450s hesitation problems

[fire_red]

I just recently got my 1980 450s reserected from the dead. It was running great and all of a sudden when I reach 50 mph it just dies. I have good rpm range up thru 4th gear. After that it just dies, no power at all. I have just tried some crab cleaner but Iwould think that would give me hesitation thru all gears. Any help would be greatly appreciated.

[chef1366]

Fuel flow problem.
Check;
petcock
Vent lines
Vent in fuel cap

Did you do a full cleaning of the carbs like here

[fire_red]

fuel

That was a very informative article. I did do most of that stuff in order to get the bike running to begin with. I did not replace any of the o ring gaskets. I feel that I am getting enough fuel to the carbs. I think it might be to much fuel. My left plug was pretty black but the right one was perfect. I added some carb cleaner to the gas. If it was gas flow why wait until it reaches 4th gear? I would think it would hesitate thru all rpm range? Would a valve cause this?I am alittle baffled.

[chef1366]

My bike did the same thing and it was the petcock. It wasn't flowing fuel properly so the float bowls would run out of gas. It doesn't happen right away. The vent lines in between the carbs can cause a problem at higher speeds when the air hits them. That's why they need to be tucked away between the air boxes. The fuel cap vent also doesn't happen right away cause the tank gradually builds up pressure and reduces or stops the fuel flow.

[fire_red]

petcock

OK will have to check on the petcock. Where is the fuel cap vent located? Did not know there was such a thing I needed to worry about.It just seems weird because The bike never actually shutts the motor off, just has no power. I move from 4th gear to 3rd gear and the bike runs good. Its like when I get above a certain speed and roll thr trottle open it just chokes itself out of gas or air maybe it fluds itself with to much gas? Will check on the overflow hoses tonight to make sure there situated properly.Some very good places to start.

[chef1366]

There is a vent inside the fuel cap. If the top of the tank is sealed there is no way that fuel will flow out the bottom.

[Nessism]

If the petcock does not fix the problem it might be the ignitor. Typically causes the igniton to shut down at high rpm. Good luck.

[550ERAT]

If the petcock does not fix the problem the problem it might be the ignitor. Typically causes the igniton to shut down at high rpm. Good luck.

I will echo this!!! I am having the same issues and so far everything is leading towards the igniter. Get a good manual so you can get the specs for the igniter and coils. Also use a timing light and check the pick up plate. When I checked mine, you could actually see the ignition miss with the timing light.

[fire_red]

problems

What is the pick up plate? How do I check the pick up plate with the timeing light? So many things to check.

[chef1366]

On the right side of the engine there is a round crankcase cover. Remove it. Under it is the crank trigger-pickups. Put the timing light on the #1 spark plug wire.
You should see some timing marks through a small sight hole. Shine the timing light in there. Give some throttle and you'll notice the timing mark "advance". It should be a nice steady smooth advance and not jumping around.