Got it assembled, it sputtered, ran for a few seconds then died

DieselTech

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Sep 18, 2021
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I did ask them for a suitable cross reference at the time but didnt know about the heat range ...lol I'm learning as i go here. I will order a couple or 3 or 4 plugs.
I've found out my engine prefers a 7 on the heat range, I believe to do with my engine mods. I'd try & get a 6&7 ngk heat range spark plug & try them. It might prefer something different, so it's not set in stone. Also your spark plug heat range will affect your engines performance/run ability characteristics.
 

digital_life

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May 21, 2019
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the manual said to use if for the break in period, it looks like it could stand to be a bit leaner
I gave mine 16:1 for the first tank and then did a couple of tanks around 25:1, I remember when I was growing up around dirt bike's a old fella told me that nobody ever killed their motor with too much oil I was around 12 or 13 when he told me that and ~50 years later I still remember that day. 🥲
 

Thatdarncat

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Mar 20, 2022
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I gave mine 16:1 for the first tank and then did a couple of tanks around 25:1, I remember when I was growing up around dirt bike's a old fella told me that nobody ever killed their motor with too much oil I was around 12 or 13 when he told me that and ~50 years later I still remember that day.
Yep that true! I rode dirt bikes in the early 70's. I remember one bike was anemic until I put a wispering smith torque converter on it...boy did it wake it up! My dad owned a motorcycle shop throughout the 60's and 70's ...lot of European bikes Ossa's Ducati's, Nortons triumphs, moto guzzi's AJS's etc etc...last dirt bike I had was an Ossa phantom.
A lot of guys coming back from Vietnam, rode those bike like the devil.
 

Cisco

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Jun 9, 2021
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nobody ever killed their motor with too much oil
Your engine might burble (with a rich mix) for a while, but the engine compression increases during break-in. A 20:1 or 32:1 mix (with your preferred oil) will provide sufficient lubrication after that. I am using an NGK BP6HS plug in my angle fire head. The 'P' stands for protrusion, the electrode is slightly extended. They seem to be readily available. I suggest not doing anything to the carburetor (except idle adjust) until any ignition or compression concerns are resolved. Then you might try raising the clip on the metering needle up a notch to lean the fuel charge. The metering needle is effective to about half throttle. After that, it's up to the main jet.
 

Thatdarncat

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Mar 20, 2022
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Your engine might burble (with a rich mix) for a while, but the engine compression increases during break-in. A 20:1 or 32:1 mix (with your preferred oil) will provide sufficient lubrication after that. I am using an NGK BP6HS plug in my angle fire head. The 'P' stands for protrusion, the electrode is slightly extended. They seem to be readily available. I suggest not doing anything to the carburetor (except idle adjust) until any ignition or compression concerns are resolved. Then you might try raising the clip on the metering needle up a notch to lean the fuel charge. The metering needle is effective to about half throttle. After that, it's up to the main jet.
LOL sounds like what I did! While chasing the problem I discovered the coil over the magnet is impossible to center and use the 4 screws that keep it in place, Unless I had a mill and elongated the holes, or sat down and filed on the holes in the direction it needs to go. But it still seems to be working with only two screws holding it in and that is after opening the holes in the coil up a good 50 or 60 thousandths.

After replacing that bad kung fu plug, Im pretty sure it was a NGK BP6HS I replaced it with. The bad plug was my problem all along after You folks educated me on what to look for in regards to Ohms then I got to chasing all the ghosts with a electrical meter to pinpoint the problem, yep it was a bad plug all along...Maybe Ive been lucky all my life but I have never seen a "bad" spark plug...sure Ive fouled my share of them out but never a "bad" plug...lol but I guess theres a first for everything too!

Yesterday, I did move the c-clip on the metering needle up one notch and drilled the NT carb cover into swiss cheese with a mutiltidue of holes.
I then drilled 2 holes about .200 thousandths in the bottom of the stock muffler, I couldn't really notice any sound difference but along with the 44t sprocket, it seems to have a little more grunt for the hills...took it out for about 3-4 miles and it seemed to do fine....when it breaks in some more I will lean it out and take it for the "rocket sled" test and use a phone app to check my mph, but for right now Im happy with the speed.
 

Cisco

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I then drilled 2 holes about .200 thousandths in the bottom of the stock muffler,
I have been really curious about modifications to the stock muffler. Some people swear that taking off the bottom end boosts power. I would disagree (respectfully) as an open exhaust would allow part of the intake fuel load to escape through the exhaust. Some back pressure is necessary. I was thinking of cutting the internal part of the outlet tube shorter. I'll have to experiment ;-)
 

DieselTech

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Sep 18, 2021
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I have been really curious about modifications to the stock muffler. Some people swear that taking off the bottom end boosts power. I would disagree (respectfully) as an open exhaust would allow part of the intake fuel load to escape through the exhaust. Some back pressure is necessary. I was thinking of cutting the internal part of the outlet tube shorter. I'll have to experiment ;-)
What little bit I've experimented with the stock muffler is, cut the pipe off that extends to the inside of muffler & then gut the inside, then take 5/8"id pipe 12-14" long, then weld that to the muffler cap for the stinger/pipe. I gained some power, or should I say torque, but never did any type of scientific test.
 

Cisco

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Jun 9, 2021
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TMI from another of my posts:

The stock exhaust is interesting. The inlet tube is perforated, then the exhaust gas has to go upward through a baffle plate to the outlet tube (which is almost as long as the muffler section). I was thinking of cutting the outlet tube shorter. I wonder if that would work better.

I have been contemplating this for a while. The outlet tube extends through the baffle plate. I assume (never assume) that the baffle provides some acoustic dampening. The baffle sits about halfway in the muffler section, above the perforations and below the top of the outlet tube.

I was thinking of cutting the outlet tube so that it extends only about half an inch through the baffle. Not much of a modification, only a few inches shorter.

I was also thinking of taking the baffle out and cutting the outlet tube much shorter. There is enough space between the inlet tube and the wall of the muffler to slip in a sleeve of thin fiberglass (glass pack).

The fiberglass could be held in place by a metal mesh sleeve (hardware cloth?). I was also thinking of drilling out the perforations that I could reach (just a few of the lower holes). So, that would give a little bit better flow-through and some sound dampening.

The external part of the outlet tube would remain the same. I have to believe that some thought went into the engineering of the stock exhaust. It's been used for decades.
 
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