1st power loss underload, now running badly?
Currently having problems with my 88 R100GS as follows. Any help would be great as am currently in Venezuela and not near any bmw mechnics:
The first problem was a hiccup/loss of power while cruising i.e with the engine under load at approx 4100rpm, if I droped the revs to 4000rpm it went away. The first time it did this I checked the spark plugs and all looked fine (i.e. all 4 tan colour- the bike is twin plugged). Eventually I thought it was me getting low on fuel as it seemed to go away once I filled up. (On the same day I had a faulty float needle on LHS carb which also ended up needing changing).
The next day for the first hour the bike was fine and then again when hot and under load the same thing started to happen. If I stopped and let the bike cool down it would go again for 1/2 hr and then when it got hotter (or so it seemded) the problem started again.
That night I checked haynes and it suggested looking at the HT leads and spark plug caps. I found the spark plug cap on the LHS lower plug was split. I tried to repair it with epoxy resin and insulating tape. The next day again after about an hour of cruising the same thing happened. At this point I cleaned all the jets and float bowls in the carbs (and accidently took out the RHS needle jet - but put it back in with the carbs on the bike, then read in the motobins `tips` i.e. you need to invert the carb as it might bend the needle so took it out and took the carb off and refitted it). After all this still had the same problem.
That night found a replacement spark plug cap so swopped it over. Also checked the carb diaphragms and the fuel tank tap filters (and changed the fuel filters). On checking the plugs I found the LHS ones were fine but the RHS ones were black and sooty i.e. too rich.
Next day the top end power loss problem was gone (so maybe the cap was the problem) but now the bike sounds terrible when at idle (really uneven and poppy) and is not right power wise when pulling away (it seems to smooth out though at highr revs) and I cannot get rid of the sooty plugs on the RHS. Up until this point I had not touched anything to do with either of the carbs set/mixture.
Since then I have changed to RHS HT leads, checked the float levels on both carbs, tried to adjust the mixture screw on the RHS carb to get rid of the rich mixture but it appears to having little effect (both when at idle in terms of the revs changing or in the colour on the plugs). I have also taken the RHS carb apart, cleaned it and reassembled it as the bike handbook said a sympton of sooty black plugs could mean the `needle jet position needs checking` - what does that mean (it only has one position as far as I can see)? I thought maybe I had damaged the needle the first time I took the needle jet out but to the naked eye it looks fine. But still I appear to have the same problem.
The only thing I can think of doing now is swapping the plugs over to see if it is them at fault? Anybody ideas?
Also will it do the engine any harm driving with one cylinder correctly set up and the other very much over rich?
Thanks in advance.