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SOHC.co.uk Forums => CB350/400 => Topic started by: wildtapholer on May 31, 2021, 05:53:48 PM

Title: CB400f exhaust gasket size
Post by: wildtapholer on May 31, 2021, 05:53:48 PM
Hi again, I ordered an exhaust to collector box gasket from David Silvers and this is what came, and it was way tooo big does anyone have their exhaust off at the moment that could measure the collector box neck and the exhaust internal measurements, mine is 38mm at the collector neck
Title: Re:CB400f exhaust gasket size
Post by: wildtapholer on June 01, 2021, 11:25:18 AM
I've rung Silvers this morning but they're not having it that the gasket is wrong, they're saying it will crush down and I'm telling them it won't go in the exhaust to crush down, and to crush down from the size what came is ni on impossible. I told them even if I put the genuine part no down on their web site, it doesn't give what the size is but they're quite prepared to order me one and I'm getting really annoyed. They suggested it might be a rouge gasket and they will take one out and measure it, but I told them when you put the part number in, what they sent is, it's dimensions as 48.9x43x30.3  I bought one exhaust gasket from M&P it was too small, I hadn't measured the collector box at this time, so ordered one from Silvers and it's too big and that's when I measured the collector box neck 38mm arhhhhhhhhhhhhhhh
Title: Re: CB400f exhaust gasket size
Post by: billywingnut on June 04, 2021, 09:03:18 PM
I recently bought a silencer and  gasket from DS and had the same problem. I used coarse sandpaper to reduce the outside diameter of the gasket until it was a snug fit inside the silencer. This means the walls of the gasket are quite thin but it did work after a couple of hours of rubbing. It now works a treat, there is a slight leak of condensation from the joint when cold which I am advised is not a bad thing as it drains the silencer, the joint does not blow however.
Title: Re: CB400f exhaust gasket size
Post by: wildtapholer on June 04, 2021, 09:21:14 PM
That doesn't tell me which gasket you got or part no what they sent or what size it was, if the collector box is 38mm and the internal measurement of the exhaust is 42mm there is no way the 48.9x43x30.3 is going to fit, this is what I had to do, pic enclosed, I had to cut more or less 2cm out out the gasket what was sent
Title: Re: CB400f exhaust gasket size
Post by: smoothoperator on June 06, 2021, 03:12:31 PM
My silencer is off at the moment and the gasket is still on, so I have taken measurements. There is some ovality so using average measurements, I have outside diameter 48.0 mm, Inside diameter (outside diameter of the COLLECTOR BOX PIPE), 42.5 mm, length 29 mm.
Title: Re: CB400f exhaust gasket size
Post by: wildtapholer on June 06, 2021, 05:45:15 PM
What's the collector box neck measure at if your able to measure that please.
Title: Re: CB400f exhaust gasket size
Post by: smoothoperator on June 07, 2021, 09:27:28 AM
Sorry I wasn't clear, the 42.5 mm is the o/d of the collector box neck that along with the gasket slides into the silencer. The silencer splays out to allow fitting the collector box with gasket inside it, with the clamp pinching the splayed out end of the silencer back in as the clamp is tightened up. I have edited my earlier reply to make this clearer.
Title: Re: CB400f exhaust gasket size
Post by: wildtapholer on June 07, 2021, 06:50:12 PM
I can't understand why my collector box neck only measures 38mm on the outside, this is going to cause me a lot of trouble trying to get the correct size.
Title: Re: CB400f exhaust gasket size
Post by: Nurse Julie on June 07, 2021, 07:08:00 PM
I can't understand why my collector box neck only measures 38mm on the outside, this is going to cause me a lot of trouble trying to get the correct size.
Have you got a photo of your collector box?
Title: Re: CB400f exhaust gasket size
Post by: wildtapholer on June 08, 2021, 10:47:48 PM
Just seen this message, I'll pull the silencer off tomorrow and try to include a picture with the vernier gauge across  the neck of the collector box, but as far as I'm aware it's standard.
Title: Re: CB400f exhaust gasket size
Post by: hairygit on June 08, 2021, 11:10:41 PM
How are the downpipes held to the collector, 2 welded, 2 clamped or all 4 clamped?

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Title: Re: CB400f exhaust gasket size
Post by: wildtapholer on June 09, 2021, 08:53:05 PM
The pipes were a bit rusty so I cleaned them up and painted them with heat resistant paint but other than that they are fine except for sourcing a gasket, so here's 3 pic's if it let's me up load them.
Title: Re: CB400f exhaust gasket size
Post by: Deano400 on June 10, 2021, 11:33:13 AM
Original double skin headers.
[attach=1]
Title: Re: CB400f exhaust gasket size
Post by: Deano400 on June 10, 2021, 11:36:11 AM
[attach=1]
Title: Re: CB400f exhaust gasket size
Post by: hairygit on June 10, 2021, 12:51:12 PM
So the fact is Bitsa will be laughing his head off again " F%*king pattern parts!"
He may have been a cantankerous argumentative old git, but he talked a lot of sense.

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Title: Re: CB400f exhaust gasket size
Post by: Nurse Julie on June 10, 2021, 01:31:39 PM
I concur, my OEM collecter also measures 43mm at the same point.
Title: Re: CB400f exhaust gasket size
Post by: wildtapholer on June 10, 2021, 03:10:20 PM
Looks like I've gotta do a lot of searching for a 38mm internal measure gasket of the right size then, off whatever fits, is anything correct on this bike.
Title: Re: CB400f exhaust gasket size
Post by: Nurse Julie on June 10, 2021, 06:37:53 PM
So the fact is Bitsa will be laughing his head off again " F%*king pattern parts!"
He may have been a cantankerous argumentative old git, but he talked a lot of sense.

Sent from my JNY-LX1 using Tapatalk
🤣🤣🤣🤣🤣
Title: Re: CB400f exhaust gasket size
Post by: wildtapholer on June 10, 2021, 09:48:48 PM
You know what, that could explain the silencer, it is not the correct silencer but it fits and looking at it, it could be off a kawasaki.
Title: Re: CB400f exhaust gasket size
Post by: wildtapholer on June 11, 2021, 08:04:18 AM
Yes it's looking like someone has cut and welded a smaller neck on the collector box, had a proper look at the exhaust and yes it is off a Kawasaki but I'm not sure which model, I've included a pic if anyone can identify it.
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