just got the powroll kit in and i am using a 142.5 main jet but it feels like it bogs going up a small hill
Is that caused by the jet being to big or to small?

 

I don't do much tinkering with ATV's but I do with vehicle engines. I do know that if you jet out a carb for a small block V-8 too big and do not do anything else to the valve train/cylinder bore and stroke or cam shaft you can do more harm than good in relation to power. If it is getting to much fuel you can run into problems. You need to make sure everything else in the valve train matches the changes you make to the carb. An example would be if you took a 600 CFM carb off your engine and replaced it with a 1000 CFM carb and don't do anything else to the engine. It will more than likely run worse.

I found this out by doing some changes to my Camaro. By matching my carb and jetting to the cam I was able to dial it in very good. The carb I used was an Edelbrock 600 and all I did was change out the metering rods and step up springs. If I went to any bigger carb it would have actually made less power. Sometimes bigger is not always better when it comes to fuel/air mixture. The ratio has to be just right to make power.

 

I do believe this means you have it jetted too rich.

I would go back into the carb and adjust it, correct me if Im wrong.

 

As with my Camaro I did a little bit of experimenting. Make a change and try it out. If it runs better then leave it at that. Along with the fuel/air mixture I also experimented with the ignition. Now I know that the ignition on my Camaro is a lot different than my ATV but after trying a few things I finally got it dialed into what I want and how I drive it. My car is mainly a street driver so the changes I did catered to a more street-able motor. If I were use it mainly on the drag strip I would have to change it.

 

Just wondering while we are on the topic of the big bores here. Since the 250ex recon, rancher, forman, all have the same basic engine design, would it be possible to put a rancher cylinder on a 250 ex? I know it would be too tall, so couldn't you deck it down to your desired compression? I really think there are to many internal differences but it sounds fesiable to a capable machinist, right? So if my theory is capable of working, you could bore the case to accomodate a 500 forman crank, and bore the cylinder to accomodate for a 500 forman piston. Then port the head and add an aftermarket exhaust. That would be one mean little ex, especially with the stock transmission gearing and rear end. this of course is always open for debate. Peace.

 

i have thought about that. when we were putting my cousin's powroll kit on his 250 we almost tried to see if my buddies rancher 350 cylinder would fit be we never got around to it.