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Finally Got the B to Run, But....

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Mickey Richaud

Mickey Richaud

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Those who have followed my ramblings know the trouble I had with getting the carbs (HIF4's) to cooperate. Finally got the B to start and run, but it will only do so with the choke activated. As it warms up, I try to let the choke off slowly, only to have it stall. Mixture is set at two turns down from the bridge, and all linkage is free and even. All settings are correct, and double-checked, including static timing. It will always start up easily and run fairly well, but won't do so without the choke. I know it's something simple, but it has me stumped. Any ideas out there?

Mickey
 
Try going a fraction of a turn richer (clockwise) evenly on both carbs a little at a time and see if it improves. My HIF's will start instantly and run without any chokeing. It is sensitive so it wont take much, just at touch. I found that if I spent a lot of time trying to get them adjusted they would end up too lean so , once set, that is the method I use. They can get too hot over extended time adjusting and the thermal mixture control compensates too much.
Bob
 
Bob -

Thanks - will give it a try.

Mickey
 
My HIF4s are also really sensitive. 2-turns is just a starting point anyway.
 
Tried Bob's idea - still no luck. I've pulled the carbs off one more time (gave up counting!), and am checking them out again. If anyone has any suggestions while the carbs are off, let me know.

Mickey
 
When you say the choke is "on" do you mean you have it pulled all the way out, or just a little bit? The first part of the choke control only speeds the idle up - then it activates enricheners on the carbs - nothing more.

If you let the choke cable in slowly does the engine just die suddenly when you get to about half choke, or does it slowly die once you let it in all the way?

If it dies about halfway then I'd think you need to concentrate on the mixture - turn both mixture controls in a little and try again (ie: lower the jets). If it runs ok until you get the choke control all the way off then slowly dies then you need to work on the throttle adjustment to get the idle speed up (and balance the two carbs).

It isn't inconceivable that you won't get this right through adjustment, it's possible you have a set of needles that just aren't "rich" enough for your setup.
 
It's definitely all the way out. Then as soon as I start letting off, it begins to stall. Don't think it's a throttle issue - really seems like mixture.

I thought about the needles. May try the old ones (if I can find them!) to see if they work.

Thanks for the idea.

Mickey
 
Found the old needles - they appear to be the same as the new ones (ABD) although it's pretty hard to distinguish if the old ones are ABD or ABO. Can't seem to find a list of needles - are these good markings? The old needles look to be in good shape - no visible wear, though their points aren't quite as defined as the new ones.

Also, never noticed the crimp on the collar before. Guess that's to "preload" the needle slightly off center? Then the spring helps center it?

I'm getting quite an education here! (I'd better - sure paid enough for it!)
 
You should also make sure the needles are set in the pistons properly and aren't sitting outside the body of the piston itself (ie: making the "reach" of the needle longer than normal).

Sounds like it needs to be richened up - keep moving the mixture in (rich) and see if it makes a difference.

You also might have air getting into the system - just a thought...but from what you describe it sounds like the carbs are lean.
 
Aerog -

The needles have been set where the shoulder of the collar is flush with the recessed surface of the bridge, per specs, and the collar is oriented correctely (slot in the collar inline with the slot in the piston). Not sure what you mean by "outside the body of the piston." But I'm fairly certain they've been installed correctly, at least they look like the shop manual and Lindsay Porter's book.

I've turned the mixture screw in as much as two full turns, little by little - no difference.

I wondered about sucking air, but can't see where it would be. I've got a new gasket for the manifolds, and the header flange is flush with the intake manifold surface. It's a Peco, and when I first looked at it, it seemed a bit off, but it's right there. Specs call for 15 lbs. torque on the brass nuts (doesn't sound like enough, but they are brass), and I've got new cone shaped washers on them. By the way, how should these washers be oriented - with the cone facing the flange or the nut? I had them facing the nut - maybe this is my problem?
 
Not sure about the washers to be honest, I would have guessed the way you describe them as being correct.

If you're using older carbs that were just cleaned up, etc, you might have worn bushings in them that allows air to enter through the carb body. I shouldn't think that would cause as much of a problem as you're describing.

You have the needles set correctly -- but, I had to cheat quite awhile ago and set my needles so they were recessed into the pistons slightly rather than flush. That gave me a little more mixture adjustment on the rich-side. When I switched to different air filters and changed a few other things I reset them flush. That wasn't exactly "correct" but it did the trick for me at the time.

You might also pull the pistons out and turn the mixture adjustment all the way rich and lean, and back again - watch the jet and make sure it moves smoothly and freely in the carb. I seem to recall that if it hangs up on the "lean" side (ie: "up") the adjustment screw doesn't do anything to pull the jet down, they just relieve pressure on the temperature-sensitive device and springs so the carb can go more "rich". Jets sticking "up" at all will cause them to run lean.
 
Thanks - I'll try the trick about recessing the needles tomorrow.

The jets are free - I checked that first. When I turn the mixture adjusting screw, they move all the way up just above being flush with the bridge, and then down quite a bit.

As for the throttle shafts, they seem tight. I didn't rebush them, but they move nicely with no slop.

The only thing I'm not sure of is how the choke works. I know about the earlier SU's - how changing the height of the jet by turning the adjusting nut affects the mixture and the choke. But I haven't quite grasped the operation of the "starter valve" in the HIF's. That seems to be a key element of the problem. As long as the choke is activated, rotating the valve, it will run. Without doing that, it won't. The carbs are out again, and I took the starter valves apart once more, and everything is clean and clear, and it all looks right. Passages are all clear also.
 
[ QUOTE ]

I wondered about sucking air, but can't see where it would be. I've got a new gasket for the manifolds, and the header flange is flush with the intake manifold surface. It's a Peco, and when I first looked at it, it seemed a bit off, but it's right there. Specs call for 15 lbs. torque on the brass nuts (doesn't sound like enough, but they are brass), and I've got new cone shaped washers on them. By the way, how should these washers be oriented - with the cone facing the flange or the nut? I had them facing the nut - maybe this is my problem?

[/ QUOTE ]
I think that the washers should be positioned with the narrow part of the cone toward the flanges. This would help compensate for any minor differences in flange thickness.
D
 
Thanks, Dave. I thought I'd give that a try tomorrow, too. Couldn't hurt!

Mickey
 
[ QUOTE ]
You also might have air getting into the system - just a thought...but from what you describe it sounds like the carbs are lean.

[/ QUOTE ]

YEEEHAAAAAWWWW!!! Finally got it!

Here's what it was: I mentioned that I had a Peco header and said that it looked like the flange was OK. I pulled both manifolds off (luckily I had an extra fresh gasket), and measured the flanges with a caliper. The header flange was about .002" thicker than the intake, due to the spot welds on the washers the factory put on them. (Wonder why they don't just use the proper thickness to start with?) I filed them down, reinstalled everything, and along with richening the mixture (again), that took care of it. Amazing what a difference .002" can make, isn't it?

I said earlier that it was probably something simple - just never thought to look there!

Now it's on to final tuning and then redoing the brakes. Should be able to test it out and terrorize the neighborhood before too long!

Oh, and the washers were on correctly. (At least, it's working the way I put them on!)

Thanks again for the help, everyone.

Mickey
 
OK - Now that I've finally got the beast to idle, I can't get it to idle lower than approx. 1500 rpm (don't have the tach hooked up, so I'm not sure). The throttle adjustments screws and the choke screws are completely loosened, linkage is not binding, and still it races.

I noticed on a website the mention of the valves on the butterfly disks, and how if the springs are weak, they will leak, causing a fast idle and lean running condition. Before I solder these things shut, any thoughts from anyone? Could have been contributing to my problem in the first place, don't you think?

Mickey
 
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