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2003 wont run anymore after sitting for a month

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So I traded a RM125 and a couple bucks for this CRF450R, and it was running the day I got it. Before I first got it the engine felt cool to the touch, started easy no matter what, ran fantastic so I made the swap. It had some issues I needed to tend too. So I replaced the throttle cables, bars, new header, new exhaust head studs, and spark plug. In the interest of full disclosure I did weld new bolts on the exhaust studs to turn them out. HOWEVER I was grounded to the stud each time so no damage should have been done else where. I weld on vehicles all the time and know how to not put amperage through a circuit of other electrical things. I even took the muffler apart to make sure it wasnt clogged with anything. I even took the kill switch apart thinking I stuck it or something when swapping the bars.

 

It was in pieces for about a month while I was doing this. I drained the carb, primed it again with fresh fuel buy cleaning the bike over until it dripped out, and I kicked it what felt like 100 times until I was sweating. I cant get so much as a fart out of it. I pulled the plug, I am getting what appears to be good spark. I tried starting fluid, still cant get it to do anything. Dried it out with carb cleaner and then tried pouring gas straight down in the plug hole and got a back fire but that was it. I put the old, known good working plug back in but that didnt change anything. 

 

Carb is clean and in good working order, air filter is clean as well. I have tried with the choke, with out the choke, with the hot start and with out, with throttle open and close and every combination of the three.

 

I seriously have no idea what happened in the last month because it ran so well before I got it and started so easy. He said the top end was rebuilt in the last 10 or 20 hours of riding but it had been well over 2 years because the bike had sat for a long time. When I changed the oil I had my doubts it actually had a top end rebuild but then again the oil could be nasty from breaking in new parts and sitting so long out side in the elements and humidity.

 

Only thing I havent looked at is valves but I dont have a feeler gage and it started so easy before this I dont know how that would be an issue now.

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buy some feeler gauges.....

start there.

i highly suspect that the valve lash is no good.

 

 

people think they clean these carbs but.......

 

when you last worked on the carb, did you remove all the jets and blow both ways through every passage with carb cleaner (barrymans b12 is my favorite) and compressed air?

if not start there

 

get a piece of electrical wire, strip it and put one strand through the pilot jet, add some brake clean and put that wire in and out a hole bunch,

 

now,

does your fuel screw have its o ring and washer?

 

how many turns out is it set to?

if you you screwed up where it was set, set it to two turns out from fully seated.

 


while your at it get a vac release plate seal

 

YAMAHA PART NUMBER

4FN-14997-00-00

 

its 8$


 

don't buy it from honda, its sold as part of an 80$ assembly

also,

 

i dont remember, does the 03 have the big old decompression assembly with the extra rocker arm?

if it does, check that the decompression assembly has proper lash.

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Ill go through it all again with what you recommended but it may be a few days I have yz fork seals to do today unfortunately. Thanks for the reply and the part number ill get on buying that and give it a shot when I take it all apart and reclean later this week

 

I also dont beleive it has the big decompression lever you are talking about. It has a "hot start" that I was told "leaned the carb out" for easy starting when warm. I dont know for sure I have never had a bike with that or a decompression lever before. And this is the first 4 stroke I have done any real work too.

 

Used to have a 08 wr250 that I mostly rode on the road and it never needed a thing, everything else I have had is 2 stroke stuff

Edited by kwhetstine

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Had 3 crfs over the last 11 years, have had them set for months on end. Only time they would not start was because of valve lash.

Find a good hill and see if it will bump start.

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Before getting to the valve lash check to see you have spark. Next thing is read up on how to start these motors. They are not typical.. No gas on start, no choke. If the pilot is not right they won't start well. You can check the valves without taking the valve cover off... roll the engine with your hand. When it comes to TDC you will hear a click and the kickstart will move a bit then should be hard to push. While holding pressure on the kickstart it should take at least 2 seconds to free up.

 

When the valves are out of adjustment you can roll the engine over by hand with no effort. It may just be starting technique.

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David thanks for the advice but this bike has a Rekluse exp clutch in it so I dont think it will bump start. Maybe if it was fast enough? I am not sure.

 

Rocksalt,

 

It has spark. Ill try no gas no choke and see what happens. Engine seems to turn over easier than my yz250 but they are totally different bikes so its hard to compare. I can turn it over by hand but it takes more than no effort. Ill give a few of these a shot and report back, thanks.

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I always give throttle two to three twists then keep my hand off the throttle as each twist pumps fuel resulting in a flood. I use the choke, get piston to top dead center then get kick starter to the top and kick it like I mean it. I try to support the bike so I get both feet on the pegs so I get a good solid kick. See 05 crf trans broken if you want to see what 100 kicks is going to get you. The kickback arm is a weak link, any kickback kills it pretty fast so even though it all sounds no brainer That's if you do the compression valve check and you have good compression.

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Interesting you say that, sometimes it feels like the kick started catches and binds for a second when kicking. 

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yup two very quick throttle blips.

 

choke on

 

kick veryyy slowly till it gets hard (get it to TDC)

 

let the kickstart retract back up and give er one hell of a FULL kick.

 

if it doesnt start in 6 or 7 kicks.  its probably your intake valves.

 

pop the seat off, pop the gas tank off (shrouds can stay attached to the tank) pop the valve cover off and check the intakes.  takes half hour if you know what youre doing.  an hour if its your first time. 

Edited by coryf89

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