2018 Hellcat carb and engine question

[DoctorTokyo]

Hello! Sorry in advance for any formatting issues or other post errors. I have never used a forum before but I have been lurking here for quite some time!

I have a 2018 Taotao Hellcat 125 and, following some minor issues, I replaced the carb once riding season came back for me this week. I got one of the vm22 26mm knockoffs (not knowing it there was a difference at the time of purchase), took off the airbox, and used it to upgrade the stock carb. I have a strange issue where when I give it throttle, there is a very airy sound accompanied by a loss of power. It sounds almost like a small steam engine.

I thought it was very lean, so I tried several larger jets and various turns on the mixture screw. It seemed to get better, but I am currently at the largest jet I have (125 from an amazon kit) and the mixture screw is as far out as I'm comfortable with. It still sounds airy and loses power between 1/4 and 1/2 throttle. I'm not sure where to go from here.

While upgrading the carb earlier this week, I also had a portion of a tube fall off of my bike. It came from the very back of the engine, but I'm not sure where the other side is supposed to go. I looked at several videos of hellcats and similar bikes but none have been clear enough to show me what it's supposed to connect to. Could this be the source of my carburation issue? It's a tube with a little clamp that's come from the rear of the engine, near the rear shock.

Thanks in advance for reading this all and hopefully someone knows what's up!

[grumpyunk]

Save 1000 words and post a few pics. Of the mounted carb, in place, and of the part that fell off.
tom

[DoctorTokyo]

Hopefully these upload properly. I'm not sure about the process here but I couldn't shrink the file sizes down enough to upload from my pc. Can't take the plastics off today due to weather and no garage, but I hopefully can tomorrow if it's not clear enough

https://imgur.com/bkRwhN5
https://imgur.com/N0Gz6D7
https://imgur.com/bkRwhN5
https://imgur.com/pEGkInN

[Bruces]

The hose is just a vent ,it just loops down behind the engine .

[DoctorTokyo]

I appreciate that! It's good peace of mind to know that I at least don't have to worry about that hose. Thanks man!

Just need to figure out why it seems to run so lean still. I might try a smaller jet just in case I'm wrong and it's rich. This whole process has been new to me lol. I don't think I'm able to do a plug chop since I live in a major city and there's nowhere to open up the throttle unfortunately.

[China Rider 27]

Does it idle well? Meaning consistent without any up and down rpm?

I would check for a leak at the manifold or carb. Air getting in would cause it to lean out but you should see that at idle.

A typical main jet is like 100 and a pilot of 17.5 but 1/4 to 1/2 throttle is not a main jet issue. Main jet comes in at 1/2 throttle. How far out are you on the mixture screw? Did it run good with the stock carb before you upgraded?

[DoctorTokyo]

Before changing carbs, I always had an issue idling until it was warmed up. After that, it would run fine. With the new one, I've never had an idle issue so far. In fact, it seems like I don't even need choke to start it up. It has been hot here recently though.

I did try running without the black spacer in the image before, but during the few times I changed the main jet I decided to put it on just in case. Both the carb and the spacer have o-rings, but the spacer is suspiciously small. I'll try this same set up again without the spacer to see if it's different at all. I'll pay extra attention to avoid any potential gaps.

[China Rider 27]

I would check your jet needle position and experiment with the needle position, raising the clip position leans it out and lowering richens.

[DoctorTokyo]

The needle on the new carb started on the 2nd to lowest position and I did move it downward to the last notch with no real change unfortunately.

[China Rider 27]

What jets are in it pilot and main? What is the mixture setting? The pilot jet from your report seems to be working fine if your idle is consistent and even around 1500 rpm. I would install a 100 main and the needle clip in the 3rd or middle position. See how it runs. I would then change the needle position one clip position at a time and evaluate. I would check and adjust the valves.

[grumpyunk]

Before doing any more jet or needle adjustments, pull the spark plug and post an image of the end that gets hot. No point in guessing whether you are generally running lean or rich when pulling a plug will give a good indication. Other than that, w/o being there, it is just a 50:50 guess.
If you take the carb off again, take a pic of the engine side of the carb with the spacer alongside so viewing the openings for comparison is possible. The spacer should keep heat away from the carb, but should not act as a restriction on air/fuel flow. If the spacer inner diameter is smaller than the carb outlet or the intake port on the head, replacing with larger, hopefully matched, diameter would be a 'good thing'. Else, you are adding a bunch of disturbance to the flow(turbulence), and possibly restricting airflow.
Have you checked your pilot jet for blockage? It is to handle off-idle to lower mid-range carburetor tasks, after which, at higher rpm, the needle takes over, and finally with the needle all the way out, the main jet controls flow.

tom

[DoctorTokyo]

I took a few pics of the plug just in case. Now I'm wondering if what I thought were lean symptoms were actually rich symptoms lol. Thanks for having me pull it so you guys can help me understand this.

As far as what pilot jet I'm using, I'm not sure. It's the stock one that came with this carb. I did look through both brass bits upon receiving the carb and they didn't look guncked up as all. Immediately replaced the main with a 115 since I saw a lot of people on here doing that, so I definitely know all the mains I tried aren't gunked up.

I can definitely pull the pilot out today and see if I can catch any numbers on it. The stock main actually didn't have any numbers on it at all. That's how I can tell it from the rest of the ones in my bag lmao

https://imgur.com/PwssvCG
https://imgur.com/3qXDxSR
https://imgur.com/lsNlE4D

[DoctorTokyo]

What jets are in it pilot and main? What is the mixture setting? The pilot jet from your report seems to be working fine if your idle is consistent and even around 1500 rpm. I would install a 100 main and the needle clip in the 3rd or middle position. See how it runs. I would then change the needle position one clip position at a time and evaluate. I would check and adjust the valves.

My bad for not putting this in the other comment but right now there's a 125 main in it after trying 115 and 120 and assuming they were lean. I'm not sure what the valves are though since this is my first time working with a carburetor

[DoctorTokyo]

What jets are in it pilot and main? What is the mixture setting? The pilot jet from your report seems to be working fine if your idle is consistent and even around 1500 rpm. I would install a 100 main and the needle clip in the 3rd or middle position. See how it runs. I would then change the needle position one clip position at a time and evaluate. I would check and adjust the valves.

Hey, so I tried those settings you suggested and it's significantly worse. I can't give her any throttle at all without her trying to stall now. I did check for air leaks, put a new gasket on, and I removed the adapter since I did notice that the hole was significantly smaller than both the carb and intake

[China Rider 27]

Tuning carburetors is not easy. Trying to help someone tune one through a website harder. We still don't know what pilot is in it or what your mixture setting is. It is time for you to take the big dive into learning how to tune your motorcycle carburetor. Search the internet for carb tuning information. Here is a link for starters:

https://www.motorcyclezombies.com/rebuild-tune-motorcycle/carbs-fuel-air/troubleshoot-tune-sync-motorcycle-carbs/

After thorough analysis and the logical adjustments according to tuning rules, exhausting all adjustments, pilot jet changes, clip positions, main jets, mixture adjustments and the carburetor does not respond, then one must consider that the carburetor is defective. Not uncommon with these cloned knock off china carburetors.

As a test to this conclusion, install your stock carburetor and see if it acts normally. If not, then you must consider some other cause. Adjusting the valves is also a critical tuning element to get it right.

[grumpyunk]

Put everything back to the way it was when it last ran, even if it was not perfect.

Change ONE thing at a time. When you make multiple changes, please tell me which one was workging and which one caused it to stall. Or, which one you should keep and which to back off? It is difficult enough to realize the results of one change, given temperature, humidity, and so on have effects varying from day to day and even hour to hour. Ir-reproduceable ... can't make it do that again... that's what you get with multiple changes and atmospheric/ambient changes occurring.
The plugs looked a little rich to me. I can't keep track of your jetting, your needle setting and your idle mix adjustment, only you can. To know, or at least get ballpark, you need to start with known settings, note acceleration/stumble/idle/startup results, figure where you need change, change, and note the results. Just throwing jets and adjustments hoping to hit upon the 'best results' is not gonna happen, unless you are very lucky(if you get there, buy a Lotto ticket quickly...), so the plodding one-step-at-a-time is the only known process.
I have better things to do than do multiple acceleration and top speed runs to get the finest tune. I want easy starting, good stable idle, acceleration without stumble and smooth high speed running. Get me that, and a spark plug report showing I am in the ballpark, and I'm happy.
tom