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Crud in Carb question...

tarafied1

tarafied1

Well-Known Member
Got home from travelling for work and the Bobcat was having some issues. My son said the vacuum line for the trans popped off twice on his way home from school and was running poorly. It was a tight connection but he put a clamp on it and it blew off a cap on a non used vacuum line. I had him pull the plugs, they looked like it was running lean. I think he was getting a lean backfire into the intake. I had him replace the coil. it looked original and I thought maybe he had a weak spark. It ran better but about half way to school today it started missing. I went to trade cars with him so he could go on to school and drive it home. I pulled the plugs again and it melted one electrode to the tip. I still think that is a lean condition causing cylinder temps to be pretty high. It's not back firing anymore though. I put an old plug in it and it ran fine again so I took it for a drive and it was spark knocking under light load. Played with the timing but couldn't get it to go away. It was running rough too. So I figured something was up with the carb. It's a brand new Holley 600 vacuum secondary. It shouldn't run lean! I pulled the float bowl and found some sediment looking crud. Pulled the metering plate also and cleaned it all out. It has 65 jets and 6.5 power valve. I get 10 to 15 inches of vacuum at idle in drive (don't ask me how I checked that). So the power valve is the correct size and the jets are not too small. I put it all back together and it ran better. Took it for a drive and no more spark knock. It runs good under load, accelerates good and drives along at steady speed. Idles a little rough for my taste but doesn't die at traffic lights and doesn't bog or hesitate. I pulled the plugs again and they look okay but haven't driven it more than 15 or 20 minutes.
Anyone have issues with crud in the carb causing lean condition?
 
we took "Bob" out today and drove around. It behaved quite well. We tried different road conditions and speeds. Everything seemed fine. So we parked it. Tonight he fired it up to go to work and got about a half a block away and it just started sputtering and carrying on. He turned around and brought it back home and drove the old truck to work.
I'm reasonably sure it has crud in the carb. We will look at it more tomorrow, it was dark and cold and I was too tired to mess with it tonight.
 
Clean the line by disconnecting it at both ends, Use shop vac to suck string thru it.
Place wire strands from 14-16 ga wire in the sting line and pull it thru line both ways and blow out line with air.
Did this to a 25 foot line on an old rv and it worked great.
 
I have hooked up a old pipe to my sand blaster nozzle and that cleaned the inside fairly well. You could try that. Have any zero rust solution? You could fill it up with that.
 
Line is cheap. I would seriously just consider making up a new line. If a line is old enough to have an issue with that much gunk in it why delay the inevitable.
 
I think that will be a great idea. I'm in Germany for a couple weeks but that should be a job he can handle all by himself.
 
You should be able to get a set of SS fuel lines and a carb rebuild kit, all for $100 bucks. That, compressed air and a weekend and I bet your issue dissipates rapidly.
 
we were able to pull both float bowls of the Holley and clean it out with carb cleaner and compressed air. It's running good again. We added a bigger paper fuel filter as well. He drives it to school everyday and works when not in school. I think he might have a day off soon that he can dig into it more but it's running well again for now. It did visibly have some very fine trash in the bowls
 
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