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 Posted: Jul 31, 2014 10:39PM
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Quote:
Originally Posted by DyeLooper

I had virtually the same problem, as time went on, it got even worse (900 rpmm at start, 1500 warm, then went to 1800). Turned out to be the choke area of my HIF44. When I pushed in on the choke assembly, the RPM's would drop back down to normal. The choke assembly on my HIF44 still has a slight amount of play in it (in and out) but the rpm's stay steady now. Not sure if that play in the choke shaft is normal though. It was a simple .50 cent o-ring.....

This^^

Whether or not it's got play in it is irrelevant; the choke mechanism is introduced to fuel nearly constantly and the o-ring will swell / shrink / crack and it will then suck in air. No two ways about it. If the carb was a well-used item, older or unknown and then has sat for any length of time in disuse, throw a seal kit at it. You don't need to do the whole jet and seat replacement necessarily, just at least do the choke seal(s).

 

 Posted: Jul 31, 2014 04:31PM
jeg
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Soldier on, keep us posted - well, I'm interested.

You'd really enjoy an afternoon with my car right now... 

It runs fantastic on the motorway, just an absolute bear to get running smooooothly at idle and not overheat at idle or send the A/F meter reading lean at idle whilst the plugs are sooting up at idle.  KC is sending a small water pump pulley to get more water moving at idle, why not, I'll  give it a try...  Tomorrow will be spent finding the needle that I used last year when I took a trip to Århus.  It wasn't perfect, but might be better now that everything's been gone through.

The peasants are revolting...          

"Gone with the Wind" - a brief yet moving vignette concerning lactose intolerance

 Posted: Jul 31, 2014 03:54PM
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US

My engine has a few other issues, so I am not following through as I should.

I did do a rudimentary cleaning and resetting of the float which seems to have changed the idle characteristics.

I also purchased a replacement bimetal jet adjuster and a new float, but I have not installed either.

At this time, the idle may go up to 1075, but settles back down most of the time.

I am also trying to use my air-fuel meter to get the mixture set right, but that has its own issues and is another thread at some point.

Terry

 Posted: Jul 31, 2014 03:28PM
jeg
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Did you ever get this problem sorted?  I'm having a bear of a time right now...

The peasants are revolting...          

"Gone with the Wind" - a brief yet moving vignette concerning lactose intolerance

 Posted: Jul 13, 2014 06:11AM
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GR
Quote:
Originally Posted by CooperTune

Thanks, I'm thinking more study is in order. If these things work can they be made to work for us? I realize as a kid we removed anything to do with polution control. Now I try and make everything work as intended. With everything hooked up and working my car is still plenty fast and may be causing fewer problems than a 747. Steve (CTR)

Steve an email to Burlen fuel systems would clarify things! At least we'll get the manufacturer's opinion on the subject. I'm kinda busy at the moment but if you have any spare time doing it and share any info! i would be thankful! 

 Posted: Jul 13, 2014 06:02AM
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US

Thanks, I'm thinking more study is in order. If these things work can they be made to work for us? I realize as a kid we removed anything to do with polution control. Now I try and make everything work as intended. With everything hooked up and working my car is still plenty fast and may be causing fewer problems than a 747. Steve (CTR)

 Posted: Jul 12, 2014 03:33PM
 Edited:  Jul 12, 2014 03:47PM
jeg
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Terry, Dan and Steve, I sent an E-mail to you -

The peasants are revolting...          

"Gone with the Wind" - a brief yet moving vignette concerning lactose intolerance

 Posted: Jul 12, 2014 12:28PM
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CA
Quote:
Originally Posted by tmsmith

It would nice to know the numbers of the temperature increase.

How much heat is actually transferred to the fuel while it resides in the integrated bowl and how that affects mixture without the bimetallic jet and the the converse of what is the range of changes the bimetallic jet makes.

There must have been a significant change or they never would have gone to the engineering level to add this function.

I haven't got any data, but I do know that as a home "mechanic" (car fixer... no disrespect to pros), my attempts to set the idle mixture were frustrated by the bimetal item's work at leaning it out. At a tuning shop with  a large fan to replicate car movement, it would be different. I don't have either a tuning shop or a big fan, so was frusrated until I eliminated it.

 

.

"Hang on a minute lads....I've got a great idea."

 Posted: Jul 12, 2014 09:15AM
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GR
Quote:
Originally Posted by tmsmith

There must have been a significant change or they never would have gone to the engineering level to add this function.

+1 its there for a reason! at least for daily use street engines!

 Posted: Jul 12, 2014 09:11AM
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US

It would nice to know the numbers of the temperature increase.

How much heat is actually transferred to the fuel while it resides in the integrated bowl and how that affects mixture without the bimetallic jet and the the converse of what is the range of changes the bimetallic jet makes.

There must have been a significant change or they never would have gone to the engineering level to add this function.

 Posted: Jul 12, 2014 08:55AM
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Yeah, saw that. This is triggered by fuel temp. Would that be more about fuel entering rather than carb body temp? What would it do if you ran a cool can? Fuel line running though ice water, what would that do? Steve (CTR)

 Posted: Jul 12, 2014 07:11AM
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Quote:
Originally Posted by dimitris

taken from britannia.org :

 

"The HIF-series carburetor differs from the HF-series primarily in:

  1. The design and location of the float chamber, which has been incorporated in the body of the carburetor, and
  2. The introduction of temperature-sensitive mixture control (a bi-metallic strip fitted to the jet adjusting screw mechanism) to compensate for varying fuel densities resulting from changes in fuel temperature.

Just to clarify that should be HS series.

If in doubt, flat out. Colin Mc Rae MBE 1968-2007.

Give a car more power and it goes faster on the straights,
make a car lighter and it's faster everywhere. Colin Chapman.

 Posted: Jul 12, 2014 06:44AM
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GR

taken from britannia.org :

 

"The HIF-series carburetor differs from the HF-series primarily in:

  1. The design and location of the float chamber, which has been incorporated in the body of the carburetor, and
  2. The introduction of temperature-sensitive mixture control (a bi-metallic strip fitted to the jet adjusting screw mechanism) to compensate for varying fuel densities resulting from changes in fuel temperature.

 Posted: Jul 12, 2014 06:00AM
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US

I have a bunch of HIF44s in service and none have had the bi metal part (other than cleaned) done anything with. I get rid of burp valve clean and kit. What do we know about this part? What does it do and why? If it does what it's intended to does this help or hurt? If it leans the mixture with heat what temp ranges and how much. Most chokes add fast idle air as well as fuel, as the engine warms it speeds up. That's air and fuel this is just fuel. You feel it's a large enough fuel only change to effect idle?

I have a 1360 with a cast LCB from SPI with aftermarket down pipes not wrapped. The ex. does have a metal heat shield in place. The Mini / Metro water ( hooked up ) heated intake manifold with throttle plate and plastic spacer. I have found a needle that works but seems rich at higher speeds. It also runs warmer at higher speeds. I'm running a 90 Cooper carbed air cleaner with snorkle. No holes have been drilled into the housing or snorkle. I wonder if the air cleaner is causing a rich condition at speeds above 75 mph. I hope to be better able to test for all this soon. Never did see if you have a poppet valve in the throttle plate. Steve (CTR)  

 Posted: Jul 12, 2014 04:34AM
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CA
Quote:
Originally Posted by turbodave


Removing the bi-met strip is VERY normal with the turbo minis where the hot manifold and turbo less than 2" away wreaks havoc as soon as there is no airflow through the engine room. Doing it to a nat-asp will be less beneficial, but I'd still do it, especially if I had big-bore stainless LCB, and no heat-sheild.

My car has a 1275cc High compression engine with a HIF6 on an alloy intake and a Cooper Freeflow type header (not stainless). Not much of a heat shield - just the extension of the throttle & choke cable base plate. Setting the idle mixture was a pain because with the bonnet up, the airflow across the carb side did not exist and the carb would warm up as fast as I could adjust. (I'm sure this isn't a problem for turbodave.) So I was chasing a moving target. Making a non-bi-metal lever solved it for me.

I have tuned for 'nice' driving conditions - warmed up engine in mild weather. Choke is necessary to warm the engine in colder weather, which is as it should be. However, I do still experience some variation in idle speed , depending on weather. The 'fast idle' cam of the choke mechanism can be used to modulate this.

.

"Hang on a minute lads....I've got a great idea."

 Posted: Jul 11, 2014 04:13PM
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Honestly, I personally wouldn't bother doing this on a nat-asp mini.

It's been fun, but this place is done. I have no hatred, and appreciate the good times. But this place now belongs to Tony and his pink mini. 

 Posted: Jul 10, 2014 05:10PM
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Image Gallery

I am finally getting back to solving this.

It looks like both of my carbs have the bi-metalic piece.

I am not too sure of may ability to craft a replacement or to remove and replace with shims. I only ever had the trouble with one of them.

Does anyone sell a replacement?

Terry

 Posted: Mar 12, 2014 08:34AM
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Appreciate all the help. I have some work to do on the weekend...

Terry

 Posted: Mar 11, 2014 07:36AM
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Removing the bi-met strip is VERY normal with the turbo minis where the hot manifold and turbo less than 2" away wreaks havoc as soon as there is no airflow through the engine room. Doing it to a nat-asp will be less beneficial, but I'd still do it, especially if I had big-bore stainless LCB, and no heat-sheild.

The poppet valves in the butterfly are simply stupid... Rover V8's struggled with these damn valves for many years - and I have replaced quite a few on those engines alone. I just cut them off, and solder up the holes if I have no solid discs on hand. Symptoms are exactly as you describe - an idle that starts off normal, and after a few miles, the engine is racing at idle

If the butterfly is solid, (remove the dashpot and you can see the butterfly, and the poppet valve if its there) then I'd pull the carb and check the spindle isn't gummed up.

 

It's been fun, but this place is done. I have no hatred, and appreciate the good times. But this place now belongs to Tony and his pink mini. 

 Posted: Mar 11, 2014 06:14AM
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CA

Steve: No you're not way off base.

Yes, idle speed will change with adjustments in timing, throttle idle screw and mixture (and air leakage too). Even a change in or cleaning of the air filter will affect rpm and mixture.  With the mixture it is much more subtle, unless of course it is way off. With your experience and practice, you're probably dialing in the mixture fairly quickly and from a fairly close starting point, so maybe it isn't noticeable to you. Those of us that do it once or twice a year (if that) aren't as quick or as accurate. We probably also aren't using a meter to sniff the exhaust for optimum mixture. (I don't know if you do.) Since we are slower at it we'd suffer the bimetal blues.

For me, who was taught to tune 'by ear', the old way was to lean out the carb until rpms drop, then richen it until rpms improve, counting turns. when the rpms drop off again, stop turning and turn back half-way. (I did say it was the old way!) Then with road testing make minor adjustments for optimum performance. Some SU's have the dashpot lift pin, but not all. It is a better way for tuning SU's.

You mention the choke fast-idle screw, which is on the throttle lever of a HIF and is supposed to just touch the choke cam at the indicating arrow when the choke is applied about 1/4. This is to allow some richening with the choke to help cold engine running without increasing rpms.

I don't know how much the bimetal movement actually is. SU carbs are failrly sensitive. Even on HS types it doesn't take much of a turn to the adjusting nut to modify mixture. I understand that the mixture should be set with the bimetal lever (ie the engine) warmed to normal operating temperature. When it is cool it provide a slightly richer mixture for improved driveability. But as i said, if one isn't quick enough, it gets too warm and tries to make thigns too lean while you are trying to set the mixture. When everything gets back to normal operating temperature, mixture is rich.  All I know is that eliminating it made my life a whole lot easier. I did it on advice of others with the same problem.

.

"Hang on a minute lads....I've got a great idea."

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