Homelite BX90 yard blower - carb problems

To establish my competence with tools, I’m an 80+ Y/O ex-mechanic of all sorts – USAC racer and engine builder, aircraft flight line mechanic (several companies), Atlas missile mechanic - and a previous “one man” garage owner. That being said:
I have a problem that is running me nuts. I have an older model Homelite BX 90 Yard Blower that became hard starting and needed its carb. overhauled. (Walbro 431) (“Guessing, I must have rebuilt dozens of these small engine carbs with no problems) I soaked it in carb cleaner for a couple hours, bought a new kit, washed it in hot water, and blew out all the passageways with 90 lb air. Choked it twice and it ran well for a couple of minutes then died. (Filter in but clean) Then it would not start. Checked the plug and it was VERY wet. Washed it with contact cleaner, turned the engine over at least a dozen times to clean out the cylinder, and tried again. (Without the filter) Nothing! Checked the plug again, still very wet. – went through this same procedure at least five or six times, still flooding EACH TIME. Twice I removed the carb. completely and double checked everything, including removing the needle valve and blowing it out - in case there was dirt or something not letting it close fully. Checked all settings, and that gaskets all were correct. My suspicions are when it first flooded, that it flooded so much it had residual fuel in cylinder, I blew out the cylinder with high-pressure air at least five or six times while turning the engine over. Put plug back in – tried again and still flooded – plug very wet. (By the way, not choking when trying to restart) Only item I found when going back inside the carb, was one gasket (on the bottom) which has the two tiny flaps that lay flat and act like check valves, One does not appear to be as flat as it should be. (But suspect it flattens out when the cover is on and tight.)
This thing is running me nuts; I am out of the normal things to check. Suggestions of what else to check or what might be causing the flooding appreciated.
Ancient One

 

Just for a goof,, check for spark with a Known good spark plug (like the one from your lawn mower) to verify spark... It sounds like you have the carb covered,, But if the plug won't spark,, it can't burn the fuel off it & may apear flooded... Only other thing is the Metering lever,, Did you adjust or replace it??? There is a tool to set it properly. Just use the old one.. Also verify the metering diaghragm is on the correct side of the gasket.. If you check the Walbro website they have an excellent service manual & parts breakdown... The carb # you posted isn't a walbro # so you may want to verify you have the correct kit... (Walbro # are like ""WT 235A etc) Check it out & let us know... Roger

 

You are correct, one thing I did not check was the plug for fire, since it was running well when it died. It did not give the normal electrical symptom ( sudden cut off,) it did slowed down and did some sputtering then died which usually is fuel.
Right again -- my error, it is a WT-431 However the kit I was given was another number - not even close. As for the "metering Lever" That terminology is not something I recognize. Probably I may have called it something else a long time ago.
Next, the gasket is on the TOP side of the diaphram.
Thanks for the info on Walbro. I'll take a look at their site and see if I have missed something. Meanwhile, I WILL check the plug -- just in case. Might as well -- have run out of other things to check. ~(:-)) Meanwhile, tell me about the metering valve you mention. As I said. I may know it by somethng ese.
Ancient One

 

The metering arm is the little leaver that hooks to the inlet needle, sets on a little spring, use the old one unless it is worn as it has the proper height setting. Have a good one. Geo

 

Will do,
Thanks,
I still am confused as to why it ran well for a few minutes then slowly shut down. My assumption is --- If things were not right in the carb in the first place, i.e. gaskets, diaphram, needle valve, etc. -- it would not have started in the first place. VERY confusing. What do you think?
Appreciate your taking time to reply.
Will continue my checking.
Bill

 

I don't know if a previous post has mentioned it, the walbro site has lots of good info. Go to their site and select the Service/Aftermarket tab, then start looking around. Have a good one. Geo
Welcome to walbro.com

 

Usually (but not always) the metering diaghragm has the gasket between it & the carb body,, UNDER the diaghragm.. The Walbro site will give you the exploded view of the carb & may verify this,,,, Roger

 

I would certainly check for spark as was mentioned, and with your resume as you listed, you should have done already
Next if you still get the same results with good spark, might be time to check the cylinder for scoring or wear or rings (Compression)....honestly, it amazes me some of these lil buggers ever run right, and it don't take much sometimes to render one to the scrap pile over being cost effective to repair.

 

~[:-)) You are right -- however - as you probably know. an engine that suddenly gets an electrical problem, shuts off - "immediately" BANG! ---- One that develops a fuel problem will usually sputter and slowly die. Using THAT as my guide for many years, it has always told me where to begin looking. But --- in this case -- it did not stop, it slowed down and sputtered and THEN quit. Result, -- NO - I did not check the plug, since it had been running fine. However, as I told the other fellow who answered ... He was right, a dead plug would continuely indicate flooding. And since I had run out of anything else to check, I would take a look at it. If it turns out to be the plug, I will be shocked -- in disbelief -- from the shut-down indicators.
Thank you for taking the time to reply. As of today, Sat. AM. I have not had a chance to get back and check further, due to unexpected happenings, but will do my best to get back to it this afternoon or evening.
If -- and when I do find the culprit, I will post it.
By the way -- for those posters who told me about the "Walbro web site", many thanks, I found -- and printed out the schematic and part numbers. Good info and useful. Many Thanks to you for your help.
Thanks much,
Regards,
Bill
Ancient One

 

I have a BX-90 HOmelite. It was given to me by a neighbor. Excellent condition but having a problem.

It starts and idels fine but when I acclerate it dies out. I cant figure out. Cleaned most parts. I did find one of the tubes going to gas tank slightly melted. I pulled it up a little and cut and re-installed. Still having same problem.

Any tips?

 

Yep! It is not getting enough fuel to the carb.
If it were me -- and I'm reasonably sure this will solve your problem --
I would first pull out the rubber grommet where the lines go into the tank, remove the filter and replace it with a new one. If that is not the problem, I would be surprised.
However, there are many guys on here that are more experienced in small engine repairs, professionally. I mainly have done it for my own use over the years.
I'm sure one of them will get back to you shortly.
Ancient One

 

Try adjusting the low mixture 1/2 turn out, then just under the same back in...likely just a bit of trash that may wash out by adjusting the mixture screws.

 

OK Roger;
Here an update. Just now got around to giving it a try agai, (Tue 29th)
BIG surprise. After trying it again two or three days ago and STILL getting flooding, I gave it a couple yanks checked it again and still flooded, I left the spark plug out in hopes of letting it dry out more until I came back. I shut down in disgust and watched TV. Today, I came back in (carb on - plug out) to check if the cylinder was dry, I gave it a good yank --- and WOW - did I get a big surprise. Holy Crap! I was nearly drowned with Gasoline. I mean it was not just specks and drops, it was pure liquid. NOW, I became suspicious I have the two lines from the tank switched. So I removed the carb completely and pulling it through a lot, I was also getting LOTS of gas out through the carb mainfold also. LOTS! Using HP air in the plug hole and in the carb manifold -- . So, I have switched the lines, and leaving the carb completely off, it took a hell of a lot of yanking and blowing to clear it out. There must have been at least a half cup of gas in the cylinder. Remember, two yanks before I quit for the day a few days ago, with the carb installed (choke off obviously) A good yank and I got gas all over me it was so much. As I said in my first post, THIS THING IS RUNNING ME NUTS. (GRIN)
SO -- CARB OFF - AND CYLINDER CLEAR (I HOPE) I going to come back after supper -- with the two lines switched, and put the carb back on (choke off,) and give it a few yanks - to check if the cyl is stil clear, and proceed from there if so, I'll get back then and let you know the results. What a fiasco! Never had a situation like this in all my days.
Bill

 

I kinda think you have the metering diaghragm & the gasket flipped as mentioned in an earlier post,,, It's possible the gasket goes to the outside,, but most I see the gasket goes between the carb & metering diaghragm...If so, the diaghragm is too close to the lever, holding it down & holding the needle open & pumping fuel right into the engine... Have you verified the assembly on the Walbro site yet????

 

Hi Roger:
Per my last mail, the cylinder was clear when I returned this evening-- and BTW yes the plug had fire. So I switched the two fuel lines -- choked it one pull and she fired up and ran like a scared rabbit. Ran it only for about 45 seconds at peak RPM and am satisfied the two fuel lines being backwards caused the problem. However,Yep, the diaphram gasket IS on top of the diaphram. Since you mentioned it, I looked at the diagram again, and you are right, it shows it goes UNDER the diaphram. Since I had to feed my dogs and myself, I shut it down -- and will check it again tomorrow, If it runs as well as tonight, I'll leave it alone. BUT -- if it has one hiccup, I'll switch the gasket to under the diaphram. I appreciate your taking the time to reply, as I have said a couple times, I have NEVER run into such a pain in thr butt problem in the past. And the fix was simple - switching the lines solved the problem --- UNLESS -- it refuses to start tomorrow. ~{:-))
Then, I'll switch the gasket and try again. Thanks again for your input -- and thanks to all the others who also gave input.
Ancient One
Bill

 

Don't worry about running into one of these things that make you bang your head on the wall,,, I'm sure we've all been there & done that, (I know I have).. Sometimes these little trimmers can be a challenge,,,, Glad you have it running,, Roger