okokok that can deff happen but i would think fuel first everyone else on hear is thinking fuel related issues so far it is alot more commen but what you are saying is possible and being under load does not increse the compression but aftre the explosion it doesn't go down as quick because the engine is under load but the compression never changes when you lug something it doesn't blow teh engine but it will slow it down and stall it it doesn't blow head gaskets high rpm will but not load.

 

<div class="FTQUOTE"><begin quote>Originally posted by: sprinter10

okokok that can deff happen but i would think fuel first everyone else on hear is thinking fuel related issues so far it is alot more commen but what you are saying is possible and being under load does not increse the compression but aftre the explosion it doesn't go down as quick because the engine is under load but the compression never changes when you lug something it doesn't blow teh engine but it will slow it down and stall it it doesn't blow head gaskets high rpm will but not load.</end quote></div>

Not trying to start an argument really. But you disputed my suggestions with no foundation. I may have only a few posts but I have many years of engine experience. So... under a load the cylinder pressures are higher prior to ignition than when under no load or a lighter load. Throttle plates farther open for a given RPM means more air in the cylinder and thus higher cylinder pressure. Yes it could be a fuel issue though. Happy?

Cheers.

 

ok i gues it would be a lil more but the engine goes down and pulls air in every other revolution wouldn't it pull the same ammont every time? I don't see those lil butterflies or slides in the carb holding back a big suction from the engine it isn't sealed that good. but ok I don''t know that much about them but yea i can see it having a lil more. ive researched engines alot and had them apart and have been diagnosing problems with my race cars atvs and jet ski.

 

<div class="FTQUOTE"><begin quote>Originally posted by: sprinter10

ok i gues it would be a lil more but the engine goes down and pulls air in every other revolution wouldn't it pull the same ammont every time? I don't see those lil butterflies or slides in the carb holding back a big suction from the engine it isn't sealed that good. but ok I don''t know that much about them but yea i can see it having a lil more. ive researched engines alot and had them apart and have been diagnosing problems with my race cars atvs and jet ski.</end quote></div>

The throttle plates by design control airflow into the engine, that is the essense and primary way you control the engine output, by controlling the airflow into the engine. If the engine pulled the same amount of airflow every revolution then the the RPM would not change for a given load, nor could the engine maintain RPM as the load increased. I can fully explain the operation in another post if you would like.

To the original poster, sorry to get your thread off topic, just trying to help.

 

im waking up this thread because i have the same issue and looking for an answer. did you end up fixing your problem? im having a misfire problem under load also and somtimes it gets so bad i cant even drive the atv.i can turn it off and let it sit for 5 minutes and then its fine for another 15 minutes or so. its a 2005 scrambler 500 but basically the same design. ive been pulling my hair out because its been a problem for me recently and im trying different things. was able to go for a solid ride yesterday for about 4 hours but it was so muddy and wet im thinking it has somthing to do with heatsoak in the stator but the resistance of the stator is 150 ohms across all wires so im confused. please share if you found your issue