Author Topic: Refitting air plenum on a 400/4  (Read 244 times)

Offline alfiembra

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Refitting air plenum on a 400/4
« on: June 23, 2022, 07:11:24 PM »
Hi all, is there a technique or tip to refitting the air plenum between the carbs and air filter box?
I’ve been struggling to get the 2 sides fitted, if I do the carbs first I can’t get the plenum to fit over the oval duct at the air filter and vice versa. I’ve tried gently warming it up to make it a bit more pliable but that hasn’t helped.
My big mitts probably don’t help but I feel like I’m missing something simple. Thanks Alan.

Offline McCabe-Thiele (Ted)

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Re: Refitting air plenum on a 400/4
« Reply #1 on: June 24, 2022, 08:59:38 AM »
I found it very difficult so when I did my rebuild I put it in place before the back wheel, mudguard & battery box were in place - that worked a treat with all four carbs fitting the flange rubbers evenly.

My best fit before the rebuild involved a shaped piece of wood lodged inside the plastic section to stop it moving I tried a bicycle inner tube that I inflated inside to make it keep its shape but it did not work for me - replacing the four rubbers grommets did not seem to help. I ended up with 3 on fully and one on but only just.

A shame Honda did not fit some sort of internal plastic supports to make the chamber more rigid in the centre. I lost half a pound in sweat during the process.



« Last Edit: June 24, 2022, 09:10:34 AM by McCabe-Thiele (Ted) »
Honda CB400 four super sport

Offline alfiembra

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Re: Refitting air plenum on a 400/4
« Reply #2 on: June 24, 2022, 01:05:16 PM »
Yep agree with all that I’ve used a t shape Allen key to push through from the airfilter box side to seat the middle two carbs but not got enough stretch in it to pull it back onto the oval duct.

Offline K2-K6

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Re: Refitting air plenum on a 400/4
« Reply #3 on: June 24, 2022, 01:24:36 PM »
I think it's this that makes the owner a "blackbelt" in 400 Four wrangling, only a select few pass the test with admiral competency, go forth and try, grasshopper  ;D

In all seriousness, definitely a very awkward process to complete.

 

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