Not sure what the problem is...help please

[Curt750F]

So I just had a stage 1 jet kit put in my 1980 750F...I have a mac 4 to 1 exhaust and that's all I have done to it as far as the engine is concerned.  The mechanic I had put in the jet kit is trusted guy I would expect him to do shoddy work or anything.  But the deal is I get going down the road and hit about 4500rpm and my bike just bogs down and almost refuses to accelerate.  I checked to make sure there was no fuel line kink or anything like that checked all the major components and things like that and cannot figure out what is wrong here.  Thanks

[Re-run]

Try this, when that happens, pull up on the choke. If it goes, then it is possibly too lean. If it is worse, then are too rich. Being as how all you have done is a 4-1 exhaust, unless you changed the air filter, a jet kit was in no way needed. You are quite possibly running too rich.