fuel starvation

mike1969 · Post by **mike1969** » Wed Oct 01, 2014 8:26 am

My 305 Dream runs great when carb is full but doesn't refill itself. Double checked petcock to make sure it isn't clogged. Installed new needle and seat and set the float to specs.
If I take the float bowl off the fuel trickles down but if I replace bowl the flow stops. I'm stumped.

garncarz · Post by **garncarz** » Wed Oct 01, 2014 10:54 am

The float is snagging on the bowl and closes the valve?

mike1969 · Post by **mike1969** » Wed Oct 01, 2014 1:58 pm

[quote="garncarz"]The float is snagging on the bowl and closes the valve?[/quote]

Thanks,I'll check on that.

Hamamatsu Nippon · Post by **Hamamatsu Nippon** » Thu Oct 02, 2014 12:31 pm

Try this. Slide a new unused length of fuel line on the barb of the carb. Hold the carb body at eye level. Put the other end of the new fuel line in your mouth. Now very slowly slide up the float bowl while blowing into the fuel line. Pay close attention to the contact of the needle valve and carb tang. Because there is no fuel, you should still be able to blow into the fuel line when the bowl touches the gasket. If you meet resistance while blowing, the needle valve is closing prematurely. I recently had a needle valve that had a stuck/too strong spring causing the needle valve to close before the fuel could fill up the bowl to the ideal level.

mike1969 · Post by **mike1969** » Thu Oct 02, 2014 3:14 pm

Thanks, I'll try that this evening. How did you correct your problem?

Hamamatsu Nippon · Post by **Hamamatsu Nippon** » Thu Oct 02, 2014 7:28 pm

The needle valve was an original part from a low miles 1977 CT125 I was working on last month. I messed around with it, trying to clean the spring inside the bore, spraying carb cleaner and soaking, but nothing would change. I bought a replacement Honda one, and problem solved.
I knew something was fishy when I tried to change the float height. I found a very narrow window of adjustment, at 22.5mm the carb would overflow, and at 25mm it would not allow a drop of fuel to enter. The spring in the valve simply did not compress to allow for the initial rise of the fuel in the float bowl. I could compress it with my finger and oddly compared to a new one it felt the same.
Keep in mind these numbers are not for any 305 but the process is the same.

mike1969 · Post by **mike1969** » Thu Oct 02, 2014 8:09 pm

Think I found the problem. Tried to check float operation like you suggested. Found there was no way it would work.
There was no float when I bought the bike so I ordered a new one. Looks like I installed the float upside down. Doing the test you recommended it now seems pretty close. However the petcock is now leaking so have get that fixed before testing the carb. Thanks for your help,Mike