An expert who has achieved level 3 by getting 1000 points
An expert that got 10 achievements.
An expert that got 5 achievements.
An expert whose answer got voted for 100 times.
Re: flat spot just off idle
It has always been my experience, no matter if it's a car, bike, lawn mower, etc, if it backfires, it's the timing. If it's a constant poping thru the induction system, it's something to do with the valve train. Flat cam. lifter out of adjustment, bent push rod, bad lifter, etc. I think you get the picture. Mentiioning that you have a "Flat Spot also points to timing. Since it's been like this since new, I would look at the possiblilty that the timing marks on the cam and crank were not properly aligned when the unit was built. It's a long shot but work looking into.
- If you need clarification, ask it in the comment box above.
- Better answers use proper spelling and grammar.
- Provide details, support with references or personal experience.
Tell us some more! Your answer needs to include more details to help people.You can't post answers that contain an email address.Please enter a valid email address.The email address entered is already associated to an account.Login to postPlease use English characters only.
Tip: The max point reward for answering a question is 15.
Hi Anonymous, popping, coughing, spitting, or backfiring through the carburator or induction module can be caused by air getting sucked in combustion chamber do bad intake seals leaking. Leaking exhaust gaskets can also be suspect. Remove air cleaner and backing plate, while engine is idling spray WD-40 or Brake Kleen around intake manifold to head area, if RPM's increase you have an intake leak and seals need to be replaced, also spark plugs will be burning whiter than normal. Good luck
These will backfire when you let off the throttle if the idle is set low. When set low enough to sound "right" you will get the backfire. Set the idle up a bit and you will lose the backfire but it will sound like it is idling a bit fast.
Your posted symptoms is as you described, running lean which can be verified by the colors of the plugs, brown, light brown to almost gray / white. While the jets and the exhaust could be worked on, the simplest try of a fix is to restrict the air intake; the lower the RPM of the flat spot, the more air restrictions should be added. Experiment by temporarily placing upholstery foam on the outside portion of the air filter. You may have to try different thickness / porosity.
I am not sure what you mean on the "running fast" statement. If idle speed then turn the idle screw outward to slow down the idle.
The backfire is caused by turning off the ignition key when the bike is at high revs. let it idle down THEN turn it off. The backfire is there because the carb idle circuit is active anytime the piston is in motion. Gas goes into the cylinder as the bike revs down then a hot spot in the exhaust pipe finally ignites the built up gas. There is your backfire.
Is the running fast question answered? Give me more information on the problem if it isn't.
With the key off and the engine "running down", the idle circuit fuel is still going to into each cylinder then out the exhaust. A hot spot in the exhaust can ignite the unburned fuel creating an explosion, ( backfire ). Let the engine run down to an idle THEN turn the key off.
Initially, pls confirm that it uses a two-stroke 50CC engine. Additionally, your description "It refuses to rev beyond idle speeds." could indicate several conditions:
throttle up above idle speed, engine stalls/dies - fuel related issue, fuel starvation, clogged jets, nozzles, too much 2T oil, contaminated fuel (water). Basically a carb rebuilt;
throttle up above idle speed, no change in engine RPM - mechanical problem, possible broken accelerator/throttle cable, stuck plunger in carb, detached needle valve;
throttle up above idle speed, engine backfires/dies - electrical issue, check CDI, stators, trigger/pulse, their physical state/mounting, electrical connections;
throttle up above idle speed, engine hesitates/flat spot - air/vacuum issue, check rubber coupling from carb to intake manifold, blocked or absent air filter.
Good luck and Thank you for using FixYa.
Pls be informed that due to my current rank and rating, even a Helpful would
be detrimental to my status. Should this solution not address your
concern, it would be appreciated if you could just not rate it at all. Cheers.
Yes the backfire is an indication of being lean. Have you checked the valves lately? May be a sign of tight valves although that often cause a rough idle as well. Have you modified the filter system or added a tuned exhaust? Any changes like that can and will cause a change in carburation in which case you may need to fatten up the mid range jetting.