Puff test on cb450 carbs, anyone done it?

Hi Guys,

Not to question "Bills 450 advice" in anyway at all, rather... I'm questioning my carbs. I've read of the puff test where you can blow with a a straw on the holes at the back of a carb and the needle should rise with a puff. Does that work for you guys? My bike breaks up as I just turn the throttle and I have rechecked everything five times, clean carbs, timing, gas lines... so I'm thinking because I have to blow hard on the straw to get the needle to rise that maybe that's it?

Please weigh in here, I thank you in advance for your help! -D

I think I did that, and it worked. Can't remember which hole to put the straw on though.

When you reassemble the carbs, make sure the pistons slide up and down easily with your finger. Sometimes I have to tweak the position of the piston cap slightly, or the piston will not slide smoothly or fall back down quickly on it's own. The mating surfaces between the piston and the piston cap have to be very clean and free of corrosion. That weird surface finish is what makes the air tight seal. These pistons do not have diaphragms like most others.

I think the "puff test" is a good way to check the airtight seal between the piston and the piston cap. Also, you can run the bike with the air filter off so you can see the piston inside the carb. As you roll on the the throttle, you should see the piston go up on its own.

Thanks! I especially like the part about the cap position. -D