83 aspencade, runs terrible

[brycath0327]

I have an 83 aspencade was running pretty good except going up hills when I give it gas it kind of bog so I did a carburetor sync got it all seems nice seems to run real nice well it's parked when I take it for a ride now I hear a lot of valve rattle and can't go over 62 miles an hour and still bugging going up hills runs really good when it's just sitting there any suggestions I'd really appreciate it thank you

[KYpondman]

Sounds like fuel starvation. Try loosening the gas cap when it happens. Check fuel filter and fuel pump output. If that checks out and problem persists, check float valve filters for sediment.
Claude

[Pony Ruiz]

I'm having a similar issue. I'm doing the fuel filter and the gas cap first up, then sync, then...
but my questions is this:
What is it about a plugged gas cap that causes a symptom of fuel starvation?

[BlueThunder]

What is it about a plugged gas cap that causes a symptom of fuel starvation?

Take a coke bottle and fill it with water. Turn it upside down. What happens? The water does not flow evenly but empties in "gulps". Now take a nail and poke a hole in the bottom of the bottle. Cover the hole with your finger and fill it with water. Turn the bottle upside down and lift your finger. The water will flow freely and uniformly.

Not to get too heavy into hydrodynamics or physics, the hole allows air pressure to push the water out of the bottle. Whereas, the bottle without the hole has to allow air to enter the bottle from the opening - thus the "gulping".

Now imagine the bottle is your gas tank. Same thing happens. The motor needs a constant and uniform flow of fuel especially at speed or load.

[Pony Ruiz]

Got it!
I should have pushed the easy button...

[RB]

Gas cap not venting, pump not working well, ,clogged filter, floats set too low or clogged main jets, are all possibilities. test in that order easy to harder.

pull the line off the pump's out tube add a tube and put into jar..crank her over see if there is good fuel flow..book says 15 oz. per minuter at 3,00 rpm is right..you can do 30 seconds for 7.5 oz....next add a line to the carb line with an alternate fuel source..so you are bypassing the pump and tank..if she runs like that..issue in the pump or filter or tank or petcock..etc. If not carbs need to cleaned and/or adjusted floats..

[Pony Ruiz]

Good thinkin!

I may have to try that my self

[hmratbam]

Mine ran like that after the winter lay-up. I ended up removing the carbs and cleaning all the little holes in the emulsion tubes. Now it runs like it should.

[brycath0327]

Thanks for all your replies I have tried with my gas cap open still nothing replace the fuel filter check the fuel pump all that's good it almost seems like I'm not getting Advance on the timing how do I fix it