Crf 450 running bad in neutral on the stand

xr284

Member
Mar 18, 2003
85
0
Crf 450 running like crap.....Please Help!!!

It all started when i got back from the sand dunes. It runs, but dies, missess, and stalls out passed half throttle. If i get on it quick, it dies. I took the carb apart thinking maybe some sand was lodged in there, but there was nothing. Then today i went out, started it, let it warm up, then when id give it some gas, if it didnt die it would miss, pop, and shoot flames out the tailpipe,also the headpipe glowed red, like it was about to melt. Like i said it just started happening right when i got back from the dunes, it always ran good up until now. What could it be??? timing?? tps?? running to rich???

Please help, i cant ride until its fixed!!!
 

Studboy

Thinks he can ride
Dec 2, 2001
1,818
0
Check your valve clearances. Also, maybe you overheated or overreved the bike at the dunes???? I have seen a lot of guys seize their thumpers at the dunes here, but mostly 250Fs.
 

kboy

Member
Oct 7, 2003
25
0
It's always difficult to tell by E-mail.., but when you tell it's running hot/"pops"/won't rev when gassed, Im almost sure it's running lean!
It takes an awful lot of gas to drown a 4stroke when you're idling, and then crack the trottle. Check accelerator pump/needle location/any leak by carb. mounting. Also make sure the HOT START slide is able to fall right back in closed position.
 

Bandit9

Member
Jul 14, 2002
449
0
Sounds real lean. Check everything the previous guy said.
Last week I installed a flywheel weight. I started it up right after the install to go for quick spin around the neighborhood. It was running like crap, sounded weird, idling real low, sputtering, cracking, popping, stalling and such. I rode it for about 10 mins like this before I got worried. I thought maybe somehow I screwed something up installing the flywheel weight. Well after tinkering with it for about 5 mins, I realized I left the choke pulled out! I felt like a dumbazz, but I had a big grin on my face though when I realized it wasn't serious!
Anyhow, it might be something stupid like that, so check all hoses, filters, and such.
 

Hick

Member
Aug 15, 2000
224
0
It sort of sounds like your accelerator pump ain't working. That's easy enough to verify if you can take the carb off, a stream of fuel should squirt out of a small brass nozzle at the bell towards the front when you lift the slide.

I do know that if I were to disable the accelerator pump on a perfectly running bike you would probably think all manner of things were going wrong, point being it does make a big difference. So I would check that first, if that is working I'd drain the fuel and replace with some fresh gas.

Hope this helps.
 

SFO

LIFETIME SPONSOR
Feb 16, 2001
2,001
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Hicks the man.
Hick, BTW, that piston kit you boosted me went to the eternal home of yz-f goodness RR.
I still owe you though...
Wanna check out the Dallas SM this weekend?
 

xr284

Member
Mar 18, 2003
85
0
I did pull the carb off and the accelerator pump works fine! I dont think it is the jetting, because it ran perfert before.. I never touched anything, it just all of the sudden started happening. And it also has a new fresh tank of gas in it..
 

Hick

Member
Aug 15, 2000
224
0
Originally posted by SFO
Hick, BTW, that piston kit you boosted me went to the eternal home of yz-f goodness RR.
I still owe you though...
Wanna check out the Dallas SM this weekend?

I'm glad somebody got some use out of it SFO, I'd almost forgotten about that.


Thanks for the offer but I'm busy helping out with the family business all month, zero free time. I can't even go riding. At least I have my health. :-)


XR, if it isn't a fuel issue then it must be ignition. It almost sounds like the timing isn't advancing with higher rpms. Just more pure speculation, hope it is helpful.
 

Rich Rohrich

Moderator / BioHazard
LIFETIME SPONSOR
Jul 27, 1999
22,838
16,902
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Originally posted by Hick

I'm glad somebody got some use out of it SFO, I'd almost forgotten about that.

Hick - I'll make sure it finds a good home in something sick and fun. :thumb:
 

xr284

Member
Mar 18, 2003
85
0
Thanks for all your help guys, but i still cannot get this thing to run right. It just pisses me off. I have had this bike for about 2 months now, and up till now i have been very pleased with it. I have only got about 15 rides on it due to having to go to school during the week, and work on the weekends. I dont have very much time to ride, let alone work on my bike. That is why i bought a new bike. Now im back to the days of my xr284, i would ride on saturday, then work on her sunday. Now i know why honda doesent give out a warranty!!! I have never seen anything that was brand new brake down after two months of riding!! I probably will never buy another crf
 

xr284

Member
Mar 18, 2003
85
0
completely went through the carb: jetting, accelerator pump, hot start, etc... Woodruff key, gas, spark plug,.

What else should i check? Valves?? tps?? ignition??
 

DougRoost

~SPONSOR~
May 3, 2001
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Valves. Have heard of CRFs eating valves with just a little dirt getting past the air filter. At least if it's a new one it shouldn't have the airbox sealing problems of the '02s, but any sand that may have gotten in there would wreak havoc.

Yet another reason I returned to the world of 2 strokes...
 

Jon K.

~SPONSOR~
Mar 26, 2001
1,354
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A tight valve would make it hard to start eh?

Popping and backfiring would lead me to think maybe the CDI has gone south. Pull all the wire connectors, grease them and plug them back in.

If that doesn't work; you might swap components with known good components. I would think CDI box or source coil.

You didn't leave a rag in the airbox eh?
 

DougRoost

~SPONSOR~
May 3, 2001
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A tight valve does usually make it hard to start. It can also affect the mechanical timing. The fact this occurred after riding in the sand is why I suspect it. In any case, it's always best to start with the basics and correct valve tolerances are a basic on a 4 stroke. Once this is ruled out you can move onto more exotic things like the CDI, which hopefully didn't go out after just a couple weeks.
 

xr284

Member
Mar 18, 2003
85
0
Thats the thing though, it starts wicked easy, usally on the first kick, its just once its running, it runs like crap.

I did see those new wolf ignitions in dennis kirk, they can change between two maps of timing at the flick of a switch, has anyone used on of these?? Can you tell the difference in performance.

I was just wondering, just in case it is my cdi (i prey its not)..

No i didnt leave a rag in the airbox, though i wish it was somethin as simple as that!!
 

Jon K.

~SPONSOR~
Mar 26, 2001
1,354
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The more I study on it, the more it sounds like ignition. You had the flywheel off, did it ever run correctly after re-installation? Perhaps some sort of damage to the windings?

Again; take a few minutes to pull all the connections apart, inspect them, grease them and plug them back in. Particularly the two small wires (perhaps there is only one) that run to the coil. And the gang plug that connects the CDI box. Heck, check them all! And check the ground (green?) wire where it bolts to the frame. Make sure there is no paint (do they paint the aluminum?) keeping it from grounding. When I worked on such things professionaly; it was absolutely scary how many ignition problems were fixed by this procedure.

Pull on all the connectors. Sometimes one will pull right off of the wire, immediately revealing the problem. Keep an eye out for a connector that feels "stretchy" when you pull on it, revealing an intact insulation with a broken wire within.

Disconnect the kill wire. Do Hondas still use that goofy kill switch that have a little widget that will fall out? If you have changed handlebars, and the widget falls out, seems like I remember that the kill wire will ground intermittedly by itself, causing all manner of mischief. Nah; no way they still use that kill switch. Is there?

And what Hick said, if nothing else helps! And you can find a willing donor.

You said you checked the plug. Did you change it? Change it anyhoo!

Please keep us posted!
 

xr284

Member
Mar 18, 2003
85
0
I took off the flywheel weight a week after i got it, so it ran fine pretty much the whole time i had it, I did put pro taper bars on it!! The plug is changed, and i pulled it out today, and it was very black and very wet, therefore its running rich...Right?? Everone thinks that it is running to lean, but if you were to see this plug, man is she runnin rich. i messed around with some connections and they seemed fine, but there is still alot more to check..


Im leaving for colorado on wednesday, so i wont have any more time to fool around with it until i get back.
 

927

Member
Apr 24, 2001
5
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CHECK VALVES!!!!!!CHECK VALVES!!!!!!CHECK VALVES!!!!!!!I have found over ten 450s with really tight valves some about 8 shim sizes out adjust them they run fine if they are that far out you should check valve and seat
 

ochster

LIFETIME SPONSOR
Mar 11, 2000
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When installing a flywheel weight on these, the contacts on the pick-up sometimes can touch the flywheel. Maybe just check and be sure there is no contact going on, or destruction to them that has happened.
 

Jon K.

~SPONSOR~
Mar 26, 2001
1,354
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The suspense is killing me!
 
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