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2002 crf450 problems

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Hey, I'm new to the forum, and since I picked up an 02 crf450 I figured now is a good time to join up!

Anyways I'm having a problem, with ignition. There IS spark, but it is very weak, and instantly floods out when I try to kick the bike over. It won't even attempt to fire. I tested the coil - its ok. But when testing for the exciter coil (the blue, and white wires @ the ecm) My manual says there should be 100v. But I'm getting nothing.

I pull started the bike behind my truck and I managed to get it going, but it wouldn't idle, and required about half throttle to stay running. I think the timing was ok tho, because it was not backfiring or bogging out with partial throttle.

Bike exp: Just had the valves redone, top end rebuilt, and a new stator.

Any help would be greatly appreciated!!!

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Check the valve lash (clearance). If its right, verify the cam timing. There is a sticky at the top of the page to show you exactly how it should look. If youre getting any spark at all the ignition is working. You must not have had a decent connection or a meter that was capable of capturing the peak voltage off the igniter coil because if you werent getting anything there, you wouldnt get any spark at all.

when you say it floods out instantly or wont idle down makes me think there might be something in the float needle or the cam timing isnt right.

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If it runs at half throttle then I would make sure the pilot circuit is clean and well adjusted (install a new pilot jet and make sure that the fuel screw is correct and adjusted to 1.5 turns out or so). The pilot circuit is a big part of what the bike is using at 1/8 throttle or less.

Also the little doodad in the carb throat where the needle slides in and out (don't know the name) has been known to ear out and make the bike run like crap).

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Its strange though, the spark was so weak, so I put a new plug and its just as bad. Even with what I'm getting you would think it would at least attempt to fire.

I'll check the timing out tomorrow! If it IS out and its firing at the wrong time, that could also cause similar problems!

Are these bikes relatively reliable once they are up to snuff? I hope I don't regret selling my kx250 2 stroke.

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Never had any problems on any of my 3 CRF 450s getting them to run. Except for the one time I let one of them sit for 6 months. Once I drained the fuel and put fresh stuff in it was fine.

EDIT: Also I had some problems with a plugged pilot jet in my '05 bike. Again, once I recognized the issue and put in a new pilot (they don't clean well unless you have an ultrasonic cleaner) it cleared it right up.

They should start in 1-3 kicks every time, hot or cold.

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Also where can I buy parts online for this bike?

For example, pilot jets, coil, stuff like that? oem replacement stuff.

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Ok so I checked out some stuff tonight.

- Timing is bang on

- intake valves are in spec

- exhaust valves were not sealing (way out of spec) but I adjusted them up.

Bike will still not start!!

Now I'm baffled, I have tons of compression, spark, Tons of fuel, and air. And it still won't even try to start. I pulled the plug and its soaked in fuel again.

As a last ditch effort, I'm going to pull the carb apart and check the pilot jet. When I pull started the bike, I was able to get it going, but only if I gave it 1/4 throttle or more. So maybe the pilot is plugged? Would this cause the problem of too much fuel when starting?

If this doesn't work I'm going to give up and take it to a honda dealer for them to check it out. Which will probably cost a fortune.

Any ideas would be great!

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The fact that the valves are in spec, but it is still hard to start, suggests that something is out of tune with the carb.

First, set the fuel screw to a base setting. Screw it in all the way until it is lightly seated, and then back it out 1.5 turns as a starting point. The shop manual has a table that gives baseline settings based on altitude and temperature. 1.5 turns out is probably in the ballpark.

Second, take out your pilot jet and clean it with a wire. Take a wire wheel (the kind you chuck in a drill) and pull a strand of wire out with a pair of pliers. Thread the wire strand through the jet and roll the jet and wire up and down your pants leg. You want the wire to scrub off any varnish from the interior of the hole through the jet. Spray it out with carb cleaner when you are done.

Lastly, your plug should not be wet. Are you giving it any throttle?

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The plug is soaked without any throttle, but the choke on. But even with the choke off it floods instantly.

I'm starting to think this could be the problem. Tomorrow night I'll pull it apart and check it out.

I really wanna taker' for a rip!

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If the plug is wet with gas, and you aren't giving it shots with the throttle, then I think something is out of whack with the carb.

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The CDI ignition in these bikes generate a very short but high voltage ignition pulse. So the spark doesn't look as fat as say a standard ignition system.

Definitely sounds like you've washed the cylinder and intake with fuel. Take the carb off the bike, hold the kill down and kick it over 5-10 times to clear any fuel out of the cylinder and intake tract. You'll want to clean (or ideally replace) the pilot jet, check the float level, make sure all passages are clear, and set the pilot screw to 1.5-2 turns out.

Take plug out, clean it, etc...You could try a new plug too, about $9..

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Put in a new plug and new pilot and set the fuel screw to 2 turns out and DO NOT pump the throttle at all but go ahead and pull out the choke.

If the gas is reasonably fresh it should start within 10 kicks or so.

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I pulled the plug out of the bottom of the plug tonight to see if the slow jet/pilot jet was plugged. THE JET FELL OUT OF THE CARB!!! When I removed the plug the jet fell right out on the floor. I cleaned it, threw it back in and the bike started 2nd kick.

I drained the oil and its grey. Sooo I'm worried the headgasket may be gone after all. I changed the oil, topped up the coolant and am going to take it out tomorrow quick to see if there is coolant in the oil after a short ride.

Noticed the bike got WAY too hot also, only idling for a minute or so. Then some coolant started to come out of the overflow. But I think I may have filled it a bit too much. I might invest in a 1.5 bar rad cap anyways.

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If it's instantly getting too hot and overheating you might running too rich on your pilot jet. You might consider looking at what size pilot jet is in your carb and comparing it to what the manual calls for

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When the jet was out I looked and it said 45 on it. It did seem to be idling a bit fast too. I'll have to drop the idle down a bit.

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The 02 came with a 45 pilot. It was bigger than it should have been though. If you want to mess with it and get it a little crisper, put a 42 in there.

The 02 was also known for having a "hanging idle". The idle wouldnt come down right away when the throttle was closed. It would idle high then idle down about 8-10 seconds later. Especially when warm. The issue was it was too rich. And the 42 pilot cured it. The main jet was also quite a bit richer too on the 02 from the 03-04 bikes.

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My 02 has a 45 piolt , and a 175 main jet ,and it idles fine. If your pilot jet was falling out , maybe the guy that had it turned the idle up to make up for it falling out !! My fuel screw is set at 1 1/4 turns out from setted. Never have i had a hanging idle , guess it can happen , but it must not be set right. I did put a 1.4 rad. cap on , seems to help. Or you mite have a bad head gasket , or your just letting it idle to long , 5 min. is to long by the way.

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Where should I get a rad cap from?

I took the bike for a quick ride, and it seemed to idle better now, maybe burning out the old fuel. Ran good, no smoke in the exhaust, and no grey oil. I'm going to take it out again for a quick ride on friday and drain the oil for a better look.

What oil should I use? I checked on here and everyone said Rotella T 15w40 but all I could find was that weight in a diesel oil. And I'm pretty sure the detergent in diesel oil would be bad. Right now I put some Pennzoil 20w50 just to use as a flush, to wash the grey crap out of the engine.

And After takin' it for a quick ride - 3rd gear catwalks FTW. lol. I think my kx250 still has faster acceleration though.

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Just to be sure, you are aware that the CRF450 has two separate oil sumps, right? It's somewhat normal for the transmission oil to be grey if you have a lot of hours on the change, or been abusing the clutch. Engine oil should not be grey ever.

About 700 mL of oil on the engine side, don't remember if that includes filter. The manual says 600 mL on the transmission side, but most people run 700+ mL, sometimes a full quart on the transmission.

15w40 Shell Rotella Diesel oil is what many people run (including me). Dirt cheap, and works good. Diesel engines undergo similar stress as these bike engines, so the oil works good. Rotella is also JASO MA certified for bike engines. You can get a 4 quart jug of Rotella for around $12. Change oil on both sides every 5-7 hours. I usually go around 6.

If you filled the radiators up to the top, it will puke out the excess even if its not overheating until it finds a happy level. Although, from a cold start, my '02 450 can idle for probably 3-4 minutes before the coolant hits ~200*F

It may seem like your KX250 accelerated faster, but unless you had some engine work done to it, the 450 should have a ~6HP advantage.

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Your lucky, here for the Rotella is $25 for a 5L.

Correct me if I'm wrong but the engine oil is on the LH side of the bike right? (Assuming your sitting on the bike). And when you drain the oil, does this drain BOTH the trans and the engine? OR just the engine? (Drain plug on LH side)

Would running 20w50 help with heating issues? Thicker oil = Cools better right?

I'm still going to get the Rotella, its just a thought! I could have swore though that in the manual it says non-detergent oils, and all deisel oil has detergent in it.

But hey, I'm here to learn not question! lol.

Oh and by the way the kx is stock, just an exhaust and a fresh rebuild. I would have to go side by side with someone to see, the power bands are totally different. I freaking love the torque of this bike though, and for $750 I can't complain!

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