Carb/Tuning Issues....HELLLLPPPPP
 

Hi everyone! I have a Bashan Storm 250 that is about 6 months old. I am very new to motorcycles and working on engines. I replaced the intake with a K&N style intake and was told I should re-jet the carb. I replaced the stock "main" 105 jet with a 110 jet. While I had the carb off, I decided to watch MotoCheez's tuning video. He suggested to modify the idle mixture as well. Mine looks different but I'm ASSUMING the below picture shows that. Well, I got distracted half way through and have no clue where it was stock and where I should put it back to. Also, it's a complete bitch to turn, is there a special tool for it or something? Pliers are definitely NOT ideal!

Anyway, I put the bike back together, getting it to start/idle is now difficult and giving it ANY gas makes it bog out and die. It runs somewhat alright on half-choke but still doesn't work right. Does anyone have any clue what I screwed up?? Should I put the 105 jet back on? I live slightly below sea level, btw. Please HELLLLPPPP! I don't know what I'm doing!!! Thanks! :thanks:

https://i.imgur.com/sCYDsOn.jpg

Had my carb on and off about 18-19 times before it was "dialed" in. Wish there was a shortcut, but is a trial n error sort of thing. Some lose guidelines are available from guys on here that know way more than me.

Would help to know if you've done any other mods, exhaust n such.

The only things I have done are aftermarket gauge and intake and remove the EPA/charcoal thing, whatever that is. As an update, I just put the 110 main jet back on there and it is starting, idling great now but still bogs really bad if I give it any throttle. How do I know which way that fuel mixture thing needs to go? Which way does it need to be turned (in or out) if it's bogging down?

Start with the idle mixture at 1 and 1/2 turns out from lightly seated then adjust from there. You will need a special D shaped screwdriver or use a Dremel or hack saw and cut a s slot for a regular screwdriver. What notch is the clip on the needle?

Mine had sat for the better part of two years.
I replaced fuel lines ( they were a bit rotten from sun) and am getting good fuel, but cleaning the carb didn't help.

Yesterday I installed a new Mikuni carb and an NGK plug.
Bike starts and runs smooth and twisting the throttle revs it up, but idle is way too high.
The info above is helpful, I'll take my Dremel and cut a screwdriver slot in the idle screw so I can back it out.

I have no idea what jet to use, I live at 6200 feet. Riding around here is 6000 to 8500 feet, but this winter if I want to ride I'll have to take the bike down to the desert, elevations there are from 1500 feet to 3500 or so.

Below sea level ? I hope you have a snorkel rigged up and waterproof everything else !
Just kidding. I am new to this carb thing myself, my last 5 bikes were fuel injected.

Perhaps back off the screw all the way out and see if you can get a replacement with a standard phillips head ( be careful, I believe there is a spring there when you back all the way out ).

First order of business for me was to buy a clone carb and rebuild kit, just to have it, its basically the heart of the bike.

I think you are going to get to a point where you strip or damage that screw and create a problem for yourself.

Get it out of there and get a regular screw in.

A good option

https://rover.ebay.com/rover/0/0/0?m...2F303210680840

If I missed something please forgive me but did you tank the gas tank off and turn it upside down and remove all the old gas and rinse with new gas?
If not do that, and I also would remove the Petcock and clean that thoroughly.

@JerryHawk250 - I'm going to try that this evening. Is there an easy way to adjust this thing WITHOUT having to take the whole damn carb off every time??? Also, we have the same bike and live pretty close to each other; do you think I should go ahead and get a Mikuni? Something's just not right with this one. I mean you (and many others) recommended a 110 jet and that just made my carb absolutely spazz out and not even start/idle! Also, do you know anywhere locally I can get this "d-shaped screwdriver" or will my only options be online?

@sandog - I PMed you but if you don't see that, the "screw" in my picture is NOT the idle RPM screw, it's the air/fuel mixture. If your bike is idling too high, there's a flat-head "screw" type of thing with a spring on it on the right side of the carb. Clockwise increases idle RPM and counter-clockwise decreases idle RPM. Just make small adjustments and listen to it. Having an RPM gauge is helpful too. I bought this one and it works pretty well: https://www.amazon.com/gp/product/B01CR2IC2Q

@NzBrakelathes - I see that's your eBay store and no offense, but I could buy a whole new Mikuni style carb for about the same price as that kit. I also don't need the sprocket as the Storm comes with the proper one.

@herbie - I really don't think it's a fuel issue. I only ever put 100% gasoline in it, the bike is only 6 months old and I rode it last about a month ago (it's been stupid hot lately).

Thanks for the input everyone! I will definitely keep you updated as to what is going on.

Not sure who would carry the D shaped screwdriver locally. If you have any problems getting it tuned I do have my original PZ30 carb that's already tuned for the stock engine plus extra jets. I have no use for it anymore if you want it.

@CaesarVis I have the PZ30 and have the same fuel mixture screw. Do NOT buy the Motion Pro D-Shape carb tool from Amazon it won't fit it's too big.


I ended up buying this but NzBrake's ebay kit version is even better. I use a small flexible screwdriver extension from Harbor Freight to reach it.


The main jet you put in won't affect the idle much. Factory fuel screw setting is 2 turns out on mine. Optimal is 1~3 turns anything else to get the highest idle RPM you should change out your slow jet.

OK guys, so here's where I am now. I took the carb off and used pliers/hemostats/tweezers to screw it in absolutely as far as I was able to...not sure if it was bottomed out or not. I backed it out 1.5 turns. The bike now idles much more stable than it did but it still bogs HARD if I give it any throttle. The exhaust also gets black when I give it throttle...what does that mean? Would a short video be beneficial to show exactly what is happening or do yall know what I'm talking about?

Check the needle clip position. It may be set on the rich side. Should be on the middle slot for starters.

Did you pull the plug yet? It could tell a story rich vs lean

Sanddog is correct, you should buy a cheap lawnmower tach to tell you what your RPMs are ..get closer to this being an exact science than a guess

Carb adjustment basics and standards.

A VERY long time ago carb manufacturers realized there needed to be a standard adjustment/setting for the fuel mixture screw so your average mechanic could accurately tune various carburetors without much difficulty. And here it is, regardless if it's on a car, bike, lawnmower, etc..

The starting position is 1.5 turns out from lightly seated (don't crank it down), and then you turn the screw in or out until you achieve your highest/best idle rpm, and then you turn the screw back just far enough to detect the slightest rpm drop. If this setting is below 1 turn out from lightly seated you need a smaller pilot jet, if it's above 2 turns out you need a bigger pilot jet.

From there it's on to the main jet. Start with a medium jet size for the particular carb you're tuning (we'll say a 110 for the stock or clone carb) and see how it runs. If it bogs at WOT but runs better with a little less throttle you're probably too big on the jet size. If it runs better at WOT with half choke or sounds revvy and poppy, or if you notice your exhaust pipe is getting really hot, you need a bigger jet.

Once you think you're close then it's on to WOT "plug chop" runs (hate that terminology). Which involves bringing the bike up to operating temperature, putting a brand new plug in it, and winding out every gear at full throttle and then hitting the kill switch before you let off the gas and let it coast to a stop. If the plug looks white or an ashy gray then you need to go up a size. If the plug looks black and sooty you need to go down a size. What you're looking for is the porcelain around the center electrode to be a brown color and the outer part a dark color.

Now it's on to the needle (needle jet jet needle is the proper term). You would have already set this at the center C-clip/or stock position for the above tuning adjustments. If you feel a slight bog as you're twisting the throttle/coming off idle then you need to raise the needle/lower the C-clip. I personally raise the needle as far as I can go without getting dark smoke and losing acceleration characteristics, you're looking for a smooth transition.

And after all of that... you go back to the A/F mixture screw and fine tune it as previously described, and then do some overall plug readings to be sure all is well. You're bike should start well with minimal choking, not bog slightly at WOT, and shouldn't snap crackle and pop when you let off the throttle. :tup:

If its bogging no matter what main jet you use, it's possible that your float valve needs to be adjusted. If the fuel level in the bowl is too high it will cause the engine to run rich.
Also what altitude are you at?

Super nice info thanks! Exactly what I need to tune my carb.


I came across this info for 2-strokes maybe for the most part it will work for 4-strokes?

The plug is VERY dark right now. @thepostman4, I'm either right at or slightly below sea-level. Would the needle air/fuel screw on the bottom being out of adjustment cause the bogging and smoking I am seeing now? It really is a pain in the ass because I have to take the whole damn carb off the bike to make an adjustment then repeat the whole process...unless I'm missing something.

That's good information for a 2-stroke with an air screw, but doesn't really apply to our 4-strokes with a fuel screw.

Float height is important too. The standard for it is to hold the carb upside down with the bowl off. The top of the float should be horizontal with the float bowl mating surface.

OK, more information. I found a picture of the carb I took the other day and I THINK I got the fuel/air screw back to where it was before but it's still bogging out. In neutral, when I rev it, it starts to crap out between 3,000-4,000 rpm and WILL NOT go above 4,000 rpm. Any ideas what would cause that?

Did you adjust the valves? That would one of the 1st things to do before trying to tune.

Alright guys, I figured out the issue and I feel dumb now! I NEVER use the choke so didn't really know what direction was what. I thought up was off but apparently up is ON. I have had the damn choke on this WHOLE freaking time. Thank you so much to everyone that assisted me and I'm sorry to have wasted your time. At least some other good discussions took place!!! Thanks again guys! This community really is amazing!

I have adjusted the valves a couple of times. Most recently a couple of days ago to 0.003/0.004 on intake and exhaust.

No problem. Just glad we could help out. You're not the first to do that. Lol

trhere is a special tool you can use to adj the screw, I dont have the link but maybe search past threads

:doh: Well atleast my fingers got a good workout.. :lmao:

Nice tool but won't work with his carb. It has the D shaped end on the idle mixture screw.

I just glue a socket or attach a rubber hose to that fuel mixture screw for now. Still waiting for new screw with slotted end to show up...

The head of mine stripped out last night. Went to turn it with a standard screw driver as normal and pop! O well.

I did the exact same thing yesterday. No choke, runs like a scalded dog!

I got mine sorted out tonight. I backed out the air fuel screw 1 1/2 turns and it was still not wanting to run unless the choke was on.
Took the choke off again (new carb has a slotted head screw) to get to the screw, backed it out another 1 1/2 turns, and turned the idle screw in a bit.

Finally, runs good with the choke off for once, revs good, and no popping when you let off.
I'm sure it still needs some fine tuning, but it runs now.
Going for a ride in the morning !

Best use the tool for the air screw - open till best idle and close off 1/8 turn.
It is adjustable for a reason and no 1 setting in correct for all.