has my crank gone bad? advice needed - Honda TRX Forums: Honda TRX 450R Forum
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post #1 of 15 (permalink) Old 05-16-2017, 05:19 PM Thread Starter
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has my crank gone bad? advice needed

trx450r 2005.
rebuilt the top end of my motor and couldnt get it to start, tested compression and it had none at all. i took it apart again and noticed big heavy scratches and peeled back metal on the case around the crank as you can see in the picture. i asked some friends and they said my crank is bad. before i go spend $300+ on a new crank and all, is this for sure my crank that is bad? it was not there before i did the rebuild. i was told that the stock 05 cranks went bad after a while but they make a new style oem crank that doesnt go bad. is this true?
thanks for any help

https://imgur.com/a/oxuZT

rod has only side to side play and crank has no play. it turns/rotates smoothly
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post #2 of 15 (permalink) Old 05-16-2017, 06:39 PM
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I can't see the picture for some reason, but all cranks go bad it's just a matter of time.
Why did you rebuild?
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post #3 of 15 (permalink) Old 05-16-2017, 07:00 PM Thread Starter
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I can't see the picture for some reason, but all cranks go bad it's just a matter of time.
Why did you rebuild?
the picture is in the link. you cant see them? heres the link again. i rebuilt it because it needed new valve seals, plus the previous owner had it sitting for years and never rode it so i thought i should just give it some fresh parts. how can you tell if a crank has gone bad? ugh i really need to find out if it is definitely this before i go spend hundreds of $$ haha. in the picture it shows lots of deep scratches and peeled back metal on the case, around the crank.

https://imgur.com/a/oxuZT
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post #4 of 15 (permalink) Old 05-16-2017, 07:50 PM
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Well the rod bearing must be super loose and there should be a scratch under the rod, the damage sem as wide as the rod big end, to me the crank is cooked

2008 TRX 450ER XC racing
FMSQ # 281
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post #5 of 15 (permalink) Old 05-16-2017, 08:07 PM Thread Starter
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Well the rod bearing must be super loose and there should be a scratch under the rod, the damage sem as wide as the rod big end, to me the crank is cooked
so what do you think i need to replace? how can my crank be crooked? the rod only has tiny amounts of side to side play.
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post #6 of 15 (permalink) Old 05-16-2017, 10:49 PM
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Not crooked but cooked, the rod got out of place to scruff the case like this, there is no parts that could be changed or repaired externally without splitting the cases, maybe just hold on ordering a crank, tear it apart and find where the slack comes from

2008 TRX 450ER XC racing
FMSQ # 281
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post #7 of 15 (permalink) Old 05-16-2017, 11:06 PM Thread Starter
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ok thanks for info. ill tear it apart over the next couple days and see whats up. what special tools am i going to need to take it apart all the way?
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post #8 of 15 (permalink) Old 05-17-2017, 07:45 AM
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The only tool that is mandatory is a box of ziploc bags and a sharpie pen, a flywheel puller. An impact is handy to remove the clutch basket nut or the basket holder tool.
Get a manual

2008 TRX 450ER XC racing
FMSQ # 281
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post #9 of 15 (permalink) Old 05-17-2017, 10:58 AM
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It's hard to tell what's going on from your pic, but a crank wouldn't suddenly go bad during a rebuild. Especially not to the extent that it would start gouging the cases. Are you sure you didn't drop something in the cases when you had it apart? Besides the crank issue I have to wonder why it had no compression after you rebuilt it and why it wouldn't start. Personally if I couldn't rebuild a top-end properly I would be a bit hesitant to rebuild the bottom-end. Something isn't adding up here. . . . . like I said, that crank wouldn't "loosen up" that much, or any at all for that matter while it's sitting there not being run unless you did something to mess it up.
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post #10 of 15 (permalink) Old 05-17-2017, 10:43 PM Thread Starter
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im gonna split cases and see whats going on with it this weekend. maybe i did drop something. i dont know.
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post #11 of 15 (permalink) Old 05-18-2017, 06:26 AM
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im gonna split cases and see whats going on with it this weekend. maybe i did drop something. i dont know.
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post #12 of 15 (permalink) Old 05-18-2017, 11:16 AM
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What does the bottom of the big end of the rod look like? Is it marked up like the cases are? Does the rod have any up/down play?

It honestly looks to me like something foreign was in the engine and got knocked around pretty good between rod big-end and the cases.

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post #13 of 15 (permalink) Old 05-18-2017, 04:07 PM Thread Starter
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it doesnt have marks on it, it looks fine. the side to side play with rod is with in spec. theres no up and down play. i think maybe there is somethning foreign in it. could the balls in the bearings have fallen out? ive heard of that situation a few times
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post #14 of 15 (permalink) Old 05-18-2017, 07:28 PM
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Try to fish it with a magnet, maybe it went trough the reed valve, it should rest on the bottom of the engine case then.

2008 TRX 450ER XC racing
FMSQ # 281
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post #15 of 15 (permalink) Old 05-20-2017, 09:24 PM Thread Starter
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taking as much as i can apart on the bottom end but i didnt make it far because i need all the special tools like flywheel puller and such. ill probably get to take more off in a few days and ill update then
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