Running issue on 450MXR

[snowman48]

I just bought the bike a week ago and it was popping and backfiring. Now i sealed the header with high temp silicone, and installed a dynojet stage2 kit. Im running at 300ft above sea level, in temps around 25 degrees celcius. I took airbox lid off, installed 136 main jet, installed supplied needle on clip two, installed spacers, and backed airfuel screw out one turn. I have stock exhaust w/ sparkarrester removed. It said that stage 2 with stock exhaust and lid removed would work!!!! I played with air/fuel screw and it ran alittle better but when i let off throttle from wide open it lets out one large bang!!!:mad: I also just bought a notoil airfilter and i will probably install tonight. Oh the spark plug looks good, its perfect!!! I also went on a derby this weekend and half way through the throttle got a lot of slack and whenever i let off the throttle it would die as if someone turned the key off???:mad: I love the machine but this running s*@& is really p*$$*&# me off!! ANY HELP WOULD BE GREATLY APPRIECIATED!!! Thnaks.

[coalrat]

Your throotle cable has some play in it, just too much. adjust it so there is very little free pull. try pulling the plug out of the throttle, and see what happens.

The others sounds lean with the 136 in it??

[wannaride4]

It sounds lean to me, I ride an 08 525 @ ~4500', it came with the 136 main which was lean @ this alt., so I think you riding @ almost sea leavel would be way lean. Most everyone I hear of is having better luck with the JD jetting kit. Give that a try.

[SSJEFF]

There is a safety switch in the throttle that kills the bike if the carb or cable sticks. Bad thing is that it kills it also if there is slack in the line. Unhook the plug going to the throttle and it will not kill it anymore.

[Outlaw19]

Its is called an ETC switch , and yes it is a safety switch , pull back the rubber cover on the throttle cable just up on the bars by the throttle housing. Adjust so there is 1/8-3/8 play , after desired freeplay , with bike running and in neutral, turn bars back and forth to make sure engine RPM does not increase. I would recommend keeping the ETC plugged into the throttle unless you have a tether kill switch. its a safety kill for a reason.

[SSJEFF]

Originally posted by Outlaw19
Its is called an ETC switch , and yes it is a safety switch , pull back the rubber cover on the throttle cable just up on the bars by the throttle housing. Adjust so there is 1/8-3/8 play , after desired freeplay , with bike running and in neutral, turn bars back and forth to make sure engine RPM does not increase. I would recommend keeping the ETC plugged into the throttle unless you have a tether kill switch. its a safety kill for a reason.

Well I do not like the thought of my bike dieing when I am going up a hill and let off to maneuver and get back on it to find nothing. I think this is a safety issue also.

[Outlaw19]

yeah i do agree about that then lol. I race CMRC MX atv up here, i unplugged the etc, and got a honda 450r throttle block and cable . love the honda throttle hundred times more then that plastic on from polaris.

[Brown450R]

That huge piece of plastic on the polaris thumb throttle should be illegal. It sounds like you need to figure out why you suddenly got slack in your throttle cable. Something is not right. Figure it out before you get hurt. These quads run good when you get them jetted right. Maybe take it to a shop that can jet it on a dyno if you can afford it. Then you know its right.

[snowman48]

ok, so for starters when i installed the jet kit it had a 138 main. I was wondering if that would be to lean, but my plug still looked good. I work on my own stuff all the time but this machine im kind of scared of. People are telling me its really touchy to slight modifications. At the derby i thought about the ETC and unplugged it. There was no difference. So i adjusted the throttle cable on the handle bars, and it worked for a little while, but then started again.

[Brown450R]

I think the first thing you should do is figure out what is up with your throttle cable. Even if you have way too much slack in it, it shouldn't die when you let off, it should just return to idle. Your idle maybe set way too low or something. When you push on your throttle there should be a little slack, but not much. Did you buy this new? If you did, it should have been easy to install the jet kit by following the instructions and get it to run decent. Something simple is being over looked here. If you got it used, God help you.

[coalrat]

If there is too much slack in the cable it WILL die when you flip it back to idle, you will get a POP then if you can catch it before it dies. Just loosen the adjuster all the way for most slack, and you will see.

Not saying this is the problem in whole, but as others say, you should not be getting periodic slack in it.

[Brown450R]

That switch is for killing the motor if the throttle sticks open. I guess excess slop in the cable could trigger it. I never tested it. If thats the case, I'd unplug it. But I have a tether kill switch also. But yes, def figure out what is causing the cable to loosen. It really shouldn't.

[snowman48]

No i did buy this bike new off the show room floor, and it worked great, except for the popping when i let off from wide open. When i let off completely, and get back on it really fast it wont die. I can usually save it. I'll back to you guys tonight and see what happens, thanks!!

[snowman48]

sorry it took so long!! LOL SO i plugged the ETC back in and it works, then i adjusted the throttle cable down on the carb and now everything is ok. It works great!! But now i changed to a 140 main jet, with lid off, and now have a NoToil air filter. The plug is a nice chocolate brown, but now i still have a backfire issue. It seems to get a lowend bog when you stab the throttle when it gets really warm.

[justin1022]

Originally posted by snowman48
sorry it took so long!! LOL SO i plugged the ETC back in and it works, then i adjusted the throttle cable down on the carb and now everything is ok. It works great!! But now i changed to a 140 main jet, with lid off, and now have a NoToil air filter. The plug is a nice chocolate brown, but now i still have a backfire issue. It seems to get a lowend bog when you stab the throttle when it gets really warm.


take it back on warenty and tell them to fix it.

[coalrat]

For the backfiring, check to be sure you are getting a good seal at the pipe joints, exp the header on the motor flange.

For the stab the throttle bog, try turning the throttle up to the upper most point you can stand it. It worked on mine. It raises the slide so the acc pump squart dont hit the slide as much.

You may have to readjust the trottle again afterwards.

Are you still running the stock pipe? you opened the air box up now you should also allow it to get rid of the exhaust more effiently

Your seat pan sits directly on your airbox ,so you might get a sag in it in time. my sollution was to drill 2 big holes in front of the lid, and cut the back intake hole bigger. flows as good as it removed, but still has a bridge across it to hold the seat up.

[snowman48]

thanks for the info. it almost seems like its time for a pipe, by what every one is telling me.