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tf705

03 450 locked up

17 posts in this topic

went for a little ride today. i was getting it pretty good in 3rd gear when the bike stalled and locked right up. tried kicking it and it wouldnt budge a bit. i pushed it home. i pulled the oil dipstick and oil just started pouring out like there was pressure behind it. what the hell happened? the oil wasnt over filled. i had checked it before i went for a ride. why would the oil pour out of the dipstick hole?

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went for a little ride today. i was getting it pretty good in 3rd gear when the bike stalled and locked right up. tried kicking it and it wouldnt budge a bit. i pushed it home. i pulled the oil dipstick and oil just started pouring out like there was pressure behind it. what the hell happened? the oil wasnt over filled. i had checked it before i went for a ride. why would the oil pour out of the dipstick hole?

Are you 100% positive you didn't over-fill the oil? I've done it on my wifes bike. The oil will come out of the hole like its pressurized. Thank heavens that I didn't run it long like that. Because over filling them (significantly over filling them) will cause the oil to foam which is probably why your crank is locked up.

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when i checked it before i rode it was just a little below the full mark. so will it free up after it sits awhile?

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i guese it had to be over filled. so are my crank bearings ruined? i just bought this bike 3 weeks ago. i cant afford to be doing a bottom end.

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i guese it had to be over filled. so are my crank bearings ruined? i just bought this bike 3 weeks ago. i cant afford to be doing a bottom end.

More often than not, when a four stroke locks up its the big end bearing on the rod. Sometimes (most of the time) it trashes the cylinder, piston, crank, and main bearings. Its not a cheap repair.

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omg..... that really sucks. i hope you don't need a lower end rebuild. but from my knowledge if your bike locks up the bearing is bad. my kx250 locked up, and when i finally got it free it would start but knock like crazy because the big side bearing was now shot. i really hope your cylinder is okay too. because mine chewed up the cylinder cuz the i guess the bearing was wobbling the piston.

how are you with mechanics? if you can, take the head and cylinder off and look down at the crank. see if the con rod has a lot of side to side play and rotate the crank slowly to see if it turns smoothly and without any clicking.

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im actually a certified auto mechanic. but im new to these four strokes. im going to tear in down this weekend. but im thinking that i will be buying a new crank and piston. im thinking the cylinder will be ok but who knows.

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It's not a very difficult job IMO. I had never had a bottom end apart but then bought an 03 with a seized crank. I think my crank ran me about $250 and although the piston was fine I decided to get a new one. The total in parts plus having a shop inspect the head and cut new seats and reassemble the head was about $500. just pick up a service manual and you should be able to do it.

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If you are certain that you did not over fill it (which seems very likely, really), what may have happened is the feed oil pump may have failed, or if you have a Ready Racing oil filter cover, you may have installed the filter backwards and cut off the oil to the engine. In either case, the return pump would keep functioning and put any oil in the crankcase back in the frame.

Overfilling usually happens when you forget to run the engine before checking the oil, then add more thinking it's low.

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well ive been looking at parts. how good are the wiseco cranks? should i just buy a stroker crank for the extra $80 dollars?

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well ive been looking at parts. how good are the wiseco cranks? should i just buy a stroker crank for the extra $80 dollars?

depends on what you are trying to accomplish....

if the goal is to get it back together stock - go oem

if the goal is to make it better/faster then look at different kits for larger bore and stroke.

here is the best:

http://www.ronhamp.com/default.aspx

or look at Athena, Luke Racing for Bigbore kits

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Stroker cranks cause a cascade of complication that must be dealt with. When the stroke is increased, the piston travels farther, which means, in a 2mm stroker, that it travels up 1mm farther than before. So, something needs to be different. In automotive engines, the simplest and most common thing done is to use special pistons with the wrist pins moved higher. Alternatively, shorter rods are used. Neither of these solutions will really work very well in YZ450/426, and only a few specialty builders make such parts.

The solution is usually to use a shim plate to raise the cylinder 1mm, but that raises the head, which can mean the timing chain is hard to install, and you may need a manual chain tensioner.

If you aren't committed to spending a lot of time and money on a project like this, you're better off using OEM replacements (try TT OEM ), or use a big bore kit as GA suggested.

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i have a 04 yz 450 and it locked up on me. what happened was the intake cam seized and wiped out my intake valves. i also found out my water pump seal went out. i put in new valves and a new cam and it seems to work fine now.

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OR you could say screw all that and i will sell you my 03! im ready for a two stroke again.good luck on your rebuild that really sucks i have used the wiesco cranks in the two strokes they have been good for me.

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i tore it apart today and am kinda confused? the crank bearings and crank seemed fine but im still not sure. the cylinder is still fine too. the crank seemed to walk to the right a little bit. the end of the right side of the crank dug into the side case. it seemed really weird! so im wondering if the crank bearings are bad. but they turn fine. im still trying to figure it out. i will post pics tomarro.

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Check to see if all the screws that hold the bering retainers in place are where they belong.

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