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Author Topic: Carb to Engine Rubber Questions  (Read 432 times)

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Offline zalion0

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Carb to Engine Rubber Questions
« on: April 04, 2022, 04:52:23 AM »
Hi all, I’m in the process of replacing the carb to engine rubbers on my 1977 CB750 F2 which has the stock PD41B carbs. I ordered a replacement set from David Silver and have been assured these are indeed the right sized rubbers. However when you take a look there is a size difference, the old rubbers on the left are smaller compared to the new rubbers on the right. Anybody seen this before?

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Offline DaveBarbier

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Re: Carb to Engine Rubber Questions
« Reply #1 on: April 04, 2022, 06:38:30 AM »
Length or diameter?
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Offline madmtnmotors

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Re: Carb to Engine Rubber Questions
« Reply #2 on: April 04, 2022, 07:23:02 AM »
My experience with the aftermarket K7/K8/F2/F3 intake manifolds is that there is some deviation. The ones I've received were often a little longer than original, with the #1 pretty close to stock and the #2, #3, and #4 gradually increasing in length to about 1/4" longer on #4. I had to elongate the hole in the air cleaner mounting tab on the right (#4) side just to be able to bolt up the air cleaner on one installation with aftermarket intake manifolds. Sad part is there aren't many options.
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Offline MauiK3

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Re: Carb to Engine Rubber Questions
« Reply #3 on: April 04, 2022, 07:57:48 AM »
Seems odd, try Yamiya, maybe they have some.
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Offline Deltarider

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Re: Carb to Engine Rubber Questions
« Reply #4 on: April 04, 2022, 08:19:04 AM »
Slightly off topic for which I apologise.
Strange as it may seem, so far I did not have to replace my 46 year old rubber boots (CB500), by the new ones that I have bought decades ago and that are still in their packages. I've tested a couple of times by spraying carb cleaner, but I have never detected a leak.* When revved, rpm drops to idle immediately and from 6000 rpm, bike pulls like a rocket. I must be an exception, I guess..
* I did detect a leak caused by a defect O-ring between the manifold and head however. This was after an top end performed by a professional mechanic. Only one so far.
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Offline zalion0

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Re: Carb to Engine Rubber Questions
« Reply #5 on: April 04, 2022, 12:38:44 PM »
I am tempted to stick with the originals. These still seem flexible and I can’t see any cracks. If I do attempt to fit and these then don’t fit doubt I’ll get my money back…
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