msimonov

iTrader: (5)

I rebuilt my carb (stock 85) a couple of weeks ago. The thing runs great outside of idle. Idle, not so good. I am looking for some feedback on the source of my problems. I have searched and read most if not all the carb rebuild and vacuum leak threads.

Here are the symptoms:

* starts right up, first crank - never did that before
* however, I have the idle set over 1100 (it bounces around) to keep it running.
* when I first start it on the choke it is idleing way high (over 2k)
* I noticed that when I push in the choke while still cold it has almost no effect until it is in almost all the way.

I am suspecting I may not have the linkage put back together correctly or having the idle set so high is messing up the ability to adjust idle speed with the choke.

* after it is warm the idle will bounce around between 900 and 1400.
* when not completely warm it will occasionally just die when sitting at idle
* it just stops, but if I pump the gas before the rpms go to zero it will recover

I am suspecting this is due to a vacuum leak. Probably the same vacuum leak that is causing me to have to set the idle high in the first place.

Anyone experience these symptoms before or care to throughout some suspected problems that could cause these symptoms.

Kentetsu

Sterling might have more input, but it sounds like you're on the right track with a vacuum leak...

Jeff20B

iTrader: (13)

I'd say vacuum leak, possibly on just one of the rotors. Sterling recently posted a list of possible vacuum leaks.

Cowboyfun

Check to make sure that you have the carb properly mounted back on the intake. Also, check all your Rats nest connections, be sure you don't have any bad lines, and check to be sure that the plate isn't cracked. Another way to check for the leak itself is start spraying carb cleaner in small areas, if it starts to rev up, then you found the leak.

74RX4

iTrader: (10)

If you still have your anti-afterburn valve installed check the large vacuum line that goes from the #2 aav to the rear of the intake manifold. The hose is directly above the exhaust and the bottom will melt. Check the end that attaches to the manifold carefully.

ray green

iTrader: (14)

Mike didn't mention it, but he also replaced his stock green plastic valves, which I assume are check valves, with smaller after market parts when he rebuilt the carb. The after market valves seem to work OK, they do check the flow one way, but could it be there is something special about those original stock green ones?

One problem he had with the after markets was that the nipple was too small to make a tight seal with the tubing, but he fixed this by adding teflon tape. But that didn't fix his problems.

I checked the half a dozen green "check" valves in my parts shed to see if I had any that "worked" but none of them checked flow like a real check valve should. Most seemed completely blocked and only one would let air pass, but in both directions, not one. It seems weird that all six were bad.

The green plastic cylinders are check valves, right?

Could it be that when Mike replaced his original green stock valves with after market check valves he created his problem?

And does anybody know where you can get OEM replacements for the green valves? That would be one way to rule out this possibility. I'd like to replace the ones on my two GSLs, since if the ones in my shed are any indication, the ones in the cars are probably bad.

msimonov

iTrader: (5)

Thanks for all the feedback.

I spent some time spraying WD40 (didn't have any more carb cleaner) around all the vacuum lines and the base of the carb, but did not find any vacuum leaks. I did use carb cleaner before to isolate other vacuum leaks. I read on the forum that WD40 could be used as well.

I did find the orange electical connection in the vicinity of the secondary diaphram was not connected. Hooked it up, but no apparent effect.

I will check the big vacuum line that runs near the exhaust tonight. I paid particular attention to that one when reassembling due to the melting and cracking issues with this hose. But, it is worth looking at again.

I tried adjusting the idle speed and the idle mixture also. But could not keep it running under 1100 rpms.

The thing starts and runs better than ever. But won't idle under 1100 rpms.

Anyone have experience with the 2 little green and white check valves? I broke the nipples off these when I was doing the carb work. I checked them and they both seem to be simple valves that allow vacuum in only one direction. As Ray mentioned, I bought some after market valves. The nipple on one side of the after market valves is a perfect fit. The nipple on the other side is too small. This did result in a vacuum leak I fixed with teflon tape. Is there anything special about these valves?

rotaryB-2000

does anyone have a sterling since he has gone full speed ahead.