4 stroking

It means the engine is so rich, it's firing every other cycle....4 cycling.
Your engine should break in and out of a 4 cycle when at a light- no load cruise and go to a even 2 cycle when you open up the throttle or start up a hil or otherwise load the engine.

hmm... but what if it isn't caused by a too rich mix? I've tinkered with the needle settings, I can make it worse but not better. I've leaned it out as much as I dare but this only helps so much.

I know these simple 2-strokes do this normally, yet it only runs properly for about 1/3 of it's low rpm range - regardless of load... 1/3 might be a generous figure too :/

It is really effecting the overall performance, you can feel a drastic loss of power when it happens. It's very frustrating, other than this one issue I love my lil machine, if I could reduce the amount of 4 stroking just a little bit more I'd be perfectly satisfied

Heh - yeah, sorry bout that lol

Well I'm at sea level, so much so it's sometimes literally as high tide invades my home from time to time... but that's besides the point It's a stock "80" (66cc) with the only alterations being a NGK B5HS plug, a replacement plug cap, and opening up the airbox just a bit to increase flow (desperate attempt to be sure).

Running 32/1, I've leaned out the mix till the plug became a light tan - got scared and dropped the clip down a notch to the 2nd leanest setting. Set to this, the coloration is a nice med/drk tan (milk chocolate) - the same I've come to expect on other two-strokes, tho maybe a touch lean. It makes very little difference, again I can easily make it worse but despite leaning it out as much as I dare it still 4-strokes excessively.

I wonder... after messing about with the needle settings for a week now I just cant figure it. Not like there's a lot of adjustment options on these things rofl

Thx Tom fer yer reply

edit: oh right hahaha - "inadaze" prolly doesn't help much with figuring out my local, its the coast of Maine USA. I'm just in the habit of not sharing my details on a forum usually, I'll fix that

I would go to the clip setting where it was tan, and run it for awhile and see what you get.
A lot of times it seems that they four cycle less after break-in.

um... well I would if it weren't for two lil things, one - I do a lot of distance at top speed and I'm concerned about running too lean a mix and two - Ima coward lol

I have it set to the second leanest setting as it is, but I just cut 1" of the internal baffle in the stock muffler and this seemed to help - particularly in combination with opening up the airbox a bit. With that thought in mind, I think I'm gonna hold off until I get the tuned pipe kit and a less restrictive air filter, a K&N if I can find one I can make fit.


Joe - you mentioned that these motors 4-cycle less after they've been broke in... This makes me wonder about friction and drag, maybe even a heavy oil mix contributing to the problem... I think that when I finally use up this seemingly endless 5 gallons of fuel I'll try a high quality synthetic oil, @ the same 32/1 ratio I'm using now (it's finally past the break-in) - or would you suggest a different ratio? A hotter plug range? (NGK-B5HS) Am I barking up the wrong tree?

Thanks for your patience, this forum is great! Although there's a plethora of small engine techs around me (I live at a marina BTW), they all just look at my bike and scratch their heads lol They're so used to the uber-complicated, super-tuned Yamaha outboards and whatnot they have no idea about such a basic motor like my lil china-girl, without a computer diagnostic port they're a little lost heh

Well, to be fair they're not performance techs and with the motors they work on it's just "broken = replace" - there's little to none of the "fiddling" involved w/a engine like ours.

If you go to a 24:1 mix from your 32:1, it will lean the fuel to air ratio. I know, that's a lot of oil....
More oil (richer gas to oil ratio) will cause a leaner (fuel mix to air) ratio.

Think about it- 16:1 is half as much gasoline to oil as 32:1.

Your right (of course lol) - I was lookin at that backwards, thinking to myself that the oil itself was causing ignition problems, not that I was enriching the mix by lessening the amount of oil I used.

/facepalm...

I'll try that AND it outa help with my paranoia about cooking the poor lil thing - thanks!!!



*BTW - did someone move this thread? I got lost

Try soldering the jet & redrilling it 1 or 2 sizes smaller... When my bikes are 4-stroking, thats what always works on them.
I can tell I've got a good jet size when the engine 4-strokes just a little bit in some throttle spots, but mostly runs "crisp". (that way I can tell its more to the rich side, than lean)

If you have concerns about not being able to do the soldering correctly, Go to a MC shop & buy a couple of smaller jets...

Well - after trying just about everything mentioned here with marginal increases in performance (every bit helps!), as it turns out vibration was my primary problem Sure - she still 4-strokes, but acceptably and about the same as everyone else mentions.

I've never been happy with the two low motor mounts on this lil engine, our roads around here are very rough and I hit the trails from time to time. I resorted to using my exhaust manifold as a third "mount" by attaching it to my Dtube, figuring three points of contact would help to prevent "twist" from chain torque.

To my surprise - it immediately ran significantly better, like a LOT better! My mounts are tight, the engine wasn't loose and I've got the fuel line mounted snugly to prevent frothing, I didn't think vibration was an issue anymore... but clearly it was.

I think at some point I'll look into a intake manifold extension and mounting the carb to the bike's frame instead, with my frame it'd be a whopping 1" extension - it's a tight fit anyway. I wonder if that will have any effect...

Thanks for all your tips guys! I rode my MB for well over 6hrs yesterday just grinning the whole time It was a beautiful Sunday, bright and sunny and I even found a new bike path to play on.

I may call in "sick" on Monday... obviously I need "test" this setup more hehe

You might try a colder not hotter plug. My motor runs better with a b7hs. 2 strokes love cold plugs.

four stroking had me baffled also, then i found this youtube vid: YouTube - What is "four stroking" ? might be easier for some people to wacth and listen rather then read