Ok so 03 sportster 1200, bike was warming up 10 minutes. Temp outside was about 65 degrees outside. Got on bike and seemed like it was spark
knocking really bad. Top of each gear the most putting a load on it. I am using high grade gas, nothing less. I got on the bike this morning and rode
it to work, bout 60 outside. Warmed the bike up for about 5 minutes and rode and no issue. Do I need to run some additive in it. We use BG fluids at work (nissan dealership) and I could score some of that. Bike runs like a top except for that. She has about 4800 miles on her.


To be honest,I Get gas from just about any gas station which I know could be an issue, but if it was contaminated it seems it would do it all the time.

 

Coulda been something in the gas. If the cyls are not getting all the gas they need, they are runing lean and therefore the spark knock.

Could be something that worked its way through the system, a slug of water, contaminates etc.

If it is all better now, don't worry about it.

 

That and the fact you let it run for 10 minutes at idle. This raises the cyl and head temps causing the fuel to burn quicker. If the fuel octain is iffy detonation will occur. The basic causes of detonation are overheated engine, low octain fuel, lean condition under load or too much timing for load condition. Excess carbon on the pistons and in the cumbustion chamber will raise compression, which adds more heat to the mix requiring higher octain, or reduced timing advance. Buying better fuel is way cheaper than pistons and rod bearings.
Ron

 

Well said.
Scott

 

Yeah but where is the answer anymore. We had 2 cars from sunoco get towed in for water. Its a tough call anymore. I will try some dehydrator. I think maybe the excessive heat may have been the issue. So no fuel additives though?

 

Sounds like not a good place to buy gas, if cars get towed in for water in fuel. Doubt this was your case for detonation, as it would run like chit with enough water to short the plugs out. Light water injestion will acutally slow the fuel burn down and behave like higher octain and not ping, but this needs to be controlled exactly for best performance. Most likely water in the tank at the gas station has taken some of the octain additives out of the fuel, giving you a lesser grade than stated by the time it gets to your tank. Isopropenal alcohol additive will suck up any moisture in the fuel, and boost will put back what's missing. Without O2 sensors shouldn't hurt much, but it would seem like it will be a pain after a while having to custom blend fuel all the time. Plus, one good overdose of water will ruin your whole day, and then some.
Ron