just installed sbp expansion pipe now problems(maybe)

I run mine with the clip on the top groove and have a .62 mm jet. Stock jet is around .7 mm.
 
so your running way leaner than stock, i will move my needle back to the leanest position and try it again but it seemed to run pretty warm

i figured opening the the carb and adding this exhaust would alow for more airflow and would lean it out i am an auto mechanic and usually when you add more airflow you have to add more fuel but i guess its diff on a 2 stroke

other than getting this thing tuned in right i love yalls exhaust i can now pull wheelies on this thing (until i get my 36t sprocket atleast)

gonna run this thing foras many miles as i can upgrading it when money permits me and look for a nice frame for my next build and will def get a shift kit on that thing
 
You would think more flow means you can use more fuel but how the expansion chamber works is it actually uses a pressure wave to force your exhaust port closed before the piston closes it. This increases the amount of fuel in the combustion chamber which is why the expansion chamber adds more power. Since it is keeping more of the fuel/air in the combustion chamber it tends to make the engine see a rich condition which is why leaning it out tends to work. The pressure wave is also why you can adjust the pipe, the trick is to get the pressure wave to do its thing at the right time to increase horse power, expansion chamber design, tube diameter all effect how the pipe works but changing the header length is what makes the biggest difference. Shortening the header means the pressure wave takes less time to travel the distance it needs to do its job. So it provides more power in the higher rpm range because the timing of the pressure wave corresponds to the rpm. If you lengthen it then the pressure wave takes longer to travel and corresponds timing wise better at a lower rpm.
 
after trying multiple carbs, multiple needle settings, stock exhaust diff plug and wire ,diff magneto diff cdi....I FINaLLY FIGURED IT OUT!!!!

well it was 2 things i replaced the fuel filter, noticed that the line had tiny crack in it pulled it off plugged the end and blew through it sure enough air blew out, replaced line and took off running great get down the road a little and it starts bogging reached down and grabbed filter and it took off like a bat outa ****

rode a lil more and looked down to find the filter full of bubbles went home ziptied filter to frame and took off again running better than ever passed a little cop radar box it said 38mph(prob not very acurate but its all i got right now) thats on a 44 tooth my 36 is scheduled for delivery tommorrow WOOOHOOO!!!

still got questions though:

whats the best way to keep fuel line from bubbling?(noticed its still doin it a little)

also should i seal the slide opening/throttle cable opening on the carb (not leaking but still for good maitnence)

how much top end should i gain with my new sprocket? (i heard 7-10mph)
 
still having a problem at wot

when i acellerate it runs good no bogging or anything until i get to around 27-30 mph it just stops reveing and bogs down a little i can roll off the throtle and it starts picking up again until i hit WOT and it bogs again

NEED HELP PLEASE!!!
 
Still sounds like a fuel mixture problem to me. All I can say is try going leaner. If that doesn't work try going richer. Since your issue is at WOT, the only way to achieve this is by changing the jet. There is another possible explanation. You may be out revving your gearing and port timing. With stock port timing these engines have kind of a built in rev limiter. You could try going to a smaller rear sprocket to take advantage of the optimum power band of your engine. You could also try shortening the pipe to see if you can move the power band a little higher in the rpm range.
 
i have changed to a 36 tooth rear sprocket and it doesnt sseem any faster than it was before maybe a little bit i know i could get it faster cause its not reving no where nearas high as it used to if i could just get through the bog soetimes if i feather around on the throttle when it bogs i can get it to rev out a little more

ima try to open up the intake tube a little to lean out the fuel a little more

also how much is the intake tube gasket restricing the motor stock havent had it off to look yet
 
if i could just get through the bog soetimes if i feather around on the throttle when it bogs i can get it to rev out a little more

I agree with Ghost0. The bogging sounds like your mixture is still too rich.
I had heaps of trouble in this area and now run the slide needle on it's lowest setting for mid-range and changed from an 0.79mm main jet to 0.73mm for high throttle openings. Made a huge difference.
What colour is the plug?

also how much is the intake tube gasket restricing the motor stock havent had it off to look yet

Heaps - it's worth cutting your own or trimming a stock one.
Rock Solid Engines sell a laser-cut inlet gasket that perfectly matches the port opening, if you don't feel like messing around cutting one. I bought one of these - wish I'd bought a few. Next order.

... Steve
 
If you get that pipe tuned right that lil motor should roar.
But timing or "header pipe length is key".
I actually made a larger dia header pipe which is 1 pc going from the manifold to the j shaped pipe.

The sound wave created in the chamber needs to arrive at the exhaust port opening at the right time.

Otherwise it lets fuel air out the exhaust or lets exhaust back in.

You want the wave to hit and compress the fresh air fuel charge.

My Grubee will rev to 8000 rpm with the stock carb and this pipe.
I sacrifice some of the low end though.

Keep playing when that pipe Comes therell be no doubt about it.
 
well i got the pipe to hit right before it starts to bog and would be exactly where i want it(if it didnt bog) ive tried the leanest settings on the carb but it ran way slower gettting up to speed

sorry if i made this thread seem bad about the exhaust cause the exhaust is actually great heaps more low end power and im sure once i getmy carb tuned right it will scream

it didnt bog with my 44 tooth sprocket just kinda sputtered at WOT but would bust out of it after a few seconds.

ive drilled the jets on my pocket bike before just dunno where all my ity bity bits went to but i would like to get a jet pack if anyone sells jets for theese carbs but i cant find any
 
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