Topic: Stalling at Quick Stop

[BrickWoll]

Hey all,

Both rapid stops and steep downhill stops almost always result in the engine stalling.  Is this a normal byproduct of sloshing gas in the bowls?

'77 CB550 K3

Thanks!

[HondaMan]

Hey all,

Both rapid stops and steep downhill stops almost always result in the engine stalling.  Is this a normal byproduct of sloshing gas in the bowls?

'77 CB550 K3

Thanks!

No, unless the float bowl levels are extremely low, or very, very high.
When too low, the engine struggles to transition from normal-burn fuel-air ratios to lean-burn ratios as it slows down. This results in a slowdown in RPM, and the inertia of the crankshaft is not heavy enough to 'spin thru' it like in old V8 engines.

When too high, the fuel actually spouts upward in the jets when the bike decelerates hard, flooding the engine like you switched on the choke.

Either one will stall the engine. Look at your sparkplugs to see if they are dark, or white. If dark, it is too rich, if white, too lean.

Some hints:
1. If you 'rebuilt' the carbs recently and replaced the brass parts (jets, jet needle and needle jet) then it is 100% TOO LEAN. All of the aftermarket brass parts for these carbs today are too lean, and are incorrectly made. Use the OEM brass parts.
2. If the mainjets will barely stay in their holes in the carbs, you have been stung by aftermarket rebuild kit O-rings. The O-ings in the kits are too thin (usually 1x4 size) to seal the jet into the emulsifier's tube mount, and the result is a lot of extra fuel sloshing up into the mainjet emulsifier. This will build up every time you decelerate the throttle from midrange toward idle, drowning the engine. If this is the case with your carbs, PM me your address and I can send you a set of 4 O-rings that will fit.

[DaveBarbier]

I had the same issue with my 550 k4 and it was indeed the float setting. Fuel level was too high. I set the fuel level to 4mm below the bowl seam and it fixed it.

The Patina Hyena link in my signature will open the table of contents of my build thread. There’s a link in there about halfway down about a stalling under hard braking and braking down hills and a link under it with the solution. Check it out.

[BrickWoll]

No, unless the float bowl levels are extremely low, or very, very high.
When too low, the engine struggles to transition from normal-burn fuel-air ratios to lean-burn ratios as it slows down. This results in a slowdown in RPM, and the inertia of the crankshaft is not heavy enough to 'spin thru' it like in old V8 engines.

When too high, the fuel actually spouts upward in the jets when the bike decelerates hard, flooding the engine like you switched on the choke.

Either one will stall the engine. Look at your sparkplugs to see if they are dark, or white. If dark, it is too rich, if white, too lean.

Some hints:
1. If you 'rebuilt' the carbs recently and replaced the brass parts (jets, jet needle and needle jet) then it is 100% TOO LEAN. All of the aftermarket brass parts for these carbs today are too lean, and are incorrectly made. Use the OEM brass parts.
2. If the mainjets will barely stay in their holes in the carbs, you have been stung by aftermarket rebuild kit O-rings. The O-ings in the kits are too thin (usually 1x4 size) to seal the jet into the emulsifier's tube mount, and the result is a lot of extra fuel sloshing up into the mainjet emulsifier. This will build up every time you decelerate the throttle from midrange toward idle, drowning the engine. If this is the case with your carbs, PM me your address and I can send you a set of 4 O-rings that will fit.

Thanks for the detailed response.  I will check the plugs to determine whether the fuel level is high or low. 
I DID completely clean and rebuild the carbs, but did not replace brass parts.  However, I don't know if the PO had ever swapped out the orig brass.  I definitely swapped all rubber so I may have an ill fitting main?  I don't remember the jets feeling loose though.  That would have been a concern at the time.

I had the same issue with my 550 k4 and it was indeed the float setting. Fuel level was too high. I set the fuel level to 4mm below the bowl seam and it fixed it.

The Patina Hyena link in my signature will open the table of contents of my build thread. There’s a link in there about halfway down about a stalling under hard braking and braking down hills and a link under it with the solution. Check it out.

Thanks for the response.  Sounds like I'm going to have to do some float assessment either way.  I'll look through your thread.