Carb/Purge Bulb Questions, JD Leaf Blower BH25

[cambells704]

This may be basic but I could use some advice on this.

As far as I know, this blower ran fine. I replaced the purge bulb on it and now it dies at no choke and full throttle. Purge bulb is located off the carb.

From what I understand, the purge bulb sucks gas through the carb (short stem) and the excess gas drains back into the tank (long stem). Since I am having problems at high throttle, I was wondering if I could somehow have low fuel pressure.

I was thinking of testing the system by draining the bulb completely, then repeatedly try and start the motor with the spark plug disconnected. If the diaphram in the carb is good, then the bulb should fill up with fuel. Is this a sound test or am I missing something?

Thanks for any help.

 

[StarTech]

Looks like an old Homelite dress as a JD

Two possibles.

1. Internal filter screen is partially clogged
2. Metering diaphragm has stiffen. A stiffen diaphragm can still open the metering needle enough to fill the primer.

Also check metering lever height as if set too low will cause this too. Use a W or Z tool helps here depending if Walbro or Zama carburetor.

 

[sgkent]

why did you replace the bulb? Keep in mind that if the bulb fails to properly seal it can let in air. I had one carb that I had fits getting a replacement bulb to seal right.

 

[StarTech]

why did you replace the bulb? Keep in mind that if the bulb fails to properly seal it can let in air. I had one carb that I had fits getting a replacement bulb to seal right.

This blower uses the Walbro 188-512 remote primer.

Now sqkent if you are using after market primer bulbs they can have defects that most OEM primer don't have. I never had a problem OEM primer bulbs in the 13 yrs I have been installing them and I install a lot of them which is why buy them 20 at a time. I had several primer bases to be bad but not the primer bulb itself.

I just had to throw out 6 remote primers for Stihl machines from Stens. All had the primer bulbs to fail upon initial use. Bulbs were defective. Glad I only purchase a test batch from Stens. Now Stens did credited me for the bad primers. Also glad they fail in the shop before delivery.

 

[cambells704]

Thanks for the replies. I changed out the bulb assembly because it was cracked. It is an after market bulb but it seems to be working correctly as it will prime and run on no-choke at idle. As soon as I try to throttle up, it'll bog and die.

After doing a little more research into this, I've tried a number of things including running it without the muffler - same issues so I don't have a problem with spark arrestor or clogged muffler. Then I pulled the fuel filter and ran it that way - same issues: It will run at no choke and bog an die as soon as I give it gas. So everything is back together and my next step is to dismantle the carb and look for any obvious issues.

I just find it hard to believe that a carb issue developed at the same time that the fuel bulb was replaced, but from various youtube videos diagnosing this exact issue it seems to be the next step.