🚀 go-pugleaf

Simon Wilson <siwilson@nodamnspamn.hotmail.com> wrote:
> That ultrasonically cleaning an HS4 SU carb is neither necessary or a
> good idea.
>
> I have spent nearly every day since my prior SU carburettor post trying
> to get the dang engine to run properly.
>
> I knew it was running rich on the two cylinders fed by the carb that I
> dismantled and cleaned, but I could not figure out why.
>
> The parts cannon got a pretty good workout:
>
> New plugs, plug leads, distributor (yeah the whole thing swapped for an
> electronic version), float needles, float needle seats, float bowl gaskets.
>
> I checked the fuel level in the float bowls multiple times. Reset the
> jet height (mixture) to the default setting multiple times. Checked the
> choke operation. Scratched head a zillion times. Gave up multiple times.
>
> I tried again this morning, I decided to set the jet heights more
> accurately with vernier calipers and also double check the butterfly
> synchronisation between the two carbs.
>
> Set the front carb so the jet was 1.2 mm down from the top.
> Set the rear carb jet by eye, but it didn't look quite right. (It's
> harder to see this one at the back of the engine bay)
>
> I looked more closely, and realised... the jet was a different diameter.
>
> WTF?
>
> Took it all apart again, and it appears that the top part of the jet
> (which is the metering part) had disappeared.
>
> Drove to Burlen and back (~80 miles) to pick up a new jet, and now it
> all works. FFS.
>
> I asked at Burlen how the two parts of the jet were held together, they
> think Loctite. Someow the ultrasonic cleaner had managed to separate them.
>
> Where the tiny part disappeared to I will never know, it wasn't in the
> bottom of the tank.
>
> Oh well.

Despite having invested in a 16 liter ultrasonic cleaner, with heat,
I'm coming around to your point of view, thinking it's really not
necessary for carbs. I got by without it for years, by simply spraying
copious amounts of solvent through all the fuel and air passages plus
of course the jets.

Your post reminded me of the carb issue I discovered on my wife's
DR200SE.  Some numpty didn't reassemble the carb correctly. The washer
#4, which keeps the jet needle #18 seated in the bottom of the slide
#8, was assembled BELOW circlip #5, which allowed the jet needle to
freely float upwards at random times, resulting in an overrich mixture
and sometimes bogging/stalling. I suspect this was why I got the bike
somewhat cheaper than the market at the time, which was being buoyed
by Covid induced demand.

https://imgur.com/a/oM2ted0

Of course I didn't cotton on to this until after I had ordered a new
needle, main jet, pilot jet, and numerous other carb bits, none of
which I actually needed.

Oh well. Runs like a runny thing now.

PS Don't use random rubber hoses you find in your junk box as vacuum
line from the intake to the vacuum petcock fuel tap. When it gets
warm, it will helpfully soften up and collapse from the vacuum,
cutting off fuel delivery and stranding your brother who took the
new bike out for a ride around the block, after being assured that
now the bike runs perfectly.

On 03/06/2025 21:03, Mark Olson wrote:

>
> Despite having invested in a 16 liter ultrasonic cleaner, with heat,
> I'm coming around to your point of view, thinking it's really not
> necessary for carbs. I got by without it for years, by simply spraying
> copious amounts of solvent through all the fuel and air passages plus
> of course the jets.
>

I really don't think they are effective as some say. I guess some of it
depends what liquid you use as well. I use (I think alkaline) specialist
carb cleaner liquid but it still takes a long time to remove the crap.
Possibly my cleaner is lacking in power too.

The HS4 SU carb is much simpler than I realised. It has just one jet,
and it's easy to check if it is blocked or not. I think the only real
problem with old ones is possible air leaks around the butterfly pivot.

With bike carbs you have all those maze of twisty passages, all alike.
The cleaner doesn't seem to get into those, and the only real way is to
remove (drill out? - I've never done it) those little brass plugs.

I spent aaaaaaaages on a set of Honda 750 SOHC carbs and never got them
right.

--
/Simon

Simon Wilson <siwilson@nodamnspamn.hotmail.com> wrote:
> On 03/06/2025 21:03, Mark Olson wrote:
>
>>
>> Despite having invested in a 16 liter ultrasonic cleaner, with heat,
>> I'm coming around to your point of view, thinking it's really not
>> necessary for carbs. I got by without it for years, by simply spraying
>> copious amounts of solvent through all the fuel and air passages plus
>> of course the jets.
>>
>
> I really don't think they are effective as some say. I guess some of it
> depends what liquid you use as well. I use (I think alkaline) specialist
> carb cleaner liquid but it still takes a long time to remove the crap.
> Possibly my cleaner is lacking in power too.

My cleaner seems a lot more powerful (it will perforate bacofoil)
than the little 1 liter unit I had previously. My biggest complaint is
that it has a digital temperature setting, and temperature readout,
but it ignores the setpoint and just keeps getting hotter until you
turn the power off. I got a partial refund from the seller over this
but in practice it's been something of a non-issue since with enough
cleaning solution it takes a long time before it gets too hot.

I've only used "Simple Green" brand cleaning solution (although I
think the variant I bought is actually purple in color) in mine so
far. I bought it to clean the GL1000 carbs, but haven't actually used
it for that yet. Cough.

> The HS4 SU carb is much simpler than I realised. It has just one jet,
> and it's easy to check if it is blocked or not. I think the only real
> problem with old ones is possible air leaks around the butterfly pivot.

Which seems like a solvable problem if you can find someone to make
new butterfly pivot shafts or fit some bushings into the carb bodies,
simple eh?

> With bike carbs you have all those maze of twisty passages, all alike.
> The cleaner doesn't seem to get into those, and the only real way is to
> remove (drill out? - I've never done it) those little brass plugs.
>
> I spent aaaaaaaages on a set of Honda 750 SOHC carbs and never got them
> right.

Maybe I've just been lucky, and never had a _really_ bad set of carbs
to deal with. Any passages with bends and brass plugs have always
cleaned out well enough by putting the spray tube from the can of
carb cleaner into them and letting it rip.

Simon Wilson <siwilson@nodamnspamn.hotmail.com> wrote:
>
> I asked at Burlen how the two parts of the jet were held together, they
> think Loctite. Someow the ultrasonic cleaner had managed to separate them.
>
Sounds like you got a very good unit!

This might be a chemistry problem more than a physical one. What was
the cleaning solution? How hot? How long? Ultrasonics speed up what happens
anyway, but I'd be surprised if a water based cleaner would dismantle
loctite. Unless run boiling overnight.

> Where the tiny part disappeared to I will never know, it wasn't in the
> bottom of the tank.
Was it aluminum, by chance? Ultrasonic cleaners with plain water will
attack aluminum.

Thanks for reading,

bob prohaska

On 05/06/2025 00:19, bp@www.zefox.net wrote:
> Simon Wilson <siwilson@nodamnspamn.hotmail.com> wrote:
>>
>> I asked at Burlen how the two parts of the jet were held together, they
>> think Loctite. Someow the ultrasonic cleaner had managed to separate them.
>>
> Sounds like you got a very good unit!
>
> This might be a chemistry problem more than a physical one. What was
> the cleaning solution?

Alkaline (I think) based carb cleaner

  How hot? How long? Ultrasonics speed up what happens
> anyway, but I'd be surprised if a water based cleaner would dismantle
> loctite. Unless run boiling overnight.

My unit isn't heated but I did tip in some fairly hot (80C perhaps) water.

>
>> Where the tiny part disappeared to I will never know, it wasn't in the
>> bottom of the tank.
> Was it aluminum, by chance? Ultrasonic cleaners with plain water will
> attack aluminum.
>

Brass or similar

--
/Simon

Simon Wilson <siwilson@nodamnspamn.hotmail.com> wrote:
> On 05/06/2025 00:19, bp@www.zefox.net wrote:
>> Simon Wilson <siwilson@nodamnspamn.hotmail.com> wrote:
>>>
>>> I asked at Burlen how the two parts of the jet were held together, they
>>> think Loctite. Someow the ultrasonic cleaner had managed to separate them.
>>>
>> Sounds like you got a very good unit!
>>
>> This might be a chemistry problem more than a physical one. What was
>> the cleaning solution?
>
> Alkaline (I think) based carb cleaner
>
>  How hot? How long? Ultrasonics speed up what happens
>> anyway, but I'd be surprised if a water based cleaner would dismantle
>> loctite. Unless run boiling overnight.
>
> My unit isn't heated but I did tip in some fairly hot (80C perhaps) water.
>
>>
>>> Where the tiny part disappeared to I will never know, it wasn't in the
>>> bottom of the tank.
>> Was it aluminum, by chance? Ultrasonic cleaners with plain water will
>> attack aluminum.
>>
>
> Brass or similar
>
The part may yet reveal itself, at a time of its own choosing....

8-)

bob prohaska

On 05/06/2025 18:19, Simon Wilson wrote:
> On 05/06/2025 00:19, bp@www.zefox.net wrote:
>> Simon Wilson <siwilson@nodamnspamn.hotmail.com> wrote:
>>>
>>> I asked at Burlen how the two parts of the jet were held together, they
>>> think Loctite. Someow the ultrasonic cleaner had managed to separate
>>> them.
>>>
>> Sounds like you got a very good unit!
>> This might be a chemistry problem more than a physical one. What was
>> the cleaning solution?
>
> Alkaline (I think) based carb cleaner
>

A long time ago I cleaned a pair of Honda carbs in an ultrasound bath
with Hibiscrub[1] added to the water. Surprisingly it worked quite well.

[1] It's a antibacterial soap mainly used in healthcare

Mark Olson wrote:

>Simon Wilson <siwilson@nodamnspamn.hotmail.com> wrote:
>> On 03/06/2025 21:03, Mark Olson wrote:

<SNIP>

>> The HS4 SU carb is much simpler than I realised. It has just one
>>jet,  and it's easy to check if it is blocked or not. I think the
>>only real  problem with old ones is possible air leaks around the
>>butterfly pivot.
>
>Which seems like a solvable problem if you can find someone to make
>new butterfly pivot shafts or fit some bushings into the carb bodies,
>simple eh?
>
>> With bike carbs you have all those maze of twisty passages, all
>>alike.   The cleaner doesn't seem to get into those, and the only
>>real way is to  remove (drill out? - I've never done it) those
>>little brass plugs.
>> I spent aaaaaaaages on a set of Honda 750 SOHC carbs and never got
>>them  right.
>
>Maybe I've just been lucky, and never had a really bad set of carbs
>to deal with. Any passages with bends and brass plugs have always
>cleaned out well enough by putting the spray tube from the can of
>carb cleaner into them and letting it rip.


I am convinced that carburettors are one of those items that starts
deteriorating on the shelf (like a torch battery) and only works
properly for about the first 6 months of being used after which air or
fuel leaks set in.
Was at a campsite in W.Sussex a while back and a convoy of vintage
British sports cars pulled in, TR4/5's, GT6's and a few MGB's and
Midgets.You could smell the petrol fumes at 150yds. At least two of the
group leapt out immediately and started fiddling with the carbs. They
work alright for a few years and then work badly for the next 30-50.
EFI has improved things greatly IMHO.It keeps working fine upto end-of
life and reduces wear in the 5mins after a cold start such that engines
last much longer.
Having said that, Japanese carbs are a huge improvement. I have a 1997
Honda with 2 carbs like the one Mark posted, replaced the float valves
and a few connecting hoses and they still work OK, still smell of
petrol though.


--
Geoff
NTV 650

Tim <nobody@home.co.uk> wrote:
> On 05/06/2025 18:19, Simon Wilson wrote:
>> On 05/06/2025 00:19, bp@www.zefox.net wrote:
>>> Simon Wilson <siwilson@nodamnspamn.hotmail.com> wrote:
>>>>
>>>> I asked at Burlen how the two parts of the jet were held together, they
>>>> think Loctite. Someow the ultrasonic cleaner had managed to separate
>>>> them.
>>>>
>>> Sounds like you got a very good unit!
>>> This might be a chemistry problem more than a physical one. What was
>>> the cleaning solution?
>>
>> Alkaline (I think) based carb cleaner
>>
>
> A long time ago I cleaned a pair of Honda carbs in an ultrasound bath
> with Hibiscrub[1] added to the water. Surprisingly it worked quite well.
>
> [1] It's a antibacterial soap mainly used in healthcare

Soap is a very effective surfactant. The only problem is that it
makes scum on contact with calcium or magnesium salts. Since
most tap water contains at least one of them, detergents reign
supreme. If you have soft water, soap is hard to beat.