It's Alive!! rebuilt 157QMJ.

[stevec]

i got the engine rebuilt and installed back into the scooter.
it is very quiet and idles beautiful, no ticks or knocks or rattles.
only problem is when it hits 7500rpm it drops down and goes back up over and over, almost like there is a limiter but i have a blue CDI.
i'm not riding it yet, i still have to finish putting it together.
i did turn it by hand with no plug for a while to prime the oil pump.
i wanted to make sure the mixture and timing was right.

[stevec]

tried to insert images and it doesn't work, i have them on my instagram under pcdj64

[2TDave]

Do you have a stock cdi to try? I'd start there.

[stevec]

i have the stock CDI still, i will give that a shot, thank you

[stevec]

swapped out CDIs and it still drops at 7,500rpm, bypassed the petcock because it doesn't shut off anyway, i will be putting in a manual one.
took it for it's first ride to get some gas, it did not cut out on the road.
doesn't have the power it did before the engine went but i believe that is because it is not broken in.
it is loud at the airbox like i am running an open performance filter but not bogging at all.
i have the hunter style box under the seat and it is sealed properly with no broken hose.

[stevec]

replaced the head, readjusted valves, made sure timing was on.
no more cutting out at any RPM! very quiet now, no loud noise in air box.

[stevec]

took for a ride for a few miles, very very quiet and strong.
i decided i am going to go ahead and get the kit for 180cc that comes with the block and parts.
i have a good crank that will match it perfectly, i should have a little bit more pep.

[stevec]

a little lost on what to do with roller weights, i have 14g in it now and it is at 8000rpm doing 50.
i will have the engine built to 180cc this week, should i be going with 17g?

[2TDave]

That seems like a big jump but I'm not familiar with you engine.

[stevec]

in it's current state as a 150cc i can go 0 - 40 in no time, it is very quick.
all my parts shipped so this week it will become a 180cc with a performance head and cam.
i also ordered new jets for the carb for the larger cylinder, the hunter style airbox is not restricted so i won't need an aftermarket air filter, i am hoping i won't need an aftermarket exhaust, i will try it with the current one.
i had it up to 55 today and the tach read almost 8,500rpm, keeping in mind it is a china tach.
the engine does not sound like it is running that fast at all, it is not winding out.
only reason i was considering heavier weights was to bring down RPM but the more i think about it the final drive gear ratio would have to be changed to remedy that and i don't want to mess with the final drive at all.

[stevec]

the new taiwan built block and top end will be here tomorrow morning.
i already took the parts out of the old engine and gave the block and crank covers to a scrapper.

i got 15/37 gears for the final drive and the gears are ready to install into new case.
i also put 15g koso performance rollers into the variator, it still has stock clutch.
variator is a stock one not a performance.
i have a stock sized carb with 125 main jet and 38 pilot jet.
new top end is 180cc with a performance head and cam.

i don't know if the setup with 15g rollers is going to work, are the rollers too heavy for a 180cc with the gears i picked??

[stevec]

UPDATE.
took all day to build new engine but i got it done and installed.
it starts and runs, no unwanted noises or smoke.
i still have to set the idle and fuel mixture before i can take it for a ride.
it starts up fast, only took one try to get it started.
the only thing is i had to use a seal for a 139QMB on the cover that has the oil fill tube because the new cover didn't come with a seal, it fits but is pretty tight, it should break in and be fine, doesn't leak oil.

[stevec]

apparently the 50cc seals don't work, took it for a ride and the seal went, didn't hurt the engine.
it has awesome pick up and top end, i didn't go too fast but at 50 it was half throttle, i have to let it break in before i go too fast with it.
i have to get an aftermarket air filter, it won't run right with the air box.

[stevec]

installed new seal behind the flywheel and when i say behind i mean ok well looks like i have to pull the whole engine cover off to put the seal in lol.
no leaks at all anywhere on the engine, after an afternoon of riding it is bone dry on the outside.
what a blast to ride with the 180cc! this thing flies, i am at 6,000rpm going 55mph GPS.
i don't want to run WOT until it has at least 300 miles on it.
i definitely need a performance exhaust, it is tearing up the stock one lol, the guts in it are rattling.

[stevec]

UPDATE on an old post instead of starting a new one at the end of the season.
the chinese crankshaft decided it didn't want to hold up, it is knocking.
the rest of the engine itself is all taiwan so i will be installing a Hoca 2.5mm stroker crankshaft.
i figured out that the cam that came with the 180 kit will work fine and the cylinder is already tall enough for the additional 2.5mm, keep in mind i am still learning, i noticed the piston didn't meet the top of the cylinder when i put the engine together with a stock chinese crank, i thought that it was just the 180 design not that oops wrong crank soo i couldn't have had all that much compression.
tomorrow the scooter is coming apart and being moved into my basement.
i will be making a complete custom wire harness to replace the chinese harness, it will have some new plastics to make it look better, new rims with pirelli tires and some other goodies.
i will have 18/36 final drive gears, a hoca transmission CVT kit with 1,500rpm springs and 10g rollers.
i will be making an album on instagram of the progress and the finished scooter.