1811 gremlin
 

My 1811 has run great up to half throttle the entire time I've owned it, but past half throttle it seems like it's being totally flooded. It smokes and tremors and seems like it's under extreme load especially cutting grass. It really sucks because at half throttle it doesn't have the guts for tall grass. I know the 18 magnums have an adjustable high idle screws but still I don't think it should do this. Any help is appreciated.

I would suggest a simple thing like checking the air filter for restriction.
Is the smoke Black? http://www.onlycubcadets.net/forum/search.php?do=getnew
What do the plugs look like? sooty carboned up? wet? are both firing?
Does it run when when you remove one plug wire? and replace it and remove the other? to see if one cyl is bad?
Is the choke fully opening? ( linkage adjustment)
Just some quick checks.
.

Brand new wix filter new plugs this spring choke goes off and I can hear the both firing especially when my muffler blew apart and the smokes kinda blue like a two stroke chainsaw I'm almost positive there's oil in it somehow but I have no idea how thanks for the tips too

Is there any oil being pushed into the air cleaner from the crankcase vent tube?
If so,then you could have a check valve problem in the valve cover or it could be more internal in nature like rings worn.
Sounds like you have a couple of problems.
Possibly running rich from a carb that needs attention,
( erratic high speed operation)
And blue smoke indicates oil into the cylinders.
If it acts rich as you mentioned in your first post, why not try to address that first by removing the carb and thoroughly cleaning it and checking it.
Although they usually plug up and run lean,
A needle & seat/gaskets are less than $10 on ebay.
There are IIRR 2 carbs for the mags, one has no high speed adjustment, the other,has one on the side, by the bowl lip but is anemic and does little, other than to lean it.
Most just use the older fully adjustable carbs from the KT series.

Thanks I appreciate the advice and I forgot to mention before but my grandpa did keep it in a dirt floored shed before I got it and the gas was pretty varnished I cleaned it out but didn't clean the jets and stuff and it isn't from operation because it even does it if I'm just setting in my driveway and rev it up to start mowing but I didn't think a cruddy carb would cause this

Would bring over full of oil cause this because I always put a little extra in just so it passes the dipstick line an eighth of an inch since they probably burn oil

Do a compression check on it