# Help Brute 750 Runs bad 2008



## hunter11 (Aug 6, 2012)

*My 2008 brute 750 started coughing,it has 30 hours on it.I only hit a little water,its all stock except a race computer.I change the easiest spark plug,That didn't make a difference.I do notice oil coming up into the air box.Any clues? why so much trouble on a 30 hour bike?? It sounds like it is missing a cylinder,Sometime it pick back up and drop off.I think this race pc doesn't have a open loop like the factory one did.Any Help in the right Direction would be appreciated,thanks*


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## lilbigtonka (Dec 30, 2008)

I would think it is the computer possibly or if it just started when you hit the water something electrical got wet.....let it dry out and it will prolly be ok if that is the culprit.....as far as the oil in the airbox that is normal your catch can runs in there and when your accelerating fast or doing wheelies it pukes it in there but don't let to much build up or you will foul out spark plugs 

the wetter the better


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## hunter11 (Aug 6, 2012)

Its been rested for 1 week, same problem, a friend said that his timing adjusted had shifted,didnt know that could happen on low hours>?


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## Roboquad (Sep 8, 2009)

coughing at idle. low speed? punched or top end??? IMO- electrical. it's hard to make the time jump. I have seen the sheer key torn out but that is very rare. unplug with some dielectric and reconnect. Also check the plugs for fouling. Start with the simple and move up. it is normally something small ,,,you will kick yourself if you start doing a tear down to find a connection came loose.


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## z24guy (Nov 27, 2010)

Do you know the difference between open and closed loop? Because I don't think you do. 

An open loop system would be a fuel injection system without an oxygen sensor. The computer has no way to monitor the combustion process. Most ATV fuel injection systems are like this. 

A closed loop system does use an oxygen sensor and the computer can see the effects of combustion with it and adjust fuel accordingly to maintain a pre-programmed set point.

And maybe try changing the other spark plug. If it seems like its only running on one cylinder you should verify spark at BOTH of them before you do much else. Then start checking and greasing connections.


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## blue beast (Feb 16, 2010)

i would change back to the factory computer and see if it was the new computer you put on..


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