Brand new mikuni carb runs full on choke

[paulsblocks]

I just bought a brand new mikuni 22mm carburetor for my predator 212. At first it ran alright but after running it for about 5 mins it shut off. It would only start again with the choke on, but when it starts it dies when the choke is turned off. usually I think this would be a tuning or carb cleaning issue, but the carb is new, and it was running fine at 1 point, so i have no idea what it could be. I have a straight pipe exhaust on it, not sure if that makes a difference

Here is a link to a video of how it is running:

https://youtu.be/U_C9u0ldrIo

Here is a link to the carb:

https://www.amazon.com/gp/product/B07H967VTM/ref=ppx_yo_dt_b_asin_title_o08_s00?ie=UTF8&psc=1

 

[bthompson224]

But were the tank and fuel lines clean?

 

[paulsblocks]

Fuel line was new, gas tank was older and was used with a 2 stroke. all the fuel was dumped out before it sat. There could have been gunk in the fuel tank, but would it really clog up the carb that fast and to that extreme?

 

[bthompson224]

Doesn't take much to impact these little carbs.

 

[paulsblocks]

Alright I'll look into it. Anything I should keep in mind when cleaning it? Will some shots of carb cleaner work to clean out the jets or should I use a toothpick or something?

 

[bthompson224]

I always use a small piece of wire and run it through the jets.

 

[mckutzy]

Sounds like you need to turn the idle way down....
Check for air leaks around the head and joint of the carb/adapter...

Did you jet the carb accordingly to a plug test?....

 

[BigWes]

A mikuni is a different animal though, you must remember the choke works differently as well. It's more like a fuel enrichment versus a true choke.

Check all the usual suspects but make sure you have the metering valve set rich enough. It sounds as if it's leaning out under normal operation. But I'm not there to get my hands on it.

 

[paulsblocks]

Sounds like you need to turn the idle way down....
Check for air leaks around the head and joint of the carb/adapter...

Did you jet the carb accordingly to a plug test?....

I dont think it's a idle screw problem because that only has an effect on about 5-10% of the throttle. I sprayed starter fluid near the head but it didnt change the idle so I dont thing theres a leak. What's a plug test?

---------- Post added at 05:06 PM ---------- Previous post was at 05:04 PM ----------

A mikuni is a different animal though, you must remember the choke works differently as well. It's more like a fuel enrichment versus a true choke.

Check all the usual suspects but make sure you have the metering valve set rich enough. It sounds as if it's leaning out under normal operation. But I'm not there to get my hands on it.

Would a clog in the choke circuit cause it to run lean? I'd think if there was a clog then the choke would just have no effect at all

 

[mckutzy]

Here's an article off hand, explains the basics...
You'll have to do more research on carb tuning for your type of carb...

https://www.tuningmatters.com/how-tos/beginners-guides/check-spark-plug-correct-carburetor-setting/

 

[bthompson224]

Would it have run fine for several minutes out of adjustment? I say do the simple first, clean it and the tank before you start turning screws.

 

[paulsblocks]

I figured it out. I bought a fake mikuni, guess I should've known by the price. I am returning, and I'm going to get a real one from gopowersports. It isn't worth the money you save if it doesnt work

 

[Mrmonk7663]

I don’t think it’s because it’s fake. I got a Predator last night from a guy and same issue. It idles wonderful. Once warm I can turn choke off. From there ANY throttle input kills it immediately.

 

[anickode]

I figured it out. I bought a fake mikuni, guess I should've known by the price. I am returning, and I'm going to get a real one from gopowersports. It isn't worth the money you save if it doesnt work

When I looked at the link, I immediately thought it's probably fake based on the price

Not all mikuni clones are crap, but there are definitely some bad apples.

 

[mckutzy]

Isnt improper jetting going to effect the running? Ie if any throttle is applied...

 

[BigWes]

Those things are tuneable across 3 ranges of throttle settings. There's an idle screw. That metering rod which adjusts mid range throttle I think and another adjustment as well.

I have a Japanese made Mikuni sitting in the box brand new in my office uninstalled because I know it's going to take a minute to get right.

My suggestion to anyone fiddling with carbs and fuel systems is to start clean. Always...any debris in that tank will find its way into some small important orifice in your carb and it will ruin your fun. You can't go wrong with a properly installed inline fuel filter either...I know they ugly...but they are a life saver when it comes to keeping trash out of a carb.

That's entirely your call on returning it or not. I don't have any personal experience with the Chinese Mikuni carbs. I think the Chinese do some things well and others maybe they rush through without enough attention to quality. A carb requires attention to detail.

Watch some tube videos on these carbs. Even all the big bike mikunis work and tune alike from what I gather. I understand they are great carbs once you get a feel for them.

 

[BigWes]

If you want you can adjust the metering rod on the slide...I would try setting it on the second groove from the bottom. Set your idle air mix to run a little more rich see if that works.

---------- Post added at 02:31 PM ---------- Previous post was at 02:20 PM ----------

After watching your video several more times I feel like it's running too fast in idle. Your throttle cable hasn't pulled it out of idle has it? It is fully returning is what I'm asking.

But hey, I like the look you are working on. That's gonna look great when you get it going like you want!

 

[Joe-405]

I got the real one and kit from gopowersports and it took me at least a week or two to run and start correctly. Still not right FYI.