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Valves, piston,?

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My Sons 2004 250 which was rebuilt in 11 with stock piston and ss valves by as racing is giving us problems. Shut her down for the season around December sometime, ran fine from what I remember. Did some maintenance on it during the long winter including, new hoses, rear wheel, other misc items. Went to fire it this last week and she don't want to start using the usual choke procedures. I get it running by shutting off choke warm it up and he takes it down the drive to warm up the motor to change the oil and it just dies. Cant get it going.

Sooo, we tear into it to check valves. sure enough their zeroed, which kinda surprised me since their ss. But it is ridden hard too so who knows. We shim it to .006 and try to fire it up. No go. I finally get it running a few times and it sure heats up quick, quicker and hotter than I remember. Then shut it off, wont start, &%$#@!. Im thinking either the valves are just eaten up and need sent off  again or we have more damage below like a piston or rings. I know I should just send off head but I was hoping to get a few rides to start the year, but now I think I have to tear into it more. Any thoughts?

Thanks, Tim and Tim 

Forgot to mention when I do get it running it smokes from the after market vent hose. I believe it is an applied racing kit.

Edited by timktm

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My Sons 2004 250 which was rebuilt in 11 with stock piston and ss valves by as racing is giving us problems. Shut her down for the season around December sometime, ran fine from what I remember. Did some maintenance on it during the long winter including, new hoses, rear wheel, other misc items. Went to fire it this last week and she don't want to start using the usual choke procedures. I get it running by shutting off choke warm it up and he takes it down the drive to warm up the motor to change the oil and it just dies. Cant get it going.

Sooo, we tear into it to check valves. sure enough their zeroed, which kinda surprised me since their ss. But it is ridden hard too so who knows. We shim it to .006 and try to fire it up. No go. I finally get it running a few times and it sure heats up quick, quicker and hotter than I remember. Then shut it off, wont start, &%$#@!. Im thinking either the valves are just eaten up and need sent off  again or we have more damage below like a piston or rings. I know I should just send off head but I was hoping to get a few rides to start the year, but now I think I have to tear into it more. Any thoughts?

Thanks, Tim and Tim 

Forgot to mention when I do get it running it smokes from the after market vent hose. I believe it is an applied racing kit.

Did you drain the fuel when you shut it down?  I would look at the basics first before thinking it is top end issues.  Is the air filter clean?  Put it away and forget to do that.  Also, depending on where it sits, critters love air boxes.  And sitting with fuel in the bowl may mean a carb cleaning.  Pull the bowl, take out the pilot, and clean it.  Some of the symptoms you describe are signs of a clogged pilot.  Also recheck the fuel/air screw and ensure it isn;t turned out too far.  Lean conditions create hard starting and also cause the bike to run hot.

 

I dropped in steel valves and noticed for about six months they continued to tighten, then for the last year it has been fine.  Not sure if that is common, but keep an eye on them for a while.  

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Did you drain the fuel when you shut it down?  I would look at the basics first before thinking it is top end issues.  Is the air filter clean?  Put it away and forget to do that.  Also, depending on where it sits, critters love air boxes.  And sitting with fuel in the bowl may mean a carb cleaning.  Pull the bowl, take out the pilot, and clean it.  Some of the symptoms you describe are signs of a clogged pilot.  Also recheck the fuel/air screw and ensure it isn;t turned out too far.  Lean conditions create hard starting and also cause the bike to run hot.

 

I dropped in steel valves and noticed for about six months they continued to tighten, then for the last year it has been fine.  Not sure if that is common, but keep an eye on them for a while.  

Fuel is new, Air filter was just serviced, carb taken off and cleaned. I hear ya on the keep it simple, Im going to go put in a new plug before I go ripping into it. Air screw was 2 turns out. 

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what ever you do, do it one at a time.  Do the plug and check it.  I am assuming you can read color.  Then, if that doesn't help, try turning the fuel screw in a full turn.  If that doesn;t work, take it back to where it was and go out a full turn.  next thing t check is the hot start.  They get stuck some times and cause all kind of issues.  Check it at the perch and at the carb.  When you cleaned the carb, did you ensure the pilot was clean.  I gotta ask because I come across a lot of folks that think they know how to clean a carb, but miss a lot of steps.  I have some that think cleaning a carb is nothing more than shooting the outside with carb cleaner until it is...clean.  Not trying to insult your wrench, just want to make sure we are on the same page with "clean" carb.

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I cleaned all the jets, trust me, after the Pain in the a;;;; to get the carb off, you bet im gonna do a good job. So, took the head off and looks like it is the head gasket. Cylinder looks good but obviously I haven't checked the piston. Check out the pics, what do you think? There was water droplets on the top of the piston, very good indication of head gasket. 

 

DSC01831_zps446fed93.jpg

DSC01830_zpsc20d2fba.jpg

DSC01832_zps4454909a.jpg

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Who did the sS upgrade, and how specifically did they do it.

It should last hundreds of hours if done correctly.

Just changing the valves to SS is not enough. The seats must be precision cut to match, and the valve train parts must be changed to match the heavier SS valves, then shimmed correctly.

 

Can't store a bike with gas in it (not matter how little in the carb) unless you treat it, and you really should drain the carb, but FILL THE  TANK with gas when you store it

 

Without know exactly how you are jetted, and if you have done the anual choke, hot start, apump, slide plate seal maintenance...I would expect it NOT to start unless you have.

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Who did the sS upgrade, and how specifically did they do it.

It should last hundreds of hours if done correctly.

Just changing the valves to SS is not enough. The seats must be precision cut to match, and the valve train parts must be changed to match the heavier SS valves, then shimmed correctly.

 

Can't store a bike with gas in it (not matter how little in the carb) unless you treat it, and you really should drain the carb, but FILL THE  TANK with gas when you store it

 

Without know exactly how you are jetted, and if you have done the anual choke, hot start, apump, slide plate seal maintenance...I would expect it NOT to start unless you have.

Agent smith did them. Gas was treated. This bike ran flawlessly for three seasons.  What do you think of the gasket pic? 

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AS Racing is as good as it gets.

 

Water on top of the piston can be condensation.

You have to taste the water for Proplyne Glycol to see if it's coolant or not (sweet).


Agent smith did them. Gas was treated. This bike ran flawlessly for three seasons.  What do you think of the gasket pic? 

 

3 seasons is what, 100 hours? 300?  So, you got the life out of the valves that would be expected then.

 

Sounds like your boy pushes that motor pretty hard huh!

Edited by TheKoolAidMadeMeSick

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AS Racing is as good as it gets.

 

Water on top of the piston can be condensation.

You have to taste the water for Proplyne Glycol to see if it's coolant or not (sweet).

 

3 seasons is what, 100 hours? 300?  So, you got the life out of the valves that would be expected then.

 

Sounds like your boy pushes that motor pretty hard huh!

Im guessing over 100 hours at least. I think last year he pushed it pretty hard. And I scolded him a few times for over revving it ( haha he is 22).Something just isn't right. it has always ran great. Im waiting for a head gasket to see if that is it. Oh and the smoke coming from the after market breather smelled like cutting oil, it freaked me out thinking the motor was grinding itself to death. 

Tim

Edited by timktm
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So, two things.  A motor ran hard for 100 hours is ready for a top end.  They last longer than two-strokes, but they don;t last forever.    Two, sounds like a certain 22 year old needs to learn how to handle a wrench and do some work himself.  A few hours in the garage to replace a top end is a pretty good method to stop the over revving.   :lol:

 

You can also do a leak down test since you have the head off.  That will let you know if they are holding tightly or not.  

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A compression check would have been valuable before disassembly. It's tough to do with the decomp Assy. But you can pull spark plug and shoot air in cylinder with valves closed (remove cam) and if there is a leak find it. Either through air filter, exhaust, crankcase or around head gasket. Head gasket not likely though. They seem to run with a blown head gasket they just push coolant everywhere.

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How do you perform the leak down test on the removed head? Oh, and my Son does some wrenching but in between his job and college I will give him a break on this one.  ;)

Thanks

Tim

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Turn the head upside down

Pour gas into the head/combustion chamber

See if gas leaks out

It will leak a tiny bit, as the head is worn, and cold.

But you should get no more than an occasional drip, I think.

Edited by TheKoolAidMadeMeSick

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Well there's your problem: your username has the evil "K" word in it.

I wanted to keep it so if I ever decide to switch back im good to go. hahaha :ride:

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You can also do a leak down test since you have the head off.  That will let you know if they are holding tightly or not.

So how exactly would you do a leak down test with the head off?

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So how exactly would you do a leak down test with the head off?

This isn't a pressurized method.  Its a simple method using a thin liquid to check the seal of the valves on their seats.

 

With the head off the valves will all be closed.  You simply squirt in some gas or brake cleaner in to the intake and exhaust ports ( I generally just do one at a time), and wait to see if the liquid "leaks" out around the seats.  Generally speaking, if it holds for a minute, they should be good.  Some folks say it is good if it holds for 30 seconds and some guys swear it needs to be longer.

 

Pretty common method and good tool to keep in your back pocket.

 

If you want, you can buy a set of gauges, reassemble the head, and do a test to get some numbers.  But if you see the liquid seeping out, you get the same results and know the seats need re-cut or lapped in.

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I see and not a bad method, I've never heard that called a leak down test.

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Leak down test would test whether or not you have good valve face to seat sealing properties. If your problem is truly a compression issue (which I doubt) there would have to be a dramatic loss in compression. Something obvious like a stuck valve or very tight valves. You said they were at zero.

Not dramatic enough to lose compression entirely.

From what I've read I'd be looking for stuck rings, with the moisture present.

A head gasket blown towards the external or oil side.

Other than that it's spark or fuel??!!??

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