Motor locked up-worst day ever

I was going to my buds house to ride earlier when i noticed my bike was popping on decel alot. So i turned the fuel screw out a lil, and it fixed it. Well about a half a mile down the road it started to tighten up.As soon as i felt it i pulled in the clutch and killed the motor.I look down, and my oil drain bolt(left side)is gone(with oil still pouring out):busted:. I always use loctite so i have no clue how this happenend. I took it home, and disassembled it, and found that everything is fine except for the exhaust cam journal has some slight scarring to it. Is there anything i can do to get this thing back running?I was wandering if i could take some 1200grit sandpaper to it to smooth it out. I know it sounds crazy guys, but im broke as a joke right now, and i live to ride. Please help me out. Im beside myself:(


I know the pic kinda sux, but its the best one i could get. Im not to worried about the exhaust cam since i can get another, but i dont have the money for a head.

The scratching on the journal doesn't look too bad. How's the piston look, if it looks ok try just putting in a heavier oil and try to fire her up. I have machines that have done that a couple of times and they're fine. If anything, use 2000g paper (available at body shops) with light oil to collect the shavings.

The piston actually looks brand new. Im guessing the crank kept it lubed up:worthy: Everything looks good except for the exhaust cam journal, and the cam itself.

Another question, are the MLS(multi-layer steel headgaskets reusable. I reused them on cars before, but never on a bike. I have some copper rtv i could use with it if you guys think it would be ok.

Like dr350 said, the journal doesn't look too bad. If your desperate, smooth it with some fine emery cloth or sand paper. Make sure the cam jornal doesn't have any aluminum stuck to it. Clean everything up and lube it during assembly. Once you fire it up just let it idle briefly, but not long enough to overheat it. When you do ride it, just keep the rpm's low for a while before you ride it hard.

Generally when there's oil starvation, the cam takes the beating because it's the last place to get oil anyway.

P.S. Tighten your stinken drain plug.:busted:

Oh yea, I have used steel head gaskets again with good results. Rinse it really good inbetween the layers with cleaning solvent or brake clean.

Thanks man. I'm 99.9%positive i tightened it. I think that the loctite i put on it didnt cure because there was oil in the threads of the hole. I usaully dont tighten them to hard because of all the stripped oil drain hole threads. Thats why i use the loctite, but i really appreciate the advice.

Ive been going over the exhaust cam,journal, and cap, and its coming along nicely:banana: All the metal deposits came off real easy. Im using 1500grit with some air tool oil, and then im going to polish the parts. I think i might actually have this thing running tommorow. I thought it was the end of the world. I got real lucky. Thanks again:thumbsup:

If you run a fingernail in the journal, does it catch on the scoring? If so, a good shop like Ron Hamp can line hone the jorunals (he'll need you cams too) back to spec. He will have to pull the valves too so unless they are fairly fresh, you might want to consider having them done while he is in there. Do not reuse the headgasket, It is a poor economy. It might work, it might not. For the cost of the gasket Vs. peace of mind and effort to replace, it is just not worth attempting to reuse. Be sure to copper coat all layers the day before assembly to ensure a perfect sealing.

My fingernail didnt really catch when i ran it across the journal,cam,and cap. Ive been working on them for about 2 1/2 hrs, and its coming along. I will post pics. I keep putting the exhaust cam in the journal, and torquing it to 7.2ft.lbs.(spec), and then turning it to feel for resistance. The valves have 57hrs on them

Let's start by admitting two things (this is going to be a little tough).

Your drain plug fell out because you left it loose. You can deny it if you want, but that's the only reason they fall out, and if you don't fess up at least to yourself, you won't learn anything from it.

Second, no matter how minor the damage seems, it locked the engine up. If you think you can straighten it out with sand paper, you could be kidding your self. You might also get away with it, but you need to be careful. Most of the load is borne by the cap, not the head, so be the most critical of that surface. Check the shaft clearance with Plasti-Gage, as shown in the manual. Engine Dynamics can repair the head for you, if you'd rather do it right.

I never denied forgetting to tighten it, but i practice very good garage manners, and could not see myself doin something so stupid. Like i already stated though im low on money, and im determined to ride.I planned on using the plastigauge, and i also have my micrometer sitting next to me to make sure the cam is still in spec when im done.The cap was the least damaged part of everything. The head took most of it, and the cam second. Not sure why, but thats what im looking at. If i had the money the head would be going to eric gorr.

SInce i started racing supermoto we have to saftey wire all of stuff, Even ow that the seasons over i keep it wired, i have these fast clips that i put on and all it takes is 5 secs to remove it. Peace of mind. TT sells the drilled magnetic drain plugs you might want to get one.

Hey qwik:

I just got done repairing the same issue. Although, mine was a bit worse than yours. I think you saved it from catastrophic damage. I don’t like the steel on aluminum scheme. Heck, I don’t like the shim under bucket scheme, but I digress.

I would not attempt to repair the damage by hand. The tolerances are very tight and it is inevitable you will create an out-of-round condition. It is possible for the errors to be undetected by the plasti-gage method. It is also possible the camshaft will begin to rotate conically around the larger ball bearing, closest to the drive source (chain). Theoretically, it will beat up the journal further. Like Gray said, the cap takes the brunt of the forces when the cam lobes are compressing the valve springs. There is also less contact area on the cap due to the oil galley. The exhaust area is a very hot place to be indeed.

I know the damage looks minor, but compare it to your intake journal. Send the head to Engine Dynamics. He will skim the cap and rebore the journal. The centerline of the shaft will be slightly lower so reshimming will be in order. He will take care of all that for about $130. No valve extraction. Recommended cap bolt torque in 5 ft/lbs. This is below Yamaha’s 7. They are very nice people. I think they are taking some time off for the holidays.

I put a new piston (oem) in while I was there. I mic'ed everything and the skirt was slightly below the low. The cylinder was like new. I was more worried about the piston changing shape. You will not pick up circularity with a micrometer. So I just put a new one in. Break the bank and get some NEW gaskets.

It’s all about peace of mind next time your busting double backflips. :busted:

Good Luck.

The gasket question was one I forgot to address. While the '06 head gasket is a multi-sheet steel gasket, it also has compression ridges built into it, and is coated with a sealant. These gaskets ARE NOT reusable.

On the question of cam cap torque, I recommend 75 in/lbs rather than the specified 86 (6.2 vs. 7.2 ft/lb) even before the caps get shaved. 86 simply feels like too much to me.

On the question of cam cap torque, I recommend 75 in/lbs rather than the specified 86 (6.2 vs. 7.2 ft/lb) even before the caps get shaved. 86 simply feels like too much to me.

the smart guys use 75. and they use a 1/4" torque wrench. and they follow the pattern in the book.

and they do it in 3 steps of 25, 50 and 75. right richard?

Thanks for all the suggestions guys.:busted:

If you think the head is toast or needs rebuilding definately send it to Engine Dynamics. They fixed my old YZ400 cam journals for around $100.


Bad things will happen. Hence why I got to learn of Engine Dynamics. Make sure to properly tourque the cam cap bolts.

You know, if he were racing, then it would be really important that he have everything perfect, but unless he has the bike at 11,000 RPM for long periods of time I think that the motor should be just fine for a season or so.

PS: Did you look at the rod bearing? If not, I'd recommend it. Those take a lot of abuse in low oil situations. Other than the cam, rod and piston, the motor should be fine.

The head actually surprised me. I Thought it was going to be way worse. Im still working on it. I think it have about 6 hrs in it now. Im taking my time and measuring everything over and over. Im using my t-gauge and mic to keep things as close as i possibly can. I do have a little machining experience so thats helping me keep things in order.Ive checked the cam for runout(.257mm. the journal diameter is still in spec barely(21.964) I got the cam turning smooth now, and the plastigauge is showing.049mm cap to cam clearance. I still need to check my cam chain to make sure it hasnt stretched out of spec.

If the bike had run for 1 more second it would have jumped time and done serious damage. Ill keep you guys posted. I should have some pics up soon:thumbsup:

You know, if he were racing, then it would be really important that he have everything perfect, but unless he has the bike at 11,000 RPM for long periods of time I think that the motor should be just fine for a season or so.

PS: Did you look at the rod bearing? If not, I'd recommend it. Those take a lot of abuse in low oil situations. Other than the cam, rod and piston, the motor should be fine.

I checked the piston,cylinder, and rod bearing, and it seems that they were getting plenty of oil. Probably getting fed oil from the crank slingin oil on them. They look normal no unusual wear. The bike still had a 1/2quart in it when i shut it off.

Until this happened i ran the bike very hard. Im going to have to gain its trust again before it see's the rev limiter. Im going to heat cycle it at least 20 times before i ride it, and i am going to have the head re-done when i get the money. Probably in a month or so.

the smart guys use 75. and they use a 1/4" torque wrench. and they follow the pattern in the book.

and they do it in 3 steps of 25, 50 and 75. right richard?

That's my view of the matter, Steve. :busted:

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now

  • Similar Content

    • By Samx22x
      Alright so I’m new to the site so maybe this question has already been asked. I have a 2002 Yz426f and I want a new exhaust, it has the stock header and silencer and sounds amazing but I’d like a little more from it, I know I want the fmf power bomb header and am kind of undecided on the silencer, I see on fmf’s website that their silencer will add low end and slightly take from top end and the other way around but I’m looking for increases throughout rpm range. I do a lot of trail, hill climbs, jumps, and wheelies so kind of need good performance everywhere in the rpms. My question is what silencer I should get and the jetting I should get for the carb. Thanks
    • By Zack Ailing
      hey guys just picked up a new project bike. Its a 2008 Yz450f with a big bore kit and a stroker crank. The total cc of the engine is now 499. It runs on race gas and will be an absolute monster when shes ready to rip. I will continue to make more videos on the bike so stay tuned Link to the video: 
    • By High On Octane
      2005 YZ450F, Athena Big Bore, Power Bomb, Q4.
      Ok.  Last fall after a decently hot day at the track, I noticed coolant leaking from the weep hole on my water pump after pulling into the pits.  Ordered an Athena re-seal kit, put it all back together and didn't really get a chance to ride it.  3 weeks ago, went out to the track, and after about 20 laps, it started leaking again.  Kept filling it with water to get thru the day, never ran anywhere close to dry or empty, jut a cup or 2 low.  Ordered a Hot Rods re-seal kit with bearing and also ordered a new w/p shaft.  Did it all again and got it back together, ran it, and as soon as it got to temp, it was leaking out of the weep hole again.
      So, what the heck am I missing?  I'm totally stumped on this one.  Is something wrong with my case cover?  Do I need to replace the w/p itself?  I'm feeling like I should've just ponied up for the Boysen in the first place, and now it's biting me in the butt.  Any help or suggestions is greatly appreciated.  Thanks!
    • By Awheeler25u
      Alright guys, my 04 YZ450f runs fine minus some slight backfires when decelerating (need to adjust fuel screw). The other day when I was done checking my valve clearances I changed the oil and filter and put the bike back on the stand, kicked it a few times without the ignition coil in to get some oil flowing got off and noticed a little drip spot on the ground, it was no bigger than a dime so I thought nothing of it. Started the bike with no issues took it for a quick 10-15 min ride, came back to the garage to find out my whole case was soaked with oil and it started pooling in the low spots on the clutch basket side. I cleaned all the oil off and took it out again for 5 mins to try and see where it was coming from, here are my three possible places but nothing directly leads me to believe it’s any of the three either.
      1. Decompression plug area
      2.  Valve cover gasket leak (not really sure because the amount of oil leaking Looks to be a large amount
      3. Oil tank (bad weld or cracked weld somewhere
      what are you guys thinking?
    • By bofar
      Hey guys. I could really use your help diagnosing an issue that came up riding today. Bike is a 2013 YZ450F. Well maintained and haven't had any issues until now. Both the oil and coolant are new and levels are to spec. 
      After riding for about an hour in the sand dunes, I noticed a grinding going on on the right side of the bottom end (from what I could tell). When I looked to see what was going on my kickstarter was vibrating and grinding really loud. This was a different sound than if you engaged the kickstarter while running. It sounded less "clanky" and more "vibrating/grinding" if that makes sense. Grabbing the kickstarter and moving it didn't help the issue.
      When I noticed it, I shut the bike off and gave it a second. Being a few miles deep into the dunes, I had to get it out of there so I started it back up and it seemed fine- no grinding. I headed back to the car and after a few minutes, it came back so I shut it off again, started it back up and nothing. That process happened one or two more times before I made it back to the truck. Seemed to run fine otherwise. 
      Once I got it back to the truck I started it up and tried to pay more attention to what was going on but it wasn't doing it. I did seem to have more of a metal on metal noise coming from the motor. I started and stopped the bike a few times and after the motor stopped there was a distinct metal clank/grinding noise that happened right after the motor shut of for maybe half a second. This doesn't happen every time. 
      I tried doing some research and have seen things that make me think it could be the spring that connects to the kickstarter, or the kickstarter stopper plate- but really I have no idea.
      Seems strange that the issue is off and on.
      Thanks for the help!