Another Weber carb question.

[baja_rich]

I have a '93 4.3lx with the Weber carb engine serial #od841489. When I got the boat it had cold start issues and I figured out the choke rod was disconnected from the choke stove spring. So I take the carb off and the choke stove and reconnected the choke linkage and reassemble everything. Adjusted choke linkage and test. Worked perfectly. My problem is as follows... Before i did anything it was a hard start cold but once warmed up it ran great. It would jump outta the hole and plane up almost instantly. Now it backfires through the carb if you go to wot too fast and wot is now about 3000 rpms. I did adjust air/fuel settings per the online manual and did replace gasket. I didn't turn the carb over or anything like that. I just lifted it off the intake, raised it high to check the surface for any remaining gasket and set it down upright. Any insight would be appreciated.

 

[jimmbo]

What else did you unhook when taking the carb off?

 

[NHGuy]

Check while it's not running that all the linkages work together and you haven't crossed the choke rod over something that actuates at big throttle openings. It it's misrouted it might not show up til then. You also need to be sure the choke opens to vertical when warm. Otherwise you will have rich fuel.

I just did a write up on Edelbrock's idle mix setup Here http://forums.iboats.com/forum/engin...rburetor-setup.
See if that does it for you.

 

[baja_rich]

What else did you unhook when taking the carb off?

​Just the throttle linkage, fuel line and choke stove linkage. That's what's got me perplexed.

 

[baja_rich]

Check while it's not running that all the linkages work together and you haven't crossed the choke rod over something that actuates at big throttle openings. It it's misrouted it might not show up til then. You also need to be sure the choke opens to vertical when warm. Otherwise you will have rich fuel.

I just did a write up on Edelbrock's idle mix setup Here http://forums.iboats.com/forum/engin...rburetor-setup.
See if that does it for you.

That's the first thing I did after warm up is verify choke was open all the way. I did read the write up, very informative thanks. I've done a ton of searching and reading before i posted the question as to try and cover everything before hand. I do have one question that is kinda odd, the intake is a spread bore design with the thin adaptor plate to square bore. Is that standard?

 

[NHGuy]

Yeah, my 350 Mag has that too.

 

[NHGuy]

Try it again with the choke disconnected.

 

[NHGuy]

Well then since you only worked on the carb, check for air leaks between the carb and base. Did you use new gaskets? On both sides of the carb plate? Could be that. Or are they still good?
You can test it with some carb cleaner. Shoot it at any spots that could leak. Carb base, choke shaft, throttle shaft. Did you make sure to connect the fuel line properly? No cracks, is the pump end snug to it's perch.
It's pretty easy to over tighten the carb fitting too. I hope you backed the carb input fitting with a wrench so as to avoid overtightening the carb fitting.

 

[baja_rich]

Well then since you only worked on the carb, check for air leaks between the carb and base. Did you use new gaskets? On both sides of the carb plate? Could be that. Or are they still good?
You can test it with some carb cleaner. Shoot it at any spots that could leak. Carb base, choke shaft, throttle shaft. Did you make sure to connect the fuel line properly? No cracks, is the pump end snug to it's perch.
It's pretty easy to over tighten the carb fitting too. I hope you backed the carb input fitting with a wrench so as to avoid overtightening the carb fitting.

Will try it with the choke disconnected. Yeah new gaskets top and bottom as they're only 7 a piece, better safe than sorry. It's raining currently so I'll do the leak test when it stops. Definitely made sure not to overtighten the brass fuel line, been there done that lol. thanks for all the suggestions and I'll report back with my findings.

 

[baja_rich]

So I took everything apart just to make sure no old gasket material was left over and all was **** and span. Ran it with choke disengaged and made no difference. Did the carb cleaner leak check and lo and behold idled up when I sprayed around the primary throttle shaft? It revved up. So i grabbed it and there's definitely some play there. Bummer. So I guess it's either rebuild time or an edelbrock swap in my future.

 

[baja_rich]

Well the rain finally broke long enough for me to get back at it. The problem was stressing me out and getting me down so i decided to do other maintenance, change oils etc. I decided what the hay I'll check timing and holy cow it was almost an inch off the timing indicator. 15* retarded would be my guess. Got it set and readjusted idle and base air/fuel. Man o man that did the trick. With any luck I'll be on the water tomorrow. Thanks once again to everyone that had great advice.

 

[NHGuy]

That's great, but still give it a spray by the shaft and if it speeds up there are ways to correct that the next time you have the carburetor off. You can drill the carb body a precise amount oversize and then fill the space with a wrap of delrin around the shaft. It's an old restorer's move.
If the hole is "X" amount oversize you get sheet stock that's half the thickness of the oversize and it fills the gap, which stops the leak. The reason for the half thickness is the gap is half at the top and half at the bottom of the diameter.
If you leave it leaking it will have a reduced performance from the vacuum leak.
If you aren't that into disassembling a carburetor you could take it to a carb guy, or change the whole carb.