Bad Running Fix

[Catrinus]

I was recently given a 1985 Madami Defiant by a friend who was at his wit's end.  (I'm assuming the Madami is a grey-market version of the Lifan LF250 -- can anyone confirm that?)  It's titled and licensed as a Madami but I can't find any information about Madami so I'm using the Lifan LF250 manual and everything seems exactly the same. 

Anyway, the problem was that the bike would idle fine, but would not rev up.  My friend bought it new via the internet and he stated it NEVER ran right, straight out of the box.  He put 300 KM on it, gave up and parked it for 2 years.  I got it and the first thing I did was pull the fuel system apart.  I found a LOT of sediment in the tank, fuel pump, carb and and petcock.  And one of the fuel lines was plugged as well.  I'm not sure if it came from the factory like this, or if the sediment was the result of sitting for so long.  I"m inclined to think it came dirty from the factory since my friend said it NEVER ran right.

Anyway, after the whole fuel system was all cleaned out it still wouldn't run right, and by trial and error, my mechanic friend found it was sucking WAY too much air.  Part of the problem seems to be the design of the air intake -- it's like a 4" opening in the frame which just sucks air like cray.  We tried a bunch of fixes, and ended up buying a large rubber plug (bought it at Ace Hardware!), putting it in the intake hole, and drilling more and more holes until it finally ran perfectly. 

So my question is, how could this come from the factory with this condition???  There is no way it would ever run right without this kind of air restricter.  Or was mine missing one that SHOULD have been in there?  Anyone else have experience with these symptoms?

Catrinus in Portland, Oregon

[countrycruiser]

Catrinus,

What you have essentually done is close the choke.  Another words, you don't have too much air (that's impossible) the problem is you don't have enough gas.  Assuming you have adequate flow from the tank to the carb, take the carb off, take it apart and really clean it out.  I would say that without a doubt, your main jet is somewhat clogged.  Although I did not have the problem you discuss, I hear that it is fairly common and more often than not it is crap in the bowl and jets.  Also check the vacuum fuel shut off (some take it off) and make sure the lines are run properly from the tank all the way to the carb since I hear many times they are not from the factory.  Before you do anything though, take out your air restrictor and let it breathe.

I just happened to think of something else.  You might also want to check the rubber manafold and all it's connections to the cylinders and carb.  You could have a vacuum leak there that could be artifically improved by choking.  Fire it up and spray some WD 40 all around the area and see what happens.  The rpms should go up and you should see some smoke from the exhaust.  If either occurs, that's your problem.

cc