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Wheelie D

YZ450F Try and disect this problem.... (repost from "technical" section)

21 posts in this topic

Who was the genius that didnt put in an engine related technical section on this forum? People only have issues with jetting and suspension?? I got yelled at so I'm moving it here.

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I'm helping my cousin with this craiglist special he picked up and we are scratching our brains, hopefully someone here can help.

The bike is a 2007 YZ450F.

The bike was bought with a trashed motor. Was told it needed a piston and cylinder but the damage was much worse. cylinder was cracked, crank out of spec, rod bent, head completely destroyed.

A new Wiseco crank was installed, new cylinder works cylinder (replaced what was on the bike)

OEM yamaha head

OEM cams (bike came with hot cams)

OEM cam chains

OEM chain guides.

The issue is, the 2007 cam chain is waaaaaaaay to tight, we cant even get it over the cams. The tensioner is removed and we even unbolted the chain guide from behind the mag. still wont go on. We ordered a 2010 cam chain which is about 4 links longer and thats too loose. The cam chain tension is fully extended and isnt even removing slack. We COULD make it work but we have the fear that there will be too much arch on the chain and that will wear away the chain guide very fast.

The gear on the crank appears to be the same diameter, the cam gears appear to be the same diameter, the cylinder is the same height, the head is the same height, the height of the cam saddles appears to be the same height. I measured with primitive tools. Even if there is a variance I cant see, it would only be 1/32 of an inch off and thats not going to take the slack out of the cams.

Not sure if it makes any difference but the OLD head was stamped Y-1, the new one is stamped Y-2 and then under that 093 is stamped under it.

I have inspected everything to the best of my ability, when I got in on the mess, the motor was already together so I cant do a 100% side by side comparison. What am I over looking? Did they re-design the chain guides to put more arc in them?????? im lost.

P.S. This bike was purcased in Northern IL, IF the person that sold this bike to my cousin happens to read this forum. You should be kicked in the face with a size 15 boot you moron! Less porn watching, more reading shop manuals. :)

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Maybe your having issues with gasket thickness?? What kind of gasket kit are you running? Also wiseco cranks are made in China and are complete garbage. I've heard many horror stories of them not being true, FW key slots out of time and just overall being poorly manufactured.

I would look into gasket thicknesses and if that checks out fine I would put the old crank back in and see if the cam chain loses a bunch of slack. I know it sucks but something has to be done I would not run it like that.

Edited by Sqwid

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Have you confirmed the timing chain is the same length as the old one? Can't see a gasket thickness making that big of a difference.

The other thing you could do is cross reference the new part number with the stock part number with a online microfiche.

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yea did you compare the timing chain with the orginal one? is it OEM? also I believe the chain guide has to go in before the head, cylinder -----> chain guide ------> then the head. just be shure it isn't the chain guide screwing you up?

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yea did you compare the timing chain with the orginal one? is it OEM? also I believe the chain guide has to go in before the head, cylinder -----> chain guide ------> then the head. just be shure it isn't the chain guide screwing you up?

This is good advice. Make sure the guides are properly installed. I had a similar issue with a Kawi and eventually figured out I did not have the Cam chain guides in correctly.

CoKTM

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Yes, new chain was the exact same length as the old one. Bought 2 thinking maybe the first was packaged wrong.

Yeah, I will agree, there is no way this is gasket thickness. I'm willing to bet if all the gaskets were taken out, the chain would still be too small.

Thanks for the tip on the crank, I will pass that info along but again, I dont think that is the root. Gear diameter appears to be the same. I'm thinking there is a boss in the head/cylinder that is pushing the chain guide out further than normal or there is a height difference on the cams but it all looks the same and with primitive tools, all measures the same.

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Silly question, maybe, but you did put the chain on before you bolted the caps on, right?

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I am not the main mechanic on this, I came in when the issue arose. Yes, I tried putting the chain on with the caps off. Even tried tilting the cams..... nothing.....

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You need to place one cam in the journals of the head and put the chain over it, then put the chain around the sprocket of the other cam and roll the cam down into the journals of the head. You cannot just set them in the head and loop the chain over the cam sprockets. Even with tipping the cams forward the chain will be too tight to do that with both cams in place in the head.

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You need to place one cam in the journals of the head and put the chain over it, then put the chain around the sprocket of the other cam and roll the cam down into the journals of the head. You cannot just set them in the head and loop the chain over the cam sprockets. Even with tipping the cams forward the chain will be too tight to do that with both cams in place in the head.

This is correct. Getting the timing marks to line up properly and may take a few tries. It's frustrating if you don't do it very often. IRRC, placing the exhaust cam in the journal and rolling the intake in seemed easier.

Post your question in the YZ400/426/450 forum and Greyracer can answer pretty much everthing about these bikes.

http://www.thumpertalk.com/topic/294291-cam-chain-replacement-on-04-450f/#entry2520291

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I will try that but I have worked on enough bikes where my educated opinion is that, if the chain does go on this way, it will be waaaaay to tight with no tensioner tension.

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This guy does it effortlessly on a 250..... does the 450 go on just as easy? With the stuff we are working with, it will not go on like this. cain is too short.

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If you can't get the chain over the sprockets as described by KJ790, you probably have a looped link hanging from the bottom of the crank. You're better off doing this job with the flywheel (magneto rotor) removed so you can see what's going on.

Ignore the video. No YZ450 will ever be that easy.

http://www.thumpertalk.com/forum/showthread.php?p=3150405#post3150405

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mag was removed. we have looked at everything................ no kinks, loops, nothing hanging up. There has got to be a difference in the new parts, we just cant peg it down.

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Measure the height *deck* of the old and new cylinders. Gasket surface to gasket surface.

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we got it. you have to unseat both cams to get the chain on and then snap them down in the saddles. Took some finessing but we got it. chain is super tight but I guess thats just how it is.

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yea, every time I have ever had to put the timing chain on a yz450 I always had to lean the cam sprockets forward and out of the journals to get the chain on it.

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