ok hive mind.. Out on the bike early yesterday morning - fast run from keppel gate to Mountain box (TT course wrong way) and waited for my mate... Bike ran perfectly Mate comes up Mountain mile, lots of traffic and he didn't seem inclined to pass it so we were trundling along at about 30mph, part throttle etc etc After a couple of miles I noticed the throttle response wasn't as good - part throttle at lower revs just seemed to lag, this got worse and eventually I pulled the clutch in, let the bike coast on no throttle and the engine died... Let the clutch out / restarted the engine.. I ended up putting the choke on and it was fine with the choke on. After work I headed home - the temperature had come up and it was running fine, off the choke quickly, good tick over and pulling cleanly.. Was this the dreaded carb icing?? There are carb bowl warmers on the bike - there is a valve in line that looks to my understanding to be straight through so the warmers aren't in use.. The haynes manual refers to them but there is no description or guidance on on/off. And reading up some people seem to think the float chamber warmers work and others say they don't...
I am no expert, having swapped to FCRs years ago, however, I would've thought that carb icing would've only occurred on initial start up until the engine has some heat in it? I have the pipe from original carbs and could clarify later if no one else does which way operates the heaters.
I have never ridden one with the oil heated float bowls so I don't know if they work or not. It doesn't matter how long the engine has been running, icing can still occur. Throttle stuck wide open on Louth bypass on my way home from watching the Sand Racing at Mablethorpe one chilly day, and unpredictable throttle response when riding up the Stelvio (in sleet near the top) was also "interesting".
Had carb icing on my 900ss a few times, it seems to usually be when it’s below 7-9 degrees and the air is heavy with moisture. Think clear crisp early morning’s When I get it the bike hesitates and runs flat out of corners then suddenly clears and pulls cleanly ( it certainly wakes you up ) When I do get it there’s condensation on the carb bodies, and if you pull up and switch off for 5 minutes it’ll clear the ice and away you go again. A lot of descending on a trailing throttle seems to make it worse Don’t know if it’s still available but I used to use Fuchs Pro FST fuel additive but IPA (isopropanol) does the same job
The carbs don't really warm up in those circumstances, as they're being fed cold, moist air and cold fuel too. Whether it happens or not is down to the dew point at the time. What happens when you stop the engine is it 'recovers' as some engine heat is conducted to the carbs to warm them up, dispelling the moisture (ice). I have no knowledge of additives mentioned above - I'd connect the oil lines if possible...
i know on old cars like ford crapies and the like back in the day they had a pipe fitted to take hot air from around the exhaust manifold into the air box with a flap valve that closed when engine warmed up assumption was it was to combat carb icing etc the oil lines on the carbs i am not an expert on as my ss is injection but do not see that they would be very effective as they heat the float bowls i believe when it is the incoming air charge that is the issue as pointed out the moisture content at lower ambient air temps is higher therefore warming the inlet of air would be more effective .....but when engine gets to running temp warm air is not the best as cooler dense air is more combustible so if you could heat the air box for the first few minutes of the ride great but how
