Replaced the fuel filter and . . .

Post by **challey** » Thu Nov 08, 2007 11:52 am

Over this past weekend, I completed some of the 24k service - a bit prematurely, since the bike has only 22k miles on the clock - but I wanted to get as much out of the way as possible before the cold weather sets in since I don't have a garage.

The 2 items I took care of were replacing the air and fuel filters. I planned initially to mod the bike with an external fuel filter but was persuaded not to do so by a number of older BMW wrenches who claimed that burst filters are a regular occurrence and you want the protection provided by the fuel tank. Though I was a bit apprehensive about renewing the fuel filter, it is actually a fairly routine job and replacing it every 3 years or so will not be a big deal.

I was pleasantly surprised by the change in way the bike ran after replacing the filters. It now seems to rev more freely and is a bit more responsive. This could be expected however. What was unexpected is that the low rev engine rattle (up to the 3k mark), which I suspected was pre-ignition due to carbonization, seems to have gone almost completely away. This doesn't make sense unless the diagnosis of the cause was incorrect; octane issues and the cam chain were ruled out as culprits earlier.

Anyone else experience this? The weather has been quite a bit cooler, ranging from the high 30's to the mid 50's (F) - could that account for things?

Charlie

Post by **boxermania** » Thu Nov 08, 2007 2:26 pm

Did you by any chance disconect the battery? If so what you are experiencing is the Motronic learning your riding style. If not, I give up on lack of too litle information to proceed.

Post by **challey** » Thu Nov 08, 2007 9:07 pm

Boxermania --
No, the battery was not disconnected. I did forget to mention that I pulled the CCP a week or so before I did the filter service. There was no noticable effect running w/o the CCP.

I had a chance to ride a bit today. The engine rattle is still there but seems to be pretty substantially reduced. I'm going to try a can of SeaFoam and some spirited riding - maybe cure the rattle for good.

Overall, the bike is running pretty well, smoother at idle than before the service too. As I mentioned, the reduced low-speed rattle is a pleasant side effect but perplexing.

Charlie

Ivan Koloff · Post by **Ivan Koloff** » Thu Nov 08, 2007 9:43 pm

I think the weather makes a diff. On cooler days 40's-50's I notice the bike runs its best. All the bikes I've had ran nicer. Also heard this from other riders

riceburner · Post by **riceburner** » Fri Nov 09, 2007 5:12 am

Ivan Koloff wrote:I think the weather makes a diff. On cooler days 40's-50's I notice the bike runs its best. All the bikes I've had ran nicer. Also heard this from other riders

Most bikes and cars will. Cold air is denser and thus for each volume of air sucked into the system there's more oxygen to react with the fuel and thus you get a better burn. With the Motronic system there's the added benefit that the system will pump more fuel through the injectors to take advantage of the denser air and maintain a certain fuel/air ratio.

Post by **Boxer** » Fri Nov 09, 2007 7:00 am

Challey, I'd be careful with the Seafoam. The can says 1oz per gallon of fuel. I've always gone by that direction and I'm not sure running a higher concentration would not create a problem.

Post by **challey** » Fri Nov 09, 2007 12:18 pm

I'd be careful with the Seafoam. The can says 1oz per gallon of fuel.

I'm with you Boxer. I use SeaFoam often, though on pretty extended interval basis. I've got a measuring jar with 5oz marked off and use it to add the SeaFoam to a full tank. It doesn't look as if it prevented carbon build-up, possibly because I don't use it religously. I'm going to try adding 5oz of it to consecutive tankfuls.

Charlie