motor spits

Mine's sputter too.

I had no problems with my 1.6 hp Robin, but my new Mitsubishi 2.2hp engine sputtered and fell flat on its face at the top end ...ALL the time. I tried the engine with friction drive and gear chain drive, with same results. The spark plug looked okay, but I replaced it anyway, with no results.

Just for kicks, I removed the ADA-1 goped pipe from my pocket bike engine and bolted it onto my Mits engine in one hour. I expected the engine to become much louder, but it's actually a little quieter, and with less engine vibration at idle. It has that "tinny" sound of old V8 headers at idle.

The low-end might've suffered a bit, the midrange power gained a little...and the top end is simply AWESOME. If allowed to, the Mits engine will now rev past its redline, so I have to be careful. There is absolutely no sputtering or falling flat on its face anymore.

Originally, I had thought maybe that this engine had a governor. I now believe my problems were caused by excess exhaust backpressure from the stock muffler.

I did have to saw off the pipe's mounting bracket to get it to fit. Everything else fell into place, after replacing the long exhaust studs and trimming the plastic exhaust cover.

I'm super happy with the ADA-1 goped pipe.

5-7
 
Did all of you start having this problem after the exhaust mod? I know I did, and after reading the other thread it became aparrent I was having the exact opposite problem as everyone else....It seemed everyone was becoming too lean after the mod, but I was majorily rich! I've been working on it and so far drilling the main jet smaller has taken care of my sputtering at WOT. However, with the main jet smaller I've had to increase my needle setting to compensate for the smaller volume of fuel...the engine runs better, spark plug is cleaner and it now pulls its own up hills. not quite finished yet however because it still sputters a bit at WOT which means my need to make the jet even smaller.
 
How do you drill the main jet smaller? Do you fill it with something (solder for instance) and then drill a new, smaller hole? Else, I can only see how drilling will make the jet's passage larger and therefore run richer.
 
Yes soldering the hole shut and redrilling works very well, I do it to all my engines. I find that after you rid yourself of the air leaks and especially with a tuned pipe the stock jetting is way too big. Stock on the happy time is a .70mm and I am down to a .60mm
Here is where you can get the drill bits.
http://drillbitcity.com/catalogue/25_piece.asp?Pt=3&St=&Sc=
I ordered the 25pc Carburetor Drill Set #R25WS74-50
 
Sounds to me like the needle's clip is assembled above the silver C-washer instead of between the C-washer and the barrel. There is another thread that describes how the manufacturer's instructions and associated pictures are incorrectly assembled.
 
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