Stuttering question...

I have a buddy that has an 81 Honda CB650.

The bike is very clean with 12.5K miles.

He experiences engine stumbling at around 60 MPH and up but only if he is at or near WOT.

If you creep up to 65 MPH or beyond it runs fine with no stumble.

Any ideas where to start looking? Carbs clogged?

Thanks

Will

I have a buddy that has an 81 Honda CB650.

The bike is very clean with 12.5K miles.

He experiences engine stumbling at around 60 MPH and up but only if he is at or near WOT.

If you creep up to 65 MPH or beyond it runs fine with no stumble.

 

Any ideas where to start looking? Carbs clogged?

 

Thanks

Will

It would appear to be a bowl filling issue. This can start at the tank, such as rust at the screen, blocked tank vent, sticking float needle valves or incorrect sizing, or carb vent restricted... Those would be the first checks then over to the slide pistons if he is running CV carbs.

my first thought would be to seafoam it a little on the heavy side for a tank of fuel and see how it does and replace the fuel filter after the seafoam treatment.

my first thought would be to seafoam it a little on the heavy side for a tank of fuel and see how it does and replace the fuel filter after the seafoam treatment.

Yes I forgot that one.

Yes I forgot that one.

Tanks people for the insight.

The lack of fuel delivery makes sense and I'll pass the info along to him.

Tanks people for the insight.

The lack of fuel delivery makes sense and I'll pass the info along to him.

No problem. Consider inviting your friend up to the bar here and join the club.

Just to reinforce the already stated opinions.

I had similar symptoms with my '81 Seca 750. t was a build up of rust debris from the tank in the fuel manifold at the #4 carb. Even with an inline fuel filter, enough sediment made it's way down the lien to eventually stop the last bowl in line from staying full at WOT.

Here is something I went thru just recently have him pull his carbs and look at float needle see if there is a ring on it, if so use a drill bit and twist it by hand in the float needle seat. no pressure just slight twist, there may be a bir up in that seat which causes the float needle to stick closed. For longest time we chased it on a buddies bike a 2007 Honda Rebel and one carb on sons 86 Honda Cb450c Nighthawk.