Yesterday, my bike worked fine. This morning, when I tried to ride it again, it wouldn't start. After a little fiddling, I found out that the black rubber thing that holds onto the spark plug was undone from the black rubbber coated wire. It had a screw in it, I guess to make the connection to the wire, so I screwed it in again with the wire around it and tested it. I once got a few teasing combustions out of it but it won't work. Is there some special way the wire has to be in there for it to work? Is the plug dead? Thanks
Spark plug won't fire
- Thread starter Jakerox43
- Start date
The kit supplied spark plug boot, the black rubber thing, is not the best quality. Any good auto parts store can provide you with automotive grade boot. Inside is a metal clip which will snap onto the top of the plug and make a good connection. To be sure of a good contact you can solder the wire to the metal clip. The other end of the wire screws into the CDI, the little black box. There is a lot of discussion about plug wires here; you can use the google search to read up on what is available. Also if you're using the kit spark plug you'd be better off replacing it with a better quality item. The new plug will come with a cap on the top end that does not need to be removed if you replace the boot with a good one but if you use the kit boot that cap will need to be unscrewed and removed.
Tom
Tom
Easy enough to just try a new spark plug, but otherwise just cut 1/2" off the plug wire and screw it back in again.
You sure the 2 CDI wires to motor are not loose?
Also, just to be sure it's not the kill button, undo it from the white motor wire.
You sure the 2 CDI wires to motor are not loose?
Also, just to be sure it's not the kill button, undo it from the white motor wire.
The CDI wires are fine. I undid the kill switch from the white wire and tried it. No luck. Now that I've cut off 1/2 an inch from the black spark plug wire, I don't know how well it's connecting with the screw of the spark plug boot. I also noticed some residue on the top of the spark plug, but I can't clean it off. And I can't unscrew the plug, it's really in there. Could it be something else, like the idle speed or choke?
Idle speed and choke have nothing to do with the spark.
They can affect starting though. Have you tried starting it without any choke, lever down? Also try giving it a little more throttle as you try to start it.
Each engine has it's own starting sequence. Some like full choke, some hate the choke all together. Some like half choke and full throttle, some like no choke and no throttle, ect.
You just have to experiment with different choke and throttle positions to find out what your engine likes.
They can affect starting though. Have you tried starting it without any choke, lever down? Also try giving it a little more throttle as you try to start it.
Each engine has it's own starting sequence. Some like full choke, some hate the choke all together. Some like half choke and full throttle, some like no choke and no throttle, ect.
You just have to experiment with different choke and throttle positions to find out what your engine likes.
The kill wire should be connected to the blue.....not the white. I ruined 2 cdi by using the white. Didin't happen right away but it did happen. After changing over to the blue....no further problems with the kill switch.
I think the choke and stuff is fine, since nothing changed. But I'll experiment on getting a good connection.
Yeah , I was a bit off base there. Sorry.... 
It think that you are on the right track, poor electrical connections can cause all kinds of problems. Soldering each connection and sealing each connection with heat shrink tubing or at least electrical tape (way messier) is the best way.
Good luck with the repairs!
It think that you are on the right track, poor electrical connections can cause all kinds of problems. Soldering each connection and sealing each connection with heat shrink tubing or at least electrical tape (way messier) is the best way.
Good luck with the repairs!
So I cut off another half inch and kept the wire, just cut off the tube, and it worked! Now my front brake is permanently closed.... I can fix that though. Must be the motorbike gnomes. Thanks for your help everyone, especially KCvale!
Now it won't start again, probably for different reasons. One of the CDI cables was burned on the muffler, but I clipped and fixed it so it should work now... should I use a wire nut or something for that? Is there any other reason an engine would refuse to start?
Hey guys got question on sparkplugs. My first build was a 2stroke still have it in Wisconsin then I went too 4strokes any have friend who has a 49cc in a little 20" bike simple but neat and clean problem is the head is so close to the frame a normal size sparkplug wont fit unless you cut the crap out of the cap some plugs you can buy are shorter but dont know if you can find one that will work there is a small one in there now but it wont start it is getting some kind of spark and gas so I figure plug is wrong. motor looks just like my Zoom motor. Any body know? Thanks Larry
Oh! my mistake. I thought you were referring to the two-stroke, thats what I get for not paying attention.
That plug is not for 4-strokes only 2-strokes that I know of. I have no ideal what plug to use for a four stroke.
I am not allowed to promote what I offer for the perfect solution to your problem in your problem topic as an answer, just suffice it say it say I have one if you can find it.
This concerns me however...
"I also noticed some residue on the top of the spark plug, but I can't clean it off. And I can't unscrew the plug, it's really in there."
(nods and smiles) hehehe...
I don't care if you have to use a pipe wrench, get that plug out!
Just to rule out some obvious stuff first, you didn't like use LockTight or Teflon tape or something on the plug threads right?
Then provided you didn't use gorilla force to put in there must be another problem, lets just hope it wasn't mis-threaded to start and forced in (shutters).
A plug should finger in all the way easy and just a 1/4 turn with the kit provided plug wrench is all you need, and it comes out just as easy.
Now to plugs...
Funny how these kinds of topics come up when I just happen to be testing the very things being asked.
I love to share here, all I have time for and know something about, but I have to direct you here for what I have learned and partially tested the last couple of days.
In brief however, the NGK B6HS is awesome and at least in a straight head 48cc, the Tri Spark LD Z4JC stock slant head plug ummm... blows/sucks/bites pick your own adjective.
Same bike, same weather, same gas, same 1/2 an hour time frame, same everything but the plugs. It is just too much to try to keep updated here too as I will start testing in GT5 slant head tomorrow too.
Get that plug out dude!
Do you still have the other LD Z8C the kit comes with?
Gap it to .028, every auto parts store sells the little wheel ones, usually right at the counter.
More later on this here in this topic if I have time.
This concerns me however...
"I also noticed some residue on the top of the spark plug, but I can't clean it off. And I can't unscrew the plug, it's really in there."
(nods and smiles) hehehe...
I don't care if you have to use a pipe wrench, get that plug out!
Just to rule out some obvious stuff first, you didn't like use LockTight or Teflon tape or something on the plug threads right?
Then provided you didn't use gorilla force to put in there must be another problem, lets just hope it wasn't mis-threaded to start and forced in (shutters).
A plug should finger in all the way easy and just a 1/4 turn with the kit provided plug wrench is all you need, and it comes out just as easy.
Now to plugs...
Funny how these kinds of topics come up when I just happen to be testing the very things being asked.
I love to share here, all I have time for and know something about, but I have to direct you here for what I have learned and partially tested the last couple of days.
In brief however, the NGK B6HS is awesome and at least in a straight head 48cc, the Tri Spark LD Z4JC stock slant head plug ummm... blows/sucks/bites pick your own adjective.
Same bike, same weather, same gas, same 1/2 an hour time frame, same everything but the plugs. It is just too much to try to keep updated here too as I will start testing in GT5 slant head tomorrow too.
Get that plug out dude!
Do you still have the other LD Z8C the kit comes with?
Gap it to .028, every auto parts store sells the little wheel ones, usually right at the counter.
More later on this here in this topic if I have time.
I OFFICIALLY RETRACT everything bad I said about the Tri Spark LD Z4JC stock slant head plug.
I forgot to pull it out and and put my iridium back in before a quick store run and it sucked so I went back and pulled it but started looking at it.
There were no guidelines I could find for these plugs but I know 'wrong' when I see it.
One of the 3 anodes was darn near touching the center cathode and had even started burning a direct path.
I just used my disc gap tool and knocked that off, then set all 3 at .032 gap and dropped it back in.
Shoot... I feel silly.
I knew it was an unfair comparison from the start and said so, but it wasn't until after I rode it and made it go that the gap problem became clear.
I made my store run and it was flawless.
No hiccups, instant start, just not quite that extra mile or two an hour the longer plugs give.
There may be better settings, there may be better everything, all I know is gaping the tri fire to to .032 on all three prongs made it work great on my straight head 48cc Grubee.
I forgot to pull it out and and put my iridium back in before a quick store run and it sucked so I went back and pulled it but started looking at it.
There were no guidelines I could find for these plugs but I know 'wrong' when I see it.
One of the 3 anodes was darn near touching the center cathode and had even started burning a direct path.
I just used my disc gap tool and knocked that off, then set all 3 at .032 gap and dropped it back in.
Shoot... I feel silly.
I knew it was an unfair comparison from the start and said so, but it wasn't until after I rode it and made it go that the gap problem became clear.
I made my store run and it was flawless.
No hiccups, instant start, just not quite that extra mile or two an hour the longer plugs give.
There may be better settings, there may be better everything, all I know is gaping the tri fire to to .032 on all three prongs made it work great on my straight head 48cc Grubee.
I was trying to post a link to the cross reference page that I found on this forum and it wouldnt let me. Sry for the double post.
My Grubee 48cc kit came with a LD Z4JC plug. I checked out this cross reference page which I am not allowed to post until I have atleast 3 posts. It didn't seem to match up. I too need that extra .25" to .5" of space because I have a fat lower tube and straight tube on my bike. Will the CJ7Y still work. I actually went and bought one and haven't opened it yet incase I need to return it. I compared the two and the CJ7Y threads looks to be a few millimeters shorter then the LD Z4JC plug. Would I be safe to use this plug?
Thanks in advance for any info.
Last edited:
