Carb holder spacers? Will they fit/benefit a 400?

[Anthonyvan]

Mikes xs sells carb holder spacers meant to improve low end throttle response and torque, but they are for a 650. Does anyone know if these would be beneficial or applicable to the xs 400? If so I'd love to grab em and see how they do.

 

[Wolfe_11B]

I have them. They are not direct bolt on for the 400 SOHC motor. The carb bolt spacing on our motor is slightly tighter. They are made of aluminum though, so a quick job on the drill press bored out the holes big enough to get everything lined up.

I noticed my motor (1981) had quite a few signs of reversion when I tore it down. Lengthening the intake runners might actually help with the issue.

 

[XSLeo]

The longer run from carb to intake valve, creates a higher velocity in the intake tract. this can lead to an increase in cylinder fill at lower rpms. More fuel air mix in the cylinder can increase the power at these rpms. Those spacers are sold to go with a poor to marginal set of carbs.
They may help but only way to know for sure is to add them to a properly tuned engine. They won't fix any issues with poor tuning.
Leo

 

[xschris]

I thought they where designed to go with the pwk flatside carbs. The xs400 makes it's power at higher rpms where the xs650 has a lot of torque (360* crank). Using the shorter flatside carbs you loose torque. By adding the spacers you get it back. At least that is what I thought I have read

 

[Anthonyvan]

I may give em a shot, they're not too pricey so if I don't like em I'll live. I just got the electronic ignition ordered, I can't wait to get this thing back on the road >_< I've only had it back apart for a week!