Engine stumbling

[atomsplitter]

No one has touched on this subject yet so I will.... NO PREMIUM FUEL !!!
High octane will cause running problems as well, be sure to use the cheap stuff from a newer, high volume gas station. QT's, WAWA's and other high volume convenience stores are good choices since they have new equipment, tanks and their fuels do not sit around long. 87 octane or even lower is best, some owners have the desire sometimes to use premium because it's a high performance bike, it's also a LOW COMPRESSION engine. High octanes don't burn well in tractors and R3's.

+1. the compression ratio is about 8.5 to 1 (one step up from my 1941 Farmall H at 5 to 1). High octane continues to burn while the exhaust valves are opening (higher octane = slower burn rate).

 

[Cdub97]

Service Manual fuel requirements Note: if 'knocking' or 'pinking' occurs at a steady engine speed under normal load, use a different brand of gasoline or a higher octane rating.

87 (R+M)/2 or higher octane rating

 

[HellFire]

You may have bigger issues if there is "Pinking" occurring ... I hear that can be some serious "tint".

 

[Jim/Maine]

No, no knocking or pre-detonation or knocking kind of sound. I,m sticking with the idea of the fuel being to too high an octane -- but I should know by the end of my ride home from work tomorrow with cheapo fuel and from a high volume station. I have added a shot of Star Tron Enzyme now and then for the ethanol. Any thoughts? So any definitive threads on the tune download for dummies? I must admit, I have become addicted to the R3!

 

[Evil Mitch]

i only ever use 98 octane in mine as recomended by my dealer.
The only time ive used 95 was when i was almost on empty in the middle of nowhere and thats all they had but i would never dream of puting anything lower than that in her ever but thats just me. ive been told that the low octane stuff is no good for bikes even by the honda dealer when i had my rice burner .

 

[atomsplitter]

i only ever use 98 octane in mine as recomended by my dealer.
The only time ive used 95 was when i was almost on empty in the middle of nowhere and thats all they had but i would never dream of puting anything lower than that in her ever but thats just me. ive been told that the low octane stuff is no good for bikes even by the honda dealer when i had my rice burner .

Octane doesn't equate to good, gooder, or goodest fuel. It's burn rate. The lower the compression ratio the less octane needed to eliminate 'ping' or pre-detonation. High compression engines (NOT a Rocket feature) run significantly higher combustion chamber temperatures. This can lead to ignition of the fuel air mix before the piston reaches TDC, thus causing a stumble as the gasses are expanding before the piston reaches the power stroke. When you get to the highest compression engines like diesels (18 to 1 or higher compression ratio) the combustion chamber temperatures reach 1000 degrees F on the compression stroke without any other assistance (i.e. no spark plugs), so fuel is added by the injectors at TDC of the compression cycle.

My Farmall can run on lighter fluid. It was designed to run on distillate (the stuff in crude oil tanks that rises to the surface or precipitates off the tank roof) which has an octane rating in the single digits. So buying an octane 98 vs. 87 just means your fuel is burning slower, it isn't necessarily any cleaner, or more purified, or better. The cost difference goes into the additives they have to put in to retard the burn rate of the fuel. So unless you just enjoy spending money on the pricey stuff you're only making the petro-producer money, but you aren't helpinmg your engine.

Note: I buy gas from petro-producers, not the secondary market to make sure they fuel is not cross-contaminated. And if you are buying the high priced stuff from a single hose pump, the first gallon is the low priced stuff that's in the hose.

OK, Class dismissed.

 

[Jim/Maine]

Atomsplitter, Isn't it true also that in addition to your lesson, well taught by the way, higher octane will, in a low compression engine, actually produce less horse power?
Bit of an update. Since my last "stumbling" ride on premium I had filled about 3/4 tank with "mid range" fuel and it is running better this morning. Next top off will be with low octane and I will report back. So ride in at 28 degrees at 70 + wind chill is what... OK, don't care really, still smile all the time on on her.

 

[oldsprint03]

Stumbling/Surging/idle at 3400RPM

Came back from an 800 mile ride to the North Georgia mountains last weekend with my friends. On the way home, bike started stumbling (almost like no fire at all for 1 sec). Then the idle speed started staying at 1800 RPM, throttle would not go back to around 750.

Then problems started getting worse, started to idle at up to 3400 RPM, would not come down. When I turned the bike off at the key, it would go back to normal 750 RPM idle. Then after 5 minutes or so under power, it would start back at 1800 RPM idle. Two different tankfuls of gas, and when i am in the 1800 RPM loop, the bike really stumbles/surges.

Have an appointment next week to take to the dealer. Looks like I'll be buying that extended warrenty before the current one runs out in October 2011. 9K miles on the Rocket III

oldsprint03

9

 

[atomsplitter]

Atomsplitter, Isn't it true also that in addition to your lesson, well taught by the way, higher octane will, in a low compression engine, actually produce less horse power?
Bit of an update. Since my last "stumbling" ride on premium I had filled about 3/4 tank with "mid range" fuel and it is running better this morning. Next top off will be with low octane and I will report back. So ride in at 28 degrees at 70 + wind chill is what... OK, don't care really, still smile all the time on on her.

Generally, yes. A lot of factors are involved to make a blanket statement though. Horsepower is derived as a function of efficiency from the combustion process. If the higher octane fuel burns less efficiently in a low compression engine the horsepower is negatively affected.

The amount of energy available from a single carbon atom being combusted with a single oxygen atom is about 16 electron volts of energy. (An EV is the amount of energy required to move one electron through 1 volt of potential). The more carbon and oxygen you combine in the combustion chamber the greater the energy available. So packing equal amounts of carbon and oxygen into two given volumes the energy released in both volumes depends on the efficency of the combustion process. The more completely burned the fuel is the more energy released. So if one volume is less efficient because the fuel is burning at a slower rate during the power stroke some energy is being released during the exhaust cycle, thus efficiency is lower and so is the horsepower.

BTW a single fission event of one U-235 atom releases 200,000,000 electron volts of energy (for comparison).

 

[atomsplitter]

Came back from an 800 mile ride to the North Georgia mountains last weekend with my friends. On the way home, bike started stumbling (almost like no fire at all for 1 sec). Then the idle speed started staying at 1800 RPM, throttle would not go back to around 750.

Then problems started getting worse, started to idle at up to 3400 RPM, would not come down. When I turned the bike off at the key, it would go back to normal 750 RPM idle. Then after 5 minutes or so under power, it would start back at 1800 RPM idle. Two different tankfuls of gas, and when i am in the 1800 RPM loop, the bike really stumbles/surges.

Have an appointment next week to take to the dealer. Looks like I'll be buying that extended warrenty before the current one runs out in October 2011. 9K miles on the Rocket III

oldsprint03

9

Appears your TPS is acting up.