Cylinder head replacement leading to constant valve shim adjustment - Possible Causes?

Hey guys,

 

So after replacing my cylinder head, everything is running great except for one problem - the valves seem to require constant re-adjustment. It was my mechanic that did the cylinder head rebuild, I did everything else myself. About 1000km of riding after getting the bike running, it was having real trouble starting from cold. Using the choke would have no effect. Once I turned the bike over enough and the exhaust warmed up I could get it running and once it was hot it would run just fine. I brought the bike back to my mechanic and he re-shimmed the valves - this made the bike 100% perfect again. Unfortunately this only lasted another couple gas tanks of riding before the starting issue happened again. In addition to the cold-start issue, it would also seem to backfire/pop a helluva lot more on my hard decels. 

 

I ride the bike fairly hard, and sometimes have my girl on the back. I'm wondering if riding too hard is causing this problem to recur so quickly? On the same hand, the bike should easily be able to handle what I'm using it for and I can't understand why the hell the valves would need re-adjustment again so quickly. 

 

Do you guys have any advice on what could be going on? I need to know whether to call the mechanic out on his work and ask him to warranty the poor work he has done, or whether the cylinder head I used may just be &%$#@!ed up and require machining or something (which would realllly not be cool). 

 

 

Here's a quick breakdown of my setup for reference/clarity: 2005 DR-Z 400sm w/newly replaced used '07 400E cylinder head. everything engine-wise is stock. 3x3 airbox mod, rejetted carb, ssw/mrd exhaust. 

 

Cheers!

Sounds like he lapped the valves and the coating is gone.

Sounds like he lapped the valves and the coating is gone.

 

 

I'm not sure what that means - lapped the valves? Does this mean it's something that is likely the mechanics fault or would it mean getting new valves?

"Once the hard coating on the valve face starts to wear, the valve clearances will close up in just a few hours. You can adjust them again to service limits, but they will rapidly continue to wear. It’s time for a valve job."

 

From the FAQ.

"Once the hard coating on the valve face starts to wear, the valve clearances will close up in just a few hours. You can adjust them again to service limits, but they will rapidly continue to wear. It’s time for a valve job."

 

From the FAQ.

 

Yes thanks for this. I saw this here: http://www.thumpertalk.com/topic/718276-drz-valve-clearance-check-and-adjustment-plus-cam-timing/

 

I'm not sure this is the case though - the valves were in very good condition from what I could see and the cylinder head/valves/cams that were used in the replacement seemed to be in excellent condition. They had very little signs of wear, and certainly not enough mileage on them that would lead me to believe they are worn out. 

Its a common mistake, in that 'engine builders' lap the valves using valve grinding compound. This is the old school method when valves were made of stainless steel, and not titainium.

Titainium is a relatively soft material and requires a coating to provide wear resistance

DRZ valves are coated to provide a hard wear resistant surface and must not be lapped else the coating is removed and the wear wears at an accelerated rate. The seats should be cut as per the workshop manual, and the valve then bed in in the first few seconds of operation of the engine

 

From what you say, its sounds very much like your valves have been lapped.

Since the trouble disappeared after shimming the valves and came back shortly after that (but stayed good for a while), i guess it speaks for itself.

it happened to me. i made them pay for my valves and i sent the head to eddie to have it done right. I didnt want this to happen to me. I wouldn't go and accuse him of doing it. I'd just go in and ask "hey how do you put new valves in?" and have him explain the process. The wrong way is by using this thing that looks like a stick with a suction cup on the end and this gritty paste. They put it on the edge of the valve and use that stick to turn it back and forth to grind the surfaces even. If he describes that then you know for sure...

it happened to me. i made them pay for my valves and i sent the head to eddie to have it done right. I didnt want this to happen to me. I wouldn't go and accuse him of doing it. I'd just go in and ask "hey how do you put new valves in?" and have him explain the process. The wrong way is by using this thing that looks like a stick with a suction cup on the end and this gritty paste. They put it on the edge of the valve and use that stick to turn it back and forth to grind the surfaces even. If he describes that then you know for sure...

 

Hmm thanks - at least this gives me something to bring to him and see if I can get to the bottom of this. In the event that the valves are worn, is the only option to get new valves? I'm worried that the cylinder head itself may need machining or something. If only there were an easy fix!!

The valve seats really should be cut (machined) before applying new valves

Sounds like the valves were lapped. New valves are needed and the valve seats should be recut

Sounds like the valves were lapped. New valves are needed and the valve seats should be recut

I dont think you can reuse the valve seals either can you? 

I dont think you can reuse the valve seals either can you?

it all depends. Unless there is a lot of miles on them I would replace them but if there brand new they should be fine

it all depends. Unless there is a lot of miles on them I would replace them but if there brand new they should be fine

i had to put new ones in after the shop messed up my valves because they apparently couldn't take out the seals without ruining them...

i had to put new ones in after the shop messed up my valves because they apparently couldn't take out the seals without ruining them...

if you have to remove them the seals are ruined.

I think you've been given good advice.  Sorry to hear your having so many problems with your bike and mechanic.  I would send the head to a shop that specializes in doing motorcycle head work.

 

I strongly recommend you stop riding your bike until the problem is solved correctly.  You don't want a damaged valve destroying your whole engine.

Yeah , don't use the bike anymore , rectify the issues .

I think you've been given good advice. Sorry to hear your having so many problems with your bike and mechanic. I would send the head to a shop that specializes in doing motorcycle head work.

I strongly recommend you stop riding your bike until the problem is solved correctly. You don't want a damaged valve destroying your whole engine.

Totally agree. I bought an 83 civic to get me by for now Hahaha. Not stoked at all about the potential costs of machining the head and buying new valves

Totally agree. I bought an 83 civic to get me by for now Hahaha. Not stoked at all about the potential costs of machining the head and buying new valves

You should be able to have the head done right including parts for $300...

I have always assumed the DRZ has Stainless steel valves. Am I wrong?

 

Not that I've opened up the engine on my DRZ yet.

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