this is related to the spark advance. The bike has been overreved a few times as it likes jumping out of second and has no rev limiter for some reason so if you are accelerating hard it is easy to loop the needle around the tach.

Video of cold start (https://photos.google.com/photo/AF1QipMoQz-grtQuAfpnVzLGVbm1HaOc61fPL0UJE-xz)

Also on an unrelated note my rear tire is getting squared off, has anyone tried the new Avon roadrider 2s? I have 16" wheels front and back and I am considering a full 17" swap as I cannot find 16" tires with good enough traction for me. The avon roadriders were great for acceleration (though awful in the wet, I don't ride in the rain really) but the profile was a little square and the braking was not impressive, front tire locked up easily and the rear wheel didn't even think of going into the air. I would rather stick with 16" wheels as putting ~$1000 into a bike worth ~$1000 is not the best financial investment but braking is important.

Any thoughts of what this rattle might be?
Thanks.