'92 XTZ660 Tenere cold start problem
 

I'm using this bike as my only transport at present. The bike starts Ok if its been in the garage overnight, even if there's been a frost. A bit of choke and it will fire up.
The problem only occures on days when I've left it on the drive a few hours before starting it, in a cold wind. Half choke is not enough. It fires up very briefly on full choke but does not catch and run, repeated efforts lead to a flooded carb, and flattened battery.
I had the bike looked at by a local bike shop with plenty of experience in older jap bikes. They took up some slack in the choke cable, checked that the choke worked, and adjusted the carb.
A cold windy day today and the same problem again. Fortunately holding a fan heater to the top of the engine for just a minute, it started with no choke!
The bike shop are willing to have it in again, but apart from checking the valve clearances and compression , they are wondering what else they could try.
I wonder if it could be a split in the carb-head rubbers, but it runs so sweet once it is running.
The weather is getting steadily colder and I dread being caught somewhere away from home and the fan heater.

Have you tried full choke, then after it's fired and stopped, drop it on to halfchoke?

Yes, tried that. Once it has made one attempt to start on full choke, half choke produces no response at all.

very easy fix! you're idle screw is set too low! turn it up a bit to start and if wanted decrease it a bit after it's running!

Vando beer

Thanks, we might try that, but as it is, once its running its very sweet, with already a slightly high tickover rate.
The difficulty is that the problem only exists when the engine is really cold. Once its run, even after standing 3 hours, it'll start Ok. Which means thankfully I can keep riding it.

I have a 91 XTZ660 and experienced this very same problem. It was the choke sticking on, which apparently is very common on this model. Once running the bike was running way too rich which sooted everything up, making it very difficult to start first thing in the morning.
The problem is actually within the carb, not the cable itself usually.

Hi I would definately check the choke mechanism. As someone said previously they are notorious for sticking. It is usually the brass barrel part that slides in and out of the carb body that causes the problem. They are fairly easy to remedy. Pull back the rubber cover at the carb and you should find a hex head 12mm spanner from memory. Undo this nut, its part of the barrel. Once out you can undo the choke cable and clean up the brass barrel with some wd40 take care not to damage the o ring. Clean out the opening in the carb where the barrel came out. Reassemble and try the operation the choke should feel fairly smooth and easy to operate. If the choke mechanism/ barrel is really difficult to remove leave as it is for now and order the choke mechanism/ barrel from your Yamaha dealer, go for an original repair kit from Yamaha. That way you can use some grips to remove the barrel if its really tightly stuck inside.

Good luck and let us know how you go.

Cheers Sam.

Thanks guys. The choke mechanism has been apart and works smoothly, and except when the engine is at its coldest, works fine. As in, when engines warm, needs no choke. A bit cold, half choke. Colder, full choke does the business. Only when it is really cold, full choke, engine fires for a few revs but dies immeadiately and will not restart.
In those conditions, a fan heater directed under the tank, towards the carb, maybe reaching the air intake under the seat, for just a minute and it will fire up and run without choke.
The local bike shop suggests dodgy coil/HTlead & condensation. Their theory being that the fan heater blows the condensation away. I am sceptical, but as they can supply new coil & lead for £21 I'll give that a try. As a 19 year old bike, with winter coming on its probably a good idea anyway.