Hello There

[dougo]

Hi; I'm new to BMW K bikes-- I bought a 92 k75rs with the intention of replacing the engine (it had 105,000 mi on it and a real mean knock--the previous owner said that he rarely changed the oil.. crazy).  I picked up an engine with transmission from a 1990 k75 that had only 22,000 miles on it, a final drive and driveshaft from an 85 K100 with the slightly taller gear ratio, everything needed to overhaul the fuel system from stock pump and filter, all the correct hoses and new (reconditioned) fuel injectors, a fresh starter (the old one was slow--the slightly used one works great) and a myriad of other small things I needed to complete the switch out. Oh yes overhauled the brakes--including the ones on the front end from a yamaha fzr600 that the previous owner had stuck on the bike..don't ask me why.. The guys on the ride44.com forum are calling it "Frankenbeemer"..

Anyway, got the bike together this week, it starts and runs beautifully. However (you knew that was coming didn't you..) the idle is great when it first starts, then as it warms up it climbs to about 2000 rpm.. I was worried about leaks in the air system--but it checks out (I did a good job on it), I verified that both the throttle and choke cables had the correct amount of play and were not binding.. and I started to adjust the idle with the screw you are supposed to use--when I looked closely--there was air in between the bottom of the screw and its strike-plate--the throttle is not closing quite all the way.. I can press it closed with my thumb on the idle screw, and the idle speed goes just about where it is supposed to, but in messing with the cables and anything else I tried, I couldnt get it to stay closed.

My theory is that the previous owner messed with the butterfly valve adjuster screws to get the engine to run (it would barely idle, stall out continuously at a stop, had weak power on the highway, and of course there was that knock..) enough to sell it. There are no paint marks on the screws as there should be. I checked the manual--of course it just says, :DONT TOUCH THOSE SCREWS" big help to me..

So I am kind of scratching my head... I did just purchase a Syncpro Motion Pro carb tuner so that I could balance the airflow in the throttle bodies--that won't get here for a week or 10 days or so...

I guess this is a pretty big hello.. sorry about that..

Doug

[Elipten]

There is a shop, whose name I cannot recall, that you can send the throttle body assembly do and the will adjust.

[vintagemilano]

Hello, your throttles might just be binding up on the throttle position switch. Two screws to pop that off see if it makes a difference. Could also disconnect both ends of the throttle cable and see if it runs smoothly.

[dougo]

The question is, who has seen this before, and what did they find was the cause after all the cables and the position sensor have been ruled out?

[Bokobob]

my experience was not exactly like yours, but somewhat parallel...To get to the point, I found that the bottom half inch or so of coated steel throttle cable was winding onto the wheel near the throttle body and was binding it..I removed that coating very carefully and it freed it up....now, it has started not to return to idle when I let off the hand  throttle, but I can turn it off by hand at the throttle grip...I have ordered a new cable..

[dougo]

Thanks Bob! I'll check it out.