2/stroke is 4/stroking?

[geebt48cc]

I'm about 2500 sea level. I was wondering why Iw would need different size jet, when it was running fine on the original jet from the start in same area?

Guess what I'm asking, is what could change with motor to need to replace the jet that motor came with, when it was running fine at top RPM's earlier?

Glen

 

[AussieSteve]

What could cause the change is:-
1. Clogged air filter, but you said you tried without the air filter with no change.
2. As I mentioned, possibly there was an air leak that is now fixed since you re-assembled and re-fitted the carb. (While there was an air leak, the mixture would have been leaner allowing the engine to rev out fully.)
3. Did you change your fuel/oil ratio? (If you reduced the amount of oil in the mix, a side-effect is that the air/fuel mixture becomes richer.)
4. Incorrect float level, but you've checked that.
5. A punctured float.
6. A dirty float-needle seat or excessively worn needle and/or seat.
7. The other thing you did was fit the new Autolite plug and new cap/lead. Why not an NGK B6HS? Won't hurt to try. Also double-check the connections on the new lead and cap. If it's a carbon lead, it's very easy to break the core while screwing it into the CDI.

8. Temperature change can make a difference to the mixture, too. I think the mixture gets richer as the temperature increases.

 

[jeffuehrer]

I had problems with my 50cc starfire "losing power" and all it was was the muffler containing too much gunk (unburned fuel). I switched to a chrome muffler and all is well in motorized bike land.

 

[AussieSteve]

A chrome muffler makes a huge difference.

 

[geebt48cc]

Mmmm, I took the end cap off this original black muffler, VERY LOUD but better power. So, I put it back on, and only good till about 17-20mph...... then the RPM's just flatten out??

I was going to get an Exp. Chamber, but I want to get 49cc skyhawk working normal before I try that.

 

[spokeytoke]

On my carburetor the threads weren't well defined, so sometimes I'd put the cap on slightly crooked. It's the big cap, the one I use channel locks to remove. I think that caused mine to run rich.

 

[jeffuehrer]

you could probably just take the whole muffler apart and soak it in gas to break down all that build-up and then slap it back on and it should run fine.

 

[geebt48cc]

Well it looks like I did find problem. I was told that the AUTOLITE 4093 plug was a cross from NGK B6HS.........................But no way--------I got the B6HS (gap 0.24 ) and runs fine at any speed. Thank you guys/Steve.

PS-Now, do you think that I should put needle E-clip back from max lean, to second notch. It's getting all the RPM's, but it acts a little slow?

 

[AussieSteve]

Don't say I didn't tell you so. (Sorry, couldn't help that.)
I'm glad it's sorted out.
Go by plug colour to determine where to set your needle, as described in 'NT Carb Tuning Basics'.
If the plug isn't white or grey, drop the needle back down and try it out. You're aiming for a tan plug.

 

[lhemrick]

Just wanted to say thanks to all who have posted on this "4 stroking" thang! I have an engine that I now believe has this problem and can't wait to get home from work to put all this information use. I've never heard of a 2 stroke engine 4 stroking, course other than this little engine all I own are four strokes. In my experience with motorcycle engines I've found that any time you allow an engine to breathe better either by opening up the air flow to carb or letting it exhaust easier air/fuel mixture will be affected. If its running to rich you can open up the exhaust (by drilling holes) and let it flow better to lean it out. I recently cut down the exhaust on a bike and removed half the baffle. It began surging on the top end. Went up several sizes on the main jet, problem solved. Air to fuel is a delicate balancing act and I can't believe this little one cylinder engine has kick my butt to this point but I'm going home to show it who"s boss.

Thanks again,
Lynn