hello, nik here.. so it begins! happytime


Mar 6, 2008
Well. where do i start. (deep breath)

hello............ motorizedbike forum peoples.. :D

my name is nik (29yo). I love bikes. i love things that go fast.... and well..
I live in northcarolina.

I have never built anything like this! I have no real mechanic type experience, only limited info ive picked up.

please let me share what ive been through over the last month...
pics of my bike below :)

I saw a motorized bike in a youtube video and decided it was for me. two months later im mounting an (happytime dax 70) engine on a bicycle. It sounded like a fun project, which it has turned out to be.

However, it certainly has its share of frustration! I was able to mount my engine after finding a suitable frame that would allow the engine mounts to fit nice. I choose a cruiser frame (old school murray). (after realizing the mountain bike frame i bought would not quite work due to derailer interferance, i need a bracket to mount on mountain bike..ill do that later)

I had some issues installing the sprocket on a coasterbrake wheel, and decided to put on a freewheel instead (coaster brake.. aggh dust cover aghh. :censored:), and mounted the sprocket on the freewheel. I did mangage to get the engine installed and running after a couple start attempts, the first couple times... then the fun began..

shut off the bike.
I notice that the fuel is leaking bad from the petcock..

The fuel petcock broke off when i tightened it (pot metal)! so i made a trip to a engine shop and got a nice replacement on/off and petcock (15$). Now, im ready to ride! So, I tweak the controls some and experiment with getting it to start.. I manage to get it start.. sometime. but after a half hour of riding and the bike sits off an hour, it does not want to start back up again. I thought maybe it was flooded,, so i took out the plug (wiped it) and walked the bike around,, and put the plug back in. . sometime this would work. sometime i would have to squirt a small amount of fuel in the spark plug hole to get the fuel going. ( i cant seem to tell if its too much fuel, or not enough.. although i try looking at the spark plug to see if its "wet", it kinda is not overly wet, but a little on the treads.

This whole story is long, so bare with me..

while checking spark plug..
My spark boot inside came out onto the spark and broke (brass piece and spring), so i went to the moto shop and got a ngk replacement (3.00$). nice. I decided to get a new plug to go with the new spark plug boot. (ngk b6hs)So I managed to get the bike started once, with the new boot (old plug z4c), after a half hour i turn off the engine and an hour later attempt to start.. nope. wont start.. why? then, I try to start in all ways, choke up, down etc. nope.
spark maybe?
I checked the spark plug boot and plug by riding bike along with plug out of engine while plugged into spark boot.. then allowed it(sparkplug) to touch engine block while i pedaled along.. i saw spark.. definately.; :eek:
so its not spark? right..?

magneto? i dont think because im getting a spark when plug is out of block.

it feels like when i go down a hill (let out clutch and peddle) that nothing is happening.. no spark> it wont pop.. which cant be. so i adjust choke up, down, nothing. i squeeze throttle some as well to test.. i looked at carb and adjusted needle notch settings.. nothing.. now it is not starting at all. 2 days

I am gettting so frustrated.. as many of you know :cry:

Im really stumped. I know the troubleshooting rundown, i havent had much luck with it. I need to triple check gaskets.. perhaps that is a problem,(air leak?) , but i am on my first gallon of gas/2strokeoil.

I rechecked all wiring and its good. kill switch works when engine is on, and needs to be shut off. its not the kill switch. i have even disconnected it to make sure.

and i havent driven the engine but maybe 10 miles max.
it drove fine when it started and ran, and did not let out to much smoke.. my fuel is 1 gallon to 6 oz of 2stroke oil

Im wondering if maybe the fuel line is creating a mild vaccum preventing free flow of gas into carb,, i read somewhere on here that a hole drilled in the top of the gas tank can eliviate vaccum in the line.

but, when i attempt to flood the bowl by pressing the tickler button for a couple times im sure there is gas because fuel wants to come out of the fuel bowl, it doesnt want to start. after i tried to open up the fuel bowl and let all of the gas out, empty, it still doesnt start. flood or to dry? rich or lean? nada.

I have adjusted the needle in the carb also, but putting it at different notches on the black washer. no luck at all.

I am aware that you need fuel, air and a spark. :cool:

which one am i not getting? the spark works when tested, but wont fire in the block. doh! no popping. doesnt even try to start.. just hear the chain turning the gear.

The gas/oil is in the line and full. The petcock (new) is open, and the (paper inline) fuel filter loaded up with gas/oil of course, and fuel bowl fills fine.

The choke is set into the up postion. to start, I have also tried bringing the choke down a little to allow more air in the engine,, no luck.

If i take the spark out and walk the bike with clutch out, the piston is pumping and making its "compression" noise. so, I think the engine piston is fine. (i also just tightened the head bolts yesterday a little to make sure) I do that to clear out any fuel in the block when i think its flooded. I just walk it for a couple minutes max, sparkplug out. To dry up some fuel.

I have enjoyed the couple times i was able to fire up the bike and ride it.. what a rush! and everybody who sees it says "whoa!, thats sweet!".. i like that.

I have also been reading the helpful posts on motoredbikes.com and they have helped. however, i am stumped :confused:

If anyone thinks they can help or would like to share please do. ride or die!

and thanks for having me in your forum. I am new so i apologize if i posted to much here :rolleyes:

-nik in northcarolina


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Last edited by a moderator:


Active Member
Feb 14, 2008
Hey nik, Welcome to MBc ! Home of many answers, and awaiting your ideas. Im going to have to think about this a bit. It sounds like you covered all of the bases.
Last edited:


Active Member
Feb 14, 2008
nik, (This is if you have good spark) I have a 90cc 4wheeler for my grandkids, and when it was brand new i could'nt get it to fire. Kind of sounds like your situation. I tried everything also. I took off the carb, shot a quick blast of starting fluid into head, put carb back on, and it started for 3 seconds. Ended up being a junk carb. Tried rebuilding it, no luck. Had to get a new one. Ran perfect after that. Also, or maybe your plug is fouled and the plug is trashed. It may look ok, but not. This may be a cheap try. graucho


Active Member
Jan 31, 2008
The interim initiatives, I found so far is "normal" learn curve procedure with HT so it seems. I had and still have my share of 1st build blues.

Check Spark Plug Gap.
Put needle settings back to what it was.

Choke half way, Throttle open full and keep going, best if you find a downhill run.
If you have spark and fuel it ought to run.

I had the most stupidist thing with my kill switch the other day. I wanted a On/Off toggle switch and wired it up correctly with crimps.
Went well for a day and then I thought karma got the better of me.
I was at the traffic lights and another biker on peddles only arrived there to. It is very hot these past few days and this poor soul looked as though he could do with a drink. The lights went green, he peddles, I motoredpeddled and the drivers at the red lights had this cheeky grin watching the show.
I grinned to.
Then, at the next lights my bike stopped for no reason, no warning. The first thing I did was act calmly and peddled to the nearest side street.
Nothing would make it run, the first obvious thing to do was trace the electricals.
No spark at the plug and I thought the worst, magneto.
But I probed the kill switch wiring to make sure by undoing the wiring I had done. It was the last wire I checked, the crimp failed. ( Next time I will use a soldering iron) So I joined the wires straight with no switch, got spark, it fired up and still going.

So look for things you would least expect, it's a ongoing journey and I am making allowances due to the fact it's only my 1st build and it can only get better.

Good Luck



Mar 6, 2008
thanks graucho
i have a new spark plug in it as of yesterday, a ngk b6hs. I tried to start it yesterday with the new plug but no luck. I did pull the plug and place it in the spark boot, then i pedaled to see if it would spark on the engine block, which it did.

My question now is, If somehow moistness/condensation got into the "magneto" would it still allow the spark plug to fire like it did (next to engine block pulled out in spark boot) does a magneto go bad, or kind of work but not just not enough to make the bike start?

It is possible moisture may have crept into that little whole.. i had my bike on my apt patio.. (ceiling of course) and it was raining hard the other day. I never rode the bike in rain, but maybe some condensation snuck its way up there.. just a thought...
then how did i get that spark? hmmm scratching head.

Is it possible a vaccum is happening in the fuel line? im not sure how because if i pull the fuel line off of the last connection - to the carb - it flows out fine.

wiring is always a possiblity and i will triple check that next. off with the electrical tape again! lol.

I have my "kill switch" wired to my "white wire" and one kill switch wire to one of the mounting nuts/and washer on the engine block. (is that ok?) seems to have worked fine in the past when engine fired (and i still am getting test sparks..). blue to blue, black to black. wiring all wrapped up tight with electric tape

ill keep checking, thanks for all the great replys!


Mar 6, 2008
ok, quick update.. i tried to start it like 5 times .. i took out the plug to make sure it was still sparking.. it was.. so i put it back in walked up the hill and tried again.. it started and drove about 5 seconds or so, then stalled. doh!

I tried to start it again 10 more times after that.. nothing at all. i noticed that i was dropping little drops of oil on the ground (ground a little wet) I started to wonder, " should i be dropping that much fuel/oil out of the muffler? it was more than i thought would come out, the hill i was trying to start on had many oil droplets , so perhaps im just running really "rich".. i adjusted my carb needle to the top postion in hopes to lean it out

from motorized forum..(Putting the E-clip on the top groove lets the needle sit lower into the carburetor, which blocks the fuel flow, which leans out the mixture. Putting the E-clip on the bottom groove gets the needle up out of the way a little, which clears the way for more fuel to go through, which enriches the mixture. Top groove = lean. Bottom groove = rich.)

Im going to let the bike sit for a little while and try again. Maybe i have been flooding the engine with to much fuel?

it did start once, so i know spark is working . i need to catch my breath after all those start attempts! sigh.

thanks again to "bolts missing and friends"


welcome nik! sounds like the air leak in the happytime carb & manifold conection, stick a nice fitting oring in there push on & tighten. i also threw away crappy carb clamp & used screw type hose clam over thin rubber strip wrapped around to cover the slots cut into carb, worked great! anyway all your answers are here for ya to read! read read!


Mar 6, 2008

ok.. What was the problem.. The spark plug gap!

thank you spark plug gap tool.

yes, i took out the plug checked the gap and it was between .25 -.30.. i thought that was good, but wondered if i made it .35-.40 would that work.. and it did.

It fired right up like a bat outta ****! yeeehaw! I adjusted the choke for air intake to around the middle, i rode it for 2 miles with a smile on my face the whole way. Too bad it is a little wet outside, luckily i read today that i needed to put a gasket on the wire opening that goes into the magneto. I patched it up and im glad i did, i dont want a dead magneto.. because now my baby is alive! lol.

I highly recommend to anyone they get a replacement spark plug and spark boot. The one that comes with the kit (HT) is not great, and NGK makes a much nicer performing one. I bought new boot and plug for less than 10$ at my local motoscootershop.

part numbers
NGK LB05EZ stock No. 8744 (black)
NGK b6hs stock No. 7534

At first i was concerned that the NGK plug was a little to long and may actually hit the piston if the opening was to big. You may notice that the kits spark plug (LD Z4) is a half thread shorter than the NGK b6hs. This concerned me. I read some great posts here that showed the inside of the cylinder chamber with a stock plug screwed in,, and it appears that the stock plug is a little short.. this makes the NGK seem to fit perfect.. (so far as i can tell)

What a relief to have this engine start. I was really starting to tear my hair out from frustration! Iam sure many of you know that feeling.. ha!

Now, i cant wait for tomorrow to ride this baby again. I also have to start working on fixing it up even more! I need a motorcycle kickstand on this asap! I do not want this thing to fall over! no. does anyone have a good kickstand to recommend? ill do a search ;)

Thank again to all of you guys for the advice and encouragement. This is a great forum. Peace!