Topic: Clogged accelerator pump jet / post

[jahmic]

I just started my 78 750f back up after a carb cleaning. She's running much better than before, but I'm still having issues with the accelerator pump.

I made sure the check valves are clear, but when cracking the throttle, I get no squirt in the throttle body. Turns out that I neglected to clean the posts properly...

I initially cleaned the carb body by soaking it in simple green...all jets including the pilot were pulled and soaked in carb cleaner. However, i failed to put compressed air through the line that feeds from the accelerator pump.

Pulled the carbs today, and using some carb cleaner and compressed air, I was able to clear  all of the posts except #3. I even resorted to using a syringe to push carb cleaner into the line between carbs 3-4, then plugged the rail  on the opposite side of 3 with my finger while shooting compressed air into the line that connects 3 and 4.  Nothing. As soon as I let my finger of the rail, carb cleaner bursts out of the end...the jet is completely clogged.

Any suggestions on how to clean this out? I've seen some people using ultrasonic cleaners...would that solve this issue?

[bollingball]

Well as you know the end of that nozzle is hard to get at because it faces the choke butterfly.
I have not done this but was thinking if you could slide some tubing about 6" long over the plugged brass jet nozzle sized for a snug fit then use the red tube on the can of carb cleaner inside the tubing on the other end and try to back flush. it is worth a try. You may have to clamp or tyrap the tubing for a tight fit. If that does not work then you have a good excuse to buy a ultrasonic cleaner.
Please let us know if this works so others will know.

                   Ken

[jahmic]

That's actually a great idea bowlingball. I just attempted that with just the syringe and some tubing, but the tubing I have is too large. I think you're onto something though...especially considering the backpressure from the can with a better fit on the tubing. I lost my straw somewhere between autozone and my house...I'm sure  a new one will help as well.

I'm going to try to mock something up, and will keep you guys posted.

[jahmic]

Found some tubing at ace hardware for the job...got a nice seal over the straw on the can at one end, and the post on the other.

So far, no change though. I used a twist-tie at the base of the post too...there was enough pressure in the line to blow the straw off the can if it wasnt held in place.

I did  see some potential progress as I saw tiny bubbles forming in the line on the post. I was tempted to leave the line on the post to let it soak, but had tested the  tubing beforehand...any extended exposure to carb cleaner causes the tubing to start to melt.

I'm going to try 100% simple green I'm the line and let it soak...and a couple other things.

Really hoping I don't have to buy that cleaner...

[BobbyR]

Take a long strand of wire from a lamp cord and feed it up or down the tube. If you can get a high E guitar string it would be better. It will take mechanical cleaning.

[jahmic]

Solution:

I sat down, thought things over, and decided I needed to mimic that "pulsing" effect of the cleaner to break loose whatever was in that jet.

I took 100% simple green, and pulled it into a standard 10ml medical syringe. The tubing I used is a 3/32 ID gas line...the kind you use for a chainsaw or mower. The tubing fits almost perfectly over the post for this, no need for a twist-tie with this method.

Filled the syringe as shown here...you want that air space.




Then, placed the tube over the post. I noticed that i had to  push the tubing down into the carb, putting a link in the line. This pulled the tubing away from the face of the post just enough to allow the fluid in the line to get between the tubing and the opening in the jet:



From here, simply pushing on the syringe does nothing. The pressure builds up and blows past the line at either end. What you need is a sharp, sudden increase in pressure. Hold the base of the syringe I'm one hand, and pull back the 'plunger' with the other. You should feel the backpressure pulling back A LOT.



Release, and it should snap down. After several repetitions, the simple green became foamy, and I noticed bubbles streaming from the post. Next pull of the syringe, and there was no backpressure.

Jet cleared.

[TwoTired]

I love seeing people think through these problems and arrive at an effective solution.

So...

Look at the big brain on jahmic!
 

I recommend "proving" that the two check valves for the pump are both clear AND block flow in one direction.  There's a valve in the pump and a valve in the carb bowl.  I happen to favor pressurized carb cleaner for cleaning and testing on the bench.

Cheers,

[bollingball]

Hey glad to see you got it. I got to write this down. Maybe put in tips & tricks

           Ken

[Spanner 1]

Very helpful post  ... I hope everyone who sets out to clean their PD carbs will include proving their acc. pumps work in all 4 cyls. before putting the carbs back on the bike..... would lead to less ' my bike runs like crap and I just cleaned the carbs ' posts 

[jahmic]

Why thank you TT.    I did come across plenty of posts on the accel pump, and definitely made sure that the check valve functioned as you described. Mine were initially blocked...both of them. I fixed that issue, and carelessly overlooked cleaning those lines after the soak.

Spanner, I admit that I too could have benefited from checking those lines before installing the carbs. Once I got them on the bike, I cracked the throttle, then noted the hesitation and lack of spray in all 4 carbs...I didn't even consider checking it on the bench. Lesson learned, because having to hook up the carbs 2x in a day is twice as annoying, haha.

If it's worthy, I can write up a proper how-to on the process...always happy to contribute

[BobbyR]

Well done. That is how you use a plunger on a clogged drain.

[Juan1]

I know this thread has been long dead, but I have another technique to solve this problem.

My #4 accelerator jet was really clogged, and I tried the plunger method listed above without success.  I ended up putting some clear tubing between the outlet of my air compressor and the fuel rail side of the accelerator jet.  I don't know the guage of the tubing, but it came with my brake bleeding syringe.  With about 90 PSI of pressure, nothing happened...until 5 seconds later when the jet began flowing freely.  Then I went through all of the accelerator jets that were working, hit them with carb cleaner spray followed by the same 90 PSI technique with my rubber-gloved fingers covering the extra outlets.