I recently installed a makoni style carburetor on my bike. But it won't adjust to any of the adjustments. I made with throttle screw, an air fuel mixture screw check for air leaks. No ear leaks was wondering while it'll only run. On choke i have checked Uber and Uber again for air leaks and that's my number one thing I go to you know, I have this problem, but there are no early leaks. Any suggestions.
New carb on my bike will not respond to my adjustments
- Thread starter Yungman
- Start date
Is the fuel tank mounted higher than the carburetor? Did you verify that you have good fuel flow into the carb?
You could open the bowl drain screw and see if plenty of fuel runs out. If you have good flow and no drips when the drain is closed, check your gaskets again. I like to use an UNLIT propane torch, directing a little bit of propane toward the intake area while the engine is running.
Should have asked you this earlier: Was the engine running before you put this carb on? Is the carb new?
You could open the bowl drain screw and see if plenty of fuel runs out. If you have good flow and no drips when the drain is closed, check your gaskets again. I like to use an UNLIT propane torch, directing a little bit of propane toward the intake area while the engine is running.
Should have asked you this earlier: Was the engine running before you put this carb on? Is the carb new?
"Won't adjust" and "It will only run on choke" are symptoms of an air leak. Nothing on the carb will tune when there's an air leak.
If the carb is not cracked there are only two places where it can leak air. Carb to intake and intake to the head. For carbs with a flange most common is carb to intake. The intake must be aligned to the carb before it is bolted to the head. You need to look down the bore of the intake to verify alignment while you tighten the bolts little by little.
Here's a picture looking down the intake that has very good alignment.
If the carb is not cracked there are only two places where it can leak air. Carb to intake and intake to the head. For carbs with a flange most common is carb to intake. The intake must be aligned to the carb before it is bolted to the head. You need to look down the bore of the intake to verify alignment while you tighten the bolts little by little.
Here's a picture looking down the intake that has very good alignment.
Generic Chinese carburetors from Amazon and eBay are a crapshoot. Quality is oftentimes poor and tuning is usually imperfect. First thing is verify no intake air leak and always verify engine valve adjustment is correct. I have boxes of carburetors that were replaced when owners replaced them, only to find out the engine had a tight valve. If you are running only on choke and have no intake air leaks, it indicates engine wants more fuel. Start by increasing pilot jet size and test. Main jet and needle can be adjusted gradually until engine runs without choke when fully warmed.
I had the exact same issue! Is it on a 200cc class engine? The chikunis usually have way too small pilot jets, usually better for something like a 100cc or so, so i recommend drilling it till it works or getting a fuel jet pack since pilot jet holes are so tiny.
Quick breakdown on what's going on (from what I can tell): Your pilot jet being too small (common mikuni clone issue) means that your engine can't idle off of the pilot jet, and is instead idling off of the main jet due to the insufficient fuel amt. Your engine only running on choke in this case means that you're artificially richening the air fuel mixture to get it to run in this "limbo state" where it does run and rev (poorly, most likely), and can't be tuned. because the choke is what is "tuning" it.
Had the same issue with a chikuni, only ran on choke, idle screw had to be turned to the max, and the mixture screw didn't really do anything. Also it overheated a ton, though I'm unaware if that's related.
in terms of jet choice, you want to find a pilot jet that allows for your engine to idle with the idle screw to be around the middle point of how far it can be screwed, though i bet you can look up whet jet is ideal for your engine, something along the lines of "best 212cc mikuni pilot jet size". Also put into account any upgrades you've done, as something like valve springs or an exhaust being on your engine for example can benefit from a richer (than before said upgrades) mixture. I also recommend messing with main jets, as the stock ones in the chikuni carbs i've bought are better for something like a 160cc engine.
Check for air leaks by spraying starter fluid on the carb while it's running. if none goes in the throat of the carb but you can hear more fuel get to the engine you have a leak.
Quick breakdown on what's going on (from what I can tell): Your pilot jet being too small (common mikuni clone issue) means that your engine can't idle off of the pilot jet, and is instead idling off of the main jet due to the insufficient fuel amt. Your engine only running on choke in this case means that you're artificially richening the air fuel mixture to get it to run in this "limbo state" where it does run and rev (poorly, most likely), and can't be tuned. because the choke is what is "tuning" it.
Had the same issue with a chikuni, only ran on choke, idle screw had to be turned to the max, and the mixture screw didn't really do anything. Also it overheated a ton, though I'm unaware if that's related.
in terms of jet choice, you want to find a pilot jet that allows for your engine to idle with the idle screw to be around the middle point of how far it can be screwed, though i bet you can look up whet jet is ideal for your engine, something along the lines of "best 212cc mikuni pilot jet size". Also put into account any upgrades you've done, as something like valve springs or an exhaust being on your engine for example can benefit from a richer (than before said upgrades) mixture. I also recommend messing with main jets, as the stock ones in the chikuni carbs i've bought are better for something like a 160cc engine.
Check for air leaks by spraying starter fluid on the carb while it's running. if none goes in the throat of the carb but you can hear more fuel get to the engine you have a leak.
I am referring specifically to most china-clone mikunis, especially the VM22 to VM26 and pz22 to pz26 clones with the round slide. Just to clarify, because I never stated that in particular, so I'm not fully sure if it's those you are talking about. I am unaware about that when it comes to the other designs though.