Hi, I have an '84 Brat that my daughter drives. She started talking about how the car would accelerate on it's own going about 50 mph in 3rd gear. Your foot is off the gas and it will continue for a little while or a long while.

 

I can't get anything to happen reving the car in the garage. I have checked the linkage on the carb and everything seems to move and return freely. Lubed up the accelerator cable.

 

Could it be possible this is vacuum related at all. Occasionally the car will just die when idling and will not restart unless i remove the air cleaner top. It is starved for air but not always.

 

This one has me baffled. I have searched the threads on this forum but can't come up with anything that matches what I am seeing here.

 

Any input would be appreciated.

 

thanks,

Darrell

I think you have a problem with the vacuum secondary on the carb. I had a similar problem in my Brat when I drove it home from Idaho, I was cruzin about 60mph on the highway for about a half hour, and I let off the gas for some reason, but the car didnt slow down I finally got to a rest stop with a parkinglot and lights, and it turned out the rubber diaphram in the vacuum pot for the secondary has sealed itself up, so it just stuck open. I poked a hole in the diaphram with my knife, and it was fine from then on, no more problems at all.

 

-Bill

You are the man if you did that in a dark parking lot at night, wow. I tried a few things with no luck of un-sticking the mechanism.

 

Then, I unhooked the diaphram and that seems to have elininated the sticking. Now acceleration suffers.

 

Did your acceleration drop by putting a hole in the diaphram?

 

Thanks,

D

In the past I have eliminated that Diaphram and modified the carburator to have a manual secondary. The linkages exist, and if done right you can force the 2nd barrel to open when throttle passes 3/4 stroke.

 

Here is a write-up I did to document the work.

http://www.subaru4wd.net/old/New/mods/carb.html

 

The only downfall is a slight hesitation when the 2nd barrel opens. This is due to the unprimed secondary.

You are the man if you did that in a dark parking lot at night, wow. I tried a few things with no luck of un-sticking the mechanism.

 

Then, I unhooked the diaphram and that seems to have elininated the sticking. Now acceleration suffers.

 

Did your acceleration drop by putting a hole in the diaphram?

 

Thanks,

D

 

I didnt suffer any negative effects from poking the hole, it accelerated like it was supposed to, and drove fine, no adverse effects at all. Later on I had a problem with it not idling, but that turned out to be the screws that hold the carb body together had come loose from a rough off-road venture and had nothing to do with the vacuum diaphram.

 

-Bill

Thanks for the info guys. I think I will try the hole in the diaphram first(always thought that was a bad thing:lol:). If that doesn't cure it I will go for the mod.

 

I appreciate the advice.

 

Thanks,

D

Bill can i ask u to clarify something? You poked a hole on the edge of the diaphragm right where the hole is supposed to be coming from the carb body correct? The first time i read this i thought you just poked a hole in the diaphragm to disable it.

If you disable the diaphram (ie. poking a hole in it) then your secondary will never open and you now have a 1BBL hitachi.

If you disable the diaphram (ie. poking a hole in it) then your secondary will never open and you now have a 1BBL hitachi.

 

Idk what I did by poking the hole, but it made it work. I know for a fact the secondary worked like it was supposed to, so Im guessing the hole I poked made up for a clogged bypass somewhere. At any rate, for being a quick and dirty fix at a rest stop at night in the cold, it worked up until the day I swapped it for a Weber

 

-Bill

In the past I have eliminated that Diaphram and modified the carburator to have a manual secondary. The linkages exist, and if done right you can force the 2nd barrel to open when throttle passes 3/4 stroke.

 

Here is a write-up I did to document the work.

http://www.subaru4wd.net/old/New/mods/carb.html

 

The only downfall is a slight hesitation when the 2nd barrel opens. This is due to the unprimed secondary.

 

thanks! I had forgotten about this.... the same thing just happened with my '86 Brat, but it's now in storage for the winter, so this will be a spring mod for me....

Is there any other ways to make the linkage open up the 2nd carb? I cant seem to get any wire in there to make it open. The diaphram on mine is broken. Maybe Its easier with the carb off the engine?

I used a piece of coat hanger when I did my mod.

 

I have a friend who welded his linkages together. However, it takes precision skill & accuracy

I poked the hole in the diaphragm. First blush is that it is running much better. Runs smoother when you rev up and did not experience the acceleration but that is more intermittent.

 

I will drive it a few days and see how this goes. Thanks again for the tips.

 

D

OK, runs better but the secondary still sticks at higher RPM and speed until you romp on the brakes. So weird. I will probably run the mod this weekend to tie the primary and secondary together.

 

Sounds like the Weber carb might be a better long term option. Where is a good place to source a Weber carb for my 84 Brat?

 

D