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Discussion Starter #1
Hi guy's, I am new here and hope I can help contribute at some point.
I have what is suppose to be a 05 yfz 450 and I purchased it not running.
It will not turn over like the battery is dead.
I got it and messed with it for about 3 hrs and tried to jump start it and it finally turned over fast enough to start and it ran good, took it for a little spin the next day again it acted like the battery was dead, I purchased a high quality battery and still the same thing, so then I tried to pull start it and it would start but ran like crap and popped and would not stay running if I let my thumb off the throttle, but for starters I need to get this thing to spin the motor.
It turns over no problems with the plug out, I check valves and exhaust is .007 and .006 and intake is .005 on both.
The starter relay was replaced and I even by passed it with no luck.
When it is hooked up correct and I put my volt meter on the out going side of the relay I only get about 7.5 V when I hit the start button, I have 12v on the battery and the new battery has 13v ( it is a shoie ) or something like that.
After Sunday I will be out of town for a week but I will be back to reply after then,
What else should I check ? I ordered a new starter but have a feeling I just threw my money away.
motor has a newer piston in it but I did not put it in.

I did do a lot of searches on the problem before posting, I did also check the black ground butt connector, it seems fine.
 

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Fuse near the battery? Stator maybe? Also, sounds basic, but be sure the battery terminal aren't bad. Tors & Tps are burdens as well.
 

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Discussion Starter #3
Fuse is good,
I do not understand how anything else could cause it not to spin over, I have by passed the relay so if it is not the starter it should spin, if not the starter then probably a bad crank baring, I hope not. I am going out of town tomorrow so when I get back I will install the starter and post back.
 

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Are the headlights installed on it?

Reason why I ask is because the charging system on 04-05 models required that the headlights had to be on to recharge the battery or something like that.
 

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Discussion Starter #5
No head lights and no light switch, the wiring is hacked probably from other mods and removing the start/light switch ?
 

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Discussion Starter #6
I installed the new starter and no change, I did pull start it and it ran great and it will start when the motor is warm with the start button but when the motor is cold it will not turn the motor over.
I even hook the positive wire off the starter directly to a battery and then touched the ground wire to the negative side of the battery and it still would not turn the motor over, I have a bad feeling it is inside the motor were it is too tight but it runs like a top when running.
Again I bought this used were the kid had this problem, I did notice that he filled the oil tank all the way to the top so I am going to drain all oil , I wonder if it is possible the motor has to much oil in it that will not allow it to turn over when cold, but that would be too simple, LOL
 

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Discussion Starter #7 (Edited)
valve shims, exhaust is .006 and .007 and intake is .005 and one of them is over .05
Would this being off make it so it will not turn over ?
 

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Could be a number of things if its internal.

Cam towers too tight?

Crank bearings going out?

Is it out of time?

I've seen stretched timing chain cause these issues...

Decompression system issue?
 

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Discussion Starter #11
Finally figured it out, it was the dang decompression lever on the exhaust cam that was stuck. it cost $0 to fix that but cost me $200 trying a new battery, new starter, new starter cylinoid,
 

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Discussion Starter #13
Pull the valve cover off and see if the flap thing ( decompression system ) moves freely on the end of the exhaust cam, it is the thing on the sprocket end, it should move one way and spring back when you release it, that is what was wrong with mine. and did u check the starter ? will it spin the motor if you pull the spark plug ? if it will not spin the motor with the spark plug out then it is not inside the motor more then likely.
please post when you find the problem.
 

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Wondering if the problem was fixed and if so what was it? Also can I take the decompression pin out of my stock cam and put it into the hot cam
 
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