New problems guys! I am starting to drive the brat all the time. I just got done with a new fuel tank, new pump, filters, new oil pump. I have new plugs, dist cap and rotor. 83 motor in 85 brat. My problem is this. It runs great when you start it up and go. You can run it forever. You can shut it off and get gas and still acts fine. If you go in a store and are gone for about 15 minutes or more, it will start fine but when you go to leave it runs like crap. It idles fine just when you accelerate with or without load it misses bad. It hesitates and will not build speed. If you push it, it will come out of it about 3500 rpms. As soon as you let off, it does it again. I can get it to quit it if I push it through it and load it say in 3rd or 4th gear up a slight hill. Keep on it and it will just not do it again after you idle back down at the next stop sign or whatever. Let it set, cool off and start again, it acts like normal. It works fine for going to work, 30 minutes there, 10 hour day, start it and go home. It is just when it sets for a while. I have not replaced the plug wires yet but that is all. I had a leaking fuel tank that was rusty but I thought the problem was sediment getting stirred up in the fuel after it sloshed around a bit. New tank and filters eliminated that. I suppose the only other thing is the carburetor. I have a kit but am intimidated by over hauling it. Please suggest what you think. thanks

Sounds more like a carb issue. I am guessing maybe something with the choke since heatsoak is still happening around 15 minutes and the engine doesn't completely cool like sitting for hours.

Mabee carb leaking feul prehsue down or iceing my 77 brat and 80 brat both were haveing a problem with pickup in tank pluging had to blowout the lines into the tank i think there is somkind of sock in there gos bad. Both will drain back into tank when sitting i can here the pump go fast then slowdown when it gets feul takes 30 seconds only after sat more than 2 hours

I would not touch the carb.

Suspect that would be a world of hurt for zero gain.

 

I`ve experienced near identical symptoms on an 84.

It was related to the underhood temperature switch located on a pedestal on the intake near the egr.Heat soak after the store run opens the vacuum switch.

Short term solution was to carry a bottle of water to pour on the switch to cool it down again.Give it a try.Good for diagnosis.

Pretty sure you can plug this vacuum line w/o adverse consequences.

IIRC,real problem was a vacuum leak upstream of the switch.

Edited April 5, 201214 yr by naru
pedestal