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BJ8 Carbs Overflowing

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DavidThorn

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The car is a late BJ8 with HD8 carbs. It's started to overflow fuel through the long plastic overflow pipes, it doesn't do it all the time but has become more regular recently.

It does it from both front and rear carbs at different times. I can clear it by removing the fuel line prior to the carbs and blowing into it (so in the direction of the fuel flow) with an air line. This always clears the overflowing but it returns, usually after the car has been standing for a few days, however it has done it whilst the car is being driven.

There is a new cheap plastic disposable in line filter fitted in the line just before the carbs and this seems clean and is not breaking up.

I was thinking that the float is sticking or sinking or that the needle valve is sticking.

Am I in the right area and if so whilst I have it apart is it best to replace both float and needle valves? If so any recommendations, presumably I have to remove the carbs to do so ?

When I have removed the carbs years ago I found the most difficult part was re fitting all the cables, especially the choke ones and getting them through the holes and then tightening without fraying the cables.

Thanks in anticipation

David Thorn
 
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Re: BJ 8 Carbs overflowing

David - sounds like you need to replace your float needles with their seats. See Joe Curto's website for lots of info and videos.

I found it helpful to notch the cable brackets for ease of install:

ChokeBracketNotched.jpg
 
David,

You don't need to remove the carbs to check the floats and needle valves. You need to disconnect the fuel line from the front float bowl (some fuel in the line will spill), then remove the bolts holding the float bowl lids on (be careful not to lose the little washers and gaskets under the heads of the bolts). You can leave the short fuel line between the two float bowls on. Lift the lids off and see if the floats are sunk and the condition of the needle valves.

I did this multiple times recently to make sure the fuel level was the same in each jet.
 
Agree with John Turney’s post.

Undo the fuel line coming to the carbs, then undo the bolts holding the float bowl caps in place. Remove the two caps and the line between them together.

Remove the floats and make sure they actually float - remove and shake them - do you hear any liquid inside? If yes, replace them. Then replace the two valves with Grosse- style float valves. The viton-tipped ones are good but I’ve has better long-lasting results with the Grosse style ones (Moss and others sell them).

Lastly, check that the small metal fork-like lever arm has the right curvature- it may be part of you issue. The shop manual specifies a clearance value and has a picture of what the curvature should look like. Use a drill bit of the specified diameter to check the clearance.

Your car should run without regularly spilling fuel through the overflow lines.
 
Ok thanks for all above. Just checking as these are HD 8 carbs that I can get to the float chambers without removing the carbs from the car. There just seems to be one bolt on top,there are some inaccessible screws underneath. Do these have to be removed as well? That would seem to mean taking the carbs out,which I would be pleased to avoid
 
No, you don't need to remove the screws on the bottom. Just remove the one bolt off the top of each lid. Then the lids come off and you have access to the needle valves and floats, which is all you need.
 
Brilliant thanks for the clear , quick reply,no need to fiddle with those pesky cables,air filters and bolts,I will be onto it in the next few days
 
There have been QC issues with the newer grose valves. Before you buy grose valves check previous thread here re washing off some kind of manufacturing goop before use.

Beg to differ re viton-tipped vs grose: Joe Curto and Tom Bryant (SU experts) prefer the viton-tipped ones.

Also, when you're removing the banjo bolt, be careful to not lose the fiber washer which resides between the banjo and float chamber lid.
 
Just back from the boozer ( an English term for bar) and am confused by the different types of needle valves . AH spares only seem to list Needle Valves,which I have ordered. Have I done wrong?
 
FUL 206 Needle Valve X 2. I didn't order the float's as I figured if they had leaked or sunk the fuel overflowing would be continuous and it is only intermittent in my case
 
DavidThorn said:
FUL 206 Needle Valve X 2. I didn't order the float's as I figured if they had leaked or sunk the fuel overflowing would be continuous and it is only intermittent in my case
Click to expand...

David - when you replace the needles, I'll be curious if you have the old-style all-brass non-viton needles, which might be causing the irregular overflowing.

For adjustment, make sure only the "tines" of the fork get bent. If the entire fork bends upward from the pivot point, the needle can fall down too far and get hung up at an angle in the jet bore, causing overflowing.
See Joe Curto's video: https://joecurto.com/su-float-bowl-covers

screenshot.1656.jpg
 
John Turney said:
Note that if your float levers look somewhat different than those above, the flat part of the arm must still be flat as shown. Somewhere in HD8 production, they changed the style of float lever and the height (when upside down) of the pin on the lid to match.
Click to expand...

Curto discusses the different float covers with their levers in his video linked above.
 
I had a similar problem with my HS4 carbs. There are two styles of float lids with different floats. The lids were the old type but the PO had tried to use a new style float and bent the metal part in an attempt to make it work. As the angle became incorrect the needles would stick and sometimes cause overflow and at times rough running (fuel starvation in one carb). I first replaced the needle valves but that did not work. When I finally discovered the problem I had to replace the float lids as the old style floats are unavailable.
When ordering carb parts, check Burlen's website before ordering from the usual sources (Burlen is the manufacturer of i.a. SU carbs). I found their prices to be much lower. As an example, the float lids for my car are around ÂŁ30 each from Burlen including a new float and needle whereas Moss Europe charges ÂŁ72,50 just for the lid.
 
Side note: In rebuild kits for other carbs, they are now often including a little spring-like thingy to grab the bottom end of the needle, presumably to prevent the needle from getting stuck inside the valve by forcible pulling it down when the float drops.
 
steveg said:
There have been QC issues with the newer grose valves. Before you buy grose valves check previous thread here re washing off some kind of manufacturing goop before use.

Beg to differ re viton-tipped vs grose: Joe Curto and Tom Bryant (SU experts) prefer the viton-tipped ones.

Also, when you're removing the banjo bolt, be careful to not lose the fiber washer which resides between the banjo and float chamber lid.
Click to expand...





Big NO on the Grose valves. Even the guy at MOSS said don't buy!
 
Too bad about the Grose Jets. I put them on my BJ8 a long time--maybe, 30 years--ago and they've been flawless. Bought them for my BN2 a few years ago and the small ball kept getting stuck in the hole. No, I didn't clean any 'coating' or whatever off either set.
 
Hi All and thanks for your help

I fitted the AH Spares provided needles and valves,they are vitron tipped and all seems to be well with no leaks.

IMG_20190411_152420242.jpg

I checked the measurement with a 7/16th drill bit and it seemed pretty close so I left well alone.


As you can see I removed both tops together with the cross feed,but then realised there was not enough room to refit without separating them.
the worst job was removing the big brass banjo nuts when it was all off the car.

Anyway all went well in the end , lets hope it all stays leak free.

By the way what are Grose jets? I never worked that out.

David Thorn
 
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