The CB1100 Community Forum

Hey guys,

I ordered these K Factory block off plates shortly after I got all of that work done, and I finally put them in yesterday. Installation was a snap, (didn't even have to remove the tank!) probably took 5 minutes per side.

Initially I removed all of the diaphragm assembly, then I noticed the dimples/detents in the block off plates corresponded with the screws on top of the diaphragms. The instructions were all in Japanese, so I had to wing it.

[attachment=13445][attachment=13443][attachment=13444]
No more popping on decel, and no more more burbles. Also, the throttle twitchiness is completely gone now!

[attachment=13446]

Those look exactly like the OEM reed valve in the valve cover of my CBR250R. It vents crankcase blow-by out of the valve cover.

Good job- but no need.

The pop off the main supply line hose to the airbox and plug it. I used a standard vacuum cap from the local auto parts store- small enough to invert and stick in the hose- worked perfect- and then put the hose back on the airbox. Easy enough to remove if needed...and my valve cover looks normal.

(04-18-2021, 10:30 AM)Stichill_imp Wrote: [ -> ]Those look exactly like the OEM reed valve in the valve cover of my CBR250R. It vents crankcase blow-by out of the valve cover.

The parts may be the same- but no, they aren't for crankcase vent- they blow in, not out. Air injection - the AI part of PAIR.

(04-18-2021, 10:34 AM)PowerDubs_imp Wrote: [ -> ]Good job- but no need.

The pop off the main supply line hose to the airbox and plug it. I used a standard vacuum cap from the local auto parts store- small enough to invert and stick in the hose- worked perfect- and then put the hose back on the airbox. Easy enough to remove if needed...and my valve cover looks normal.

(04-18-2021, 10:30 AM)Stichill_imp Wrote: [ -> ]Those look exactly like the OEM reed valve in the valve cover of my CBR250R. It vents crankcase blow-by out of the valve cover.

The parts may be the same- but no, they aren't for crankcase vent- they blow in, not out. Air injection - the AI part of PAIR.

The parts may be the same- but no, they aren't for crankcase vent- they blow in, not out. Air injection - the AI part of PAIR.
Thanks Powerdubs,

I also did the air injection removal with my Thruxton, and there was a very similar procedure as you describe above for the Triumph aircooled twins. Either way, very pleased with the results! Now for suspension....

Oh and a new battery as the OEM died this morning. 7 years, not too bad.

(04-18-2021, 10:34 AM)PowerDubs_imp Wrote: [ -> ]Good job- but no need.

The pop off the main supply line hose to the airbox and plug it. I used a standard vacuum cap from the local auto parts store- small enough to invert and stick in the hose- worked perfect- and then put the hose back on the airbox. Easy enough to remove if needed...and my valve cover looks normal.

(04-18-2021, 10:30 AM)Stichill_imp Wrote: [ -> ]Those look exactly like the OEM reed valve in the valve cover of my CBR250R. It vents crankcase blow-by out of the valve cover.

The parts may be the same- but no, they aren't for crankcase vent- they blow in, not out. Air injection - the AI part of PAIR.

Well, I'll defer to your knowledge, 'Dubs. It may serve an identical function on my CBR. I thought it was a vent due to the amount of toasted carbon on the parts underneath it.

Would someone explain to me what these do? I have never heard of them.

They have been around in one form or another for a long time. Many might not use a valve though and can be much more rudimentary. There is a nice article here on it. You many of seen crankcase breathers near the crank area of the engine with little pod filters on them. This is to allow the engine to get rid of excess pressure without feeding the oily mist back into the inlet side of the bike.

https://motorcycleinth.com/article.php/C...rformance/

Like Dubs said, this isn’t crankcase ventilation. The reed valves are part of the PAIR system. Per the manual: “The pulse secondary air system introduces filtered air into the exhaust gases in the exhaust port. Fresh air is drawn into the exhaust port by the function of the PAIR control valve.”

If you have a service manual the explanation and diagram is shown in section 1. Is part of the emission controls.

The crankcase breather is also shown in section one. “The engine is equipped with a closed crankcase system to prevent discharging crankcase emissions into the atmosphere. Blow-by gas is returned to the combustion chamber through the air cleaner and throttle body.”

(04-22-2021, 07:39 PM)Lord Popgun_imp Wrote: [ -> ]Like Dubs said, this isn’t crankcase ventilation. The reed valves are part of the PAIR system. Per the manual: “The pulse secondary air system introduces filtered air into the exhaust gases in the exhaust port. Fresh air is drawn into the exhaust port by the function of the PAIR control valve.”

If you have a service manual the explanation and diagram is shown in section 1. Is part of the emission controls.

The crankcase breather is also shown in section one. “The engine is equipped with a closed crankcase system to prevent discharging crankcase emissions into the atmosphere. Blow-by gas is returned to the combustion chamber through the air cleaner and throttle body.”

Oh very cool, no doubt driven by Euro or Californian emmission regulations. I like the little pop on the over run myself.

... and to think some owners (not just CB owners but all makes and models) just rip all these earth-saving-related components out so to gain a few horsepower, and in some cases, an extra +40 dB of rumble.