Author Topic: Yet another Carb Rebuild question  (Read 484 times)

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Offline Mossy

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Yet another Carb Rebuild question
« on: August 06, 2023, 09:15:17 AM »
Gents,
These new jets are sitting by the ones I removed from the carbs at teardown. Will they work in the carbs for my 350 Four?
The other question I have is where do I measure the float height from (center or an end of the float)? I've seen 26mm height in my old Clymer Honda manual and 22mm online. As you see in the pic, the float doesn't sit parallel with the float bowl mating surface.

Thank you
« Last Edit: August 06, 2023, 09:23:55 AM by Mossy »

Offline bryanj

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Re: Yet another Carb Rebuild question
« Reply #1 on: August 06, 2023, 09:51:39 AM »
Clean the original brass and set the floats to whatever the HONDA  manual says
Semi Geriatric ex-Honda mechanic and MOT tester (UK version of annual inspection). Garage full of "projects" mostly 500/4 from pre 73 (no road tax in UK).

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Offline Mossy

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Re: Yet another Carb Rebuild question
« Reply #2 on: August 06, 2023, 09:53:24 AM »
Do I measure at the highest point of the float?

Offline bryanj

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Re: Yet another Carb Rebuild question
« Reply #3 on: August 06, 2023, 10:14:32 AM »
From memory the floats should be level and adjust float height by bending the tab that touches the needle
Semi Geriatric ex-Honda mechanic and MOT tester (UK version of annual inspection). Garage full of "projects" mostly 500/4 from pre 73 (no road tax in UK).

Remember "Its always in the last place you look" COURSE IT IS YOU STOP LOOKIN THEN!

Offline Mossy

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Re: Yet another Carb Rebuild question
« Reply #4 on: August 06, 2023, 12:15:05 PM »
Thanks Bryan. The new float valve appears to be a bit longer than the originals.

Offline AlekStooge

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Re: Yet another Carb Rebuild question
« Reply #5 on: August 07, 2023, 05:58:31 AM »
Follow this video. It's better to do it holding the carbs as if they were on the bike. It's a drag but do it.


Online HondaMan

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Re: Yet another Carb Rebuild question
« Reply #6 on: August 08, 2023, 08:12:45 PM »
DON'T use aftermarket jetting, nor needles, nor needle jets, in the 350F carbs. The bike will barely run with that crap.  And, it IS crap.
Jets do not wear out, nor change calibration over time. Even the MTBE we suffered in American fuels for over a decade didn't hurt the brass parts (it did hurt the carb bodies, different topic).

The modern float valves will be stiffer (in their springs) than the OEM versions. For this reason I set the bowls 1-2mm DEEPER of fuel than OEM settings, so the bowls won't run dry when the engine is at speed.

Just replace the rubber parts (O-rings and hoses - ALL the hoses, and especially the little bowl-vent hoses). The rest can be cleaned unless the float valves are just frozen from sitting for decades (although this can often be cleaned by soaking them a few days in lacquer thinner, keep them with their original valve seats).

This is how I've rebuilt all the 350F/400F carbs sent to me, for decades. No one has complained, yet!
See SOHC4shop@gmail.com for info about the gadgets I make for these bikes.

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Offline Deltarider

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Re: Yet another Carb Rebuild question
« Reply #7 on: August 09, 2023, 02:31:51 AM »
OK, a few thoughts.
Float adjusting runs like an epidemic in this forum and not in the other SOHC CB Four fora.
Personally I've never had to adjust any floats on a CB500/550. Never ever and on my CB500 they have travelled 140.000kms.
This video from 17:00 - 18:20 shows what goes on in practice. Note how gentle the movement is and how little force is exercised. Note also the little pin does not compress. It's there to absorb eventual shocks.
Unless you work in a professional workshop and service all kinds of bikes, you don't have to buy any measuring tool. Below is mine cut from some old membership card.
Video courtesy Gruzzel
« Last Edit: August 10, 2023, 12:53:32 AM by Deltarider »
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