A while ago I replaced the carb on my pressure washer (B&S) with a 3rd party carb, for the most part it is easy to start and run. But I noticed when I pull the trigger the engine seems to surge and I notice the arm going to the butterfly plate is moving back and forth. Does anyone know if the spring is too soft, or other issues. I transferred the original butterfly plate over.
pressure washer surging
- Thread starter PoorOwner
- Start date
sounds like it's hunting for fuel under load . means it starving for fuel and the main jet is too small or needs adjusting
they can be drilled out. you need a set of number drills ( small sizes) find the size that just fits , then ream it with the next size drill, try it, rinse & repeat. you don't want to overshoot it , which is easily done.
it is possible the OEM one from the other carb will fit too.
if you drill, do it by hand very carefully, those small drills break easily
it is possible the OEM one from the other carb will fit too.
if you drill, do it by hand very carefully, those small drills break easily
ron350
Well-known member
This video shows how to fix the hunt and surge.
You only need to ream the jet out 2 or 3 thousand'.
The drill bit in the video is about .030"inch O.D. If you ream the jet much larger the motor will run pig rich. The 10 small drill bit set in the video is stepped about .005" between drill bits and the color bands are different depending on who or when they were made. So measure the drill bit or try the sixth drill bit from the smallest.
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You only need to ream the jet out 2 or 3 thousand'.
The drill bit in the video is about .030"inch O.D. If you ream the jet much larger the motor will run pig rich. The 10 small drill bit set in the video is stepped about .005" between drill bits and the color bands are different depending on who or when they were made. So measure the drill bit or try the sixth drill bit from the smallest.
Shiftless
Well-known member
Absolutely!
Increments of 1/16 inch is not to be considered.
Look at this chart. The size increments are just a few thousandths.
Get or borrow a set of number drills.
ron350
Well-known member
I purchased one of the top three drill sets just to get the 10-piece mini set like the man uses in the video.
https://www.ebay.com/sch/i.html?_fr...Pcs+Mini+Micro+Hand+Twist+Drill+Bits&_sacat=0
https://www.ebay.com/sch/i.html?_fr...Pcs+Mini+Micro+Hand+Twist+Drill+Bits&_sacat=0
Shiftless
Well-known member
That would work too. The steps are a tenth of a millimeter which is about the same as the number drills (.003 to .004 inches between each drill.)
joshmodelskidoo
Well-known member
Did you try cleaning and putting on your old carb or stealing the jet from that. You can Try to clean the carb that's on it to to see if there's junk in the jet. Running rec fuel aka 100% gasoline. Regular pump gas has ethanol in it and that eats rubber that can break down and sludge up a carburetor and it also collects water. You can buy it from some gas stations or in a can from the hardware store but in the can it's like $15 a half gallon or $1-$1.50 more per gallon than regular gas and it's got like a 2 year shelf life vs regular pump gas is like 3-6 months. If o a Google search for rec gas in your area
theoldwizard1
Well-known member
Most aftermarket carbs **** !
Surging is almost always caused by a blockage in the primary (commonly INCORRECTLY called the idle) fuel or air passage. These are extremely small. You need a fine wire to ream out these passage.
That guy in the YouTube video is WRONG !!
Surging is almost always caused by a blockage in the primary (commonly INCORRECTLY called the idle) fuel or air passage. These are extremely small. You need a fine wire to ream out these passage.
That guy in the YouTube video is WRONG !!
Motown
Well-known member
Most 5-6hp engines, you can drill the jet to 0.034. I do that to the Harbor Freight engines, they tend to run lean.
I reamed the jet, the bit that went up was 0.6mm, I did find it was noticeably running better, it was the slightest bits of brass removed.
I went and mess around with the next drill size, 0.7mm I believe. After a bit of friction the bit broke. Turns out it was very difficult to find a jet for this carb as a B&S part. I attempted to fix the jet I have from this aftermarket carb.
By miracle, I used a pick and blowing with compressed air I was able to slowly get rid of the stuck bit. I see I can put the smaller drill bit in again. I then ream it again with what's left of the 0.7mm bit. This will be the first real drilling to increase a full 0.1mm size increase.
I went and mess around with the next drill size, 0.7mm I believe. After a bit of friction the bit broke. Turns out it was very difficult to find a jet for this carb as a B&S part. I attempted to fix the jet I have from this aftermarket carb.
By miracle, I used a pick and blowing with compressed air I was able to slowly get rid of the stuck bit. I see I can put the smaller drill bit in again. I then ream it again with what's left of the 0.7mm bit. This will be the first real drilling to increase a full 0.1mm size increase.
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Hi here is an update, I had to get another clone carb because my jet was messed from drilling. it seems too rich and stalling with a puff of black smoke. I got a new spark plug, it made it easier to start but no change in the surging.
If any one wants to see a video of my washer running in the zip file you will find a video I capture from my phone.
Under load the throttle linkage move in towards the head (plate open more) and then and out, causing the engine to surge.
If I hold it in the linkage position with my hand (stopping the throttle opening all the way) then the engine and pump run consistently, perhaps not at it's full power.
Thanks for all the help but I am not sure if this too lean or not? The OEM carb from B&S is quite expensive about $80 and they no longer carry the jet either. One detail is that if I back the speed control from "rabbit" back just one notch, the engine is slower but I don't get as much surge, about once every few seconds instead.
If any one wants to see a video of my washer running in the zip file you will find a video I capture from my phone.
Under load the throttle linkage move in towards the head (plate open more) and then and out, causing the engine to surge.
If I hold it in the linkage position with my hand (stopping the throttle opening all the way) then the engine and pump run consistently, perhaps not at it's full power.
Thanks for all the help but I am not sure if this too lean or not? The OEM carb from B&S is quite expensive about $80 and they no longer carry the jet either. One detail is that if I back the speed control from "rabbit" back just one notch, the engine is slower but I don't get as much surge, about once every few seconds instead.
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sqznby
Well-known member
Should have never replaced the OE carb, most if not all aftermarket replacements are junk when all you needed was a good cleaning and possibly a new gasket.
The surging is caused by gunk built up inside. No need to drill anything out just clean it thoroughly.
I use CRC mass airflow sensor cleaner, blast it in every orifice with the tiny hose attachment, most of the time I don't even remove the carb, only the bowl.
It cleans and dries faster than brake cleaner and leaves no residue.
Use non-ethanol fuel.
The surging is caused by gunk built up inside. No need to drill anything out just clean it thoroughly.
I use CRC mass airflow sensor cleaner, blast it in every orifice with the tiny hose attachment, most of the time I don't even remove the carb, only the bowl.
It cleans and dries faster than brake cleaner and leaves no residue.
Use non-ethanol fuel.
Yes, too late now I threw it out as soon as my engine start I thought I was good, the aftermarket carb is new so it does not need cleaning.
It does seems like it needs more fuel, behaves similar to when I shut off the fuel supply and let it starve out.
Update: removed the bowl nut / jet of the "new" carb and reamed it out with the next size drill bit. It does appear the fix the problem at least towards usable.
Although the idle is a little more rough (richer), it still has has a little surging with the wide angle "delicate" nozzle (previous video was with this nozzle). After drilling, I find it runs "perfect" under the medium and highest pressure nozzle. So I am ok for now until I may one day get the B&S carb. Possibly I have an issue with the pump / unloader too, but I just need to wash at full throttle.
I attached a video of idle and then medium nozzle under load.
I want to mention, the drill bit step pretty drastic, but I don't have anything in smaller increments.
Another thing I noticed is that when it shut off it doesn't make a backfire sound after the drilling.
Thanks for all the troubleshooting
It does seems like it needs more fuel, behaves similar to when I shut off the fuel supply and let it starve out.
Update: removed the bowl nut / jet of the "new" carb and reamed it out with the next size drill bit. It does appear the fix the problem at least towards usable.
Although the idle is a little more rough (richer), it still has has a little surging with the wide angle "delicate" nozzle (previous video was with this nozzle). After drilling, I find it runs "perfect" under the medium and highest pressure nozzle. So I am ok for now until I may one day get the B&S carb. Possibly I have an issue with the pump / unloader too, but I just need to wash at full throttle.
I attached a video of idle and then medium nozzle under load.
I want to mention, the drill bit step pretty drastic, but I don't have anything in smaller increments.
Another thing I noticed is that when it shut off it doesn't make a backfire sound after the drilling.
Thanks for all the troubleshooting
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rust in the eye
Well-known member
Something also worth investigating may be spring tension on the speed governor.
My luck with the Chinese knock off carbs has been good. Before I started making irreversible alterations I'd be very sure no vacuum leaks and governor isn't the issue.
My luck with the Chinese knock off carbs has been good. Before I started making irreversible alterations I'd be very sure no vacuum leaks and governor isn't the issue.
