1979 Honda CM400A cutting out when stopping

[Mongeau308]

Not sure why but after bike gets nice and warm like a after a long ride or going on the highway when i come to stop signs or lights my rpms drop significantly and then the bile cuts out. Anyone have any idea why this might be happening?

 

[LongDistanceRider]

Usual cause is idle speed set too low.

 

[Mongeau308]

When I’m in neutral, everything is fine and the RPMs are where they should be but when I’m in first gear and I slow down the RPMs drop below with the recommended idle speed should be

 

[EzPete]

When was the last time the carbs were synced?

When you’re in gear and stopped, the timing stays advanced, slightly out of sync carbs may struggle here with the internal load of the torque converter, etc.

 

[Mongeau308]

Probably 20 years ago. Lol. Aight ill check that out when i get a vacuum kit. Thanks!

 

[Mongeau308]

Got any links to a good gauge set or any walkthroughs on how to make the process easier….

 

[Boosted]

Yeah, I made my own manometer after watching this :

 

[Mongeau308]

How did you attach the tubes to the vacuum ports?

 

[EzPete]

Adapter Kit - Vacuum Carb Sync - 5mm

Color/Finish: Brass Material: Brass Dimensions: Length: 4 in, 2 in OD: 5mm ID: 0.8 Fits: Universal

www.dimecitycycles.com

If you want to get crafty, you can make your own. It’s an M5 standard (0.8 pitch) thread.

 

[Boosted]

How did you attach the tubes to the vacuum ports?

I bought a couple of these :

Vacuum Adapter, Brass w/Cap 5mm x P0.80mm (Ea) - Motion Pro

Motion Pro - High quality cables, tools and controls for motorcycles, ATVs, snowmobiles and personal watercraft.

www.motionpro.com

 

[Mongeau308]

Does anyone know a rough rpm for being stopped in 1st gear should be?

 

[esmith250624]

 

[ancientdad]

Does anyone know a rough rpm for being stopped in 1st gear should be?

A quick look at the FSM supplement for the 400A shows this for idle speed, so I'd assume whatever rpm it decreases to in gear is what it will be.

 

[Mongeau308]

Thanks! Looks like my issue was the carbs being un balanced.

 

[ancientdad]

Thanks! Looks like my issue was the carbs being un balanced.

Do you not have the FSM and supplement? Let me know if not

 

[Mongeau308]

Do you not have the FSM and supplement? Let me know if not

I do have one. Thank you!

 

[EzPete]

Thanks! Looks like my issue was the carbs being un balanced.

Nice! Easy fixes are the best.