2004 won't start. valves checked etc

hi, i've just had my 2004 crf450r engine completely rebuilt after the balance shaft drive gear broke through the right case. $$ouch$$. it now has new right case and cover, new balance shaft, new cam chain, rebuilt crank, new piston, new valves etc etc, you get the idea. the bike started easy, ran and reved sweet. 1st ride, about 5 minutes of riding it wouldnt idle.sounded like the idle was too low. then took about 5 minutes to start. i thought the tune up must be a bit wrong. after another 5 minutes i couldnt start and tried clutch starting it with 2 mates pushing. no start. tow started but took atleast 5 seconds winding over fast from the tow. it runs good up in the rev range but tries to stall at low revs. loaded it on the ute and it hasnt run since. carby was cleaned while engine was out and has been pulled apart and cleaned again even though it was spotless. valves checked, cam timing checked. it has spark but its not a super strong spark. seems to have heaps of compression. how strong is the spark on these things? the best we can get is an ocasional pop from the pipe when we kick it. it has the engine builder stumped. could something be wrong with the ignition or coil even if it has spark? he tells me these things hardly ever have ignition problems. he's never seen an ignition fail on 1. please help

If it were me and a rebuilt engine ran like that, I'd bring it back to the builder and expect it to be running properly before he gave it back to me.

Coils and CDIs do go out on these things, sometimes the plug wire gets a bad connection. Check the manual for the resistance or voltage checks to troubleshoot it. A stator problem can do this, and the timing can also get off. It's usually very obvious when something electrical goes wrong. Your spark description in the post is "subjective", but if your buddy's bike has a strong spark and yours doesn't, then that's a clue. You can check for loose or corroded connections or bad grounds with a multimeter, but the rebuilder should be responsible for checking the bike out before he delivers it to you so I'd take it back (assuming that you brought him the entire bike to begin with).

he has the bike now. i took him the engine only. i put the engine back in and took the bike to him for the 1st start and tune. the bike ran sweet when i took it home. i am not sure how strong the spark should be and he is not too sure either. he mainly works on road bikes. he insists he will find the problem and is not charging me to fix it. i'm hoping someone might be able to tell us where to look next. he does know somebodythat works on these a lot and he is going to get him to look at it and possably swap some parts to get it running.

Cool. That's a stand-up kind of builder that anyone would be glad to take their work to - especially if he finds that it's not related to his work and goes easy on any additional repairs. :thumbsup:

Post a follow up and give the guy a plug if he does you right in the end.

not sure how long the bike sat during the build, but if it was a couple months it could be as simple as the pilot jet or something in the carb being clogged. When fuel with ethanol sits for a time, it gets nasty..

the carby has been checked twice. both times it was spotless. blew everything out anyway. sprayed a bit of earostart in there just in case it wasnt sucking fuel in. still no go. the bike sat for 3 or 4 months. keep the ideas coming. even stupid ideas are welcome.

The cam timing jumped when you rode it the first time. Maybe he forgot to release the auto tensioner, or it failed, which can happen.

What ever the case, Id bet the cam timing was off and its retarded at least 1 tooth.

he has just checked the stator with a multi metre and the ohms were way out of spec so he is going to borrow a stator and see if the bike starts to confirm it is the stator at fault. do the symptoms sound like the stator is at fault? ie, not running at low revs and won't start without being towed. i wouldnt have a clue. thanks for your ideas and keep your ideas coming incase its not the stator. i will let you know how this goes asap.

he has just checked the stator with a multi metre and the ohms were way out of spec so he is going to borrow a stator and see if the bike starts to confirm it is the stator at fault. do the symptoms sound like the stator is at fault? ie, not running at low revs and won't start without being towed. i wouldnt have a clue. thanks for your ideas and keep your ideas coming incase its not the stator. i will let you know how this goes asap.

super easy to re-check timing as suggested one post earlier..

when my stator went out it acted like that then it wouldnt start at all

he has just checked the stator with a multi metre and the ohms were way out of spec so he is going to borrow a stator and see if the bike starts to confirm it is the stator at fault. do the symptoms sound like the stator is at fault? ie, not running at low revs and won't start without being towed. i wouldnt have a clue. thanks for your ideas and keep your ideas coming incase its not the stator. i will let you know how this goes asap.

Yep, stators don't lie unless he measured across a bad connector, cold solder joint, or bad ground. Solder joints can be touched-up with fresh solder and a decent-sized iron, so you don't necessarily need to buy a replacement stator if that's all that's wrong with it.

ok. it turns out his multi metre crapped itself so it was giving wrong readings. the bloke went over the bike again. kicked it and the bloody thing ran. he is thinking there was a loose wire or something but not sure. i havnt ridden it yet. got a few other little things to fix. throttle cables are buggered and might give it some new front wheel bearings and new chain and sprockets. hopefully i'll get to ride it next weekend. will let you guys know how it goes. thanks for your help

A dirty connection at the stator wire to the harness will act just like a bad stator. High resistance there will require the thing to be push started.

Guys, get some dielectric grease and assemble those things clean so you dont have these kinds of stupid issues that force you to chase your tail around looking for ghosts...

Hello sounds just like a plug to me I have had the same type of problem good one day then doing the same sort of thing your bike is doing. Chaged the plug then sweet as.

plug was the first thing we changed

Sounds like your builder missed and easy but important step which cause major confusion. I have been riding CRF's forever and currently riding an 03 crf450, the electronics is the last thing I check and has never been the issue.

Most likely your builder forgot to plug something in :thumbsup: or it it was loose and when you rode it broke loose. But the good part is it seem likes its running.

I wanna Ride in the Bush!

well the bike finally gave a descent symptom to what may have been the problem. it quickly put a lot of water into the oil. we ripped the head off and found a faulty head gasket. the gasket was odviously getting worse and worse. the engine would have about 30 minutes run time on it. my mate (the engine builder) was actually happy that it did this. he has been chasing the problem for ages and it finally showed him something. he rang me today after spending most of the day working on it and said its running sweet. FINALLY. he has spent countless hours working on it over the past few weeks and reckons he finally has it fixed. ALL AT NO CHARGE. i reckon theres not many people that would do what he has done at his cost. he doesnt work at bike shops anymore, this is just his litle 2nd business that he runs from home after work and his rates are half what a shop would charge. i'm happy with his work and very happy that he has finally found the problem. i'm not sure what brand gasket he used but he reckons he won't use them again. i reckon he is more releived that its going than i am. i think it was haunting him. hopefully i get time to take it for a run in the bush this weekend.

Good to see that it's running well. The head gasket thing doesn't really fit the original symptoms you posted, so it's lurking in the back of my mind that maybe there were two issues to deal with. But, if the bike keeps running fine, then clearly he took care of it and that's a good thing! Always good to read about a builder that stands behind their work and in your case, goes the extra mile to go over the whole bike when they only had the engine handed to them originally. :smirk:

he reckons a small amount of water may have been getting into the cylinder and thats why it was soo hard to start. i am very happy with him. he certainly did go the extra mile. i couldnt thank him enough for the effort he put into it and to do it all at no charge was amazing. he sayes he is going to fix a couple of other things for just the price of parts also. it needs throttle cables replaced, a couple of bushes in the rear suspension and chain and sprockets. i think he just loves working on bikes. he is also very fussy. he wants me to change the oil after every ride which is a max of 3hrs run time. i guess he wants me to really look after his engine. thanks for everyones ideas trying to find the gremlin that was in my bike. i will ride it sunday morning and let you know how it goes.

Got it.

Every 3 hours for an oil change is pretty excessive, IMO, and costly. Even MX racers don't do that (at least no one that I know of); not a single privateer/team that I know of either, unless they're in the engine for something else. Maybe talk to him about using an Ester (Group V) synthetic oil and getting the run times up to 10 hours or so. Your wallet should thank you, and so should the bike since the Group V oils (like Motul 300V that I use in mine) are SO much better than OEM Group 3 dinosaur oils at minimizing wear and keeping the film on the metal surfaces during startup.

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