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Carburetor Issue

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#16 Benoit_Dupont

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Posted 04 October 2019 - 05:27 PM

ok, so,

 

i'm here to put the final nail on this problem's coffin. Hope this helps someone eventually.  :proud:

 

So in last resort, I had to resign to call the Man, and he came pick-up the car to work on it in his shop because clearly, I could not figure it out. even on the leanest of the leanest, the carb was spilling fuel like the Bellagio fontains if connected to a gravity fuel tank. 

 

So, several thing: I was actually right about the fuel pump: it was scrap.

 

and turned out I did nothing wrong while puting back together the carb. I was very afraid of having messed up this one. even though I did it twice, by the book and all, step by step to make sure I did not screw it up.

 

once he replaced the fuel pump, his diagnosis was the same as mine: could not set it lean enough.

 

so he dismantled the carburator again, looking for issues. and turned out that the faulty part is the lil tube that plunge into the carburator tank to pick-up fuel. It was sligly too large an a bit oval. and of course, because of that, you could lean it as you want, fuel was still getting up the jet.

 

not so fun fact: this part was new, genuine SU part, from the HIF carburator repair kit. my fault was not to suspect a brand new part from being faulty. such a messed up story...

 

So, if you do refurb your carb, check the parts that you get from the vendor. it will save you some money and trouble. Lesson learned, the hard way.  :goaway:


Edited by Benoit_Dupont, 04 October 2019 - 05:27 PM.


#17 postve

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Posted 30 October 2019 - 11:59 AM

Not sure the needle is correct but it might not be far off try;

As a starting point;
The mixture adjusting screw is on the outside of the carb, turn it in clockwise [right] for richer
Remove the dashpot [top] from the carb [3 screws]... don't drop the piston or bend the needle !
You can then see the brass jet in the middle, the needle on the piston dangles in it.
The jet will have a hole in the middle either 0.090” or 0.100” HIF38 or HIF44 respectively
The top of the jet needs adjusting so it sits 0.080” below the bridge
Before refitting the dashpot piston assembly check the number of the needle...
Small screw on side of piston, undo remove needle...number on thicker part at top [very small you may need binoculars.]
Make sure there is the small spring on top of the needle
When refitting the needle the holder should be flush with the bottom of the piston
The needle should move and is spring loaded slightly
That may be enough to get it running but may be miles off, guaranteed to need mixture adjusting and ignition timing setting.
Assuming you can then have it running
If you can get it up to temperature that’s good. You may find it coughs and sputters...and even back through the carb, this usually indicates a weak mixture, so turn the adjuster screw in to the right clockwise maybe a turn or more, this is quite a lot and richens the mixture.
Set to a fast idle 1200 to 1400 revs, and with the engine warm….
Lift the piston in the carb [not too quick]...there is a small lifting pin on the side of some (with a small spring on) if not use your finger under the piston from the filter side and only lift about ¼ of an inch.
If the engine dies the mixture is weak (as above to richen) then adjust idle down
If the engine revs up the mixture is too rich (so turn the adjuster screw out anticlockwise) then you may have to adjust idle up
The aim is when the piston is lifted the revs should rise and then settle back. That means the mixture is somewhere near at fast idle
If the engine has a high lift cam this is more difficult and may well have to be done at higher revs.

This is just a starting point and remember anything you adjust [timing or tappets] or fitting other parts, including exhaust can influence the mixture.

Ultimately you need a rolling road, but a colourtune can help and or a gas analiser...



#18 postve

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Posted 30 October 2019 - 12:15 PM

Sorry for posting incorrectly was looking at this awesome review and clicked the wrong button

Kudos to retro man for a well thought out post

#19 postve

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Posted 30 October 2019 - 12:27 PM

Benoit, can I ask what spring you have in your hif44?

#20 Benoit_Dupont

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Posted 30 October 2019 - 02:22 PM

Benoit, can I ask what spring you have in your hif44?

 

Benoit, can I ask what spring you have in your hif44?

yellow spring. I tried the green one, but it's too harsh



#21 postve

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Posted 30 October 2019 - 03:59 PM

Interesting as I was looking at the red spring - any experience ?





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