jpz

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.

Ok, so more interesting problems related to this ATV. Hopefully someone has some suggestions. I can't find a quality coil. Rocky Mountain ATV doesn't stock them. I went through a google search and couldn't find anyone that sold the coil. My local dealer no longer services Kymco because "they could never get the parts". I even tried searching for the Kawasaki Brute force, since they seem to be mechanical siblings and no luck. Any suggestions for where to buy Kymco parts online would be great. I even went to their website, and they still list my local ATV place as a dealer, beyond that the next closest one is an hour drive. Is Kymco really this difficult to work on/with? Or have I just found the read headed step child in their lineup?

Thanks guys. I'll reach out to my local dealer about a factory coil. What a project this has become.

My struggle is I have 2 coils and both function exactly the same. I unfortunately have no idea what a "good spark" is supposed to look like on this bike since I only have it to hopefully fix it. If the pulser is only for timing, and I have already replaced the coil with the same end result I'm stuck with not many options. Definitely a frustrating bike so far.

This is where I'm struggling. I have 2 coils. 1 came with the bike, 1 I bought because the factory coil tested outside the factory manual specs. Both have similar resistance readings, and both test identical on the bike and on the bench. That's why I started leaving towards the ignition unit. I'm having a hard time because typically ignitions work or don't work. Where this one is working poorly. Does the pulser unit in any way factor into the current for the ignition? Or is it solely for timing?

The condensers I mentioned were described as being part of the ignition unit, not the pulser. That was the other reason I was thinking ignition unit over pulser. I was under the impression the pulser just controlled the spark timing. The only test I performed on the pulser was to check resistance which was 120 ohms. The shop manual said it should be 105-110 ohms. I was thinking similar to the coil, (which tested slightly off) 120 ohms was not enough of an issue to cause my problem.

I wouldn't say "good spark" from the coil(s) I have. It is still a small spark, but they are comparable to each other. So, I would assume since both coils produce the same spark when bench tested they are both good. When you say "pick up coil" are you referring to what the manual calls the pulser? It appears to be connected to the crank on the engine going off the shop manual photos. Or are you referring to primary and secondary sides of the coil? I agree with your statement of ignition units either "work or don't work". That has been my experience also. However what is really driving me nuts is when I bench test the coil, using the correct resistor plug that is correctly gapped I can jump that gap with what I would call a weak spark. When I connect everything back to the bike, and crank it over I can not jump the same gap on the same plug. I need to reduce the gap on the plug to .3mm (half factory spec) to jump the gap. Also, for some clarity when I say weak spark I would compare it to the spark I see on my 2 cycle engines. No where near the same spark that I see on my snow blower (208cc 4 cycle). I have never looked at the MXU spark when it is running correctly so I can't say if this is a good spark or weak spark for this machine. Reading the shop manual, it speaks of condensers in the ignition unit, which I assume function like a capacitor and help during start up. Also, now knowing that the owner possibly connected the battery backwards I'm assuming something was cooked in the ignition unit. I hate to just throw parts at anything too, but I'm not able to find a smoking gun other than comparing the bench test of the coil, to the fully installed ignition assembly on the bike.

I have actually tried using a car battery when bench testing the coil, and the result was the same type of spark that I get now. So I have to assume that the bike battery is good (and it is brand new). I'm a bit lost with the spinning of the back tire in an attempt to start the bike. Wouldn't that produce the same result as using the pull start? I have done the pull start as well, and get the same result. As for the headlight in place of the bulb, I wouldn't really say it got "brighter" as I cranked. It only very slightly made the filament glow as I continued to crank it. It was not even enough to produce light, just a slight glow. When putting the 12v supply of the coil to the battery, and then a jumper to ground the bulb fully lights up when turning the ignition switch on. The owner of the ATV just told me that when he replaced the battery he "may have" connected the battery backwards. No fuses are blown, but I'm wondering if this could have damaged the ignition unit and be causing the weak spark that I am getting. It just really makes no sense, and something is causing a weak spark when the ignition system is fully connected. When I bench test the coil alone, I can jump the spark of the proper resistor spark plug when gapped to .7mm. However, when installing the ignition system to the bike, and cranking the engine I cannot jump the spark on the same spark plug unless I reduce the gap to .3mm. So something in the system is causing a weak spark. I have 2 coils, and have tested both with the same results. The battery is brand new, and on a battery tender so it is fully charged. The pulser unit only controls the timing correct? If so, then I have to assume something in the ignition unit is causing the weak spark? I can't duplicate the test in the manual for the ignition unit due to not having the correct tester they call for. It appears that I would need a multi-meter that produces more voltage than your standard Fluke meter.

Ok, some additional info to the above message. I bought a spark plug without a resistor, when touching the plug to the block I get a consistent but very weak spark. So weak, that in order to see it I need to turn off the lights in the garage. In my opinion this is too weak of a spark to run the engine. Of course, I had no reason to check the spark before on a running engine so I am assuming this is a weak spark. Could this be all the more ignition this thing needs? I pulled the carburetor and it was pretty clean inside. No restrictions, no gumming of old gas. Needle and jets look good. I installed the carb back on the bike, and even with starting fluid I get nothing from the engine. Just cranking and cranking. No attempt at firing. I have checked the grounds, and even cleaned them up. This is brand new battery. When I test the coil remotely with the battery and test leads, I get the same weak spark as I'm seeing when cranking the engine over. As mentioned above, when installing a car headlight in place of the coil it will make the filament glow slightly, but certainly in not "lighting up" the light bulb. I tested the ignition unit for resistance (which I believe to be a CDI unit, at least that's how it is listed when shopping for replacement parts), I do not get resistance readings like in the chart for the shop manual. So all that being said, this seems to me to be an ignition problem, however I can't pin point which item is the bad item. When I check resistance on the pulser unit I get readings above what the manual calls for. For the coil, I get readings below what manual calls for. I actually have 2 coils, and both test outside of the shop manuals specs. The ignition unit also tests below the manuals specs. I really don't want to start throwing parts at this, but I don't know where to go from here. Any thoughts would be greatly appreciated.

Well I'm back on this, and still having zero luck. First, I installed a car headlight to the leads for the coil. I cranked the engine, and after a few rotations the bulb started to flicker. The longer I cranked, the brighter the bulb got but it never came close to full illumination. Was more or less making the element glow slightly. Second, I went through the ignition unit inspection chart, and not a single one of my readings came back as mentioned in the chart. They all come back significantly lower than what the chart shows. I'm really stumped here. I can't make sense of this machine at all. Functionally I can get every individual component to work. It just seems like the ignition system is working poorly and not generating enough spark to jump the gap on the properly gapped plug. I still need to try a regular spark plug without a resistor. I'm open to any additional suggestions. On a positive note, I seem to have been released from Admin approval as my last post appeared right away.

We seem to be on the same page with our troubleshooting. However, I'm still under "admin review" for each post so it may be a few hours before you see this and my previous 2 posts. I will try connecting a headlight bulb in place of the coil and see what the result is. I actually have connected a wire between the capless coil and the spark plug. The spark was intermittent and weak (had to turn off all the lights in the garage to see it). I didn't try starting the quad that way, just had the plug against the block. Also of note, in order to see that spark I had to decrease the plug gap to .4mm. When set to factory speck of .6-.7mm I do not get a spark. The plug I have is a resistor plug, so I'm very curious if you are onto something. The plug itself has about 6 ohms, the boot had about 5. combined they had about 11 ohms. I'll have to look into finding a non-resistor plug. The ignition unit has me completely stumped when trying to test following the information in the manual. If I'm understanding the chart correctly, one side of the diagonal line is for the positive lead, the other is for the negative lead. When testing this way, I don't get anywhere near the same results in the manual. Am I misunderstanding the chart?