HIF 38 Carb

Post by **mowogg** » Thu May 07, 2009 9:48 pm

Has anyone found a good way of sealing up the unwanted outlets on a HIF 38 Carb? I have tried a couple of motor factors, but all i can come up with is a piece of hose with a screw in which does not look very good, and is not exactly a good job? Surly you can buy some bungs somewhere?

Post by **bmcecosse** » Thu May 07, 2009 9:49 pm

You muist NOT 'seal up the unwanted outlets' - they all have a purpose! Why on earth do you want to seal them ??

Post by **mowogg** » Thu May 07, 2009 9:56 pm

I think a couple need to be capped -some are breathers which obvioulst need to be taken to the appropiate place, but others are not required? I think i have bought one which used to works as part of a pair

Post by **bmcecosse** » Thu May 07, 2009 10:19 pm

You need fuel IN and an open breather from the float chamber. There will also likely be a port to accept oil fumes from the engine -for burning. That should be all!

Post by **Declan_Burns** » Fri May 08, 2009 7:01 am

I wasn't sure on how to plumb in the HIF 38 either but got a lot of sound advice on this forum. Perhaps the photos below will help. The open breather from the float chamber that BMC has mentioned can be clearly seen on the last two photos, just to the right of that black knob. The little vertical nipple as shown on the third photo goes to the vacuum advance on the dizzy. The fuel inlet is visible on the last photo to the left of the black knob. The jet adjusting screw is just about visible slightly to the left and below the fuel inlet. The brackets for the throttle and choke cables are DIY.
BTW, I tested this arrangement on the weekend, although still with the original head-the difference in performance was quite amazing. There is quite a roar off the K&N replica filter. You can certainly hear the moggy before you see it!

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Post by **bmcecosse** » Fri May 08, 2009 9:44 am

Excellent pictures there Declan! The 'black knob' is the breather from the float bowl - not all HIFs have it like that - some just have a pipe to be led away from harm with a rubber tube. The brass pipe beside the knob (on the right) is the inlet for fume from the rocker cover breather - or any other breather if you don't have one on the rocker! The manifold has a vacuum connection for a servo - obviously this should be blocked if no servo exists. The water connections each side of the manifold are optional - connect them if you want best economy (but it's marginal) but not ultimate best power, otherwise leave them open.
It also appears that your manifold has a vacuum connection for the dizzy (just beside the accelerator cable connection) although I can't see if this is open or closed. If you use the carb connection (with your black pipe already fitted) then the manifold one should be closed. Again most manifolds don't have this - just the normal connection on the carb.

Post by **winger300** » Fri May 08, 2009 10:55 pm

That looks like the HIF38 Carb I am using. It's probably from a Metro.

The rubber hose you have connected is an "Economy device" that makes the mixture more lean at mid throttle.

It was more trouble that it was worth in my case though, so I removed the pipe and blocked off the connections using the little dust caps that come on new brake cylinders, they were a perfect airtight fit.

Post by **bmcecosse** » Fri May 08, 2009 11:01 pm

Ahh yes - the infamous 'economy device' - I've read about it, but not seen one in action. Well spotted winger!!

Post by **Declan_Burns** » Sat May 09, 2009 6:53 pm

I did some experimenting today but have found the jet adjusting screw had to be screwed fully in (AAA needle). I blocked off that "economy device" that Winger mentioned and find that it runs smoother. I think it was still a shade too weak even with the jet screw fully in. This means I have no possibility of setting it richer-just in case I have to when I fit the 940 head. Should I be looking for a richer needle-any suggestions?
The inlet manifold I fitted is slightly different to the one in the photos above. I have the rocker breather going to the air filter-is that correct ?

Post by **bmcecosse** » Sat May 09, 2009 7:41 pm

Rocker breather is best going to that brass fitting on the side of the carb - if it's lying open that will be allowing too much air into the carb at idle. All needles are much the same in the idle zone - so no point changing the needle for that. Check the needle is not too far up inside the piston. Let's see a pic of your inlet manifold. Running mixture is what really counts - so take it for a good blast - switch off and coast to a halt, and whip the plugs out. Tan/beige is just right. White is too weak - but I doubt with AAA it will be weak!

Post by **Declan_Burns** » Sat May 09, 2009 8:09 pm

Thanks BMC, here's the photo. The plugs are tan on the electrodes, I'll see if I can take a close up tomorrow.

Post by **Declan_Burns** » Sat May 09, 2009 8:13 pm

The only port open at present is the one on the third and fourth photos above. Maybe that is why it was running so lean.

Post by **bmcecosse** » Sat May 09, 2009 8:49 pm

Yes- that's where the rocker breather should plug in - but unlikely to make much difference - it will just suck slightly oily air instead of clean air! Tan is correct - so - how does it go ?? Probably more noise - but any better GO? Worth checking you have full throttle when the pedal is to the floor - get someone to press the pedal all the way - then check at the carb if it's fully open. Also best to do the reverse check - when carb is fully open - is the pedal still some way off the floor ? If so - in time you will snap the cable ! So - best to put a stop (rubber pad or even wood) under the pedal to match exactly the full-open position on the carb.

Post by **Declan_Burns** » Mon May 11, 2009 6:35 am

I took it out for most of the afternoon yesterday, made some slight adjustments and is really going well and idles fine. I tried to get a close of of the plug but the camera is not great at the close up range.
Good point Roy with the cable. I noticed that problem when I fitted the carb. I fitted a new cable, pedal to the floor and throttle fully open. On releasing the pedal, it does not come back to the fully up position. I had to set it the other way with pedal fully up and throttle closed. I will make up a bracket with an adjusting screw to restrict the movement as soon as I get a chance. I have a spare cable in the boot just in case.

Post by **bmcecosse** » Mon May 11, 2009 7:32 am

I would say that plug is 'slightly' on the rich side. Probably best setting for performance - but perhaps not the very best economy! The AAU needle may be a better bet at the moment - but since you are planning on changing the head - maybe just wait and see?
I thought there were 'rules' in Germany about modifying engines - is it ok to do as you are doing ?

Post by **Declan_Burns** » Mon May 11, 2009 11:26 am

Thanks Roy,
Yes, officially engine mods have to be certified by the TÜV (MOT) and the log book has to be updated and the insurance informed. I have to go there before the end of the month, but I'll bolt the HS2 carb back on and discuss the modifications with them. If it's too much of a hassle I will leave well enough alone.
BTW, the carb came with an ADS needle bu I never tried it-is that richer or leaner?

Post by **bmcecosse** » Mon May 11, 2009 10:11 pm

It's much much weaker! Try it - out of interest - but I doubt the engine will run well.