Need help with GY6 50cc Vitacci Rocket after BBK

[chrisbarclay0503]

Hello all,
I am trying to get my sons Vitacci Rocket scooter running again. My son passed away this year at 20yrs old and this was the last project we did together. We put a Big Bore Kit on it a few years ago and it ran with a jump start. The battery was to small and felt like it had to much compression which sounds crazy on such a small engine. I recently bought a new 330 CCA lithium battery and it will not start. I put a new bendix also. He had a kick start on it but it broke off. I put a new starter and relay on it. I put a new carb on it today. I checked the valves and both were 0.04 like it says. It’s getting spark, gas but when the starter kicks on it only get like one rotation then stops then goes again. I am very frustrated at this point and asking for help if anyone could help. If it wasn’t for the sentimental value I prob would have set it out to the curb. I basically redid everything on it had all the plastics painted, some of the metal parts powder counted thinking it just needed a battery. Please help I will try anything at this point. I’m not a mechanic but can usually figure this stuff out. I ordered a new EDI just to make sure it wasn’t that. I’m not sure what he did last to it so I am replacing everything new as I try to narrow it down. I think it has to be the compression though. I’m not sure if just replacing the engine would be wise at this point. Thanks in advance for any help. I can post pics videos what ever it takes. Thx..

[GrumpyUnk]

Most starters have little problem with BBKs. If your starter will not turn more than one revolution before quitting, I would suspect the large cables or the relay. Both power and ground should be checked as should the starter relay. Any looseness or corrosion, or even a too-thick coating or paint can reduce available current leading to a weak starter. If the relay has corrosion or worn contacts(internal), or loose cable connections, it cannot pass enough power to the starter. If the starter itself has gotten oil soaked, it may have an oily armature and/or brushes, which tends to insulate them from good contact, limiting current flow.
Noting the new parts at this moment, it would tend to point to the cables and terminals having problems. You can test using regular jumper cables to connect the battery + to the starter relay, and the battery - to the bare metal of the chassis or the bare metal of the engine. If that does nothing, connect the between the out side of the relay and the terminal on the starter. Essentially bypass the current cabling/terminals.
tom

[chrisbarclay0503]

So I installed a new CDI, ignition coil voltage regulator relay. He had a blue “racing” CDI installed. I went to try to start after and now the starter is actually turning over like it should. The battery was drained so I just stopped to put it back on charge. Hopefully it will start up today when I try after work. I will post results later. I don’t understand how the CDI would make the starter work differently but I guess im not really sure what it actually does. I ordered larger guage wire and new jumper cables before installing the new ignition parts. Thanks for the help..

[chrisbarclay0503]

Well it did not start just cranked little faster then it use to like it’s trying to start. I guess I need to start just checking the basics. It has brand new plug and is getting spark. I assume it’s getting gas because I can see where the pitcock is gas is flowing towards carb when I hit the starter. I am going to try and spray starter fluid into the carburetor. It’s in a tight spot the starter fluid I have kinda trickles out so I don’t think it’s getting in there. If that doesn’t work what should I do next. Is there a way to see if the carb is getting gas to it without taking off completely. Also should I mess with the adjustment screws on the carb ?

[chrisbarclay0503]

Update: Just sprayed starter fluid directly into the carb and it did absolutely nothing. Pulling the plug and triple check it’s getting spark now.

[chrisbarclay0503]

Sorry so many updates but pulled plug getting spark of course. I even sprayed some starter fluid down that hole and got nothing. Any ideas on what to do now. Any help is greatly appreciated .

[chrisbarclay0503]

Ok. If anyone is still reading these I know it’s a mess lol. I’ve gotten it to at least tune over better. Spraying starter fluid into does nothing. I started thinking about parts he may of changed and I think the carb that was on it wasn’t original. It has a fuel discharge hose on it with a set screw at the end of it. I looked it up and the original does not. So I may of bought the wrong carb because I bought the same one. I’m not sure if this would make a difference but I bought the original o e and should have it tomorrow. They’re exactly the same aside from the discharge hose. I will update. Thx

[GrumpyUnk]

When you tried the starting fluid or choke cleaner sprayed into the carb, did you crack the throttle open a bit? Could be the idle is set low, and it needs a bit of throttle to allow some air to go with the fuel.
tom

[chrisbarclay0503]

Yes, I turned the throttle full open sprayed some starter fluid in there. Went and bought new starter fluid thinking maybe it was old but same result. Last resort I sprayed a lot in it and still nothing. I got the new carb (2nd one) and nothing. Took the carb back out sprayed some starter fluid into the manifold. Sprayed in air intake and still nothing. I am about to give up I re checked the valves all good there checked for spark all good and I can see fuel going into the carb and it’s full when I remove it. The only possible thing it could be is the timing I think. If I was to buy a replacement engine what would you recommend. I would like to swap to a 150cc but don’t think it’s possible or at least fairly easy. I have Vitacci 49cc Rocket.

[pili]

Sounds basic but have you made sure fuel is flowing by disconnecting the fuel line at the carb and cranking? Any time the scoot sits for long periods the gas in the float bowl evaporates. In those onstances I disconnect the vacuum line that goes to the petcock and apply vacuum to it to let fuel fill the float bowl. As long as you have spark and didn't mess with the stator the timing should be fine.

[GrumpyUnk]

If your exhaust is clear, and I have had mud daubers clog them severely, then ignition timing would be my next check. If the spark occurs too late or early, the engine might not fire. If the spark plug is wetted with fuel or anything else, it may not produce a usable spark. Has it been inspected for dryness and proper gap? Does it have deposits? I cannot keep track of all threads, so if this has been covered, never minds...
tom

[chrisbarclay0503]

Sorry if I am not posting in the same thread I thought I was.

I checked gap on plug, bought new plug.
Definitely getting spark when checked.
When I pull plug out I can smell gas but it’s not dripping wet.
I sprayed starter fluid into thru air filter with throttle opened.
I took carb off put new one on when off I sprayed fluid into it.
The carb had fuel in it and when u start it you can see the fuel getting vacuum and going to carb.
I re checked the clearance on valves both were perfect I even tried adjusting them but no luck.
I started taking it apart and got the back swing arm off and the back wheel. I thought a new engine would be an easy fix. When i was ready to order one I realized the 49/50cc GY6 long case with long shaft is hard to find and cost way more then what I expected. I don’t understand why the 49cc cost more then the 125cc but I found out you can’t use those because they have different mounts.

With your last post I think it has to be the timing ignition is off not sparking when it should like you said. I think my last Hail Mary will be purchasing a new big bore kit and installing it myself and make sure the timing is correct. That’s the only part on the bike I am not sure if and fairly cheap to buy. I’m not sure how the timing works on these but I’m sure I can find a video. I appreciate you taking the time to help. If this wasn’t sentimental I would have sat it out for the trash lol. Now I am really vested in getting it going. Anyway thanks.

[GrumpyUnk]

AFAIK, the only timing thing that can be fiddled with on these is the cam timing. To check, remove the blower fan cover and look at the flywheel for a T mark. That is the TDC mark to be aligned with the mark on the case.(at about the 10:00 o'clock position).
The cam timing is not so easily ignored, and must be set properly. If it is off, the valves will not open and close at the proper time in relation to the piston position.
With the T aligned with the case mark, the cam must have the large hole in the sprocket at the top, and the two smaller holes aligned with the top surface of the cylinder head.
You can check and post pics for comment by the peanut gallery. Do NOT place peanuts on the site....
Actually, pics will help to affirm proper timing. If you have spark, compression, and fuel mixture available and compressed, and it sparks at the right time, it should fire. fuel, air heat and compression... as I recall.
tom

[chrisbarclay0503]

I removed the engine to have easy access to see the timing marks. The holes are aligned correctly and the T line was set perfect. Removing everything will help me understand everything I think. I ordered a new BBK and should be here Friday. I don’t think it will be the issue but it won’t be a lingering thought. I did notice at the bottom of where the vacuum lines connect there was no vacuum lines on the bottom. It’s called “pair system” I think. The carb had the vacuum lines on correctly I’m sure I double checked. It definitely was drawing fuel into the carb. Is there a diagram that shows 49cc Vitacci Rocket gy6 vacuum diagram anywhere I can’t find any. By the time I am done I will have touched every part on this bike lol. I guess that’s how you learn. I just know it’s going to be something simple. Can I post pics on here I didn’t understand what you met by peanut gallery..? Again thanks for reading and helping.

[GrumpyUnk]

I do not understand the logic behind getting a different BBK and installing it. If the current piston & cylinder are functional, you should have enough compression for the engine to start.
Replacing those parts will not make a fig bit of difference if they are sealing properly and have good compression.
If I understand, you have tried adding fuel to the inlet of the carburetor, spraying down the throat into the intake with no results. If true, either you have poor spark, or poor compression, that is if you have good compression. Most engines will at least pop and make noise if fed liquid fuel down the carb, and then cranked over with spark working and compression. If you have compression, that points to something in the ignition system. It is possible the pickup that tells the CDI to fire is not working properly and you can check for its signal with a VOM. It is possible the spark plug has an inherent problem that causes it to fail to produce spark... the coil could be weak... in short, NOT the piston, cylinder and rings.
Replacing the BBK likely will turn out to be a waste of money and time. I could be wrong.
tom