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Unread 12-12-2010, 12:32 PM   #1
cj-ing-rj
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1974 CJ5 
 
Join Date: Oct 2010
Location: Cedar rapids, Iowa
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74 CJ5 carburetor replacement I258

I know there are a lot of topics on this but I'm a bit confused. Some say keep it others say replace. I've got a carter YF 643lS on my 74 CJ5 It seems to run alright in warm weather but now that it's cold as H*#l here in Iowa (-9 tonight) it will start the first time then not again till it's completely cooled down again. Also it runs like crap while driving it in cold weather. So I guess what I'm wondering is what to do. It's been rebuilt (2 years ago). Do I replace with something oh 37 years newer or try to rebuild/tweak it???? Any ideas or suggestions are appreciated in advance.


On a side note i also have a YF7001S sitting in the garage off a donor 73.


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Unread 12-12-2010, 01:13 PM   #2
RoscoeJ
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1986 CJ7 
 
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I have a new weber on my 258 . I have no problems. It works great,and I would recommend the Weber.
How is your choke working? How is the fuel filter? It may just need a cleaning,or I have seen ethanol gas causing lots of problems in carbs.You could try some High octane fuel and see if this helps your problem, if it does help, you may have to richen your carb to run regular 87 octane gas.

I also did away with the fuel pump and am running an electric fuel pump !
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Unread 12-12-2010, 02:28 PM   #3
cj-ing-rj
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Well it's an auto choke soooooo????? I guess IDK. Living here in Iowa it's getting a bit harder not to put ethanol in the tank so maybe I'll try on the next tank to put the 91 in her. What Weber carb did you put on there RoscoeJ????
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Unread 12-12-2010, 02:28 PM   #4
baldfatdad
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You just need to rebuild it. Kits are around $20 a can of laquer thinner to soak the metal parts in. Not the plastic. What air cleaner do you have and is the hose that goes down to the exhaust manifold in good shape. That hose picks up warm air to keep the carb from iceing up in the winter. Yes it will get ice in it. Look down the inside of the carb when it acts up, when its cold outside and you might see the ice.
You can't put a weber, 2100 or BBD on your jeep without a new manifold or adapter, cause you have a one barrel and and the weber is a two barrel.
You don't need 91 octane either. No normally asperated vehicle with a compression ratio less than 11 to one needs anything more than 87 octane.
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Unread 12-13-2010, 02:47 AM   #5
John Strenk
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Well they do make a 1bbl to 2 bbl adapter for the Weber but the YF has been good to me so far. I would try to rebuild it. Not to knock Webers but many people praise the Weber fixed all their problems when really it's just the case of putting a NEW and CLEAN carb on the engine as opposed to running an old dirty worn out carb. Probably any New, Clean Carb would work great on there.

Check the throttle bushings. they do wear out and become oblong. Causes a mean vacuum leak.

I would check the Choke also. Maybe it's not opening up properly in the cold weather. If it stays shut all the time because the heat is not getting to the choke housing it will be running to rich all the time. I could be getting carboned up inside the choke housing also. Maybe blocking the flow of hot air to the choke housing.

I have a manual choke on mine and if I leave it fully closed for more that 20 seconds after starting. the jeep runs very rough and has no power. A good reminder to open it up earlier.
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Unread 12-13-2010, 08:41 AM   #6
RoscoeJ
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I have electric choke version of these carbs...
Weber - Auto Parts Warehouse
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Unread 02-25-2011, 12:53 PM   #7
cjarmyjeeper
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cj-ing-rj, not sure what you decided to go with.

I had a similar situation. YF on my 78 was horrible, leaking fuel. I looked long and hard at all the options. After hours of discussion, I ended up talking to the owner of a jeep shop here. He swore by the 350cfm Holley 2bbl. Said he'd been putting them on jeeps since the late 80s. I got a chance to see 2 of the jeeps he put them on (ride along and talks with their owners.) Their owners loved them. One of the guys replaced a Weber with the Holley.

Long story short. I bought a 2bbl intake off ebay, got the Holley and took it to the shop to get set up.

I love it. Runs like a scalded dog. Idle's in the right RPM range and since I got it done (2 months ago) the jeep has fired up first time every time. I've got a manual choke, but I've yet to use it even on the cool 30 degree mornings.

Cost a little more than a rebuild but I've got piece of mind. I got tired of playing games with tuning the YF.
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Unread 04-13-2013, 05:09 PM   #8
trevord
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1974 CJ5 Vacuum Routing Pictures

Hi,

Could you zoom out on the picture of the carburetor vacuum lines? I bought a mangled Cj5 with a 258 and want to know where the lines go.

Where does the hard line on the choke come from? Bellow the carburetor the vacuum line below on the left. Does that go to the distributor.

There are two vacuum line ports on the bottom of my carburetor? Where do they go to?

Trevor
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Unread 04-13-2013, 05:18 PM   #9
trevord
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The pictures are attached.
carburator.jpg   carburator2.jpg  
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Unread 04-13-2013, 05:20 PM   #10
trevord
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Sorry. This is picture #2
carburator2.jpg  
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Unread 04-13-2013, 07:39 PM   #11
cj-ing-rj
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Sorry don't have any more pictures. That Carb is long gone and I have gone with a Weber 38/38.
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