I switched this summer to non ethanol with an octane rating of over 90-- maybe 92 or 94. The effect was immediate and substantial. Throttle response was radically different and got better as the older gas worked its way through the system. The man who repaired my chain saw recommended I try it and said to never put the ethanol fuel in the chain saw.
Also another word on the ethanol fuel and rubber pieces. All you have to do is drop a float bowl and take a look. Fragments of rubber-- little bits of fuel line. I am fortunate to live just afew miles away from a station that sells high octane non ethanol. Not cheap about $4.70 a gallon.
Funny I've never found anything made of rubber in my float bowls. I use regualr pump gas. Now ask me about sediment and find sand particles....
Well, let's see...
There's the rubber bowl seal, an O-ring on the 550, that swells to +4mm when this ethanol soaks it as anyone who has removed one when wetted has discovered. After drying out for an hour, they shrink back to size. In both excursions, they leak a little bit.
The tiny rubber O-ring that holds the mainjet in place on the 500/550/400F/350F carbs: when they swell from the ethanol, they leak a little more fuel thru the middle groove of the mainjet. This causes the smaller 400F/350F bikes to act rich when hot, causing them to not want to rev up like they should.
On the post-1975 750F bikes (PD carbs), there is the tiny rubber O-ring in the pilot jet's hole, which swells with ethanol and then cracks after the ethanol has removed its elasticity. Then the bike won't idle on that cylinder.
The fuel tees of the 750 pre-1975 carbs have 8 O-rings (only 4 on the K0) that try to prevent leaks, but don't after the ethanol has made them hard: about 2-3 years.
Those same 750 float bowls are sealed with a flat rubber gasket, some of which recently have dissolved when ethanol soaks them (see last year's posts). Most of these are gone now, thankfully...
The OEM rubber fuel hoses in the coveted 5.5mm size, without the red (or yellow) stripe on their sides, shrink about 0.75mm ID on average after 2 years passing ethanol. This makes them brittle, and usually leak. The 5.0mm hoses shrink slightly less, but become so stiff that they will not let go of their spigots when removed, and are known for pulling them right out of the carb bodies and petcocks if not cut off with a sharp blade.
Then the is the total loss of lube to the top piston rings and valve guides that is caused by the detergent of the ethanol, but that's not a carb...
Ethanol is nasty stuff in these bikes.
