About 4 weeks ago my father-in-law bought my two sons two used bikes. My youngest was given an Apollo DB-21 70cc and it was running fine until last week. I am not a mechanic so I called my father-in-law to try to help me fix the issue and he had me put on a new carburetor that came with the bike. That worked for a few days, but now the bike won't start unless it has some throttle and it dies immediately when the throttle is released and it will not idle. The bike honestly sounds "off" when it's running too. I called my Father-in-law again and he said I need a different carburetor because the choke is on the wrong side. Again, I don't know engines from a mechanical standpoint, but it doesn't seem to me that the choke being on a different side would have any effect on the bike starting. If anyone can help me find a solution I would greatly appreciate it.
Need help finding the issue for a Apollo DB-21 Youth bike
- Thread starter shiverman
- Start date
If after you clean the carb, it still has the same symptoms, I would then check the valve clearance, wouldn’t hurt to check for air leaks between the carb and engine either.
I took the old carb apart and cleaned it and even put in a new one after testing the old one. The bike won't even start now. I have a new spark plug in it, cleaned the tank and the fuel line. Before It would start if I gave it a little gas and held the throttle, but now It won't even start.
I’m assuming you checked for spark by now….was there any valve clearance?
I put in a new spark plug today and checked it, it works fine. I'm not familiar with valve clearance or what that entails. If the fix is anything other than the carburetor I won't be much help sadly. If I do need to pay someone to fix the issue, it may be cheaper to get a new bike.
YouTube is your friend, I looked it up, and the valves are adjustable with a screwdriver, no shims involved. At least for their 250 model, I’m betting that the rest of the bikes are the same design, Give it a shot, the worst thing that will happen. Is you’ll still have a bike that doesn’t run.
I haven't looked at valve adjustment yet, but When I try to kick-start it, it sounds like I'm losing air somewhere. I did a compression test on it (cold engine) and I was only getting about 60 psi out of it.
If it has an auto compression release valve, then those compression test results may not be valid, a leak down test would be the best way to go, just make sure that the piston is on top dead center on the compression stroke, if you do not have a leak down tester you may be able to rent one from an auto parts store.
I bought this used Apollo for my son about a month and a half ago and it ran fine. About 3 weeks ago it would only start and stay running if the throttle was held down. 2 weeks ago I couldn't get it to start at all. I have put on a new carburetor, cleaned the lines, and checked for junk in the tank but still nothing. It has Fuel, spark, air, and some compression. I ran a compression test on it last week, It had to be on a cold engine because I can't start it and the meter stalled at 60. Any advice is appreciated because I'm trying to get this thing to run so my son can enjoy this nice weather.
I have attached a video link of me trying to start the bike with no throttle and then some throttle. I don't know if you can tell anything from just sounds or not, but it might help. https://vimeo.com/821815868?share=copy
I have attached a video link of me trying to start the bike with no throttle and then some throttle. I don't know if you can tell anything from just sounds or not, but it might help. https://vimeo.com/821815868?share=copy
Yes, I did try that, and still the same result. I tested the spark plug again and I do have spark, I checked to make sure I'm getting fuel and I am receiving fuel, the carburetor I put on is brand new, but just in case, I did check the float, pilot, etc.Have you tried starting fluid in the carburetor? It's one way to verify if the engine is having a fuel or spark issue.
-BIG DAN
If it didn't burp to life on starting fluid, but you have spark... then the timing is wrong, or not enough compression.
Compression is usually lost through the piston rings or a bent valve.
These motors are very easy to work on and gaskets and parts are dirt cheap.
I just re-ringed my 200 Lifan for $11
-BIG DAN
Compression is usually lost through the piston rings or a bent valve.
These motors are very easy to work on and gaskets and parts are dirt cheap.
I just re-ringed my 200 Lifan for $11
-BIG DAN
I did a compression test on it cold because it won't start and the needle topped out at 60. I'm not a mechanic so I am not confident in my abilities lolIf it didn't burp to life on starting fluid, but you have spark... then the timing is wrong, or not enough compression.
Compression is usually lost through the piston rings or a bent valve.
These motors are very easy to work on and gaskets and parts are dirt cheap.
I just re-ringed my 200 Lifan for $11
-BIG DAN
The only way to become more confident is to turn wrench.
Disassembly is Free.
60 PSI would probably be too low, but not the correct test for a 4T motor.
A leakdown test can tell you what percentage of pressure is lost through the engine giving a better idea of health.
Compression tests are usually used as a comparison to a previous reading.
These motors only require a few bolts here and there to check the piston rings for end gap. Valves can be leak tested with isopropyl alcohol and gravity.
www.youtube.com
This video is just to make you more comfortable with what's inside.
You don't need to remove the valves or valvetrain unless you find they are leaking.
-BIG DAN
Disassembly is Free.
60 PSI would probably be too low, but not the correct test for a 4T motor.
A leakdown test can tell you what percentage of pressure is lost through the engine giving a better idea of health.
Compression tests are usually used as a comparison to a previous reading.
These motors only require a few bolts here and there to check the piston rings for end gap. Valves can be leak tested with isopropyl alcohol and gravity.
HOW TO: Complete Tear Down & Rebuild of a Chinese ATV Engine Head. Every step you'll need covered!
~Parts Used~Valve Set for 125cc - https://www.vmcchineseparts.com/collections/valve-set/products/chinese-atv-engine-valve-set-with-springs-clips-for-125cc-ve...
www.youtube.com
You don't need to remove the valves or valvetrain unless you find they are leaking.
-BIG DAN