What is this things problem!?

[450R NOOB]

So I did a bottom end rebuild consisting of crank, bearings, seals, and gaskets along with a new JE 12:1 piston. Since the rebuild(and also before it) it has had a terible hitting sound in the top end. It only happens at low rpm and sometimes shuts off the quad. the timing is on, the valve clearance is right, and I see no piston or vavle damage. I decided that I was just going to ride it because letting it sit because I didn't want to mess it up would be a waste. Well a couple days ago, after riding for a few hours, I started to wash it off and water began to boil when it hit the engine. I waited 30 minutes and it did the same thing. Come to find out it had NO coolant. I assumed this was the mechanical seal and went ahead and ordered one. While I was waiting, I decided to investigate what the hitting could be. I took off the head and found the piston like this. I don't know if it came from the engine getting nuclear hot or the hitting. Could the hitting come from the decompression mechanism engaging while its running, causing the sound and build up on the piston? I will inspect the cam assembly tonight but it all seems fine. I'm very fed up with this thing and to top it off my dirtbike locked up a couple days ago too.

[450R NOOB]

piston only has maybe 5 hrs on it if that.

[dran714]

yes that thing is cooked! probly ruined your head too bad luck.. sorry man

you could have bad fuel, or fuel that doesn't have enough octane in it. the knocking at low RPM's sounds like detonation. and if your motor is detonating it will cause a lot of heat. i would drain your oil, coolant and gas. and put all brand new in. and if in any doubt put in half race fuel and half 91-93 pump fuel.

If something was in fact hitting (metal on metal) your bike would not have ran for a few hours like you stated it did. if your decompressor is broke it will not make any noise while running but will be a b!tch to kick over.

Hope this helps you.

[450R NOOB]

Now that you say it, it sounds exactly like detonation. The gas is pretty old(like months old) and I can hear the sound in the exhaust. I will throw a new spark plug and gas, oil, and coolant and see what she does. And I did this with a wire brush, carb cleaner, and a paper towel.

[450R NOOB]

^

[DnB_racing]

make sure you re-coat the inside of the cylinder with some 2 stroke oil, the carb cleaner took off all the existing oil and much wear can happen on a dry start!!! the carbon build up is normal your piston looks fine!!!!

[450R NOOB]

Thanks for the tip.

[BlaineKaiser450]

Yeah sounds like detonation. Run higher octane gas and be sure to use the 2 stroke oil like stated above. If that doesn't work, check back in

[450R NOOB]

I was putting the cam assembly on today and I stripped the threads for both front bolts in the head. What are my options other than getting a new head?

[TCracin440ex]

heli coil it.

[DnB_racing]

Originally posted by 450R NOOB
I was putting the cam assembly on today and I stripped the threads for both front bolts in the head. What are my options other than getting a new head? if you dont use a torque wrench any place else this is the place to use it!!!!! the tower bolts really have a huge effect on the valve clearance!!and not to mention that this probably wouldn't have happened

[450R NOOB]

I used a craftsman at 14nm.

And probaly didn't get half that; I think overheating it contributed because the back holes were fine.

[Scro]

If you used a click type torque wrench on these bolts, then that's probably the issue. They work fine for head bolts and the like, but they are just not accurate enough for torque values as low as the tower bolts. I've found that the beam type torque wrenches work much better.

[450R NOOB]

Ah, well that might have been my problem, I might pick up one if they aren't too much. Does anyone know the thread for these bolts; I'm going with the helicoil route but it will be my first time dealing with helicoils so any tips are appreciated.

[310ESR]

Take the bolt with you when you get the Heli-Coil set. If you've never done one before TAKE YOUR TIME. The best way would be to drill the hole with a drill press to keep things square with the world. When you run the Heli-Coil tap in use a tap holding tool, once you get started with the tap back the tap out and in (that will keep the tap cleaned out).

[450R NOOB]

Yeah I picked one up today. Its a M6x1.0 if anyone needs to know. I plan to start on it later when my dad gets home and I'll post results.

[450R NOOB]

Successful helicoil install. Hopefully everything else will go smoothly and I'll post back when I run it again. I wish I had taken some pics and stuff so I could put it in the how-to section because I couldn't find any; maybe another day and another problem.

[rageatvlawson8]

Dont see any signs of denotation. That will leave pitting on top of piston. My guess is that since your timing chain is holding itself up....its bad. If they are kinked ANY they are bad. Sometimes a worn out chain will making a clanking noise thats intermittent and usually only at low rpms. Also anytime you replace the crank its a good idea to replace the chain

[d3ktrix]

That cam chain is shot for sure, probably from the heat.

[450R NOOB]

After a year of my 450 not running right, its running perfect. I put in a new cam chain, spark plug, and new gas and it hasn't missed a beat. Thanks for all the help and here's a comparison of the cam chains. Might have contributed to the problem :eek2:

[DnB_racing]

Originally posted by 450R NOOB
After a year of my 450 not running right, its running perfect. I put in a new cam chain, spark plug, and new gas and it hasn't missed a beat. Thanks for all the help and here's a comparison of the cam chains. Might have contributed to the problem :eek2: looks like a ginger bread man!! LOL...

good follow up to your problem!!!
hopefully others with these issues will read and be able to find the problem, congrats on finding and fixing ... happy riding

[d3ktrix]

haha that is a great picture.