ZZR 250 power loss

Hi,
Just bought a 92 zzr250 and it's been almost perfect bar one issue I can't get my head around. It seems to get a bit upset when riding in rain or cold air. May be just a coincidence but the story goes something like:

Riding from Melbourne to Central Vic and ran into a rain storm about 1.5 hours into the 2.5 hour trip. Very soon after hitting the heavy rain experienced almost complete power loss (ie flat out in second would hold about 4000rpm). Pulled over for a few mins and on I went without any trouble. Then,

Next day riding to work (in rain), same thing about 10 mins into the trip, but ran like a dream on the way home that afternoon.

Next day riding to work (no rain) but cold and same issue at same point in journey, then perfect in the afternoon.

Since then I've done about another 100kms without a hitch - all in warmish conditions.

Very new to bikes so nothing to compare to, ideas would be much appreciated!
btw air filter and sparks are new and clean, haven't got any deeper than that tho.

Alas this is relatively normal in really cold weather.

I also live in central Victoria and it's likely to be your carburettors freezing, as it happened on my ZZR600 quite regularly in winter in the Macedon Ranges. Once this occurs you lose all power, but when you pull over the problem mysteriously goes away as they defrost really quickly. FWIW my first car had the same issue, so it's not just bikes that suffer.

There's a few things you can try.

1. Run a denser fuel like the dreaded Shell Optimax (if it's still available) in winter. People normally bag this fuel, but it ran in my bike with zero issues.
2. Block off part (not all) of the radiator with a cardboard or plastic shroud. This cuts the airflow through the radiator and the engine will run a bit hotter. A few caveats with this one. Take it off in summer and on warm days and if you are in a lot of start-stop traffic.
3. I'm not sure if later models of ZZR250 came with heated inlet manifolds (my 1998 ZZR600 didn't, but the 2000 model did). If they did see if you can find one in a wrecker and replace yours. You may find that there is a hot water connection from the water pump up to the manifold, so you may need the water pump housing as well. The good thing about the ZZR250 is that it was basically the same from the beginning of the model run to the end, so you might get lucky with parts.

Anyway, good luck with it, it's a pain in the arse and it may be easier just to pull over for a few minutes and let everything thaw out. I know the plastic/cardboard approach works, although it looks odd and you have to be careful not to damage the radiator fins when attaching it. If you are worried about looks you could always paint it black .

HTH, Mick

Ha, funny that carby ice was actually my first thought (being a sometimes pilot) but never heard anyone mention it with relation to bikes so assumed it was a problem specific to aircraft.
Certainly hope that was the issue!
Cheers

This very common on zzr both our 600 and the 1100 suffer from iced cabys . more so the ram air models.

check you wiring is all connected properly, especially to your ignition module. And make sure no water leaking in through the top of your spark plug leads, and the leads themselves can also contain moisture leading to similar issues.

Carb icing shouldnt affect the 250 like it does the 600 & 1100 , they both were very bad for it (had a 600 for 100K), it may be something else - farked if I know what though

Thanks guys,
Had another major bout of the slows on a very cold morning a few days ago, struggled to hold 80km/h for the first 90 mins or so and this time stopping for a few mins didn't help at all, then returned to normal after the outside air had warmed up a bit. Seems like pretty good evidence towards carb ice... That said, just went to go out for a cruise and the thing wont start at all.... may be a bigger issue.
Suppose I'll go and pull it to pieces again

Ok so now in definite need of some help!
Turns out the carbs have begun squirting fuel from a point underneath. I don't know much about them but can only assume this means they're filling up and the fuel is overflowing at some point. For anyone that's interested I managed to get a photo of the culprit area, the red arrow points to the screw that the fuel seems to be coming from.

The bike runs perfectly for about a minute and then starts to deteriorate as (i'm guessing) the fuel builds up and drowns it to death, then will start again after being left alone for a few minutes.
Are they just in need of a good clean or does it sound like the carburettor in question is cactus?
Any sharing of knowledge would be much appreciated!

That sounds like a problem with the float bowl, the screw you are pointing at is a mounting screw to the carbie rail. guess would be that the carb is filling up & you have a leak from the rubber o ring between the float bowl & top casing.
My suggestion get the bike to a mechanic or pull the carbs off & get them to a mechanic for an overhaul

And the fun continues.... after changing the carbs (diaphragms were both completely gone... hence the power issue and the subsequent fuel overflowing) I did about another 10kms and the thing turned off as if I'd flicked the stop switch! Perhaps a sign that I should have paid somebody to sort out my problems... Oh well, I have enjoyed the learning... just getting rather sick of diss/assembling the bloody thing. Anyone got a nice friendly, reliable bike they want to swap for an angry, but otherwise lovely green zzr250?