Seized vaccuum piston

Left my bike with a friend, whos an actual mechanic, to get some work done and got it back in even worse shape. Have a had a falling out since lol.

But, as the title suggests, 1 of the 4 vacuum pistons is completly seized. Not sure this is anything he could have done but Ive disassembled all of them on the rack as far as I can, 2 others had trouble moving and i got them going but this one is stuck as shit. And its all the way down, will not go up. I dont want to pry on it with anything heavy duty but im running out of options. Soaked for weeks in penetrating oil - nothing. Soaked in diesel for 3 weeks nothing. No amount of prying or jimmying will get it to budge.

I was thinking of breaking the rack and putting it in a sonic bath but i dont even know if thats going to make a difference. Anyone encounter a scenario like this. Keep in mind, Im not very mechanically minded. And it was running before, although not great.

 

What model and year is it? Your bike can run on 3 cylinders, maybe it was and therefore wasn't running great.

 

83 xj 650 maxim. Sorry forgot to mention that

 

Hi @Chon. Sorry to hear about that $h!t show. Really sucks.

If anybody around here really knows about the carb stuff, it's probably @hogfiddles. Maybe he may have some advice.

I've had one that was seized really good like that - it did not end well. Like you, I tried various fluids and potions to try to break it loose. Heat. Whatever. Nothing worked.

Worst case scenario you'll have to find a replacement carb body. Not great, but you can find one.

 

I would wrap a pair of screwdrivers in tape and use them as levers, one from each end of the carb to try to lift the slide out. Most likelt scenario he's got grit in it - was anything sandblasted? You could also get an assistant to pour boiling water over the carb as you're doing this, but pleas be careful.

 

I like to use a "Q" tip and B12 chem tool with the carb on the back side. The vacuum piston can be stuck in two places. The needle can be stuck in the emulation tube and the sidewalls of the piston can be stuck to the carb. Using the clean and the Q tip, just add a little at a time around the piston and then see if you can move it with a rag around that flat tipped screw drive.

If the needle is stuck in the emulation tube, you will have to break that free from the bowl side. Good luck.

 

Thanks guys. Ill try some of these suggestions out. And yeah, worst comes to worse ill find a replacement, just wanted to avoid that if possible. At this point getting it fixed up is a winter project so I have time

 

Chon, send me a private message and we can talk