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Tips
Tips

SU carbs on BJ7

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Are the jets properly fitted in the float bowl body? If not the needles cannot create a good seal because they will not land flush in the opening. On my Courier (HD6 carbs) I had to take a bit off the length of the jets to get everything sealing up nicely and maintain the right fuel level in the bottom of the carb.

A properly fitted and matched jet and needle and a non-leaky float should close against 2-4 psi. Again on the Courier I use a Holly blue fuel pump and take the fuel pressure down via a regulator mounted just before the carbs to 4.5 psi with no problems.
 
I acquired a set of "M" carbs with my basket case BN1 that had been rebuilt by Joe Curto over 10 years ago and never installed. I called Joe to see what he recommended I re-do before using them. He said that in the past he used Grose Jets and I should check. If they had Grose Jets, he said throw them away and replace with Viton tipped needles. Our local LBC Guru won't use Grose Jets unless the owner insists. Then, he leak checks them and rejects a significant percentage.

Marv J
 
I put Grose jets in my BJ8's HD8s a long time--maybe 20 years and 80K miles--ago and have never had a problem with them. Has the company changed hands or had quality issues?
 
:savewave:
Me too in both of my BJ8's they do not know what a needle valve is.---Keoke--- :laugh:
 
Bob_Spidell said:
I put Grose jets in my BJ8's HD8s a long time--maybe 20 years and 80K miles--ago and have never had a problem with them. Has the company changed hands or had quality issues?
Click to expand...
I think there's been a company change or quality control issue. The first Grose jets I had worked and then the following didn't so I went back to original ones. Also, the Grose jets are subject to leaking fuel past the "mechanical" seals when the engine is running due to engine vibration.
Patrick
 
Keoke

I'm having problems with my floats on my HS6 carbs, maybe it's because ther old and worn but how ever i set them i am struggling to get the same amount of fuel in each.
I have repalce the needle and seat kit and tried some replacement floats from AH spares but these don't seem right, looked at Burlens website https://www.sucarb.co.uk/ProductDetail.aspx?Id=33997
and saw these stay up floats which actually look like the originals, thought i would get these and try unless you have any other options i can try.

Rob
 
Chicken--

Be concerned with the fuel level at the bottom of the carb, not how it appears in the float bowls when you lift the lids off.

Those look like nice items and I have always wondered when someone was going to bring out a float filled with closed cell foam.

The arms on HS carb floats such as I have on my Elva Courier are a bit more difficult to adjust than the brass "forks" on the H carbs such as on my 100 and it is easy to bend them too much or too little with the fuel level changing commensurately. The hinge pins in the float lever arms need to be oriented in a forward-aft direction. Sometimes people switch them around so they are "athwartship" and this will not work. Make sure your float bowls are as level as possible and please let us know how the new floats work.
 
chicken said:
Keoke

I'm having problems with my floats on my HS6 carbs,
Click to expand...

Rob

The HS6 carbs have a strange connection from the the jet back into the float bowl. The fuel line at the bowl end relies upon a metal insert, a rubber washer a plain washer and a threaded 'nut' through which the fuel line passes. It all acts as a stuffing gland, keeping the fuel line connected to the bowl and providing a seal. If the rubber washer is damaged it can close down on the fuel line blocking the bore and then you will get problems. It is worth getting them onto the bench and checking everything.

On another note - the stay up floats sound interesting. The metal fork broke on one of my floats two years ago and I called into Burlen to get a replacement. They did not make them any more and I had to buy new new tops complete with the new float design. If this float has forks I can use the old tops again, I will give them a call.


Bob
 
How, exactly, did you take a little bit off the length of the jet? Looking at mine again, the float arm hits both the Grose-jets, and replacement needle valves at a considerable angle, so I'm thinking shortening the base of the Grose-jets by .025" or so might allow the float arm to land closer to a 90 degree angle.
 
Kent--

Remove/unscrew the jet from the lid and grind or mill off "a little bit", then reinstall. The decreased length will lessen the angle at which the arm makes the needle close the aperture.
 
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