WOT Performance, top end bogging

Discussion in 'General Questions' started by Kielohawk, May 25, 2007.

Tags: Add Tags
  1. Kielohawk

    Kielohawk Guest

    I have read many threads with issues about the WOT "bogging" topic. It seems like a lot of people have had or is having this problem. Lately, When I get up to around my cruising speed at WOT around 30 MPH the engine seems to get to a point and then "bogs" down a few MPH, then picks back up to the bog point.
    I have changed the intake gasket, put better connections on the electrical connections, adjusted the little brass float clip in the bowl, I opened the gas cap while at WOT and it didn't seem to affect the performance.
    So I am almost to work this morning and I reach down to make sure my choke is completely off and when I put my hand on the aircleaner assembly, the engine smooths out and picks up a few MPH. Hmmm, everytime I put my fingers around the air cleaner, the engine runs better at WOT. Could the engine vibration be affecting carborator performance? I think so.
    I am about to change to a better spark plug from the included chinese plug and switch to 40:1 mix from the 25:1 I am running ATM. I am also thinking of getting a better, lower resistance spark plug wire.


  2. Guest

    Guest Guest

    From what you describe the fuel in the float bowl could very well be frothing and that would lead to a lean condition.

    You say you are running "ATM" what's that?
  3. gone_fishin

    gone_fishin Guest

    at the moment
  4. lotsa_mpg

    lotsa_mpg Guest

    I think bikeguy joe be onto something. However, I am a bit confused :???: when you say that when you put your hand around the air cleaner, it runs better. When you put your hand around it, are you actually blocking off the air intakes at the bottom of the cleaner? Or are you simply grabbing the cleaner assembly on the upper part and steadying it (if that's the case, bikeguy is probably right). If you are blocking off a portion of the intakes resulting in improved performance, one would suspect that your fuel/air mixture is too lean......and by partially restricting the airflow to the cleaner, you are, in effect richening the mixture causing it to run better. I find my engine is quite sensitive to the weather...It seems to run at it's best when the outside temps are around 66-70 degrees F. What temperature was it this morning when you were riding it to work? If it's cold, say 45 degrees F, I find my mill runs better if I leave the choke just very slightly closed. Of course, every engine behaves differently, and what works for me might not work for you.

  5. OldPete

    OldPete Guest

    You will be better off running a secondary wire with resistance. They actually help increase the ionizing voltage that starts the spark.

    Change the oil ratio and plug first, then continue the diagnosis. Going from 25 to 40 to 1 WILL richen up the fuel mixture, Maybe about as much as fingers on the air filter.
    Check the fuel filter and carb flote level. One might be clogged or filled with water and the other might be low.
  6. Kielohawk

    Kielohawk Guest

    Ok!!! While at work, I got to mess with my engine mounting. THis morning I grabbed the air cleaner body and held it using my arm as a vibration dampener pretty much. I chalked my full throttle bogging down as engine vibration affecting the carburator performance. I think the fuel was frothing (foaming). Model aircraft 2 cycle engines are affected by this as well. If you don't pad you gas tank enough, the vibration from the engine will foam the fuel and you get small air bubbles that affect the performance or can even stall the engine.

    So, ever since I first mounted the engine, I have noticed that no matter how tight I tighten the engine mount nuts ( I have had 2 actually shear off) the engine always seems to rotate a little on the frame of the bike so that eventually the carburator intake is pushing against the seat post. I have actually trimmed the plastic intake a little to accomidate. And adjusted the chain tension because of this. I had 2 water bottle mount screws on top and bottom of the front mount. I loosenedd the 4 mount nuts. Moved the engine angle back to original position which increased the space between the seat post tube and the air cleaner on the carb, and used a very thick piece of sheet aluminum (1" x 2"), Prolly 1/4" thick, and measured and drilled a hole. I mounted the aluminum block on the front tube above the engine so that the engine would not ride up the tube. Pretty much acting as a stop. I then tightened the mount nuts again.


    On the way home, I had absolutely no bogging. The engine ran consistently, and I was able to get it to a 33 MPH max steady speed. I actually backed off that down to 30 cruise. It ran like it did when I first mounted the engine on the bike. I hope this info helps. I was surprised to see how many people were having this issue. So the tighter and more stable your engine is mounted to your bike frame the less vibration. Less vibration makes the carb perform better = more speed and better engine sound.

  7. Kielohawk

    Kielohawk Guest

    Oh yeah, and last night I took the big cover off on the right side (clutch side) to grease the big gear, and you know that big regular slot screw that goes into the little gear in the center? Mine was unthreaded and just floating rubbing against the cover. That would account for some of the noise I was getting. Luckily it wasn't stripped too bad, I was able to get it threaded back in and tightened. Greased the gears a little and its running a lot quieter now.

  8. Guest

    Guest Guest

    Exellent thinking! Nice way to diagnose and fix a problem.

    As for the gear....I have read here before to check that periodicly.

  9. Muckem

    Muckem Guest


    Hey Kielohawk, nice job on the fix.........common sense goes a long way in having and keeping one of these bikes running good.

    Now let me ask ya........are yall hiring? I need a job where I can get paid while working on my bike.....hahahaha. :D
  10. gone_fishin

    gone_fishin Guest

    i found that my 70 also likes to find it's own spot, which is slightly pulled back from what appears to be the correct angle. if i let it settle, then re-tighten, it stays put.

    i've also learned that a loose front mount will give you a slight "clanking" that will make you think something's wrong with the engine...always check your mounts for tightness.

    that is a good fix, btw, let us know how it works out for you 8)