octane question for 02' 640 adventure...

[paddythesmith]

So, being pretty sure that my bike does not have the alterable ignition like the newer LC4 (high flow) engines - my question is:

Has anyone put regular unleaded in an 02' era LC4 engine. I have the FCR carb on mine and was just wondering what would happen if I needed to (in a pinch), short of doing some experimentation myself.

Thanks in advance.

[Hammer]

2 things:
One, I would think you have the later style ICM and "switchable" timing. If so, take the easy way and just unplug th wire when you need to.
Two, I ran regular in my '99 640 Adv on several occasions. Nothing at all happened. I didn't even hear it ping, tho it could be argued that one might not be able to hear it.
If I were in some 3rd world country and could only get regular, I'd just pour it in and if I felt at all "skeert" about it, just not honk on it hard. The only real danger is when the engine is heavily loaded, which is a bit difficult to do for any length of time on the 640 Adv.

[disconnected]

On some recent West Virginia trips, many gas stations only have the 87 octane to offer.. I did not notice any change, so now I just stick to the medium grade and it seems to be okay.

[halfcab]

I have thought about the "WHAT IF" of using low octane fuel also in my 01. I have not seen anything in my manual about unplugging any wire for low octane fuel. My 01 motor does call for 95 fuel, 93 octane is as hight as it gets around here.

So for the spark plug has showed no signs of detonation with 93 octane.

[ChrisC]

Originally Posted by halfcab

My 01 motor does call for 95 fuel

That's the RON (research octane number). In the USA we use RON+MON/2 to get our octane spec.

91-93 is fine...

[bmwktmbill]

Hey guys,
Here I am in Latvia having just crossed the border from Mother Russia into the EU riding on my '02 Adventure.
I am one happy camper to be back in the West.

On octane, I ran almost exclusively regular gas on this trip starting in Wisconsin and going west to Seattle and then by air to Korea, ferry to Russia and then rode to Mongolia and then Bikial Lake and more Russia to the border west of Moscow.
Now I am about 3/4 of the way around the world including the detour south into Mongolia where I ran 80 octane in te Gobi desert area(nothing else was available). I had installed the '03 and later switchable ignition but never even bothered to make the switch for 80 octane. The bike always ran too well.
I blew a head gasket coming out of the Gobi so I had the cylinder head off to replace the gasket.

The piston and valves showed no untoward signs of detionation and I am convinced the gasket blew because the two external head bolts loosened up due to general vibration causing the failure. The headgasket began to weep and finially failed after running another 400 miles without repair.
We were in the 7th day of a desert ride and everyone wanted out.
Stopping wasn't an option when the weep started.
On top of everything else, I had 3 cracked ribs and a bad attitude.

On 80 octane gas the bike ran a little rough at idle but had plenty of power and ran fine at speed with NO ping of detonation.
I am running the stock jets with the Competition pipe and the pre muff
replacement pipe.
Inside the combustion chamber the color was medium grey with a fine carbon that cleaned up easily. No sign od lean running, no burnt aluminum. Just a nice clean grey burn color.

I am running regular because I think the bike runs better on it.
Specificially I get less vibration at cruising speeds between 60-70mph,
5000-5500 rpm.
Just for the record I have always run regular.
The bike has 28.5K miles at present and is running very strong.
Lately I have been calling it MaryAnn Faithfull, it's been speaking to me in Broken English.
Humor me, I didn't hear English spoken for the last 10 days.

Headed for Budapest now and the KTM factory rally at the Hunguoring.
If I have some luck I will get to ride the 690 SuperMoto on the track.
Can't wait to feel that engine.
b.

[humdinger]

Higher octane rated fuel is 'predominantly' only beneficial (with regard to performance) with combustion engines that have a compression ratio upward of 'around' 9.5:1. Someone correct me if I am wrong but the higher the compression ratio, the higher the octane rating of the fuel 'should' be to allow for a slower burning rate, beneficial when running at high revs.
I prefer to run (what we have here in Australia) the 98 RON fuel and try to purchase it from a 'busy' gas station as it is definitely cleaner. Even though my '05-640 Adv. has a 'stated' comp. ratio of 11.5:1, the only noticable difference I can feel is when idling as it seems a little smoother. Maybe a tad better at high revs but I find I'm splitting hairs.