L20b Weber dgv issues

[Anonymous Waffle]

Hey people, I got a new issue with a Weber I've installed on my l20b in my 620. The Weber came off of a running l16, it's a dgv 5a, stock jets, and ran just fine at first, but sputtered when I hit above 4000 rpm. Took the carb apart, replaced gaskets, power valve, the accelerator pump (which was torn). Now the new issue is reversed, low rpm (typically 2k-3k) and take off is sluggish and sputtery. But only occurs when I'm on the primary of the Weber. If I add the secondary, it pulls real hard and accelerates great. It can pull hard as long as I have more than half throttle. I checked to see if I had a lean primary, but plugs look pretty decent.

 

Timing is correct, no vacuum leak, new plugs, vacuum advance works, 0 vacuum at idle.

 

Video of me driving around so you can hear the issue.

 

[datzenmike]

Hard to tell in the vid but poor acceleration and then it just takes off????

 

The Weber is progressive, so primary begins to open first and as you get about half way the secondary begins to open. This is simply the way the linkage is set up if you floor it both will open just saying that they don't open together. This is so you can drive it anywhere below half throttle any way you like without it falling on it's face from too much opening. To drive a 32/36 you floor it half way (or below the opening of the secondary) and when the RPMs get up high enough add in the rest. Trial and error to find the best place for this.

 

If it runs poorly at low speed on the primary drive only on the primary and read the plugs. If you floor it into the secondary it will just change the plug reading. Jets can't run richer than they are, well they can if they vibrate loose, but they can run leaner if blocked. I'm expecting the plugs will be light in color indicating a lean condition. If black or dark the jet is loose or too large. If light there may simply be some dirt in it.

 

 

Dead spot at low RPMs is likely the accelerator pump not filling in the lean area just above idle.

[Anonymous Waffle]

Hard to tell in the vid but poor acceleration and then it just takes off????

 

The Weber is progressive, so primary begins to open first and as you get about half way the secondary begins to open. This is simply the way the linkage is set up if you floor it both will open just saying that they don't open together. This is so you can drive it anywhere below half throttle any way you like without it falling on it's face from too much opening. To drive a 32/36 you floor it half way (or below the opening of the secondary) and when the RPMs get up high enough add in the rest. Trial and error to find the best place for this.

 

If it runs poorly at low speed on the primary drive only on the primary and read the plugs. If you floor it into the secondary it will just change the plug reading. Jets can't run richer than they are, well they can if they vibrate loose, but they can run leaner if blocked. I'm expecting the plugs will be light in color indicating a lean condition. If black or dark the jet is loose or too large. If light there may simply be some dirt in it.

 

 

Dead spot at low RPMs is likely the accelerator pump not filling in the lean area just above idle.

Yeah I'm aware of how the weber is progressive and feel how it is supposed to drive. But if I try to drive sensibly and economically, I'll drive below half throttle, and that causes it to fall on its face, and in the video you'll see parts where itll just take off, that occurs when I start transitioning into the secondarys. I have done primary only driving to check the plugs, with minimal idle time, and the plugs are Ash gray and tan, but not charred, black, or pure white. I can go drive and take a few pics of the plugs if it will help. I have cleaned out every jet and every fuel passage, but to no luck.

[racerx]

U said weber came of a running car, is this what the previous owner said or was it yours? Did you check ur primary and secondary jets to make sure they are the right size?

[datzenmike]

Hey people, I got a new issue with a Weber I've installed on my l20b in my 620. The Weber came off of a running l16, it's a dgv 5a, stock jets, and ran just fine at first, but sputtered when I hit above 4000 rpm. Took the carb apart, replaced gaskets, power valve, the accelerator pump (which was torn). Now the new issue is reversed, low rpm (typically 2k-3k) and take off is sluggish and sputtery. But only occurs when I'm on the primary of the Weber. If I add the secondary, it pulls real hard and accelerates great. It can pull hard as long as I have more than half throttle. I checked to see if I had a lean primary, but plugs look pretty decent.

 

 

 

 

 

It would seem the jets were accidentally swapped?

[Anonymous Waffle]

U said weber came of a running car, is this what the previous owner said or was it yours? Did you check ur primary and secondary jets to make sure they are the right size?

It's a guy in my club, he was running the Weber before going to turbocharging. I looked at the Jets, 140/135 for a dgv 32/36.

[Anonymous Waffle]

It would seem the jets were accidentally swapped?

I'm guessing you're implying that the main Jets were swapped? I checked and it should be correct.

[banzai510(hainz)]

If ran fine at first for a while I always look at the distributor.

 

Since its a 5A manual try driving with the choke on. and see if better. then its a jet plugged issue to me.

[kelowg]

Ck Idle jets, they not just for idle on a weber. Or water/debris on fuel bowl? 

[racerx]

Could be diapram, how old is the webe? If jets are okay, something else.

[Anonymous Waffle]

I've fixed the problem just slightly, my air corrector jets were swapped. But the problem is still there. The lean bog typically happens around 2300-3100, into the transition to the secondary, and boys a little at take off. Also I'm 2 screws out on the mixture screw.

 

Can anyone elaborate what controls the secondary transition circuit?

[banzai510(hainz)]

 2ndary is machanical opening so if you open to fast you get the bog. try ousing slower and see if smoothens out

 

 

o