450r cutting out on top end

[leager440]

My 450 starting missing real bad a few months ago. It was like you were just hitting the rev limiter at half throttle. I put a new coil, new stator, spark plug on it and cleaned the carbuerator and air filter. The compression seemed a little low (75psi) and the valves were tight, so I just went ahead and put in an 11.5:1 piston and adjust the valves. The valves were tight, I mean real tight. The intake valves had 165mm shims in them, I ended up putting 120mm shims in them and they came out perfect. So, quad fires first kick, all is well, it revs good, no more rev limiter action, but, I go to ride it today and once I hammer the throttle open, it just cuts out, I mean nothing! I know that when the compression is raised, sometimes you have to go down on the main jet, I'm currently running a 185 main, LRD Full race exhaust, and a K & N filter, no air box lid. So, does this sound like a jetting issue, or is there something else that I'm not catching??? Thanks for any replies!

[Ex_Rider43]

mine started to do the same thing yesterday when I was practicing. I gonna try a new CDI box. I have the stock CDI and when I hit the throttle in neutral , it just bogs down and it doesnt rev like usual.

I will clean the carb and see if the main jet didnt came loose , the same thing happend with my 400ex and the main jet was loose in the carb.

[leager440]

I tried a different CDI two months ago when this first happened, nothing! Good luck with yours!

[Ex_Rider43]

well... nothing special in the carb , Ill see if the CDI might be the problem but I have no idea.

[groundhog_464]

my 06 450R was doing this right after i got it, it has a hrc kit. the honda shop changed a jet and took the air box lid off and it ran fine. i didnt like the idea of running without the air box lid so i cut the lid like the hrc lid and run an outerware. runs great!

[atvRiDa400ex]

sounds like a real jetting problem to me... JMO

[Over-land 450r]

check and see if the neddle didnt come undone.

[quadhauler]

Had the same symptoms on a Raptor a couple years back and finally figured out my carb float had somehow gone out of adjustment. Never seen anything like it before in a lot of years of dirtbiking...

[leager440]

Ok ,here's where I'm at. After a long, frustrating day of tuning, I'm more confused than ever! Yesterday I dropped in a 170 main. Quad ran great. When I get into a turn and come out, it was bogging real bad. My needle was on the very bottom clip, it's an HRC needle. So I move it up one notch. It started missing and running terrible. So I put the needle clip back on the bottom notch. Still ran terrible. So what changed? Now it just misses like crazy, whether in a turn or not. I just can't figure this out, at first I thought that it just needed to be jetted correctly, but now I'm not so sure. A friend that I ride with just redid his 450, same piston I used, Curtis sparks pipe, hotcams stage 1 cam. He is running it with the air box lid on and stock jetting, it runs great!!! So how can his run so good with stock jetting and mine be so touchy????? I don't get it!!

[Grant Casey]

my friend had the same problem it turned out that his fuel line was clogged wit ****. clean it out wit a air compressor.

cheers grant

[leager440]

I tried some new things last night and I even further confused myself. I started out by putting the 170 main jet back in. Ran it, no good. Went to a 175, then 180, then back to 185. It ran the same with all 4 jets. There was no difference at all! I runs fine with any of them, except if you hold the throttle at a steady speed, it starts to miss, or if you put it in a strain, like sliding through a corner! I thought maybe the float, like was stated earlier, but most of the time when the float is out of adjustment or wore out, any time the front wheels come off of the ground it will miss, I can ride a wheelie all the way down one of the straight streches and it won't miss a beat. So I'm not thinking float anymore. Thanks for the input, I can use all the help I can get, I'm getting close to becoming impatient with my fourwheeled friend!

[leager440]

Here's an update. I put a completely different carb on my quad last night that came off a fourwheeler with the same setup as mine. Still ran the same. Cut's out when the throttle is held at a steady speed or put under a load! Any ideas? I'm completely lost.

[Ex_Rider43]

one of your valve may be bent a little , thats what my mechanic told me. I will try a diferent carb today also to see if my needle or something might be done. I hope its the carb , this way I will be able to ride this week end with another carb.

[fatkid400]

This might be a dumb ?...but hows your head gasket look?and chech your boots and all breather tubes Including your gas tank tube.

[leager440]

thanks for the post, but I just redid the top end, so I have a brand new head gasket. I've had this thing apart so many times this week it's not even funny. I've checked all of my lines and boots. All seems well.

[hypersnyper6947]

I know this is a really old thread but i am having this problem and was wondering if anyone ever figured out how to fix it, if i floor it, it will start to cut out, if i slowly floor it, it will still cut out just not as quickly. My mods are in my sig, any input would be greatly appreciated. I have never been able to floor my quad and its starting to piss me off, i want to see how fast this thing really is, plus i want to smoke my friends on there raptor 660s. Please help me.

[gmcsonomaex]

what is ur quad? is it a honda 450r? it could be many things it could be the float or the jet is the wrong size for the sea level your at. and the needle on mine is 2 notches from the top. the carb could be dirty i used starting fluid and whipped mine out. the air filter might need to be changed and on mine i didnt want to take the air box lid off so i drilled like 20 holes in the top of mine and mine doesnt cut out any more runs full out! let me kno if i helped or if you need nething else

[hypersnyper6947]

My quad is a 400ex, my air box already has no lid. Im wondering if i shoud put a bigger main in there, right now i think there is a 175 in there right now. I had a different motor before and had it professionally jetted so im sure that it was cleaned by them and that was only 2 months ago and i dont ride that often. I also clean and oil my air filter often. It runs great from 0 to 1/2 throttle so i assume it is the main that is the problem. Im thinking about just putting a 195 main in just to see if it gets worse or better.

[gmcsonomaex]

um that still seems wierd that its doing it. take your air filter off then start your bike and c what it does if it runs better than your air fuel screw on your carb might need to be ajusted if it gets worse then you might need a bigger jet. mine is a 170 in the main but i dont oil my filter it makes it clog up with dust and the it cant breathe well let me kno or pm me if you want.

[Turboderf]

check you vent hose on the gas cap i had the little piston for a cool look but it was dirty and causing to stall on top end it would idle allday good luck

[WilRideAnything]

Trya new petcock.

[Turboderf]

Originally posted by WilRideAnything
Trya new petcock.
yes they go bad also i forgot about that

[hypersnyper6947]

I will try all of these and keep you guys updated, please keep the suggestions coming though

[Eastcoast08]

I'm having the same problem with my 450! Ugh....I dont know what it could be either, im gonna check my valves next.

[gmcsonomaex]

Eastcoast08


i dont think it would be your valves but i rebuild and fix many four wheelers in my garage so if you cant get it goin and want to trade for a perffectly running 400ex with bolt on mods and just rebuilt carb let me kno


another thing for both of you check your plug it could be going bad or your gap might need to be off and check your coil and make sure its a good spark if you dont kno how to do that let me kno and check your gas and make sure its not watered down.

[Eastcoast08]

Thanks for the advise, im not interested in trading though, my 450 runs amazing just gotta get this kink worked out. Its a $20,000 450r mostly built by Eastcoast atv that i use for nationals, so if your 400 is of equal value that must be one bad***** 400!! A lot of the stuff that is done to my 450 is listed in my signature at the bottom

[gmcsonomaex]

nah i wish my 400 was like that but if i have the money i would have a 450 but where i live i cant find a job to save my ***** that is good payn neway i have 2 years of precision machining with mills and lathes but nothing around here it sux!

[slainwarrior]

you might wanna try putting a bigger pilot jet in... and also probably going down a few sizes on the leak jet

[motoguy450r]

have you changed the gas, i had the same probablem with my r, i got bad gas at the pump, and after wiring harness, cdi, stator, carb and a hole lot of other s**t it was the gas. just a shot in the dark but worth a try.:rolleyes:

[leager440]

This will not apply to the 400's, but will for the 450's. I orginally started this thread forever ago. My problem was that my hot start cable had stuck in the carb. I pulled it out and cleaned it real good and it ran like new!

[hypersnyper6947]

Im out of town for the holidays so i have not been able to mess with it, but i do have a new monster coil so its not that b/c it was doing the same thing before that, it has a new tank of 110 fuel in it so its not that. Im still going to spray my intake boot with some starting fluid when its at idle to see if there is a leak there. I will get a new plug too and see if that helps, thans for all the advice guys keep it coming. I will update as soon as i get back in town.

[hypersnyper6947]

So I was not able to get a new plug but i did take it out and clean it and it looked fine, a little black though. I check for leaks and found none, anywhere i though there could be a leak in the boot i taped it to get a good seal with electrical tape. I upped my main jet from a 175 to a 190. I also checked my gas cap and it still vents great, and the fuel line is good also. It still cuts out when i hit it to WOT. The head gasket seems to have a good seal i see no oil leaks anywhere on it. Please any help would be great thanks guys.

[fox945]

Had a buddy that had the same problem, sounded like his would hit rev limiter but not really reving high at all, switched cdi's and still didn't fix. Everybody I spoke with swore it was an electrical problem. I decided one day to just take his air box hose to the carb off and start playing with it. With all the times I cleaned the carb and I never noticed it but the throttle valve the the needles connects to was not pulling up all the way like it should. The lever that pulled it up came loose. It may be the problem you are having it may not be but I would take a look. Hopefully this long story helped.

[hypersnyper6947]

Originally posted by fox945
Had a buddy that had the same problem, sounded like his would hit rev limiter but not really reving high at all, switched cdi's and still didn't fix. Everybody I spoke with swore it was an electrical problem. I decided one day to just take his air box hose to the carb off and start playing with it. With all the times I cleaned the carb and I never noticed it but the throttle valve the the needles connects to was not pulling up all the way like it should. The lever that pulled it up came loose. It may be the problem you are having it may not be but I would take a look. Hopefully this long story helped.

I am going to take the carb apart today, maybe thats it b/c what you described is exactly what is happening to me. I will post pics of the carb apart and maybe you can take a look, i have never really messed with the internals of the carb to much just the main jet.

[hypersnyper6947]

I took it apart today, i seems to open all the way when i floor it here is a pic, let me know what you think.
http://i74.photobucket.com/albums/i276/aclasson86/IM000583.jpg

[fox945]

Looks like its opening up all the way to me. So that shouldn't be your problem.

I haven't messed with a 400ex much, if yours has reverse and if they can do anything like a 300ex, you have safety switches inside your case and if they go bad they can do that. I know on a 300ex you have two wires that plug in the side of your case behind your brake lever. You can ground those 2 wires out and bypass the safety switches on a 300ex. If they go bad it acts like your hitting the reverse rev limit but in your forward gears.

But like I said I don't know much about a 400ex to say if yours can have that problem or not but I'm assuming so if it has reverse.

[hypersnyper6947]

well i cleaned the carb really good by taking it apart and spraying it with carb cleaner, then i put a 48 pilot(same as before), 178 (down 2 from a 180) main and moved the needle to the 4th notch from the top(which is only one notch from where it was before went from 3rd to 4th). Now it runs like a champ and pulls hard through the whole throttle and gear. So im not sure what fixed it but now it works, thanks for all the input guys.

[gmcsonomaex]

could have been the pilot holes were dirty or the needle but i have a 178 jet in mine and it runs awsome. but i glad to hear you got it running. hope it stays that way!

[Turboderf]

WHOO HOO lets ride

[hypersnyper6947]

Originally posted by gmcsonomaex
could have been the pilot holes were dirty or the needle but i have a 178 jet in mine and it runs awsome. but i glad to hear you got it running. hope it stays that way!

Im sure something was clogged, so lesson learned keep the carb clean. lol

Turboderf where do you ride im down

[Turboderf]

we ride l-cross , thundercross , croom , race FTR and SSQSA we are racing tomorrow in okeechobee check it out www.ssqsa.com floridas ATV XC racing tour come on out say hello # 992C

[hypersnyper6947]

My buddies and I ride at croom often but i want to hit a mx track. Do you know where the closest one is, at Biflo they dont let quads on the track. Im in orlando near UCF

[Turboderf]

try thundercross in okeechobee not sure how far it would be from you