R100 idles too high
Hi all, hope I can get some advice. I recently rebuilt the carbs on my R100, it was standing for a couple of years before I got it, so never had it running myself, but at one point it was used until the owner got a new bike. anyhow, after cleaning and reassembly, on the first start, the bike fires up, but on idle, the revvs are at approximately 3000rpm, this is way too high. I have checked that the throttle and choke cables are not tight, I have backed off the idle screw and made sure both butterflies closes completely, I have tested for airleaks and there are none. The engine revvs right up without problems on both quick open throttle and by slowly opening the throttle, but revvs don't come down to lower than 3000. If I disable either cylinder, then the rpm comes down to about 2000rpm, so I am thinking whatever the problem, it is common to both sides. I have tried with and without the airbox and by adjusting both carb idle mix screws all the way in and out without much change except for black smoke on the one side when the mixture becomes too rich. It is not hard to start and also does not backfire when blipping to open throttle and backing off. Anybody with some advice as I am really stuck now...
Check the diaphragms, I suspect they are torn.
However before anything make sure the valve clearances and timing are correct.
you can email me should you want more info.
Hallo Max, thank you, I did check both diaphrams, no tears or pinholes (even thou the one is showing signs of wear and they will be replaced), but I did find the problem yesterday evening. My dad helped me, said to blow into the air port of the choke while is it closed, the left choke valve would not close all the way when on the bike, turns out someone replaced the cable at some point with a modified or too short cable, because even with everything adjusted fully out, the choke is still just a little open, but atleast it can now idle so next step would be to set them up and balance them properly...
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