Throttle Cuts Out!?

[Atreyu]

Finished putting my new a-arms on todayand took it for a ride. Started ok, ran strong. Then I took it down my trail fullbore and came back..I let it idle for about 10 seconds then my throttle started cutting out at about half throttle. If you have it at half throttle-it doesent go anywhere. Anyone know what this could be? Air leak??:confused: :mad:

[Foxnake42]

i'd follow the throttle cable

[TheFontMaster]

Does the motor sound like its hittin the rev limiter

[Atreyu]

Originally posted by TheFontMaster
Does the motor sound like its hittin the rev limiter


Doesent sound like it's hitting the limiter. It can be gassed more pass half throttle. I'll check the line soon but I doubt thats it. Thanks for the help so far.

[Foxnake42]

check intake clamps on the carb too

[Atreyu]

Originally posted by Foxnake42
check intake clamps on the carb too


Checked most of that too.

[KY Woods Rider]

I noticed a post below where you said that you just went to an 11:1 comp 416, so I assume it had been running fine after the rebuild and then just started acting up. If so, the head gasket would be my first suspect, especially if you didn't re-torque the head after a bit of break-in. If you listen closely you should be able to hear it if there's a leak and/or see oil seeping from around the gasket.

[Atreyu]

Originally posted by KY Woods Rider
I noticed a post below where you said that you just went to an 11:1 comp 416, so I assume it had been running fine after the rebuild and then just started acting up. If so, the head gasket would be my first suspect, especially if you didn't re-torque the head after a bit of break-in. If you listen closely you should be able to hear it if there's a leak and/or see oil seeping from around the gasket.


Thanks a lot...I'll check it out.

[QuadRacer041]

Originally posted by KY Woods Rider
I noticed a post below where you said that you just went to an 11:1 comp 416, so I assume it had been running fine after the rebuild and then just started acting up. If so, the head gasket would be my first suspect, especially if you didn't re-torque the head after a bit of break-in. If you listen closely you should be able to hear it if there's a leak and/or see oil seeping from around the gasket.

i would have to agree with that, it happened to my freind too. for some reason when u boost the compresion a little bit the head stud stretch out and you start blowing head gaskets.
also check the intake boot i had a problem with mine cracking.

[Atreyu]

Originally posted by quad041
i would have to agree with that, it happened to my freind too. for some reason when u boost the compresion a little bit the head stud stretch out and you start blowing head gaskets.
also check the intake boot i had a problem with mine cracking.


Did you have a 99? The intake boots tend to crack on 99's because it goes from alluminum to rubber. But I thought CandGCycle updated that. I'll check the head gasket. Thanks.

I'll be at walden next saturday if you wanna meet up. But this time I'll actually be on my own quad.

[cals400ex]

Originally posted by quad041
i would have to agree with that, it happened to my freind too. for some reason when u boost the compresion a little bit the head stud stretch out and you start blowing head gaskets.
also check the intake boot i had a problem with mine cracking.


did you have a problem with the one connecting the carb to air filter or carb to the head?? i know they revised the boot that connects the carb to the head in 2001 on the 400ex's. the other ones had a tendency to come apart.

[cals400ex]

Originally posted by Atreyu
Did you have a 99? The intake boots tend to crack on 99's because it goes from alluminum to rubber. But I thought CandGCycle updated that. I'll check the head gasket. Thanks.

I'll be at walden next saturday if you wanna meet up. But this time I'll actually be on my own quad.


sorry, i didn't see this post when i made my post. :D

[QuadRacer041]

Originally posted by Atreyu
Did you have a 99? The intake boots tend to crack on 99's because it goes from alluminum to rubber. But I thought CandGCycle updated that. I'll check the head gasket. Thanks.

I'll be at walden next saturday if you wanna meet up. But this time I'll actually be on my own quad.


walden is having open practice next satursay, i think i may go then.

yes my ex was a 99 i think i remember hearing that they revised that too.

[MIKE400EX]

99's and most 2000's have the "old" rubber and aluminum carb insulator. Later ones were changed to a rubber boot with a phenolic (heat insulating) flange.

[660RaptorRider]

yup i have a 99 and it cracked and was really about to cause some damage im glad i checked it out. just a suggestion but make sure ur main jet didnt come or is clogged from anything since it controls top.

[Atreyu]

Just fixed it. It was the mainjet. Thanks for the help!