400ex wont rev up [Archive] - ATV Riders Forum

REC

04-10-2003, 03:52 AM

My friend has a 1999 400ex that sounds like it is hitting the rev limiter way to early. If you rev it up at idle you get blurb, blurb,blurb,blurb... Rev limiter is stock and i think he has been thru the carb and all looks well.
Any ideas.

Thanks

spliffy

04-10-2003, 04:33 AM

What does the plug look like??

REC

04-10-2003, 05:00 AM

dont know yet, I will be looking at it tonight after work

oynot400

04-10-2003, 05:05 AM

Sounds like a jetting problem. Check the plug and go from there. How does the air filter look? Make sure it is clean. ;)

REC

04-10-2003, 06:22 AM

I rode it at lunch and it does not feel like jetting, but it might be.
The guy was racing and went off a jump on the last lap and this problem started. It feels like the rev limiter is jumping in too early.
Do you think the CDI box took a crap?

gojk

04-10-2003, 06:30 AM

Clean your precharger. i am almost positive it is that.

Big - D Racing

04-10-2003, 10:26 AM

there is no way it is your rev limiter, it sounds like jetting, or a fouled plug. When your plug is fouled or has a weak spark it may still syart up, but bogs heavily in higher rpms.

ZSK

04-11-2003, 04:55 AM

This is going to sound dumb but it might be the choke, maybe landing it caused it to come on a little. I get the blurb when the choke is on and you take off. Does it happen all the time or what?

kaneman23

04-12-2003, 07:02 AM

I had the same problem after doing a few laps on an MX track. I don't know the name of the part but it's a tube inside the carb. I think it's called the slide. Anyhow the screws in feet that attaches to the bottom of the slide had backed out completely. Therefore the slide was stuck in one position. It still idled but it wouldn't rev(no top end). Just reattach the slide and everything should be fine.. Worked for me..

frogburner

04-13-2003, 06:46 AM

Kinda sounds like when I had my timing off one tooth... Has the motor even been taken apart????? Might be something to think about... Mine wouldnt even raise the wheels in 2 gear,,, Thats sad... But the timing was off a tooth....

honda250xrider

04-13-2003, 06:51 AM

the only things i know it could be is the spark plug weak spark may cause it?, or it could be the air filter if you have water in there or if its dirty it will bog down, or the choke which is the most likely, i broke a peice inside my carb before and the choke would stick and if you have ever drove with your choke on you know what it feels like, but you said it sounds like that in idle, im not sure but maybe when at idle the rev limiter may kick in earlier?

Porkchop

04-13-2003, 07:14 AM

i think its the choke too.. i went to ride mine yesterday and it did the same thing, and i thought it was the air filter so i cleaned it and it still did it!! so then i thought for a few and finally checked the choke and it was half way on!! ran mint after that..

ramfan

04-15-2003, 05:58 AM

i did the exact same thing hit a big jump and thought i broke it all it ran fine at a low speed but when i went to go go go it cut out and blurbed, all it was is the black air tube from the carborater to the air box had come off of the carb. too much air. i'm sure by now you have it fixed though if that is all it was with your problem