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And the final report on this project. The governor has been removed, and the quad is a beast. Runs up to about 37mph now. What a project this became. Glad it is finally over. Once again, thanks to all that helped me along the way. It is much appreciated!

Well I finally have some good news to report. The bike is running great! After going through all we previously discussed, and not finding anything wrong, I decided to plug the pair valve. The bike immediately ran better, full throttle with no problem. Runs great up to 20mph, which is the Kymco limiter in the CVT. After months and months of fighting this, to say I was excited would be an understatement! I have to assume the pair valve is defective, and was letting unmetered air into the engine. Now I need to work on removing that limiter in the CVT. Thanks Mech and all that contributed to this battle. I really appreciate the help!

I will look into all that you mentioned. Thanks for taking the time to type it all up. You know, it's really funny that you mentioned the "pair solenoid". In my most recent troubleshooting, I was looking for any type of vacuum leak that could be causing the lean run condition and I found the that pair solenoid (so the 270 does have it). I was a little thrown off by it, and assumed it to be something emission related and decided to leave it alone. I will also go back, and take a much more detailed look at it, and see if in fact it is defective. The kids return to school next week, so we have some back to school shopping to complete this weekend, so it could be a few days before I report back. Also, really weird that the hole in the carburetor under the starter jet is normal. I thought for sure this hole would be a problem. I spend a few hours looking through the internet trying to find any pictures/videos similar to the one you posted. All I found was images from the opposite side. Glad you solved that mystery as well. Thanks again!

I'm thinking the same thing as you, that opening would restrict fuel from entering the idling circuit. It will idle all day if I just let it idle, so I'm assuming it gets enough gas for idle. Once you start to increase the RPM, if you go quickly it cuts out, if you go slowly it will steadily raise RPM. It sputters, and hesitates and at times seems like it will die but will eventually get to higher RPM, I don't think it has gotten to full RPM yet. I have not adjusted the idle mixture much. It has a security screw and I don't have the right screwdriver for it. I ordered a set off Amazon, and to my frustration they don't work. If I'm careful, I can adjust the screw with a set of slim needle nose pliers. What I did was verify the factory setting of 1.5 open from close. Shimming up the needle made a minimal improvement. When I first got it to run, any increase in throttle would cause it to stall. Now, I can slowly increase throttle and get the bike up to about 20mph. I'm not familiar with the side diaphragm you mentioned. I am fairly certain this does not have a side diaphragm. I'm not at home at the moment, but I can post additional pics at a later point if needed. I will double check the air metering jets next to make sure the big one goes to the main jet. I have removed the main jet brass tube (emulsion tube I think it's also called?), and the additional piece that actually protrudes into the carb body and cleaned them both, and carefully installed the small piece correctly. When the bike was first given to me, it was not running. Would not start. The history told to me by the owner who is not mechanically inclined is: The electric start stopped working, so we used the pull start, it became harder and harder to start using the pull start to the point that it no longer started, at that point we left it in the garage. It sat in his garage for a good 6-8 months before it was given to me. He did not stabilize the fuel, ever. I don't believe he was even familiar with Stabil. A new battery fixed the electric start "problem" I think the history, or lack thereof is what is hurting me the most. I'm torn, because it clearly runs lean but I can not find a vacuum leak, or a fuel clog anywhere. I was debating on installing a jet kit but the bike is stock so there shouldn't be a need for one. I'm getting to the point of thinking about replacing the carb. Our area uses Ethanol gas, the bike is 3 years old, and has never been stored correctly. I'm wondering if damage was done to the carb that would require replacement? I think I got all your questions answered. Thanks for your help, and I'm curious of your thoughts for me to move forward. Definitely getting to the end of my rope, but I really don't want to give up. I've put in so much time, and want to see this thing run again.

Hey guys. Back on this project. Bike still runs lean. See pic of spark plug. I have tried shimming up the needle, with no luck. still runs lean and is very slow almost impossible to accelerate. I did find something today that is bothering me. In the pic of the underside of the carb, the red arrow points to the bottom of the port that the starter jet threads into. When I spray solvent in the treaded area where the jet would be, the solvent comes out the small hole marked by red arrow. This doesn't seem right to me. I feel like this hole should be plugged? Thoughts on both pics?

That's what I figured as well. Never heard of limp mode on a carbureted model.

Hey guys. Back on the saddle. Minor progress, but still not running correctly. Had carb soaking for a few days to hopefully clean everything. Replaced petcock, drained and added a few gallons of fresh fuel. Quad started immediately, and idled great. Now it will Rev a bit higher, and smoother than before but still not to full Throttle. I'm torn on taking the carb back apart and trying to find something I may have missed. Alternatively I have been reading about "limp mode". Before I dig too far into the carb again are you guys familiar with these bikes having a limp mode? I would have assumed that was specific to FI models, but some facebook pages are telling me it is on carburetor models as well. Any thoughts on the mentioned limp mode before I dig back into the carb?

I had to order the petcock online, found a resource with the help of local dealer. Unfortunately the local dealer couldn't even get it, as it is on B/O from Kawasaki. Just hoping the place I ordered from is correct when they say "4 in stock" and I get 1 of them. Haha. Carb has gone through a very meticulous cleaning just before deciding to disassemble the petcock. I never tried starting it or introducing fuel since the cleaning. Keeping my finger crossed this finally helps but I won't know for a week or so. My son plays travel baseball and we are leaving the state for a week long tournament on Friday. I'll update this post once we return and I can get back to working on the ATV.

The tank is actually plastic. It may be hard to see in the pic, but that's not rust, it's the gasket that broke down. I'm assuming from the owner not treating the garbage ethanol gas in our area. I did perform a thorough cleaning of the carb, and only decided to disassemble the petcock for S&G's before trying to run the engine after the carb cleaning. So now I'm at the point of needing to replace the petcock so I can get back to troubleshooting. I broke open the old fuel filter, and shockingly it was clean with no debris. So I'm hopeful the carb will be OK once I can get a new petcock installed. Stopped at the dealership today, and unfortunately it is on B/O with no return date. I found a few "universal" ones on Amazon. I may need to go that route if I can't source an OEM one or a rebuild kit. The dealership said they haven't sold rebuild kits in years, people just replace them.

Ok guys, found something that definitely needs replacing. The petcock is shot, I'm assuming the lovely ethanol gas we have is to blame. I'm trying to avoid the dealer again, since the ignition unit took almost 2 months to come in. Anyone have a resource for a rebuild kit, or a replacement fuel tap? It sure seems like Kymco parts are tough to locate. See pic for as found condition of fuel tap

I agree, and that's what I initially did. However, due to this thing being such a bear to work on, I decided to run a straight fuel line to eliminate the fuel filter. It ran the same so my next task is to go through the carb as mentioned a few posts back.

Thanks guys. I picked up a new fuel filter today. Will try to install that in the next day or two. I did replace the plug, and have very similar results. Still wants to stall when revved. The plug looks lean as well, so I agree with all the above that I have a fuel deliver issue. If the fuel filter doesn't fix the problem, I'll pull the carb back off and give it a more thorough cleaning. I'll report back with my results. As I have said before, and I'll say it again, thanks all for the continued help. I'm hopeful to report a running quad one of these days!

I'm back again, working on this quad. First the good, it is now running and idling great. Starts every time, idles forever. I ended up working with the above mentioned dealer, and we agreed the most likely problem was the ignition unit. I ordered one from Kymco, and it took practically 2 months to arrive. Once installed, and quad immediately started. However it would not run unless the choke lever was held closed or partially closed. If I tried to rev the engine, it immediately died. I took the carb back off, and cleaned it again this time soaking all the parts overnight. Once installed, it started much easier and idled great. However it still stalls if revving the engine above 1/4 throttle. I removed the spark arrestor, but still have the same result. I'm going to check the spark plug, and remove the fuel filter. Beyond that I'm stumped as the idle/air adjustment screw is blocked off from the factory. I'm sure I could remove the cover and adjust it but this was a running quad so I'm hesitant to think it needs a carb adjustment. Any suggestions from the forums? Really been killing myself with this thing and hoping some fresh eyes will have an idea I'm overlooking. Thanks,

Well after taking some time off this frustrating project, I'm back on it. I found a dealership that even though they don't service Kymco, they do service Kawasaki. Exercising this grey area, they agreed to test the coil for me. haha. The coil tested fine, and apparently was able to jump a 8mm gap on their tester. The service guy was very helpful after testing the coil, and expressed that they have seen a number of these (Bruteforce) ATV's have a bad stator or pulser early on in their life. So that's my next angle, I'm going through the process outlined in the shop manual I have (Mongoose 250) for testing the stator. If anyone has an actual section from the MXU 270 or Bruteforce 300 that covers the pulser I would be forever indebted to you if you could post it. Also, any tips or suggestions on the stator would also be appreciated.

This ATV is going to be the death of me. I may end up calling the dealer that's an hour away and see if they can ship it? Of course, that's assuming they are still a dealer for Kymco. haha.