SU HIF 6

[artrider50]

I fitted a "new old stock" HIF 6 Carburettor, and it set up and run fine, in the 2nd half of a recent PCT it suffered from fuel starvation, on stripping down it was full of solidified fuel gunk from many years ago. I cleaned it all up and freed the bi-metalic strips that control the jet and put it all back together. It now refuses to start, when lifting the slide and blowing down the Float chamber vent, fuel comes up the jet hole. verything is clear there are no blockages anywhere, the only thought I have is the sprung screw that holds the bimetallic strip that controls the jet, does this have to be set in any way and if so how?
Any help gratefully received.

[dogoncrazy]

Re: SU HIF 6

Adjust the mixture screw [the sprung one you mention]to bring the jet level with the bridge in the mouth of the carb[you can see this clearly with either the dashpot removed or looking directly down the carb intake.Now turn the screw two to two and ahalf turns clockwise to lower the jet.If you have put all back correctly the motor should start,and a little fine tuning with this adjustment screw may be required to give a even idle.Goodluck,it really is that simple with SU's

[b_caswell]

Re: SU HIF 6

Not as easy as that. The HIF carb has a cold start unit that provides the enrichment and it has a write way up fitting IE with the notch in both the body and the inner cyl upper most.It may be cable operated or driven by a step motor that uses a management system. Also check the bias needle is mounted correctly with the etching on the needle mount facing inbetween the piston vents. The bi metalic strip only compensates for fuel temperature/viscosity for tight emision control.

[paulhyder]

Re: SU HIF 6

Quite correct Ben,though I thought that by saying 'assuming that all has been assembled correctly'that I 'd qualified my comments.I stand by my statement that the actual setting up of mixture in my experience is a simple one.Nothing wrong with pointing out these often overlooked re-assembly procedures though.

[b_caswell]

Re: SU HIF 6

No fair comment if its not starting from cold I'll have a fiver on it being the cold start device.Best bet is get a copy of the Haynes manual for SU carbs.Still gives you something to do Christmas morning doesnt it.Merry Christmas.

[artrider50]

Re: SU HIF 6

Thanks Guys,
got her running and set up at the top end of the rev range but was virtually stalling in between closed throttle (tickover at approx 800 and even) but the initial throttle opening was causing problems. The only way to overcome this was to set her up and then readjust the "spring screw" in the float chamber until she ran just right.

She does start from cold on the manual choke OK now.

Once again thanks for all your help.

Chris

[b_caswell]

Re: SU HIF 6

It seems I may have lost a fiver!