Rattle 101: Rattling Noise on reving up=usually worn connecting rod bearing......Rattling Noise on reving down=usually timing chain slap, which mean stretched chain, or shot mechanical tensioner, or both.......Rattling on way up and down=usually piston slap........rattling all the time=trade in.

 

I see nothing wrong with using 50/50 AV gas and pump gas. You just have to be over 18 and sign a piece of paper stating the fuel is for use in an off-road vehicle only.

 

Its not a "rattle". Its more like a, "pop" sound. LIke I said before, it is NOT a sound that is in harmony with the RPM. It does not hit a certain RPM, or load, and start knocking with every stroke. Nothing like that.

If I hit full throttle in 5th gear at low RPM, the RPM will rise obviously, and when they start to get higher I will gradually start to hear this noise. And importantly, like I said before, it is NOT a noise that matches any noise the motor naturally makes. (like a pop every stroke, or a pop every time a valve closes.. ect)

-Matt

 

an update. Got some Vp100 107 octance race gas and mixed it about 50/50.
noise is still there. Took the plastic off to see if it was something rattling like that clear/opaque colored plastic piece under the tank. Nope, not it.
I checked the exhaust valve clearance, its at .005 in. PS. You are supposed to actually be able to feel the rockers moving up and down slightly, right? I can tighten them down to where they do not have any clearance, and are tight up against the valve, but this is obviously to tight.

Man, this is bumming me out. I have a glamis trip planned in about two weeks, and not to mention I am trying to sell the bike. (for older cheaper 250R/Banshee)
Getting upset about this now. [img]i/expressions/face-icon-small-sad.gif[/img]
The sound is like a clatter in the top end when under WOT.

-Matt

 

Its a 99? a 440 kit? orignal crank and rod? Id bet 100% that you have a mechanical problem.....suggestions: drain oil, inspect it for shavings, catch and save shavings.....pull clutch side case, do an inspection......use a paper towel on a stick and swab inside of case to pick up shavings or fragments, or take a magnet on a stick and swab around.....if no shavings, and nothing visible with side case off, your problem could be in your valves.......stock cam? big cam? harden rockers? and by the way, with the big bore kit, and at that compression, your valves usually need to be snug.....it think at .004 on the intake, and .005 on the exhuast, I may have it backwards.....this is tighter than what honda recommends, but what the hell do they know anyway? (haha)....seriously, I learned the hard way, Id figure it out before I rode it anymore.........

 

I know it's not just a California thing since people in other states have had the same issue in obtaining avgas. Different taxes (or none), problems with emissions, etc. have made getting the stuff much more difficult for most folks I've talked with.

If you can get it, good. Mix it with the pump fuel to avoid the above mentioned performance issues, but it's simply not going to be up to race fuel standards for max performance. If it's available to you and cheaper than a race fuel or Toulene mix, go for it.

Mr350X, keep us posted...