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Tony's [RATCO] High Idle

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martx-5

martx-5

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I know Paul has been interested in what's going with Tony's high idle problem since he went over to the Triple SU's on his TR250. He had Weber DGVs on there and always had all kinds of issues. I sorta talked Tony into the Trips, and he says the car has never run as good as it's running now. Well, except for that high idle problem. He has down work on the engine. Compression increase, a crazy cam (310 deg duration maybe), header etc. His tach in the car is out of whack, but that's another issue that I think I have answer to.

Anyway, we looked at the car today, and used an electronic tach attached to the coil for RPM readings. After the engine was warmed up, the tach readings were in the 1400-1500 range. Definitely too high. I printed out the info you guys said might be causing the problem and we went through the list. Surprisingly, the linkage between the carbs didn't appear to be causing any problems, however, I did notice that his carbs seemed to be way lean. He confirmed that, as he said he did lean them out. The carbs he has on there are the SU HIF type, which have a seperate enrichment screw on the side. I enrichened the carbs by just using the "lift the piston" method, and the idle dropped to between 1000-1100 rpm. He said he could live with that, but I thought that there still has to be a problem.

And what I did discover, is that one of his carbs (the front one) you could not really close the throttle all the way. I could adjust the screw, but at one point, it would just start to leave a gap between the adjustment screw and the carb body. If I physically pushed down on the screw, the throttle would close down more and the idle would drop. I think at this point, that the relationsip between the throttle shaft and the butterfly is a little out of whack, and not allowing the throttle plate (butterfly) to completly close down, or at least enough to lower the idle below 1000 rpm.

We ran out of time, but what I suggessted we do is take the carb off and see why that front carb is having a problem closing the throttle plate.

Anyone have any other ideas?? Especially these being HIF's. I'm not as familar with them as the H's & HS's.
 
Is he choking 2 of the 3 carbs for starting purposes? I moved the chokes from #1 and #2 to #2 and #3 and moved my RATCO cable linkage to between 1 and 2. I then soldered stops on my choke cables to make sure I was completely turning my chokes off after warmup. Both chokes were never completely disengaging, now they are. I idle right at 1100 with 3 ZS carbs.
 
Tony's choking #1 & #3 carbs. The choke linkage and cables etc. did not appear to be causing an issue, remember, he has the SU HIF carbs and they choke differently. He is also running the RATCO cable between #1 & #2 carbs.
 
I share your thoughts on the linkage. It may have happened during the synchronization. It's possible to rotate the throttle shaft of one carb while tightening the interconnecting link. I've done it.

Best way to check would be to loosen the linkage between it and the adjacent carb(s) and see if adjusting the idle stop lets the throttle disc close like the others.
When you retighten the interconnecting link, put a little pressure in the closed direction on the tighened side linkage while you tighten the loose side.
 
OK, so far so good, but if PB's suggestion doesn't completely work, just loosen that carb slightly and twist it a bit. The bind may go away either from linkage alignment or throttle plate to manifold/gasket bore fit.

If that doesn't work, then take it off.
 
I had a set of Strombergs that I could never get to run properly. I eventually found that the butterfly had at one time been forced shut while out of adjustment, forming a bur on the carb body, not allowing the it to fully close.
 
Do the SU's have a vent lever like the ZS's? This vent allows the float bowls to breath when under throttle,and the lever (with valve) closes the vent, at idle. If this lever valve sticks at all, air is allowed into the system and the idle will go up. Hardly noticalbe to the eye, but it made my car run at about 1100. Spraying cleaner in the vent hole and working the lever freed it up and the problem is now gone. Just a thought, however, may not apply to SU's.
 
You're right about the trouble that vent can cause if it sticks, Crisis.
It's not always the first thing that comes to mind when things go downhill.
The SU's don't have that kind of set up and neither would the ZS carbs, were it not for adding the Anti Run-on Valve.
At idle, the lever closes the main float chamber vent and opens the port (brass nipple) to the Carbon Canister to receive the vacuum from the anti run-on valve/ intake manifold.
I'd start by loosening the interconnecting linkage and make sure all things are equal there.
 
Are all the spring clamps set with the all the carb's butterflies closed. Just thought that it would be the simplest place to start
 
poolboy said:
and neither would the ZS carbs, were it not for adding the Anti Run-on Valve.
Click to expand...
I disagree. The vent valve allows fuel that evaporates from the bowl with the engine not running to be directed into the carbon canister; but keeps the partial vacuum in the canister from affecting mixture under cruise conditions.

It can also be found on some engines that did not have the anti-runon solenoid, like my 71 Stag.
 
Could be, Randall.
But you know, the 69 thru 72 models didn't have an ARV or the float chamber vented to the Carbon Canister. I believe the vent to the Carbon Canister/ ARV started with the 73 carbs.
Before that, wasn't there just one vent for the float chamber, that being the one thru the air box mounting flange ?
 
Triple carb alignment is tricky. The couplers can even become an issue if they are too stiff.

This will take some tweaking, but nothing that all of us with tri carbs hasn't done.
 
Touch wood - never had a problem with my tripples.

One thing to check if you have high idle problems is the butterfly. You need to make sure it is aligned properly so that it makes a tight seal to the carb throat when closed. Easy enough to do - just loosen the two screws that hold the round butterfly to the shaft and with the idle screw all the way out, make sure the butterfly sits tightly in the throat. Then tighten the two screws again. Easier done if the carb is off the car, but you might get away with it in-situ.
 
Jeff Palya is sending me a new set of carb couplers.
Thanks for the headsup, Paul.

Now I should order a half dozen new, red rotors from
Advanced Distributors and one of J.M. Wagners valve
cover gaskets.

dale
 
Think we've got the reason behind the high cost. So many multiple parts in the trunk....(And other places).
 
RonMacPherson said:
Think we've got the reason behind the high cost. So many multiple parts in the trunk....(And other places).
Click to expand...

<span style="color: #990000">There is actually logic behind my spares.

If a part breaks down, I have now identified a weak component
in the car. I know from past experience, the quality of the
replacement parts is just one grade above scrap metal.

Therefore I order two replacement parts since one will be
defective. I then order the third replacement part as backup
for when the replacement part breaks down again.

And yes, in one attempt at driving 40 miles, I had two
mechanical fuel pump failures. Real glad I had 2 spares in
the trunk.

I think every car varies across the board. My car is one
of those unreliable cars that breaks down often. Other
folks can drive for years and not break down.

later gator,

dale</span>
 
You need to change the tense of breaks down.

Should now be reading WAS, not IS....
 
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