Crf 450 running bad in neutral on the stand

[High Lord Gomer]

While you've got the cable off, lube it. When you put it back on, adjust it so it has some obvious free play, then go back and start adjusting the carb again.

Chances are you had adjusted the carb to compensate for it running with the hot start open a little.

 

[Jon K.]

I just happen to have looked at a 450 hot-start circuit Wednesday. This carb was to be installed on a Quad, but my buddy swore that it came off of a brand new CR450f. I got a good look at it.

That hot-start circuit works exactly like an enrichening (choke) circuit; that is, it has a little piston that fits into a bore in the carb.

When the piston is pushed down into the bore, it seals off all the little holes, and the carb functions normaly. When the cable is pulled, the piston is lifted out of the bore, and all the little holes open, allowing some fresh air into the intake tract. Simple stuff actually.

A fool-proof way to check it is to unscrew the plastic fitting from the carb. The piston should pull right out of the bore. Carefully remove the cable from the piston, taking care not to lose the spring . . . . . hmmmm . . . . . You do have a spring on top of the piston eh? This spring is what pushes the piston down into the bore. It fits sort of over a peg on the end of the piston, and goes into a recess in the end of the plastic cap. If yours has been lost (it happens all the time!) then your hot start has zero chance of working properly. Make sure you have a spring!

Anyway, back to the foolproof part. Remove the piston from the end of the cable, remove the cable from the plastic fitting, and re-install the piston, spring, and fitting with NO CABLE. Make sure that the piston is indeed sliding all the way down in the bore. Skeet a little WD on the parts before re-assembly.

While you are at it; look over the hot-start piston thoroughly. It has a rubber "plug" on the end of it that seals the hole in the bottom of the bore, and a little "O" ring around the circumference. Look for any damage or missage.

This should effectively eliminate any chance of the hot-start circuit giving you the headaches.

Muffler bearings! That's a good one! :laugh:

 

[Ol'89r]

Originally posted by xr284
When you say broke valve spring, do you mean broke, or weak spring, because when i checked the valve clearence i no i didnt have a broken spring, but a weak spring i have no idea.

xr284.

Many engines use two valve springs per valve. An inner and an outer. It is possible for one of those springs to be broken and the engine will still run until it gets up to a higher rpm and then the valve will start to 'float'. (stay open). On your CRF engine you only have one spring per valve. If the spring were to be broken, the engine would probably not run or would run badly throughout the entire range. Although, the spring could be weak and cause the valve to float. The only way to check for this is to remove the springs and check them with a spring tester.

This was not a big deal with the old style XR based engines but, with the modern type engine that turns 12,000 to 14,000 rpm the valve springs have to be in good condition.

Sounds like you could be on to something with the hot start circuit. Like Gomer said, check for free play in the cable and then re-adjust your carb. Good tips from Jon K.

Oh yea, and tighten up those muffler bearings. :laugh:

 

[xr284]

I checked the tps with an ohm meter, and it is fine, i checked the hot start and it is fine, i checked all the valves again.. I am almost positive it has nothing to do with the carb, it idles perfect, starts first kick usally, and it dosent overheat. I know its timing, and im sure its either the stator, or the cdi. Which one do you think i should order??

 

[Jon K.]

Stator. (Surprise!)

But then, it ain't my $$.

 

[High Lord Gomer]

It might not be *the* problem, but it is definitely *a* problem if significant changes in the fuel screw setting doesn't affect the idle response.

 

[RAH RAH]

Is this thing fixed yet? Im wondering if I should let this one bike steer me in another direction.
I sure like hondas thou.

 

[elwoodandi]

I have a brand new CRF450R and after the obligatory 20 miles of gentle riding I took it out for a little "let's see what she's got" mud, creeks, and trail riding. A half an hour into it... same symtoms as xr has (missing, tough to restart, red hot pipe.) I am taking it to the dealer this week to have them diagnose/advise a course of action.

 

[xr284]

I have a brand new CRF450R and after the obligatory 20 miles of gentle riding I took it out for a little "let's see what she's got" mud, creeks, and trail riding. A half an hour into it... same symtoms as xr has (missing, tough to restart, red hot pipe.) I am taking it to the dealer this week to have them diagnose/advise a course of action.

Are you serious?? So im not the only one, and its not that i got a lemon of a bike!! :whiner: Now you see what i have been going through, its sick isnt it.. Please le me know what the dealer says to you....

Thanks
Sean

 

[elwoodandi]

I should have an answer by this weekend or early next week. I hope that they do have a solution for this because the half hour that it ran well for was unbelievable.

 

[xr284]

I should have an answer by this weekend or early next week. I hope that they do have a solution for this because the half hour that it ran well for was unbelievable.

I know what you mean!!! Work on it for about 2 months, then still be stumped, and then you will be were im at right now... I am still glad i bought it because when it ran right it flat out screamed :thumb:

 

[Matt W]

I have a riding bud who purchased a brand new 2002 YZ426 two years ago. Thing ran great the first 25 hours or so, then out the blue (no pun intended) it started running like crap. Would pop like mad when he revved the hell out of it, and it seemed like it was missing up top. After chasing his tail with jetting, plugs, carb cleaning, etc., he took it back to the dealer and found the CDI was bad. Sounds a lot like your problem. Maybe you can find someone close by with the same bike and swap CDI's before you purchase either item. The problem is you typically can't return used electronic items for a bike. If you live any where near Harrisburg, PA I'd be glad to let you try mine.

 

[xr284]

Thanks for the offer MATT, but im in seattle, washington so your a slight drive away from me.

The cdi or the stator is what i have it narrowed down to, I just dont know which one to buy first!! Im leaning towards the cdi. Can I return the cdi if it is not my problem?? Or is it no returns on electrical??

 

[Jon K.]

Thanks for the offer MATT, but im in seattle, washington so your a slight drive away from me.

The cdi or the stator is what i have it narrowed down to, I just dont know which one to buy first!! Im leaning towards the cdi. Can I return the cdi if it is not my problem?? Or is it no returns on electrical??

No returns on electrical.

Have you asked your dealer to swap boxes with you? I can't imagine that they would have a problem with it, unless they are a bunch of cretins.

 

[crwtf?]

i have an 03 crf 450 and I had to replace the stator already. CDI boxes rarely go out in my experience. Try the stator. Its more than likely probably the exciter coil attached to the stator, but they only sell the stator assembly from honda. I am sure that if you were really in a pinch for cash you could find a company that sells just the exciter. You would have to splice or solder it in, but it would work. Definitely try to swap boxes with a known runner first though.

 

[xr284]

Any word yet ELWOODANDI????

 

[tillertracker]

I live on Camano Island and you can come up and try my CDI out on my trails. This whole thing is killing me! Make it stop! For the love of God!
Cedric.

 

[robrm250]

I live on Camano Island and you can come up and try my CDI out on my trails. This whole thing is killing me! Make it stop! For the love of God!
Cedric.

Its killing me too!!!!!!! for the love of god somebody fix this thing or tell us what it is.I can't eat,sleep,I check it 10 times a day and the worst thing is my wife says I can buy a new bike and I want the cr450f but I got to know whats wrong!!!!

 

[RAH RAH]

pleasa man I cant sleep either... somebodies got to be wondering what in the hell could posibly be wrong with a brand new honda? whatver it is dont do it again. dang your stressinus all out ;.)

 

[xr284]

Ive been doing alot of reading over at thumpertalk, and alot of people have had problems with stator's, and some people have had problems with cdi, then i seen this one thread that was in the past, the guy had the same exact symptoms as mine, and his dealer said it was normal, that in neutral if you rev it up it will pop, miss, and shoot flames. But if you where to put it in gear, then it shouldnt miss. Its something in the igntion that makes it do this, and yamahas have a thing in there ignition so it dosent do this. So i went out, started it, let it warm up, then i revved it out in neutral and of course it popped, then i put it in gear and WINGO, it was gone!!!! So i dont know if what this guy said is true or not.

So im asking someone to please go out and rev there crf in neutral, dont over rev it, just go to about 5,000 rpms then hold it there. Let me know if it pops!!!

Man im going to feel pretty dumb if this whole time i was missing out on riding because i was paranoid that my bike was broke done!!

 

[Jon K.]

xr284;

I read through all your posts again, and no-where did you infer that the problem was happening in the FREAKIN' GARAGE!! :eek:

These things are important.

Please let us know!

Don't get the wrong idea, I'm just baggin' on ya. I hope it turns out to be nothing. :thumb:

 

[frankrock363]

I just read all of these posts myself and you never said if the bike ran fine when you were riding it or not? Now that I think about it I only rev the bike in netural just before the gate drops. I hope for your sake this is not the case. Otherwise your going to be kickin your self in the but.

Hey look on the bright side. Just think how much you learned about your bike.

 

[jboomer]

I just ran out and had to try mine. It was popping and shooting fire at about half throttle. Every dog in the neighborhood is barking now, so I had to shut it down pretty quick. I only ran it for about 3 minutes. It took about 4 seconds for it to start popping, etc. when I held the throttle at half.

 

[xr284]

Man i feel pretty stupid right about now. :ugg: But what the heck it didnt cost me anything, except for some good rides :debil: I have never owned or worked on a motor that was supposed to pop and shot flames WTF.. I need to find some riding buddies that own CRF's...

Thanks for all the help guys!!

 

[frankrock363]

Better that you found out now than in the middle of summer. :thumb: