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gtsmpuc

07 450 Motor, what all is wrong with it???

18 posts in this topic

Does anyone have pics on the best set up they have to check the end play on the rod? I am going to borrow some guages from the machine shop, but i figured why not ask what works best, vs just shooting from the hip. I have the manual, so i know where to measure and the specs, just wondering if there is a great method to do it. Iv wound up with a bike, that i knew there was motor problems with. Guy said the needle bearing was shot. Cylinder has a slight score mark, on the right side, from where at some point the ring got rolled over the edge of the piston. Im going to start with checking the crank, and work my way up from there. Motor is all torn down, to the cases still in the bike. Anything else i should check for at this level? Im picking up a flywheel puller tomorrow and then checking the crank tomo night.

Edited by gtsmpuc

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If the crank is out of the engine, use a magnetic dial gauge mount and a dial to check the rocking play in the rod as shown in the manual. DO NOT allow the rod to slide left to right on the journal while taking this measurement.

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If the crank is out of the engine, use a magnetic dial gauge mount and a dial to check the rocking play in the rod as shown in the manual. DO NOT allow the rod to slide left to right on the journal while taking this measurement.

No, its still in the bike, in the cases. I was going to use a dial gauge and clamp it to the cases. Is the play measurement total from side to side, full left to full right. Or is it from center to left and center to right.

Also there isnt a way to check trueness of the crank, still in the bike, is there?

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No, its still in the bike, in the cases. I was going to use a dial gauge and clamp it to the cases. Is the play measurement total from side to side, full left to full right. Or is it from center to left and center to right.

Also there isnt a way to check trueness of the crank, still in the bike, is there?

There is a clearance spec for rod side clearance, which is simply how much clearance there is between the sides of the rod big end and the crank. Push the rod all the way to one side and measure with feelers.

Then there is the rocking check that test clearance between the rod bearing and crank pin. For this check you should try to hold the rod against one side or the other and rock it on the bearing without letting it slide along the bearing. Take the measurement at the rod eye. The more vertical clearance there is, the more the rod will rock.

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well side clearance was fine, .013" and im going to have to get another gauge to do the freeplay. I was coming up with .035" but it may be less, i couldnt get a good clamp on the gauge to the cylinder. If these two are within spec, would you say the crank is good to run? I still need to pull the flywheel, to take the cam chain off, to make sure i the rotation feels smooth. Im going off the previous owners word, that he thought the needle bearing was bad. He said he was riding the bike, the motor stalled in a corner and he coulndt get it started again. It would still kick over, just not do anything, he even tried to pull start it a few time. He said he tore it down and the crank was bad. Before i got it, he slapped the motor back together. I turned the motor over at the crank and that felt ok, a little tight, but you couldnt kick it at all. I took of the head, and you can see the carbon barely rubbed off of in one spot on all three intake valves on the edge. You can also see the same small spots, about half the diameter of an ink pen, on the piston. When i took the head off, the timing wasnt even close, basically the cams where pointed in and there was only 11 pins between the cams. Im hopingn he just didnt pay attention when he put it back together and this wear is from me turning it over 4-5 times by hand. Once photobucket starts working I will post pics.

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If the rod is within spec, and the mains look good, yes, you can run it. You'd be amazed how many people take one look at the heat discoloration on the crank and immediately think the bearing is smoked. The color comes from the factory assembly process. Brand new ones are just like that.

But it sounds like you need to carefully inspect the head/valves to be sure none are bent and no guides are damaged. New cam chain and tensioner.

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Pull the clutch/waterpump cover and look for metal in the oil that drains back out of the crank. Also pull the oil pump and check for wear and damage. The bottom rod bearing will crumble and the metal flakes will destroy the oil pump and everything else.

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I cant figure out how to post pics from Flickr, so you will have to follow the link. But here is the marks on the piston and valves.

head1.jpg

piston1.jpg

Edited by gtsmpuc

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On the mains, do i just look for play between the crank and the bearings, heat discoloration, grinding or lack of smoothness in rotation?

I think i found out what also caused the scaring in the cylinder. I cant believe i didnt see it when i pulled it apart, but it was a long day. One of the rings was rolled over. Now im not sure if he did this, when he put it back together, but i dont think the motor was ran like this. Im starting to get more of a feeling, that for some reason, he went through the top end, put it back together out of time, maybe rolled the ring when doing so. Tried and tried to start the bike, then pulled it down again, saw the color on the crank, the ring pulled from the piston, and then figured the crank was bad.

All the oil so far has looked great, like he just changed, it, but i cant find any shavings or specs of metal anywhere. Im a newbie on dirtbikes, but work with machine shops on alot of projects, so im asking basic questions, making sure im not missing something, since im not sure what he actually did to the motor.

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Here are the pics of the cylinder and pistion. You can see the ring rolled over, and the wear on the cylinder from it. On the opposite side of the cylinder, you can see a heat spot, Im not sure what this is from. The ring was rolled on the right side of the bike.

pistonring.jpg

cylinder1.jpg

cylinder2.jpg

Edited by gtsmpuc

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Look at the surfaces of the bearing races and balls for any signs of pitting, excessive looseness, etc. All it takes is one spot on one ball or race to have flaked off, and the whole show goes downhill quickly. They will always feel rougher when dry than with a couple of drops of oil, but if they raise questions in your mind, just change them.

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Ok, i checked the freeplay and it is coming out either .030" or .055" everytime, depending on how tight i hold it against one side. When it reads .055" it seems like the rod is just about to stop moving, then its like it drops off the side of the bearing, and falls another .025". Like i mentioned before the side clearance was fine at .013" and the crank width it right at 2.440", but its hard to get a good reading, being still in the cases. Here is a link to a video of me moving the crank back and forth quickly. You can hear it ting, if i move it quickly w/o any pressure. Is that normal? This is also when it reads .055"

http://www.flickr.com/photos/61674939@N07/5614920012/

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Rat Racing down in Alvin Tx can fix the jug real easy. I'd put a top end on it and start it and see what you have. Some of the questions you asking, the manual does not give answers to. (For end play)

Edited by skull1971

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.055 is .015 over the limit.

Thats what i was actually just reading over on the manual i have. It says .016-.039" standard, but the limit is .080". So wouldnt i still be ok? Also i didnt know if that feeling i had when i moved it the last .025" was the rod actually sliding on the crank, not rocking. Did you listen to the video, not taking into the actual measurements i have been posting, but can a crank move enough to make that taping noise?

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Thats what i was actually just reading over on the manual i have. It says .016-.039" standard, but the limit is .080". So wouldnt i still be ok?
Ah, right you are.

Sorry, it was a long day.

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