K75S vibration

[commando71]

Earlier I had posted on the wrong forum a problem with vibration in my handlebars during normal road travel that left my throttle hand numb. Several people on the site made some suggestions and I checked every one. the bike has new tires and the balance was double checked last weekend at the dealers. The throttle bodies were syncronized, the engine mounts were checked and the exhaust system was checked. The annoying buzz( vibration) was still present. While trolling one of the other K Bike websites I came across a post involving just such a problem albiet on an 87 K75S with considerably higher mileage. The post indicated that changing the plugs and ignition wires had tamed the beast. So I ordered new plugs OEM and brand new plug wires made by NGK for the K75. I installed them last night and took the bike for a 78 mile run this evening. I am pleased to report that this has cured the problem and I noticed that the bike is smooooth and pick up is much improved. Thank you Lee for your help, just thought I would pass this on for future reference.Craig

 

[roncooper]

Thanks for the update. Can you give more details on the plug wires?

 

[lkchris]

Probably will get better fuel mileage, too, as you no longer have an engine miss.

 

[pauls1150]

Ron, the K75 wires have a built-in "open" instead of their using resistance wire to provide the proper impedance to the ignition coils' output. This means that they can't be effectively trouble-shot, and if suspect, should just be replaced with extreme prejudice.
It also means that you really need the "Right" plugs, not just any ol' cross-referenced substitute.

 

[commando71]

Plug wire particulars

I purchased the plug wires from Beemer bone yard, beemerboneyard.com. They cost about 60 bucks and are made by NGK. I run NGK wires on my Triumph and Norton and am pleased with their performance and expect them to perform well on the K75. The plugs are the Bosch OEM stipulated by BMW and I would believe them to be available from most BMW Motorcycle distributors. The K75S that I have has very very low mileage but the plugs and wires were original, nearly 29 years old, so it was a good bet to replace them. I have replaced most of the rubber items on the bike and will continue to replace items as they present themselves during operation. This bike has turned out to be what I expected it to be and so far I am very happy with it. Craig

 

[kentuvman]

Just out of curiosity, what is your new and improved MPG and at what speed and riding conditions?

 

[98lee]

So was it the plugs or the wires that were to blame?

 

[commando71]

Plugs or wires

I initially removed the plugs and checked all three. They looked decent, no wide variation in insulator color burning light tan on all three. The electrodes checked out at .025 +/- each and the electrodes were square. The plug wires were a different story. Each one showed corrosion on the metal connectors and the interior rubber seals were somewhat hard. It took some real effort to remove them from the plugs. I cleaned the plugs looked at the wires and did not find any obvious problems. Took the bike out for a run , about 40 miles and there was no change in the vibes. I replaced the plugs and wires as a set and believe that the wires were the problem. Craig