BoomCat BDS-125 carb set up

[Aecker]

Hello to all, just wanted to give a hand to anyone that need help with the carburetor set up on the Boom. Seen some videos on YouTube of guys running the stock set up and with some tuning the bike can run much better than stock.
Here what I got going.
Stock set up is a pz20 with very small jets, both jets are unmarked so can’t tell what size they are but I suspect they are #78 main and #26 pilot, I believe they are sized for a 50 or 70cc engine. This being a 125cc they are too small. Also the stock carburetor does not have a needle adjustment. The bowl screws are sealed as it’s the air adjustment screw, u can replace the bowl screws and pop the seal off the air screw, I did both. U can try re-jetting but I don’t recommend it because the lack of a needle adjustment and the pilot jet is very difficult to find, it has a unusual shape. The jets are 4mm tread not 5mm as most carburetors. So I decided to change to a pz22, this carb is about the same size but run slightly larger jets, the needle and piston is also larger however they are also unmarked, it uses 4mm tread jets not 5mm like the Mikuni, the needle has 3 groves for adjusting. This carb looks very similar to the original but does not have the carburetor gas shut off like the stock. The carb gas shut of is not necessary and ad complexity to it. All the hose hook ups are the same and it fits perfect in the manifold and air boot. U can run the Pz22 it as it comes and the bike will run better but not perfect, for that you will have to re-jet it. You can buy a Mikuni carb but they are more expensive and u will have to re-jet it also. So I decided to go with the Pz22 as it look stock and I don’t have to delete the charcoal canister. You should swap the spring that go on top of the carb piston, the spring on the Pz22 is softer than the stock pz20 witch is stiffer and gives the throttle a nicer feel. After playing with the jets I finally found a set up that works for my bike. You will have to buy the jet kits and they come with a few jets for you to play with, the jet kits run about $10/15 and the carb is about $25. The gasoline filter should be changed as it is very low quality and mine was collapsed inside and letting dirt go through into the carb. FYI every bike is different but this will get you close.
Hiaors Pz22 model Cb054-22mm from Amazon
Main jet is a 4mm tread #92
Pilot jet is a 4mm tread #30
Needle jet on lowest/bottom setting
FYI I’m still playing with jets sizes as I don’t ride the bike often, I’m still trying to up the performance as much as possible but so far this setting is working.
Air screw 1 1/2 turn out
New gas filter
No mods to air intake
Exhaust muffler end, mini baffle removed
Here some pics of the Pz22, the needle and the comparison of the 4mm jets to the 5mm jets in size, hope this will help

[PepaPowah]

Hey Aecker!

thanks for this post, was really helpfull, was looking for a carb I could used without having to remove the airbox the bike comes with stock. found the Haiors Pz 22, seems like the exact same you have in here, however, I have not been able to find the jets with a 4 mm (0.7mm) thread. so if you could share some links for those would be amazing.

moreover, the stock carb, has three lines, and this one all i can tell is that it has two plugs the fuel line, and the one on the bottom. what do I do with the third line that goes from the choke to the "black cylinder" on the right side on the stock carb.





https://www.flickr.com/photos/192703...posted-public/

https://www.flickr.com/photos/192703...posted-public/


excuse my terms, not really a mechanic, just learning with my lovely boomcat.

hope you find the images usefull,

[Aecker]

Hello sorry didn’t see ur post earlier. The jets I found on eBay just do a search for pz22 4mm jets should come up u will need main jets and pilot jets. I was running 98 main and 36 pilot but was running rich so I’m down to 90 and 30 and needle on bottom air 1 1/2 turn out. After checking the spark plug notice bike was running lean, re-jet is main 92, pilot 30. Will update after test driving. The extra hose that comes from the middle of the oem carb and goes into the charcoal canister u run to the top plug in the Pz22 carb just like in the pic, the hose in the back of the canister just run it up to under the tank to the tank overflow connection. It’s under the tank in the middle of it. Hope this help u can email me if u want at angeloecker@hotmail.com

[Aecker]

Hope this help.

[PepaPowah]

Originally Posted by Aecker

Hello sorry didn’t see ur post earlier. The jets I found on eBay just do a search for pz22 4mm jets should come up u will need main jets and pilot jets. I was running 98 main and 36 pilot but was running rich so I’m down to 90 and 30 and needle on bottom air 1 1/2 turn out. After checking the spark plug notice bike was running lean, re-jet is main 92, pilot 30. Will update after test driving. The extra hose that comes from the middle of the oem carb and goes into the charcoal canister u run to the top plug in the Pz22 carb just like in the pic, the hose in the back of the canister just run it up to under the tank to the tank overflow connection. It’s under the tank in the middle of it. Hope this help u can email me if u want at angeloecker@hotmail.com

i managed to install the car, did not have any luck finding the 4 mm thread pilot that would fit the car, but had another carb with a #35 pilot, and seems to be working just fine!

thanks so much for the help!
best,

[Michiganboomcatter]

Hi,

Great write-up. hopefully this thread isn't completely dead. I wanted to ask if there was a specific reason you didn't go with the vm22 carb as it seems from other forums to be a higher quality carb and not too hard to tune. Looking into upgrading my carb sooner than later.

Thanks!

[Aecker]

Hello, I just wanted to try this carb, it was cheap and works, the jet size 4mm thread is unusual, because of that I don’t recommend it. I may upgrade to a Mikuni down the line.

[Aecker]

Hello guys, just a update, I took the full emission egr system out of the bike, run the tank breather hose to the top nipple in the Pz22 carb, that carb nipple used to go to the charcoal canister. Also closed the manifold nipple with a rubber cap, that hose used to go to the egr valve. Block the head egr valve pipe with a home made block. Removing the egr system was easy. I did some research and found out that egr valve sends co2 from the combustion back into the engine that is not good for performance as the co2 takes the place of fresh oxygen. I can say it was a immediate improvement in the performance of the bike, I was also having a issue with vapor lock in the tank but this fixed it. The vapor lock was causing surging at high revolutions, when I stop and open the gas cap it would make that vacuum release sound. The bike is running cooler the idle is better and the spark plug looks great. I recommend everyone remove the egr system. Also got a new fairing on. Bike is cruising at 55mph in 5500rpm and I got it to 65mph at 7000rpm with some throttle still available. I think this bike will hit 70mph at 8000rpm but that’s pushing the engine to the limit and I don’t recommend it.
I’m running a 16t front pinion and a 37t rear sprocket. The bike still have plenty of torque at low speed. I may upgrade the rear to a 35t or 33t for more top speed. FYI if u gona drive it this fast, do a good pre ride inspection on the bike bolts tire pressure, etc to make sure it’s all good.

[Aecker]

Hello, it’s been a while, I bought a Zuma 125cc pit bike, it sputter badly on idle and cut off on throttle, so I transplanted the Boomcat carb on it, had to jet it again, running 85 main and 35 pilot, needle on middle slot(3 slots on it) bike runs perfect, idle percent also. The stock carb on the Zuma uses 5mm main jets but the pilot is a short stile like a keihin carb instead of the long Mikuni type. Order a new Mikuni VM22 for the Boom but it did not fit right as the Mikuni is bigger, and the jetting was not right, stock it had a 100 main and 30 pilot. it can fit but require some mods, I had a new spare Haiors PZ22, the same carb i took of the Boom, perfect fit and this time I just installed and try and the bike run perfect without jetting. Last carb was identical but need jetting? I guess it shows not all carbs are the same even if they are!
Stock jetting in this PZ22 is 85 main and 35 pilot.