Bike Suddenly Dies

Hello,

Really at a loss of what my problem is right now. I'll be riding and the bike will suddenly lose all power and die. It will then take me 5-10 minutes to try and get it started. The bike sounds as if it wants to turn over but just won't idle. When it does idle it is pretty steady and the bike rides well.

I've ridden the bike 1200 miles this season and the issue just started. About 400 miles ago I put new ignition coils and spark wires on and I recently put a new battery in, but I have a strong spark. I also synced the carbs and cleaned them as well as put on new intake boots. Over the winter I put a 3 phase stator and a regulator/rectifier to accompany it. Anyone have any ideas of what could be going on? Could the rectifier be failing or what is common with sudden loss of power?

Thank u!

It happened to me with my Harley. I had also put a new aftermarket battery in. After about 300 miles, my bike would lose electrical power and the radio would turn off. The contact to one of the battery post was loose. The post design on that battery was not good and prone to problems.

It was something really simple. I swapped the aftermarket battery to an OEM and the bike was perfect after that.

First check that the fuel cap vent is not blocked causing the tank to vacuum and cut off the fuel supply.
Easiest way to tell is by opening the cap immediately when the bike next dies.
If it opens with a loud hiss when air rushes In that is the problem.
Also check the tap is clear, the fuel line is not kinked and the float heights are not set too low..
If that all checks out ok it's time to check the kill and ignition switches and the wiring for breaks, intermittent shorts or bad connections.
Partial blockage of the exhaust and many other issues could also cause your problem..

If the engine cuts out entirely suddenly I would look at the electrics. If it continues to run but lacks power I would look at carbs/fuel flow. Are you running a fuel filter? Dirty /partially blocked? Could also be tank cap breather partially blocked creating a vacuum in the tank and thus starving fuel. After a while the vacuum is equalised and fuel flow returns. All guess's obviously but without experiencing exactly whats happening its difficult to suggest where to look.
Snap zed1015!

Thanks for the suggestions! I'm not running a fuel filter, but I'll check to see that the fuel cap vent isn't blocked and that the tap is clear. At first I suspected it was an electrical issue but now I'm thinking it could be a carb issue. I did not set the float levels when I cleaned the carbs and have been meaning to address that.

I checked the spark plugs and they looked like the bike has been running lean. I've had issues adjusting the pilot screws in the past, could this have an effect on the bike dying? Previously I was running rich and leaned them out because the bike was dying when it warmed up. I just turned them in a little bit to richen it and it seems to have helped. Does the hot weather have a significant effect on the mixture or would that not be enough to kill the bike?

Low fuel float levels would make it run lean. Start by getting that correct. Which carbs do you have. If they are vm24s with airscrew they should be 1 1/4 to 1 1/2 turns out to start with then colourtuned to fine tune.
Weather shouldn't affect it, at least not to the extent your experiencing.

Have you check and adjust the valve clearance in the past.
If the valve clearance is near zero on a hot engine, blow by gas/compression lost have the same effect you describe.
The valve shafts extend on heat and reduce the valve clearance.
If the engine cool down every thing working normal.

I believe they're the vm24s because they have an air screw. I had been running the bike with them 2 full turns out and the plugs read slightly lean, but any richer and it seemed to die at idle once it had warmed up. I turned the screws in to about 1 1/4 turns out, and the problem of the bike dying has been resolved. But now one of my carburetors seems to be pouring gasoline out the overflow nip every time i rev it.

I adjusted the valve clearances a few months ago. One of the exhaust valves was only measuring 0.1, but it was at the smallest shim size. one of my intakes is slightly too loose at 0.2.

Have you done a wet test on the fuel float levels? The fuel level needs to be 3mm +/- 1mm from the bowl / body mating surface. If its lower it'll be lean if its higher it'll be rich, and possibly over flow out the overflow tube. Whilst you cleaned the carbs did you clean the fuel inlet seat and needle.