HS6 Float Flooding

[Mark]

Hi all

Gave the Vitesse a run yesterday as a change from the GT6. On the way back I could smell petrol. Almost home, so cut the power and rolled to a stop. Checked, and could see fuel peeing out of the overflow on the rear carb. These are from a Sprint, I purchased them from a member off here or Club Triumph years ago, can't remember. I had bought a rebuild kit in preparation, but when delivered they were in such great overall condition, I just fitted them and they have been running great. Found the SU rebuild kit and everything was in there apart from the needle valves. Took the tops off the float bowls, and it looks like I had previously fitted them. I possibly changed the float tops to give  better routing of the fuel pipes, and could be off of a Spitfire etc. so probably replaced the valves with new at that time. Must start writing things down, owning a few triumphs, it gets confusing.

Anyway, the valve appears to be working. Using the blow test, whilst lifting the float has my cheeks looking like a glass blowers, so can hold that pressure, but maybe it needs more than a puff to fully test, but the method I have always used? 

If its not the valve then maybe the float is catching on the inside of the float bowl but there's a fair gap around the float, and no real noticeable play where the float pivots/swings. 

Whats your thoughts?

[Nick Jones]

What pump are you using?

Also, have you tried it again since dismantling and checks. Experience suggests that debris sufficient to cause problems apparently is so small/elusive that you never find a smoking gun but all works fine again afterwards. Presumably you have filter?

[RedRooster]

As above, check pressure and fit a filter. 

Try and blow back the lines if you can. 

[Mark]

3 hours ago, Nick Jones said:

Presumably you have filter?

No, Good point! Well I have in the glove box, glass type that can be unscrewed and cleaned out. Fitted them inside the boot of a couple of Spitfires and effective. I have the feed from the bottom of the tank on the Vitesse, so it would need to go under the boot floor, being glass I never fitted it and forgot about it. I will buy a plastic version and fit one tomorrow.  Fuel pump is standard. The bowls look clean, I'll remove the valves and clean and blow everything through, refit and give it another go.

Thanks both.

Edited August 7, 2023 by Mark

[PaulAA]

I had this occur with the HS6s on the TR.

At some point, I changed all the fuel lines to R9 and the flooding in one float chamber occured some time later. I found that I must have shaved off an eyelash-sized piece of rubber as I was squeezing the line onto the inlet, and this had lodged itself in the supply valve. I dismantled the chambers several times until a better pair of eyes than mine spotted the tiny sliver of rubber wedged into the valve.

Paul

[Nick Jones]

Yes, exactly this ^^^

[Mark]

Hi all

Finally got around to having a proper look at the carbs. The fuel in the float chamber had looked clear, and a couple of days ago I emptied each float bowl, soaking the fuel up with a clean rag. It started getting dark so I left the car in the lock-up, and went home. Yesterday I went back to investigate, and I'm ashamed to say, after a closer look both float chambers, they are full of crud, trapped in the little sumps either side of the outlet. This is what I get for not fitting a fuel filter! Sure the float flooding was down to this.

At first I couldn't really see anything, It was only when I poked around at the bottom of the float chambers with a scribe I disturbed the sediment, time for new reading glasses.

I am surprised its ran so well for this long with the amount of crap that was in there. Looks like very fine rust particles from the fuel tank. Expected the pump filter to be full but surprisingly little debris inside compared to the carbs. The mesh filter inside the pump is very fine, and the rust particles in the float chamber are as fine as talc. I think the car has done less that 800 miles since its been back on the road.

Anyway, stripped both carbs, and fuel pump, Fuel lines, thoroughly cleaned, blown through and used new jets and gaskets from the rebuild kit I bought several years ago. I bought an inline plastic filter that I am going to fit under the bonnet. Not a lot of space between where the fuel feed enters into the engine compartment, through passenger side front outrigger, and the fuel pump. I always thought it was preferable to have an inline fuel filter horizontal, but it would fit easier in the space vertically, so probably fit it that way, any thoughts?

The Jets in the SU HS6 kit I bought appear to have a smaller diametre hole. These carbs are from a Sprint but I thought all the jets on HS6 carbs where the same size. The needle goes all the way into the jet flush with the bottom of the piston when tested, so the original jet may be enlarged through wear?

 

[DeTRacted]

There are three different sizes of jets for the HS carbs, 0.090",  0.100" and 0.125"  Obviously they need the appropriate needles to suit.  The Dolly Sprint uses 0.100 jets. AUD9106 (front) and AUD9105 (rear). 

The sizes are marked on the jets by rings around the top of the shaft.  No ring= .090, one ring .100 and two rings .125

The 'service kit' for the sprint is listed as CSK63 and the rebuild kit  CRK 253

 

 

 

Edited August 14, 2023 by DeTRacted

[Mark]

Thanks for the info. I didn't know about the rings around the jets, that's useful. Just checked the SU rebuild kit box, and it is CRK 253, so hopefully the correct jets were in the box. I think the original jet appears to have a bigger hole because it has a chamfered edge.

Edited August 14, 2023 by Mark