Break In Looking for tips, New Build

Daedric_Angel

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Jul 20, 2019
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About a week ago I built my 66/80cc Dragon Fire kit on a cruiser bike. I have been tinkering with the tune off and on since(its very hot right now). It is idling great at no choke but is seems low power with throttling. I assuming its just part of the break in period but wanting to see if perhaps the needle needs to be adjusted for rich/lean. Carb needle is a 4 notch and the clip is on the 2nd notch from the top |-+-->(the way it was in the box. Checked plug and it is an ash grey color. Also the plug is a 3 tip not a standard 1 tip, though I do have a standard 1 tip as well that is still new. A few other details i can think of is that aside from idling good without choke it starts fine without the choke(might because we are under a heat advisory(90F+). Oil type is a full synthetic for air cooled and mixed to 16:1. If you need more details or pics let me know and I will get to it asap. Thanks.
 
Well this extreme heat we are having is not helping the tuning, the extra oil mix isnt helping you out either. Everyone had thirst own opinion on oil ratios but you can safely go up to 20:1 myself I use full synthetic 36:1 right from the start. Ngk b6hs is a good plug you may want to try b7hs with this heat wave. Have you done any mods to the engine? Is it 4 stroking while accelerating or bogging?
 
About a week ago I built my 66/80cc Dragon Fire kit on a cruiser bike. I have been tinkering with the tune off and on since(its very hot right now). It is idling great at no choke but is seems low power with throttling. I assuming its just part of the break in period but wanting to see if perhaps the needle needs to be adjusted for rich/lean. Carb needle is a 4 notch and the clip is on the 2nd notch from the top |-+-->(the way it was in the box. Checked plug and it is an ash grey color. Also the plug is a 3 tip not a standard 1 tip, though I do have a standard 1 tip as well that is still new. A few other details i can think of is that aside from idling good without choke it starts fine without the choke(might because we are under a heat advisory(90F+). Oil type is a full synthetic for air cooled and mixed to 16:1. If you need more details or pics let me know and I will get to it asap. Thanks.
The first thing you should do is decrease your oil to 30:1 if your running full synthetic, after a full tank switch to 40:1 full synthetic. 16:1 may be fine in China where quality oil isn't readily available but here in the states it's just overkill and creates excessive carbon deposits leading to premature wear and tear.

With a stock NT carb, the choke is basically unnecessary to get the bike started (at least in my experience) so I wouldn't worry about that too much.

I'd swap that 3 prong plug for an NGK b5hs/b6hs,b7hs (if your in a hot climate like AZ go for a b7hs otherwise a b6hs is fine for summer use, b5hs for cool weather) and if your feeling up to it, do some plug chops to determine if your running rich/lean (Pick up a 4 pack, that'll give you 4 chops)
https://www.mopedarmy.com/wiki/Plug_chop
Basically, get the bike good and warmed up, go somewhere with a 1/4 mile stretch that you can max the bike out without issues.
Swap in a BRAND NEW PLUG, start it and proceed to travel that 1/4 mile at WOT.
Once you hit the end of the 1/4 mile, with the throttle still wide open, hit the kill switch, grab the clutch and come to a stop.
You must not let the engine idle down or it will affect your readings.
Pull the plug out, swap in your old one and ride back to the start/home.
Looking at the base of the insulator where the metal touches, the 1-2mm band of color will tell you your tuning.
Sometimes this requires you to cut the threads off, hence being called a "plug chop".
This will help you determine if your running rich or lean on the top end. This same technique works for anywhere in power band, you just simply need to hold the motor at a specific RPM under load for 1/4-1/2 mile to get a reading on a fresh plug.
Honestly, on a stock NT carb, this is completely unnecessary.

On your carb needle, you are on the 2nd from the leanest setting (lean = top, rich = bottom) which according to the ash gray on the plug, might be a hair lean.
Try dropping the clip one notch and take it for a spin. If you get points where it's sputtering you may have gone overly rich (that sputtering is called 4 stroking, it means it's firing every other time instead of every time due to an excess of fuel) and need to put the clip back.
Lean conditions are a touch harder to tell, it'll run really strong but it'll have a weird hollow sound and the motor will get quite warm/hot.

At the very least, you should see a little increase in power once you reduce the amount of oil in your mix and if you want another small bump in power, grab a copper head gasket.
 
Wow, That was one heck of a response! I appreciate the info, I have the carb needle out right now so tomorrow I will change it and give it a shot. A far as fuel goes I'll have to see if I have another empty can and do the math to get it to around 30:1. Its a 1.5L and the can was exactly 1 gal gas and 8oz oil. So that would be 128+8-about 51(1.5L) so 85 oz left in the gas can. If I transfer 17 oz out then top off the 1 gal can that should put it pretty close to 30:1. Yea I was doing the math while replying and decided to leave it, lol.

As far as the spark plug its labeled as Z4JC-LD but I was considering getting a NGK, infact I have one in the garage I think but don't recall what I got it for or if its the box even lol. I will look into getting one. As far as 4-stroking I haven't noticed that happen and It only seems to bog uphill. This hills by me aren't super steep, I made it up the less steep hill very slowly without bogging out and the steeper I made it slowly with peddling with throttle. I tried coming back around the loop and it didn't make it up the opposite side of the less steep hill(which is steeper than both). Only upgrades from stock are the muffled expansion exhaust and boost bottle/intake manifold, unless you count the 3 prong plug.

Anyway Tomorrow I will pick up a NGK b6hs and maybe 7 as well. Also will balance out the remaining fuel to the 30:1 and lower the clip a notch. I have a store credit that I can use to grab the copper head gasket when I order my double brake lever.

Thanks again for the help, I'll update as I go.
 
Always glad to help :).

I did a little more research into plugs and that 3 prong Z4JC-LD shouldn't hurt anything, they are just known for failing fairly early. You'll probably be fine with b6hs plugs, I only mentioned b7hs as that is what I use here in the Phoenix Valley (with NGK, the # is the heat range. Lower = hotter. The general rule of thumb: Cold plugs for hot weather and hot plugs for cold weather.)

If you have a boost bottle hooked up, try removing it, capping the hole, and taking the bike for a spin. For these 66/80cc 2 strokes, a boost bottle is purely a decorative item and in most cases reduces power slightly. Here is some info on the science of boost bottles:
http://www.dragonfly75.com/moto/YEIS.html

Best of luck with everything and welcome to the fun (and frustrating) world of 2 stroke bicycles :)
 
I have the original Intake manifold, I can swap it out If I can't find something to cap it to test.
 
In a pinch, you can pinch off the line to effectively delete the boost bottle for testing.
 
Okay, first off its still freakin hot so I could only do a lil testing. I changed the needle down one, replaced the cheap rubber/plastic pedals with metal ones, drained the 16:1 from the tank, changed the boost bottle/manifold intake to standard riser/angle intake manifold, refilled tank with 30:1 and fabricated a new stronger coaster brake retainer(standard one was super thin and already broke). Testing didn't go well since I couldn't throttle and seemed to have slack on the throttle cable. I think the throttle my have gotten stuck in the carb. It was idling/reving loud and pulling w'o throttle. Once the bike and myself cool off I will pull the carb/throttle cap and see if the spring is stuck on the cable. I am also searching for a bike place near me that has a good price on caliper/push brakes because I don't trust it to just the coaster brake, lol. Tomorrow is support to be a lot cooler (70s instead of 90s) so I may get more done tomorrow.

So besides possibility of the spring/cable being stuck, any other ideas for this?
 
You'll definitely need to get the throttle cable sorted out before you'll know if you have successfully made any progress. I definitely wouldn't relie on the coaster brake, they have been known to cause catastrophic injury to the bike and rider. Do you have any disc brake mounts on your bike? Or any other brake mounts? Ideally disc brakes are the way to go
 
It sounds like your throttle cable is getting bound somewhere. Any sharp turns or anywhere it's getting pinched can cause that, however since you had it open to mess with the needle, it's probably the spring binding weird like you suggested.

Otherwise, it sounds like you're on top of it! Hopefully, you can get some good/better brakes hooked up soon, nothing worse than needing to stop in a hurry from 30+ mph and not being able to.
 
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