Boom vader dieing after riding please help
 

So i bought a boom vader around 2 months back and havent had the best experience. Out the box i changed the oil, carb, and sprocket. I didnt clean the gas tank or replace the fuel line (I will probable replace fuel line soon).
Problem is, the bike starts when it feels like it and on a good day itll drive for like 30 minutes, then starts jerking, dieing and not starting anymore. then a few minutes later it might start again for like 5 minutes. I already replaced the battery and spark plug. the spark plug got dark as hell for 50 miles. Im new to bikes and carbs so if someone could please help id appreciate it a lot.

Check the valve clearances. You want approximately .06 - .07 mm, or .0025" - .003". Exhaust valves always run a little hotter than intake, so if anything they should have a larger gap. Chinese bikes are notorious for having valve clearances too tight from the factory, causing overheating of the head.

Edit: Overall I agree with 4T_Goblin's post below. Intake .003"/.08 mm. Exhaust I'd go with .004"/.10 mm. These are the recommendations for Lifan's new KPX. Before the KPX they said .06 mm for both valves on the X-pect for instance, and you would often find them from the factory much tighter than that even, like .02 mm, and require immediate adjustment. Finally they are getting their act together with valve clearances. Any time you get your hands on a Chinese bike, check valve clearance so you have a baseline for troubleshooting.

IMO .005"/.13 mm might be a little too loose, since the exhaust valve will not be opening as far. That also contributes to heat buildup, and a bit of power loss due to inefficient exhaust breathing. So the trick is to find the happy medium for valve clearances. For me that would be .08 mm intake and .10 mm exhaust. However, it depends on how hot the individual bike runs, so maybe for 4T_Goblin this is proper.

AFAIK, no one in the history of the universe has ever gotten a burned intake valve, because the fuel coming in cools off the valve. But the hot expended gases exiting thru the exhaust valve heats it up, so it is more important to make sure its clearance is not too tight or too loose. If the clearance is too tight, then as the exhaust valve stem heats up and lengthens, the valve does not fully seat and you lose power. If it's too loose, then it does not open enough, and the hot gases can't fully leave the combustion chamber. Screwed either way. The intake side is less critical.

As far as the dark plug goes, your replacement carb is running too rich. There is plenty of info on here and YT for tuning carbs.

Check all vents are functioning properly. Did you delete the egr system? Are you sure the carb is tuned correctly?

I run my valves at .003" and .005".

Sounds like the common issue these have with the fuel tank vent line being pinched. Check it under the left side plastics.

Another way to verify if this is the issue, after it stumbles and dies (sounds like fuel starvation), is to then open the fuel cap, give it a minute to refill the float bowl, and see if it re-starts and runs normally. if so, fuel tank vent line is pinched and plugged.

Do you have a guide or video on how to do a valve adjustment on these? I know how to do them on cars but im sure its not the same at all lol.

People are using the word 'vapor lock' when it's actually a vaccum being drawn in the gas tank from improper venting.


Ride the bike and when it starts acting up, quickly stop the bike pop the gas cap and see if that elevates the problems. https://mymotorcycleblog.com/boom-va...-lock-no-fuel/



Or just due what we all do. Upgrade the carb and manually fix the venting problem. :D
https://mymotorcycleblog.com/boom-va...cc-grom-clone/



Tom

Same idea as cars. Do a YT search on adjusting motorcycle valves and watch several. One critical thing that you can get wrong is using the wrong TDC. Other than that it is pretty straightforward.

Edit: Couldn't resist.

https://www.youtube.com/watch?v=vJgpDQ4RbwM

https://www.youtube.com/watch?v=5VJ8KFqXLYw

I like this guy:
https://www.youtube.com/watch?v=dDhGnXz5yKI

popping the gas cap might have solved the issue. i will try more some other day.

Thanks a lot man. once ill test if it is because of the gas tank while im waiting for the adjuster tool, if its not due to that ill use those videos and adjust the valves. (unless you suggest to adjust valves regardless?

I'd always check and adjust valves on a new engine, or check them on one that is experiencing improper running symptoms. Once they're within spec, you shouldn't need to check them for quite a while.. a couple thousand miles usually.

I'd test the fuel tank vent issue now.. just so you know or not.

Ah found the issue. When I was deleting the old carb system I plugged up the vent tube with a screw. My valve adjustment tools come tomorrow so I'm going to do that. Someone said I'm running rich that's why my spark plugs are caked with carbon, how do I tune my carb properly? I'm not able to tune it while the bike is running cause the adjustment valve sits on the bottom of the carb which is where the head is.

That's more likely a drain on the bottom of the float bowl. Don't know of any way to adjust a carb from there. The jets are inside, after you remove the float bowl. There's about a zillion YT vids on adjusting motorcycle carbs. Do a search, and watch several. The air/fuel adjustment screw will be on the side somewhere. Possibly under a cover you would have to drill out, very easy. Watch videos.

Lol my air fuel adjustment is on the bottom I think. Last couple of times I tried tuning the carb I have to remove the carb adjust then put back. Tedious.

Carb in question https://a.co/d/1HuFPCk

OK, mouse over the first pic on the Amazon page.
The screw on the bottom lets you drain gas out of the float bowl.
See what looks like a little brass BB embedded in the body? And above that, a brass tube.
The tube is for gas going in from the tank, and the brass BB looks like what you need to drill out to access the air/fuel mixture screw.

That is incorrect. The idle mixture screw is on the bottom of the carb between the bowel and engine side of carb.