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Riddle Me This (Help With Carb Running Issue)


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#16 SuperDeLuxeNick

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Posted 24 May 2020 - 06:37 PM

 

Again, took float chamber lid off and met with a lot of air pressure coming out...

 

Looks like the air breather on the float chamber lid is blocked, there shouldn't be a AIR pressure build up there. Also when last was fuel filter changed.

 

How do i check this? there is just one fuel inlet pipe that i can see, no breather?



#17 SuperDeLuxeNick

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Posted 24 May 2020 - 06:38 PM

Should add its a HS4 non-waxstat



#18 SuperDeLuxeNick

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Posted 24 May 2020 - 06:39 PM

scarp that, i see the little vent underneath now with a google image search... i shall take that off and clean tomorrow.



#19 SuperDeLuxeNick

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Posted 04 June 2020 - 07:12 PM

** update **

 

the annoying issues continue - so the fuel issue was down to a blockage in the jet. all sorted.

 

got it back together and it ran well, and after another mixture and timing setup, i had it running lovely.

 

I did notice however that it developed a really high pitch squeaking. I suspected an air leak and was correct. The manifold was cross threaded so couldn't tighten up the carb properly. Replaced this no problems. When doing this i noted that one of the gaskets between the carb and the manifold was incorrect, it was for a HS2, narrower hole than the HS4 - I'm sure that didn't help! Anyway i put in all new and correct ones.

 

Once again, gave it a a little tweak and away we went, really good driving.

 

EXCEPT, the symptoms are now as follows:

 

1. Accelerating we have constant smooth power, with no flat spots and good performance.

2. However, when you come off the pedal, the revs drop smoothly but then stick at around 2000, then drop again down to idle.

3. When cursing in say 3rd or 4th - at around 2000, it isn't happy, a bit lumpy/juddery.

4. as soon as you give a tiny bit of gas it picks up lovely, no probs.

5. After use, the car STINKS of petrol but i see no signs of leakage whatsoever, but it hums, most seems to come from the crankcase breather (should i blank or connect to carb?)

6. If i press the crab piston lifter, the revs die off instantly (meaning its too weak usually?!) but this doesn't correlate with other symptoms

7. also the idle is a little up and down - say between 900-1100 - again like an air leak but i have checked everywhere for any leak and can't see.

 

Any help, much appreciated as always :)

 

Nick


Edited by SuperDeLuxeNick, 04 June 2020 - 07:13 PM.


#20 gazza82

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Posted 05 June 2020 - 10:23 AM


5. After use, the car STINKS of petrol but i see no signs of leakage whatsoever, but it hums, most seems to come from the crankcase breather (should i blank or connect to carb?)

Have you got a mechanical pump? If so it might be leaking via the diaphragm and fuel is getting into the oil ..



#21 cal844

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Posted 05 June 2020 - 11:06 AM

You may need to lean the fuel off (however I dont think it will be a fuel issue.)

What to do is drive the car... perform a few plug chops,

You'll need a spark plug socket and ratchet with you in the car.

To do these you simply find an area of road on your test route (keep going the same test route to remove variables)

Switch off the ignition with the car at speed, gearbox into neutral and slow to a safe stop in a safe area.

With the ignition off remove each spark plug in turn making note of the colour of them (pictures or a pen and paper, I just keep a mental note though.)

Refit the spark plugs and continue testing.

You want to take one reading with the engine at a cruising speed that the engine isn't giving the issue.

Repeat once more in the same location but with the car giving the issue.

This will tell you what the issue is, if its electrical or fuel.

The above post is a good shout with the mechanical fuel pump leaking fuel to the sump.

Edited by cal844, 05 June 2020 - 11:09 AM.


#22 SuperDeLuxeNick

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Posted 05 June 2020 - 12:04 PM

Thanks for the replies guys.

I should add - the fuel smell and sticky revs have only surfaced since I took the carb off To change the inlet manifold. Ofcourse I was very careful etc and can’t see that I knocked anything

#23 SuperDeLuxeNick

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Posted 05 June 2020 - 01:30 PM

taken carb back off - jet leaking on the flat chamber end, loose, could just pull it out! will order new seal etc and re-do that... I'm sure that wasn't helping but ill have to wait and see if it cures anything.






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