MMM yum trx bending and breaking valves!!!

[beck125]

Ok so i am on head number two now, my previous piston slapped the valve and i was not aware of this when i did my rebuild and it barely touched my brand new shiny wiesco piston and pushed the valve through the middle of the head. Aka why i am on head number two. So today i made sure my valves where lashed to specs. its a Magnum stg 2 Racing cam, they said .004 and .006 well i set it and guess what it bent another F**CKING VALVE! is this all because its tightened to far down? what should i do to lash these damn things? thanks for listening to my vent lol
jordan

[bherriman]

Is your piston facing the correct way in the jug? If you put it in backwards it can bend valves and such.

[drew416ex]

Is that a "drop in cam"? If this is the second time this happened it may not be your lash, you may have to do something about your piston to valve clearance. Or like bherriman mentioned your piston could be in backwards or your timing is off.

[rubbersdown]

was it the same valve that bent last time?

[NacsMXer]

Originally posted by drew416ex
Is that a "drop in cam"? If this is the second time this happened it may not be your lash, you may have to do something about your piston to valve clearance. Or like bherriman mentioned your piston could be in backwards or your timing is off.

Exactly my thoughts. I recall the Magnum cam being kind of an obscure cam. There was a member on here asking about the specs for that cam and was unable to find any info on it. If there is too much lift then you are going to have piston to valve clearance issues.

[honda400ex2003]

something seems a bit fishy here thats for sure. Also, we need some pics of the carnage! I would be apt to go with piston in backwards or the cam is messed up. I would probably contact magnum and see if you can get a replacement or at least find out some tolerance specs for the lobes and such to diagnose if there is a lobe that is ground wrong or something. This is def strange to have happen twice. steve

[beck125]

yes of course the first time around the piston was in wrong the wiesco do not specify where the damn arrow goes !lol :P
but i will post pics here in a few min. I cant remember which one but they are both exhaust valves... i may try my stock cam and see if i break yet another...

[beck125]

http://i197.photobucket.com/albums/aa292/jordanbeckjcnrg/66006_452907538117_502483117_5277031_3489301_n.jpg
old head look close ... you can see the hole where the valve pushed into the head
http://i197.photobucket.com/albums/aa292/jordanbeckjcnrg/72767_452910683117_502483117_5277056_5408_n.jpg

[bherriman]

Yea a backwards piston will bend exhaust valves everytime. Arrow points to the front of the jug, pointing at the oil cooler. You say it was in backwards the first time and it bent a valve. So you replaced that valve and corrected the piston I am assuming. Are you sure it didn't bend both valves the first go-round and you just didn't notice. I think that if your timing was that far off to cause piston to valve clearance issues, the dang thing wouldn't even run. In correct Valve lash is also not very likely. My guess is it bent both valves the first time and you just didn't realize it, or possible the cam lobes didn't get ground correctly.

[honda400ex2003]

NICE carnage! I would def say that you should try the stock cam just to test the waters. did you turn it over at all before starting it up? the arrows usually face toward the front also. sorry to see that, the only way to see if there is anything messed up is to tear it down again. good luck man. steve

[bherriman]

Thats a broken Intake valve...I thought you said you messed up the exhaust valves. I don't know if you have the retainer and keepers off the other intake valve, but if you don't that thing is for sure bent its not even seated all the way ....while it was apart I would wire brush all the carbon off those valves and combustion chamber and then lap the valves in before re- installing....can we get some pictures of the piston and jug?

[beck125]

oh trust me i tore it down agian, and the valve is bent to where there is a gap of almost a quarter of an inch so i have to replace the valves but i guess a good note is that it didnt snap off and push the head agian :*)

[beck125]

oh i know that heads jacked up i threw it in the parts pile i have a new head and new valves except they bent again... the jug and piston are normal. now that its in the right way

[dustin_j]

When installing new parts, it's always a good idea to turn it over by hand a few times to make sure there is clearance. Especially if the parts aren't readily used. You can even put clay or something in there to measure clearance later (since parts will expand with heat). Also, make sure you check timing after the cam chain tensioner is engaged. Hope this helps.