DBXL 2.0 DBXL 2.0 - What are your final low- and high-speed carburetor needle settings?

This site may earn a commission from merchant affiliate
links, including eBay, Amazon, and others.
R

rajul

Well-Known Member
Messages
85
I am still running-in my engine with the carb needles at factory settings i.e. high-speed at 1 7/8 and low-speed at 1 3/8 turns out. The engine is definitely running rich - when throttling up, the engine hesitates, and the engine floods and dies after running for about 20 mins at low speed. I find that the fastest way to drain the excess fuel in the engine is by removing the carb and tilting the engine sideways while pulling the starter. The needles definitely have to be leaned out, but I would like to find out from DBXL owners how much have they turned in both their low-speed and high-speed needles. Thanks for sharing.
 
Needle settings are irrelevant to what vehicle it's in. The dbxl 2.0 I just worked on came with a carb that had its metering spring popping at 30 psi. Your carbs pop pressure is way off and causing that issue, pop pressure needs to be 20psi and you'll be able to tune the richness out of that carb.
 
Clubin said:
More complicated than that.

Temp
Elevation
Where you are running

If it’s flooding that bad pinch the low and high needles in. Then run it.

Post a pic of the plug.
Click to expand...
Agreed on the external factors. The plug look ok and it is sparking when the starter cord is pulled
 

Attachments

  • IMG_6401.jpg
    IMG_6401.jpg
    32.5 KB · Views: 11
  • IMG_6404.jpg
    IMG_6404.jpg
    33.6 KB · Views: 11
Rep732 said:
Needle settings are irrelevant to what vehicle it's in. The dbxl 2.0 I just worked on came with a carb that had its metering spring popping at 30 psi. Your carbs pop pressure is way off and causing that issue, pop pressure needs to be 20psi and you'll be able to tune the richness out of that carb.
Click to expand...
I have checked the metering lever height and the check valve and they are both fine in this WT1107 carb. I have a 100c aircraft engine with a WJ71 carb, also having a pop-off pressure above 30 psi but the engine is running fine. It seems like many Walbro carbs do have a high pop-off pressure at factory setting https://www.flyinggiants.com/forums/showthread.php?t=50741&page=3
Rep732 said:
Plug is very lean
Click to expand...
It's a new plug and the engine has only ran for about 20 mins. I have not been able to get it started again at the factory needle settings, even after many starts, due to engine flooding. I typically prime the bulb 2-3 times only, then choke, pull starter 4-5 times, but no pop. I also temporarily removed the air filter. Looks like I have to try to turn in the needles a bit. However, since I already have the carb out, I will test the engine by spraying some fuel through the plug hole, as well as through the carb port, and see if the engine runs. In this way I could isolate the problem to either the engine or carb
 

Attachments

  • IMG_6417.jpg
    IMG_6417.jpg
    40.1 KB · Views: 10
  • IMG_6424.jpg
    IMG_6424.jpg
    43.2 KB · Views: 10
Last edited:
I'm not going to argue with you, that's not how you check pop off pressures either. Also you cannot compare a wj carb to a wt as there 2 different series of carbs. Your clearly having an issue and I explained what it is, it's up to you to make it right.
 
Rep732 said:
I'm not going to argue with you, that's not how you check pop off pressures either. Also you cannot compare a wj carb to a wt as there 2 different series of carbs. Your clearly having an issue and I explained what it is, it's up to you to make it right.
Click to expand...
I am using a Walbro pressure tester. The metering lever height is currently at factory setting. What would you suggest to lower the pop-off pressure to 20 psi? Thanks
 
Walbro doesn't actually seem care what the pop pressure is, normally they site the needle has to hold so much pressure. If your flooding the engine, pop pressure isn't the issue.
Idk how your checking pop pressure, but I can quite assure you where your tube is in the second picture isn't where it goes.
The wj series of carb is similar in construction to the wt series, but designed to flow a lot more air and fuel. Different pop pressures for them both. I'm running one an a 101cc chain saw that pops 25psi and runs just fine.
Another thing to look at is if the diaphragm has any links holes in it. It will bleed fuel into the impulse port and never run from an overly rich condition.
 
I've also seen improper technique applied while trying to start these engines which is flooding them out as well. Choke on, slow pulls till it pops then shut choke and give it a few rips and it should start.
 
@Rep732

Thanks a lot for sharing your method to reduce the pop-off pressure! I will try this when I have a spare repair kit for the WT1107. Any idea what is the Walbro part number for the repair kit?

Actually the second picture you referred to is a mouth tube used to test the function of the check valve, as per Walbro Service Manual

Also noted on your comments on the proper starting technique. I never had any problem with my weed whacker engine, nor with my DA100 aircraft engine, and choking/starting has been a breeze. Unfortunately starting my DBXL 2.0 engine is still a pain, and I have only managed to start it once and it ran for about 20 mins and died due to flooding.

@Seandonato73

Thanks a lot for your inputs. I checked all the diaphragms and they look ok without any obvious defects or holes. I tested the pop-off again and it is about 30 psi with a reseat pressure of about 21-22 psi.

I would like to also confirm if there is supposed to be any reed valve between the carb and the engine port? Thanks
 
No problem, you need one of these. Not sure what country your from but im sure you can find similar by you. https://www.harborfreight.com/dual-vacuumpressure-hand-pump-kit-56803.html

Also this test needs to be done "wet" meaning the carb has to have fuel applied to the fuel feed barb. You put a bit of fuel in the hose and apply pressure until it "pops" off. You keep doing the process until you get down to 20psi.
You can just cut down your spring but do it coil by coil and you won't miss the mark.

Here's how much I had to cut off. Stop at the arrow

walbro_carb_wt627_assemble_meter_needle.JPG
 
Last edited:
@Rep732 Noted with thanks! The handpump kit you're using is much superior to the walbro version, which leaks after some time.
Any idea what is the Walbro part number for the repair kit for WT-1107 carb?
I would like to also confirm if there is supposed to be any reed valve between the carb and the engine port? There is none in my engine.
 
Last edited:
The kit is k20-wat but doesn't include the spring of all things. I just checked and some places have the spring included and some don't so im not sure what that's about. I've purchased the kits in the past and haven't had the spring included. @Seandonato73 would know the part number for the correct metering spring. I believe there's a kit floating around with various height springs but the method I've been doing has kept me from searching for it.

No valve of any kind between the engine and carbs pulse port.

Also to clip the spring you need a sharp tool that can clip the coils clean and believe it or not out of all things a nail clipper does a great job at it.
 
With the carb removed, I sprayed some fuel into the spark plug hole, then reinstalled the plug, and pulled the starter, no pop at all. Then I sprayed some fuel into the carb port, pulled the starter and still no pop. It seems the problem may not be the carb. I checked the spark and compared it to the spark from the plug in my weed whacker. The brightness of the spark seem to be less than that from the weed whacker engine. Could it that the plug is too "cold" or there is some fault in the magneto? At this point, I am feeling like sending in the whole thing back to Horizon. Any other ideas before I throw in the towel? Thanks again guys
 
Last edited:
I'm gunna say the spark is fine as if you lay different points of the plug on the head and pull it will give you various degrees of brightness.
If the spark plug is wet it will never fire as the fumes is whats flammable not the liquid. If the rig is flooded and you've yet to be able to start it then it's still severely flooded and you have to clear the old gas out from the crankcase before you can move onto the next step.
 
Just to chime in again, I just did the pop pressure on my boat carb which is a wt-1048. First check it went over 30 and it ended up blowing the line off so I cut the top group of coils and it brought it to 30,half coil it went to 25 and then one last half brought me to 20. It doesn't hurt to make sure your spring is right, sometimes you get lucky which I did on my new 5t 2.0 but most of the time no dice.
 
First off, if your not using a spark tester your wasting your time. All a spark plug firing in out of the engine tells you, is exactly nothing.
As Rep has said there is actually a walbro spring kit that hasn't been available in some time. I have enough loose springs laying around to swap them out instead of clipping them.
The proper carb kit is a kt20-wat. Typically you should be reusing the old metering spring anyway. They used to come with the springs, or at least the last batch of kits I have here still have them, but I got them a few years ago.
At any rate I upgrade them to the spiral diaphragm, which uses a different spring anyway.
20 ish psi for pop, and reset should be 10ish. Don't get too hung up on hitting it bang on.
 
Back
Top
✖
AdBlock Detected

We get it, advertisements are annoying!

Sure, ad-blocking software does a great job at blocking ads, but it also blocks useful features of our website. For the best site experience please disable your AdBlocker.

I've Disabled AdBlock    No Thanks