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why is my mgb reving so high?

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Straight4 Avatar
Straight4 Michael V
Bakersfeild, CA, USA   USA
I finally got my car running it has a weber downdraft carb and its idling on choke at like 3500 rpm. maybe even more.

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GMB3 Avatar
GMB3 Silver Member George Badger
Soquel, CA, USA   USA
1965 Jaguar E-Type Coupe "1QUICK E"
1968 MG MGB "1QUICK B"
Vacuum leak.
Idle set incorrectly.
Throttle linkage/cable incorrectly installed.
Faulty carb install.



---
GEO

lewk Avatar
lewk Silver Member Keith Lewis
Cambridge, ON, Canada   CAN
What does it idle at with the choke in?

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Straight4 Avatar
Straight4 Michael V
Bakersfeild, CA, USA   USA
3500 about there

DrewM Avatar
DrewM Silver Member Drew Maddock
74 MGB roadster, Southern California, USA   USA
I've had that happen. One time the throttle linkage had gotten hung up because a return spring had broken, so the linkage wasn't being pulled back down when I lifted off the gas pedal. I stared at it for a long time and saw nothing wrong. Then I got a bright light and went over every little thing until I noticed one of the throttle return spring that wraps around the throttle shafe had broken its "tang" so it wasn't held being in place. It just sat there loose. You could turn it around loosely. But since the spring remained where it was, you saw the spring there, so the failure wasn't obvious. I had to play with it awhile before I realized what had broken. This is on SU's, though, and that's a pretty easy fix with new springs. But the same principle applies to any carb -- something could be misadjusted or broken and you'd never notice it if you weren't careful.

I screwed up the idle adjustment on the carbs a few times. Easy to adjust the idle down.

A vacuum leak will do the same thing. Search for a cracked or loose hose. With the engine running, you can spray carb cleaner at every hose and hose junction. When the engine revs up or stalls as it sucks in carb cleaner, that could be the leak.

If you've been working on your engine, rebuilt your carb, or reinstalled the carb, it's more than likely one of those steps wasn't done quite right, you have a misadjustment, or something is loose, or you've got a leak somewhere. Go back over everything, and take your time.



Drew Maddock, So. Calif. USofA

lewk Avatar
lewk Silver Member Keith Lewis
Cambridge, ON, Canada   CAN
Here is the best advice I can give you considering the questions you've been asking. Go to the "Library" at the top of the page ad and click on "Tech Library", you will find answers to just about everything you're having problems with. In this particular case go to "Carburetors and Fuel" there is a whole bunch of articles and advice for your Weber DGV.

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