Tuning and 4-cycling

soccerrj88 · #1 10-23-2009, 01:05 PM

Hello to all again. Got a couple questions for the 2-stroke educated. I know how they work but this 4cycling is a mystery to me. I have an 8 hp outboard 2 stroke that stutters at mid range rpm. Now that I have a cheap 2 smoke to tinker with, I now think it's 4 cycling. But so is my bike engine. At idle it runs good, with throttle open it runs perfect with power, at mid range just keeping it running it bucks and 4 cycles and jerks... open throttle it smooths out. How do I fix this?

pedro5189 · #2 10-23-2009, 01:12 PM

Change the needle height in the carb, just experiment one notch either way

What do others think?

soccerrj88 · #3 10-23-2009, 01:15 PM

Well I did that last night, and I went up... Seemed to run worse. not really the 4cycle part, but just not top end, possibly starving for fuel. But thats what I didn't know. That carb pic post on here said stock was 2 from the top, well mine was 3 down from stock and I didn't know which direction made it richer/leaner. I have to go get some spark plugs today b/c the original is all black from break in.

Venice Motor Bikes · #4 10-23-2009, 01:20 PM

If you put the C clip on the top notch, that will lower the needle & restrict the fuel flow a little, making it run leaner.
If you lower the clip, it will raise the needle allowing more fuel to flow!

Just look at the thing, & think about how it works...

Also... the needle doesn't do anything @ WOT; it only works in the mid-range area.

soccerrj88 · #5 10-23-2009, 01:39 PM

ok that makes sense, but I thought it was the high speed needle, so why wont it effect WOT? what effects that, just the hole size in the jet itself?

xlite · #6 10-23-2009, 01:43 PM

Quote:

Originally Posted by soccerrj88

ok that makes sense, but I thought it was the high speed needle, so why wont it effect WOT? what effects that, just the hole size in the jet itself?

Correct-a-mundo!

Venice Motor Bikes · #7 10-23-2009, 01:47 PM

Give 'em the 'Malachi crunch'!!

soccerrj88 · #8 10-23-2009, 01:47 PM

So I opened the air intake a little by opening up the holes a little and cutting off the back of them. I also opened the baffle up, by uncrimping the two pipes comeing up. I should make it richer to componsate for this correct?

Venice Motor Bikes · #9 10-23-2009, 01:49 PM

did you finish breaking in the engine yet?

soccerrj88 · #10 10-23-2009, 02:15 PM

Well I have about 170 miles on it and according to everyone on here, break in period is between 50 to 500 miles and anywhere from a 16:1 oil mix to 100:1 so I'm not quite sure. Right now, I'm using between a 18:1 to 24:1 mix. I put in 24 but add a little bit here and there to make sure it's oiled well because of the break in descrepancy.