[mdwman]

1970 CL175. Ran with no issues until I put a new TIGHT fuel cap on. After riding about 20 min. normally, it lost power and quit. Took off the cap, it started back up and I made it home where it died again. I replaced the old original cap and rode again with the same scenario. I'm wondering if increased pressure in the tank caused by the tight cap shook loose some gunk got into the system. Fuel petcock and tubing were replaced earlier this year. I'm replacing the inline filters now. Any harm in draing the carb? Is that the screw at the base of the carb?

Thanks for opinions.

 

[middletons]

Yep, screw is at the bottom of the bowl. Check the petcock sediment bowl as well, might be clogged.

 

[J-T]

There is no pressure in the tank when all is operating properly. If the cap vent is plugged fuel draining from the tank to the carbs as the engine burns it will cause a vacuum in the tank causing lack of fuel flow/fuel starvation. Waiting a few minutes or opening the tank will allow the bowls to fill and you can run again, for a while, until the cycle repeats. Since you've had the same problem with two different caps it seems unlikely the cap is the problem, but...................................

 

[Richard_Pitman]

Easier to drop the float bowls than wrestle with seized up drain screws, and that way you'll be able to see if any gunk has landed in the bottom of the bowls.

Also easy to unscrew the main jets and blow through them when the float bowls are off. Don't be tempted to take the floats off unless you absolutely need to, it's a pain getting the needle valves back into place when the carbs are the right way up ie on the bike.

 

[mdwman]

I thought I would update this thread. To address my ongoing problem I changed fuel line filters and drained the carb bowls. Didn't see any crap in there. I thought the petcock would be fine since it was replaced less than 2 years ago but I removed the sediment bowl and here is what the screen in there looked like:

Is this the result of modern gas on a cheap part? I went ahead and just replaced the petcock (with original Honda part) and all is running smooth now.

 

[chaindrivecharlie]

I thought I would update this thread. To address my ongoing problem I changed fuel line filters and drained the carb bowls. Didn't see any crap in there. I thought the petcock would be fine since it was replaced less than 2 years ago but I removed the sediment bowl and here is what the screen in there looked like:
View attachment 280006
Is this the result of modern gas on a cheap part? I went ahead and just replaced the petcock (with original Honda part) and all is running smooth now.

Never seen anything like that, but the screen looks like it went thru a chemical reaction.

 

[Richard_Pitman]

Looks like mechanical damage to me. Pliers or screwdriver …….