Loss of power

[paradox1559]

I've recently gotten a 1976 gt750, barn find running after 2 rounds of carb cleaning and some light electrical work. It runs just fine most of the time, however, sometimes it will lose all power until it dies. I can usually bring it back if I work the throttle just right, but I'm not sure what's causing it. I have an external fuel filter so I'm confident I don't have an obstruction. I'm about to seafoam it and see if that helps.

[teazer]

Look at the fuel filler cap. Sounds like the breather holes in the cap are blocked so as teh gas comes out, it should be replaced by air. If it's blocked it creates a partial vacuum and fuel flow stops.

With an old cap, the seal isn't perfect, so it may allow enough air in as you sit juggling the throttle. Pull the cap off and check it out.

[barney01]

You say you have cleaned the carbs thoroughly but have you cleaned the petcock filters and bowl too?

[paradox1559]

I have cleaned the petcock, it's getting good flow. The tank is a bit rusty though, I have an inline filter at the moment to catch anything that may make it through. nothing has settled yet.


I will try running with the cap open and see if that makes a difference. I can't believe I didn't think of that before, as I've experienced this issue on other vehicles.

[barney01]

The next time the power starts to go quickly put the petcock to prime as the diaphragm may be sticking so carb bowls could be running low

[paradox1559]

Would it hurt if I put a regular on/off petcock on there? I tried the petcock trick before and it made no difference.

I've also tried riding with the cap open and that did nothing.

I'm about to clean the carbs again and reset the jets, if all else fails that is.

[paradox1559]

Side note: my ignition switch is very loose, and takes some fancy turning techniques to make a connection. When it connects though it seems to stay on, but occasionally will lose continuity.

[barney01]

You can fit another petcock but I think they work out expensive. I would deffo sort that ignition switch fault it could cartainly could be the problem
https://m.ebay.co.uk/itm/1974-1977-SUZU ... 1011861320
Or
I've heard some people have used these
http://www.pingelonline.com/prodcat/fuel-valves.asp

[paradox1559]

Can the key switch be rebuilt? It feels like the spring contacts are loose. It would probably work fine if I could bend them back.

[teazer]

Side note: my ignition switch is very loose, and takes some fancy turning techniques to make a connection. When it connects though it seems to stay on, but occasionally will lose continuity.

Sounds like the problem right there. I would think that you should be able to find a new one on ebay, but in the meantime, you could strip and clean it