In-line fuel filters...good or bad

[clone432]

I have a 1976 R75/6 6500 miles on her. She is having issues idling and has an occational miss while in 1st gear...say when creeping through a parking lot.

She still runs great at speed and the power is as it should be.

I think that it could be a fuel issue in the right carb.

The bike came with in-line see through fuel filters and I really never gave them much thought. It is better to have inline fuel filters or not?

Thanks
Sean

[ducatipaso]

I have a 1976 R75/6 6500 miles on her. She is having issues idling and has an occational miss while in 1st gear...say when creeping through a parking lot.

She still runs great at speed and the power is as it should be.

I think that it could be a fuel issue in the right carb.

The bike came with in-line see through fuel filters and I really never gave them much thought. It is better to have inline fuel filters or not?

Thanks
Sean

I would never consider running without them. I use the smallish cone shaped units available at most motorcycle shops.

[20774]

It would seem that the fuel filter would cause you more problems (if any) at higher demands like running along at 60-70 mph, and not working your way through a parking lot. My guess is the miss is due to something else other than fuel flow. It might be that your carbs aren't synched very well. Synchronization is done usually just off idle at around 1500 RPM where the vacuum differences between the two sides is more accentuated.

[clone432]

I am going to check the sync today. I need to find a tool for the job though!

Thanks for the input.

[20774]

You don't really need a tool:

http://bmwmotorcycletech.info/synchcarbs.htm

If you want to build a tool, try this:

http://www.airheads.org/content/view/183/98/

[Boxerkuh]

I am running external fuel filters and change them on a regular basis. Also, I would also change the internal filters in tank every 4 or 5 years. I consider that part of my maintenance.
Cleaning and putting your carbs in synch. will probably cure your problems. Check the float levels too. Good luck. My food for thought anyway....:eat :drink

[lbrackr756]

Never had 'em on my original 75/6. Don't have 'em now; No problems in 50k miles. What can I say?

1976 R75/6
Maybe soon, R100/7

[richard t]

when did you last check you valve adjustment? a tight valve will cause that problem on a /6 been there a few times
Richard T
2 R75/6's and a K75

[ebeeby]

I do not use them. The screens in the tank are sufficient to keep any 'chunks' out of the carbs. Some fuel filters cannot pass water and will actually stop the flow of fuel.

The /5 (and /6 for that matter) are really a low tech high tolerance machines. I have gotten used to pulling carb bowls and dumping them (and the water therein) and finding a cure. Before you launch on a carb sync, try dumping both bowls first - might solve your problem.
Just my 2 pfennigs. YMMV.

[sumran]

I like them because they provide instant information without taking anything apart. If I have trash or water in the tank I know and can deal with it quickly.

[Isamemon]

I too run the small inline as they filter better then the intank screens
and before the inlines I have had junk get to the carbs

[Bob_M]

Those little plastic cone filters get brittle with age. Keep an extra on the bike in case one breaks.

[ducatipaso]

Whenever I'm at the dealer purchasing the stuff for an oil change, I grab a pair of these filters. They're super cheap, and I must concur with the 'visible indicator' value.

Reminds me, I need to get a new pair. :thumb

[sumran]

Those little plastic cone filters get brittle with age. Keep an extra on the bike in case one breaks.

I agree with that. I always keep one under the seat. Because I change them annually, I have never had one break (on a car or bike) but I have given some away.

[dlearl476]

The bike came with in-line see through fuel filters and I really never gave them much thought. It is better to have inline fuel filters or not?

Thanks
Sean

Yes, as long as they are clean. Sounds like you need to "think" about replacing them. :p

But I agree with others: I doubt that is the cause of a low speed miss.

[James.A]

In line fuel filters=good.

[osbornk]

They were already on mine when I bought it 9 years ago and they clearly weren't new at that time. I have never touched them and never had a problem. I only use one because I never open but one side (so I won't forget and I'll always have an extra reserve.

[20774]

I only use one because I never open but one side (so I won't forget and I'll always have an extra reserve.

You really ought to use both petcocks or at least give the other side an opportunity to burn the gas down below the "main" level. There's crud (including water) floating around at the bottom of the tank and it might be a good idea to let the other side burn down to reserve to help flush some of that out. Better still is to clean the tank out once in a while. Water resting in the bottom of the tank can rust from the inside out.

Does anyone play "games" with the petcocks and the fuel mileage to back figure how much gas is above the main straws and how much gas is above the reserve straws on each saddle of the tank? On occasion, I've had to go to second reserve but I've done enough figuring to know the amount of gas in each of these conditions. It's come in handy a couple of times to do some on-the-fly calculations to see if I'm going to make it to the next town...one time lately I was really in a pucker situation (severe headwinds complicated things) but managed to make it...

For my 6.3g tank, I get 4.6g on the main tank and about 0.7g on each reserve...there's probably a quarter of a gallon that's below the reserve straws (part on one side and part on the other) that I could get to by taking the tank off and sloshing the two halves together into one side...I've never had to play that game...yet!

[ducatipaso]

on my old R100RT I used to use the reserves as a way to gauge how in sync the carbs were. I had no crossover line on that bike... and when I had 'em really, really dialled in one carb would die out then within seconds the other would die out. :thumb

[PeoriaMac]

Bought altermarket cleanable in-line filters from a Harley dealer years ago...removed the BMW filters from the petcocks....the crud collects where I can see it. No problem with fuel flow, and after 100K no problems.

Mac

[skiteach]

I would look at sync'ing the carbs and valve adjustment. BMW (and other) cars are susceptible to carbon build up on intake valves. This causes low speed sputters and coughs. Have not heard of it on bikes. Easily checked by removing carb and looking at backside of valve. If there's a build up of gunk, they need to be cleaned. The reason being that fuel collects in the crud, hangs there until enough collects to "drip", causing brief very rich mixture.

[osbornk]

You really ought to use both petcocks or at least give the other side an opportunity to burn the gas down below the "main" level. There's crud (including water) floating around at the bottom of the tank and it might be a good idea to let the other side burn down to reserve to help flush some of that out. Better still is to clean the tank out once in a while. Water resting in the bottom of the tank can rust from the inside out.

I figure that the gas tank is one container and the sloshing around of the gas as I ride (especially on our crooked and rough roads) that the gas will be constantly mixed and there won't be anything settled on the bottom. On a couple of occasions when I ran my reserve dry last year, I switched over to the unused side to get to a gas station and everything worked fine. With my prior K-bikes and now my oilhead, I have hard enough time remembering to turn off one petcock.

[20774]

I figure that the gas tank is one container and the sloshing around of the gas as I ride (especially on our crooked and rough roads) that the gas will be constantly mixed and there won't be anything settled on the bottom. On a couple of occasions when I ran my reserve dry last year, I switched over to the unused side to get to a gas station and everything worked fine. With my prior K-bikes and now my oilhead, I have hard enough time remembering to turn off one petcock.

You might be right on the sloshing around...but when I've had my tank off on my /7, I notice that the tunnel is fairly tall and wonder how much mixing there is. I don't do a lot of canyon carving, anyway...

I suppose turning off the petcocks is a habit one develops. It's such a habit for me that I forget I've even done it. I go back to the bike just to be sure and realize I wasted the trip because they're off. I generally run both petcocks on, then left to reserve (because that's the non-throttle side), and finally right to reserve. I don't make it to the right side all that often, so every once in a while, I do the petcock dance...when it bogs when running out on the main, I quickly get it back again with the left reserve. Then, when I can put the throttle lock or when it's convenient, I switch the right to reserve and then put the left back onto main. :dunno Just a goofy thing I do...

[tuber1]

You really ought to use both petcocks or at least give the other side an opportunity to burn the gas down below the "main" level. There's crud (including water) floating around at the bottom of the tank and it might be a good idea to let the other side burn down to reserve to help flush some of that out. Better still is to clean the tank out once in a while. Water resting in the bottom of the tank can rust from the inside out.

Does anyone play "games" with the petcocks and the fuel mileage to back figure how much gas is above the main straws and how much gas is above the reserve straws on each saddle of the tank? On occasion, I've had to go to second reserve but I've done enough figuring to know the amount of gas in each of these conditions. It's come in handy a couple of times to do some on-the-fly calculations to see if I'm going to make it to the next town...one time lately I was really in a pucker situation (severe headwinds complicated things) but managed to make it...

For my 6.3g tank, I get 4.6g on the main tank and about 0.7g on each reserve...there's probably a quarter of a gallon that's below the reserve straws (part on one side and part on the other) that I could get to by taking the tank off and sloshing the two halves together into one side...I've never had to play that game...yet!

sure I always did that, turn on one petcock, and when it went dry, REALLY look for a gas station,lol.

fuel filters: on the older bikes,sooner or later the tank coating will come off, or wear out from the kind of gas we have nowadays. extra filters can't hurt

[clone432]

Thanks for everyone's opinion on the Fuel filters.

As for the miss and failer to idle. Valves, I had a tight exhaust valve on one side and a tight intake on the other. As soon as I re-adjusted the valves the idle and the miss was gone. She is running like a top!

[The_Veg]

I think in the grand scheme of things it probably doesn't matter very much if you use them or not but if you do use them, make sure to do a flow-test. Don't quote me on this, but I think the number you want is at least 125 ml/15 seconds. Somebody correct me if I have it wrong.

[crazydrummerdude]

This is handy to read:

http://www.w6rec.com/duane/bmw/petcock/index.htm

I personally just installed (about 400 miles ago) fuel filters after my carbs got pretty clogged with some crap. So far, I've had no problem.