100cc BBK - Won't start

[robb]

I had a 100cc BBK installed into my son's moped 50cc Taotao scooter. It ran great for a few days until yesterday. He drove it to the Mall and it stalled when he was almost there. He thought he may be out of gas. We filled it with gas and that seemed to be the problem until he tried to drive it. Each time he sat on it and tried to go it stalled. Now it won't start and smells like gas. He also tried to adjust the idle screw. With the BBK we didn't change any jets because the Carb was sealed and we didn't replace with a bigger carb. I also haven't yet replaced a timing chain tensioner that seems to be a little stripped. Any idea what the problem might be? I appreciate any thoughts on this problem. Thanks!

[tortoise2]

This thread is a reminder of how often relatively reliable stock TaoTao 50's are transformed into a pile of excrement by owner enhancements!

[fugaziiv]

Robb,

Couple of things: First off, there is no such thing as a 100cc kit. What size kit did you install? The piston diameter in MM will tell us quite a bit. Also, where did you source the BBk from? Determining the brand of the kit might help as well. Did the kit come with a head, or did you reinstall the stock head?

It sounds as if you didn't do any tuning to accommodate the BBK, so you should take a look at your spark plug too and come back with a picture of that as well, that'll help.

I'll be frank here, more than likely it's borked and it's going to take some work and money to get back going, but the above info will help.


Matt

[robb]

[robb]

Thanks Matt,

I really appreciate your thoughts. I had a friend of a friend install the kit. He is supposed to be a mechanic that works on cars and motorcycles. I have only slightly worked on motorcycles in the past. nothing major. The moped ran great the first few days. I'm really not wanting to turn a $ 700 moped into a massive investment but I would like to get it running because my son uses it to get to work. Thanks.

[robb]

[fugaziiv]

May 23, 2018 10:40:34 GMT -5 robb said:

Thanks Matt,

I really appreciate your thoughts. I had a friend of a friend install the kit. He is supposed to be a mechanic that works on cars and motorcycles. I have only slightly worked on motorcycles in the past. nothing major. The moped ran great the first few days. I'm really not wanting to turn a $ 700 moped into a massive investment but I would like to get it running because my son uses it to get to work. Thanks.

Honestly, if you want a somewhat reliable ride for your son take that bike back to stock. Unless you really like to tune (and that's fine, many of us do), a cheap 50mm ebay kit is going to give you nothing but problems in the end.



Matt

[robb]

After watching many moped videos about troubleshooting mopeds that won't start I figured out the problem and fixed the moped myself! I started with process of elimination between fuel, spark and air. I have a performance CDI, Carburetor, and air filter on the way because I thought these items might have corrected the problem before I solved the problem. I had NO spark. My son said every time he sat on the moped it would stall. It was the connection to the CDI box! Sitting on the moped would cause the connection to pull apart until it finally disconnected. It is running GREAT now!

[fugaziiv]

May 25, 2018 15:49:08 GMT -5 robb said:

After watching many moped videos about troubleshooting mopeds that won't start I figured out the problem and fixed the moped myself! I started with process of elimination between fuel, spark and air. I have a performance CDI, Carburetor, and air filter on the way because I thought these items might have corrected the problem before I solved the problem. I had NO spark. My son said every time he sat on the moped it would stall. It was the connection to the CDI box! Sitting on the moped would cause the connection to pull apart until it finally disconnected. It is running GREAT now!

Good job! I had a Honda with a bad plug wire and it took me quite a little bit to figure it out.


Matt

[robb]

Thanks Matt!

It was very rewarding to solve the problem through research and help from this forum. Now I just need to decide if I still want to put on the new performance parts that I ordered when the moped wouldn't start. I guess I have time to think about it. Thanks for your help. Much appreciated!

[GrumpyUnk]

From what I understand the 'performance' CDI, especially the orange models, tend to advance the spark timing more aggressively than stock, make it a slightly harder to start(advanced timing), and don't do much. 90GTVert tested and he went back to stock.
The air filter .. will/should need jet tuning to match airflow change. Not good in rainy/wet conditions.
The carburetor -- may add some volumetric efficiency, but run for a while and see if the spark plug looks 'lean' or more normal. It likely will add a bit of performance.
I'd use the carb and the factory air cleaner assembly. I would remove the small 'snorkel' just inside the air inlet at the front of the box.
tom

Added:

 The kit shown seems to include a new cylinder head.  It should accommodate the increased volume of the 50mm cylinder & piston, and keep the compression ratio close to stock.  That is a good thing.
 If installed properly, it should last as long as the rest of the engine is not revved beyond normal.  If it is taken to the redline all the time, I think the life is more limited.
tom

[bluebob71]

i have the same kit as this runs great hit 51 today gps varified didnt even max out rpms same kit with a upgraded exhaust, carb and airfilter. a lot of ppl on here have very off info lol, glad u fixed it tho.

[scootnewb]

May 23, 2018 9:37:12 GMT -5 tortoise2 said:

This thread is a reminder of how often relatively reliable stock TaoTao 50's are transformed into a pile of excrement by owner enhancements!

I think i am going to top that.