Needing some insight...I accelrated off a stop light rather quickly (engine reving high) as i shifted from 2nd to 3rd gear suddenly my ‘85 K100 loss noticable power, the muffler became louder abd sputtering and as i nursed the bike home on the highway there was way more vibration coming up through the handlebars. I replaced the sparkplugs and a fuse i found burnt out, but the bike still lacks power (never stalls while ideling though), the noise is still more of a sputtering sound and the vibration continues, especialy in 4th or 5th gear.

Do any of these symptoms sound familiar to anyone here.

Grateful for any help,

Thomas

#1 - Fuel filter - NAPA 3032

Awesome! Going to change the fuel filter then!

Check the condition of the fuel pipes, if one is collapsing or not connected properly.

What is the condition off the spark plugs?? Are they the same, are they wet or dry??
Regards Martin.

Update...kinda

I was out driving the bike around the neighborhood trying to burn off the remaining gas before changing the fuel filter and after a few backfires (while low on fuel) the bike suddenly gained its missing power back, no vibration, and the bike no longer sounded like a Harley chopper bike...I haven’t changed the fuel filter yet and still plan too, but does all this still sound like the fuel filter?

Stumpy I will check those also

MartinW - I replaced those, but when I pulled them they were black and looked like they hadn’t been changed in a while. One thing I did notice was the plugs I pulled had more of a round bulbous end and the plugs that came up for K100’s at the auto parts store are very straight and narrow. They seem to work, but I don’t have enough experience to know if this is normal or is/will be an issue...feedback?

Plugs definitely needed changing. Problem might have been a dirty injector or injectors. Run a couple of bottles of Techron through the bike 1/2 bottle per tank.
Regards Martin.

tjh1985 wrote:MartinW - I replaced those, but when I pulled them they were black and looked like they hadn’t been changed in a while. One thing I did notice was the plugs I pulled had more of a round bulbous end and the plugs that came up for K100’s at the auto parts store are very straight and narrow. They seem to work, but I don’t have enough experience to know if this is normal or is/will be an issue...feedback?

You may have take off Bosch plugs which have the round end OR you may have take off NGK plug which have a screwed on round end and put in NGK plugs which come without the round end. The narrow straight top you will see is threaded and you need a screw on bobbin with that round shape. If possible get it off the old NGK plugs if you had them. The Bosch one is not removable. You can get those bobbins but maybe someone will have some to send you? Don't run without them because you will cause arcing inside the plug caps and destroy them before long.

92KK - they were Bosch plugs so I’ll go buy those instead. Thanks for the wisdom on this. Damn I love this Forum

UPDATE

1. Fuel Filter replaced
2. Correct spark plugs
3. 1/2 a bottle of Techron added
4. No collapsed fuel line
5. Back on the Road

Thank you to;
Duck
MartinW
92KK
Stumpy

Didn’t all myself and it cost about $25. This forum never ceases to amaze me!

Maybe look closer where fuse blew also,  to find maybe why.

Oh yeah, there was a fuse blown and I replaced that as well

Just curious but did you try blowing through the old fuel filter to see if it was clogged?

The fuel filter is probably the easiest and cheapest maintenance item that is often overlooked on the old Ks. (Maybe because car ones seem to last much longer.)

I did not try to blow through it, but I saved it and will try that. Not sure how old the filter is but it’s an original BMW fuel filter and I’m pretty sure the previous owner I bought it from did NOT get an original BMW fuel filter installed so my guess is it’s been in there a while.

@duck - I blew through the fuel filter I replaced. I had to blow pretty hard to feel air through the other side. I’m not sure if that’s what to be expected or not...thoughts?

tjh1985 wrote:thoughts?

I think it would be interesting to determine how many psi—or bars—you can produce by blowing through a tube with the inside diameter of a fuel hose.  Is your gauge handy? 

No gauge...

Sawing in two lengthwise a used filter reveals a very blacky paper accordeon.
You then realise that blowing in such a filter hoping its cleaning is a waste of energy

Poupy wrote:Sawing in two lengthwise a used filter reveals a very blacky paper accordeon.
You then realise that blowing in such a filter hoping its cleaning is a waste of energy

The purpose of blowing through a used fuel filter is just to see how much it might be restricting flow, not to clean it.