New Member, first build. 80cc china girl on a fixie

[jerrywelz]

few more pictures, shameless bump on the question about the mixture!

I am running a stock NT jet, SHA carb, banana pipe, 36 tooth sprocket mounted to the fix gear with the rag joint (solid).

the Bike four strokes pretty bad, always at top speed WOT and sometimes through all RPM ranges. Once the engine is warmed up it 2 strokes in the mid range and always when climbing hills.

I've got the Champion CJY7 plug with 2 washers on it so it doesn't contact the piston. tried running the b7hs and it ran poorly i don't think the NGK sits far enough in the combustion chamber.

i'm running 12:1 2 cycle sport oil by masterpro with 91 octane. the engine is broke in but if run less oil the bike will bog even worse. do i need a smaller jet to run a leaner oil fuel mix and not four stroke at WOT?

 

[jerrywelz]

don't mean to double post but i forgot the pics

 

[HeadSmess]

some may argue the point, but im ferpectly happy with 50:1 oil mix, contemplating changing to 100:1 for a while just to see what happens.

nice to see a reasonable looking sprocket on there now take a link out of the chain and readjust the tensioner or its gunna cause a nasty accident! and it wont be to a bystander


(edit....looks like you pre-empted me and have already done so )

i gave up on the 700c wheels altogether, had way too many flats, a wheel collapsed on me, and well...i prefer the ride on 26" mtb tyres. the poor old trusty shogun came out of storage roads are really bad around here...

all i can say with the effect of adding some pipe to the pipe... the banana pipe itself is tuned (if its tuned at all?) to peak at about 12000 with the port timings on these engines. so they do sweet f all down low(but more than the stock exhaust, if thats any consolation?). adding some length to the stinger will increase back pressure slightly, which assists for power up high. more noise than genuine boogie fever, them things... now, if you were to get your stock muffler, cut the can off, and welded the banana on that length of header pipe instead...then you "should" get a noticeable powerband.


yup. smaller jet required. way smaller by the sounds of it... the plug isnt the issue. a box of micro drills, a pin chuck, and some solder, and away you go im happy with 0.55, but whats ideal is engine, rider, and atmosphere dependant! or, just start inserting very fine copper wire into the jet, one at a time, carefully tacking them in place until it feels right.

i now would feel safe with ngk 4, after discovering a champion with the equivalent of an ngk 2 (rj19hx) causes preignition after extended full load runs. ngk b4hs is probably not commonly available so ill stick to using whatever looks like it will do the job and seriously...i use whatever looks like a spark plug with no discernible differences in running, unless its one of those nasty chinese junk plugs. they just land in the bin depending on how drunk i am at the time :wacko: so, champion l82y, cj8,rcj7y, um... ngk bpmr6hs, b5hs, br9hs, (even bushed out to take ngk b5Es at one point) whatever, they all run much the same bar that one particular plug. its a very very hot plug, stays spotlessly clean no matter how rich the mix (the plug is only a good mixture indicator WHEN THE HEAT RANGE IS IDEAL, jet by feel, not plug colour)...but just doesnt appreciate the way i ride/jet (as lean as i can get it and still hold WOT). it came from a mower, and back into the mower it has gone.

as for depth in the chamber... i can run a good old cj8 that is about 3 threads too SHORT, without the projected tip, with no issues. in fact, the projected tip plugs, while logically seeming better, actually arent as the flame kernel is too close to the piston crown. all good with these engines, not so good with highly tuned and stressed engines, so really, its a moot point

 

[jerrywelz]

thanks for all the time invested in your reply's HeadSmess. I appreciate you sharing the knowledge/widsom.

I know the direction to go with the spark plug. I can't really fabricate much here for the exhaust. I only have access to basic hand and power tools. I can understand your vision for making this pipe ideal and giving it some more torque and useable power band.

On the wish list for fridays paycheck:

Air filter, i'm planning on this

I've got some jets in the cart @ http://www.racingplanetusa.com
I plan on ordering 54-68 ish

I found what appears to be the perfect tensioner sprocket on ebay. There are a few options here
link
link
link

I hit 38 downhill today 4 stroke thumping the whole way. Can't wait to get everything dialed in. The air filter with proper jetting should make things significantly quicker. The sprocket tensioner pulley should increase longevity. Then i'll start messing with the pipe, I'm considering a pocket bike exhaust.

The never ending project continues

Edit: it's 2:48am and raining here in Southern California. This motorized bicycle thing is quite addicting.

Edit Edit: I could probably save my $$ on the filter. the pantyhose filter works well on this carb because it can accommodate the adjustable clamp.

 

[jerrywelz]

Brainstorming. exhaust keeps coming lose, i need some better lock washers and i'm gonna use red locktite this time.

some pics:


ran out of gas intentionally today on the way home. switched over to some echo powerblend full synthetic @ 25:1 89 octane it's ISO L-EGD and JASO FD certified. supposedly the second certification is Japanese and ensures sufficient detergent to keep the rings from sticking on our hot running engines. the marine or ash-less oil which is what everyone is selling is supposedly bad for our engines because it has zero detergent, cooler running water cooled engines don't need it.

the bike feels MUCH quicker compared to the 12:1 conventional i was running before. it actually seemed like it 4 stroked less?

Anyways I ordered some 5mm 50-68 dellortos from the UK for $16

gonna cut the header off the banana pipe tomorrow and the can off the stocker. i'll try using brass pipe, metal clamps, and heat resistant tubing to hold the two together

 

[jerrywelz]

got the brakes all sorted. they work good now with the dual pull handle (important)! I took Head's advice on the pipe and i'm very satisfied, the bike has torque now.

aome pics. my friend gave me the aluminum exhaust spacer.

 

[HeadSmess]

someones found the "rohmell roll your own"

why is the scr so black? looks like it was tack welded on!


pot the thing up in some polyester/epoxy cus boy...they can BITE!

not sure if you can see it on this pic, but thats whats running this lil sucker on the stand made it from an old bug zapper (edit...oh yeah, nice and clear...it IS covered in resin but)




might have to transplant it on my ride now, i need it! the black box has had enough and died on me! something always goes wrong just as im almost home...almost.

 

[jerrywelz]

someones found the "rohmell roll your own"

why is the scr so black? looks like it was tack welded on!


pot the thing up in some polyester/epoxy cus boy...they can BITE!

not sure if you can see it on this pic, but thats whats running this lil sucker on the stand made it from an old bug zapper (edit...oh yeah, nice and clear...it IS covered in resin but)


View attachment 53945

might have to transplant it on my ride now, i need it! the black box has had enough and died on me! something always goes wrong just as im almost home...almost.

I'm not sure if my DIY CDI works, tried using it when my magneto coil was bad. the scr is black because i was soldering the heat sink to it.

I'm currently having trouble with flats on both tires. does the DIY CDI work better than the stock china one?

what purpose does that china girl serve? your very inventive man! i'm still 4 stroking @ WOT, currently opening up the exhaust port more. i've read your posts about the wire in the jet. still don't fully grasp how i should put it in there though

 

[HeadSmess]

they work, thats about all i know so far, or care about. and will take just about ANY type of ignition coil ive thrown at them the scr doesnt need a heat sink. its only on for a very brief time. well within their ratings. (i tested one out with a standard AC transformer...it was the 1watt, then the 5watt resistors that fried! but works on the engine with 1/4 watt ones fine. duty cycles i believe. ) if you made it per the instructions, it will work, and works at a much lower voltage to boot remember it needs a separate ignition coil.

its my dyno brake in the making, the threads in "performance mods".

just waiting on a tacho still so i can start testing various things out, rather than the standard forum board system of some truth getting all mixed up with a lot of complete and utter B.S., with absolutely no real conclusive evidence. definitive,un-biased answers. and im perfectly willing to destroy engines in the process it saves removing and re-installing the engine in a bike for each and every test, of which i have a LOT planned. id leave the exhaust port alone for now, btw

wire in the jets... very carefully? with a small soldering iron... i dont actually have a pic handy... i got drills. try to tin "just" the top and bottom edges of the jet, tin the wire, thread it through, and then simply bend it over and tack in place.


flat tyres is why ive gone back to 26" wheels. smoother ride, less flats...haha. i just had a flat the other day ... pot hole induced flats would be more appropriate. cant avoid nails or screws still! (or keys. yes, i once had a flat on my motorbike that was caused by a KEY!)


this must now be one of the longest threads in this section of this forum board

 

[jerrywelz]

i guess it's long because i'm always going at it. looking at the progression of the bike makes me smile. haha. sooner than later this thing is gonna be bullet proof.

here are some pics of what's going on tonight. off work tomorrow so i have time for it and my girlfriend. gonna get the whole tire tube thing sorted.

that dyno brake looks sick. i'll have to read your thread. i'm gonna solder the jet tonight, i have acces to many different types of wires. looking for a REALLY tiny one