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Siezed engine after 10 minutes.

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The company I emailed has forwarded it to there technical team to look into so I will hopefully hear something back from them soon.

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Yeah im hoping I dont seize and it is tighter then the book recommends so I hope she dont seize and the break in gives me the space I need. Also I recommend everyone goes by the book and doesnt go this tight on their own engines. I am only doing this cause im less worried about $500 damage and more worried about riding and with only a few more weeks of riding before the mountains get snowy I am rushing.

Let me know what the company says.

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easy with the muratic acid, it will damage the aluminum, Millenium says use a Q tip, let it soak on the aluminum piston material a few minutes and rinse away.  use a little at a time until the aluminum is gone then clean with scotch-brite and if the cross hatch is damaged a ball hone with oil is required.  The acid wont hurt the nickasil.

Edited by ramjetV8

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Ok here is where the mistake is being made in this. Clearance recommendations are in inches not mm. .01 inches is .254 mm. I have been building motors for years and a to d will not make your clearance to the point where it will squeak a piston. There is a underlying issue here whether you believe it or not.

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easy with the muratic acid, it will damage the aluminum, Millenium says use a Q tip, let it soak on the aluminum piston material a few minutes and rinse away.  use a little at a time until the aluminum is gone then clean with scotch-brite and if the cross hatch is damaged a ball hone with oil is required.  The acid wont hurt the nickasil.

 

Muratic acid is just sulfuric acid isn't it? What strength would you use it, does it need diluting? I'll post some pictures of the cylinder damage and see what everyone thinks about whether it can still be used or whether it needs replating.

 

 

After a fair bit of reading I think this has all happened due to ignorance and lack of tools on my part, I obviously need to get myself a micrometer and a cylinder bore gauge for measuring clearances before I put the piston in. This is a step which up until now I have never done nor known about after the 10 or so top ends I have done and I guess I have just been lucky to not have this happen before. Does anyone recommend any brands or where I could pick up some good measuring tools?

 

They actually have a fair amount of information on the site I purchased the piston kit from which I should have read I guess:

http://www.motocrossparts.co.nz/motoxparts-motorcycle-parts.php?id=128

 

The part I don't understand is the honing of your cylinder to seat every set of rings, I always have heard never to bore a nikasil coated cylinder as you will ruin it as seen here:

 

Thanks guys for all the help so far!

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Clean it up, check the specs, and run it

Edited by Kirkes

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dial bore guage and mics

 

Its actually cheaper and more accurate to use a telescoping snap gauge and mic versus using a mic to measure the piston and a dial bore gauge for the the cylinder.  The reason being is that with a telescoping snap gauge you will be using the same micrometer to measure the bore and to measure the OD of the piston skirt.  Which should yield a more accurate reading.  The telescoping snap gauges take a bit more skill to use but will be better in the long run.  I just picked up a Starrett telescoping snap gauge for about $45 and a mic for about $100.  A decent dial bore gauge will run you several hundred dollars.

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Muratic acid is just sulfuric acid isn't it? What strength would you use it, does it need diluting? I'll post some pictures of the cylinder damage and see what everyone thinks about whether it can still be used or whether it needs replating.

After a fair bit of reading I think this has all happened due to ignorance and lack of tools on my part, I obviously need to get myself a micrometer and a cylinder bore gauge for measuring clearances before I put the piston in. This is a step which up until now I have never done nor known about after the 10 or so top ends I have done and I guess I have just been lucky to not have this happen before. Does anyone recommend any brands or where I could pick up some good measuring tools?

They actually have a fair amount of information on the site I purchased the piston kit from which I should have read I guess:

http://www.motocrossparts.co.nz/motoxparts-motorcycle-parts.php?id=128

The part I don't understand is the honing of your cylinder to seat every set of rings, I always have heard never to bore a nikasil coated cylinder as you will ruin it as seen here:

Thanks guys for all the help so far!

You can lightly hone a cylinder with nikasil. To give you peace of mind, millennium tech told me that it totally ok to do light hones. Properly that is

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Hey There Hyperglow. 

I see you have Pm,ed me and I have replied. 

I understand that you live in Blenheim and i am also in Blenheim. I have sent you my number via the chat.

Looks like there is a four corner seizeure and as previously mentioned it could be due to a number of things.

We are rebuilding engines here at "Clean Rebuilds" and it is a hobbie for me.

I have the tools that have been talked about and I will be happy to measure the piston and bore for you for free.  

It is very important to note that there are many reasons for a seizeure and to try to provide a repair from this side of a computer or smart phone will not work. You need to have it checked so you can eliminate some problems. 

I have a pressure tester here that could test that engine but it would have been better to do it before it was stripped down. 

I would have to note that some of the information you have been provided here with regards to the honing of that Nikasil cylinder, I would be cautious of. 

That cylinder can be honed with a ball hone but if you cylinder is out of round and out of taper the the ball hone will not work. 

It will only provide a cross hatch. It will need to be a special Aluminium oxide ball hone to provide a factory cross hatch for ring bed.

https://www.google.co.nz/url?sa=t&rct=j&q=&esrc=s&source=web&cd=2&cad=rja&ved=0CDUQFjAB&url=http%3A%2F%2Fwww.flexhoneblog.com%2F2012%2F11%2Fthe-flex-hone-for-niaskil-engine.html&ei=ETdaUqyeOIemkAW834HIDg&usg=AFQjCNEW0IJQwPVlorS1KU8ooP_KJhT7hw&sig2=ZQXg3lwfU3Qx6_N4I6Wzcg&bvm=bv.53899372,d.dGI

 

https://www.google.co.nz/url?sa=t&rct=j&q=&esrc=s&source=web&cd=3&cad=rja&ved=0CD4QFjAC&url=http%3A%2F%2Fwww.enginehones.com%2Ftechnical.html&ei=TThaUpT_HITlkAWs0ICADQ&usg=AFQjCNHSKUutMMJk-5j3aq8gaKQnDevBjQ&sig2=G_Mvv8vMQfMpASxOEqkoZQ&bvm=bv.53899372,d.dGI

For me it will be a process of elimination. 

 

Piston to cylinder clearances

jetting

premix ratio

premix oil type

Fuel octane

Reed and carb condition

and engine pressure tested.

 

These are but a few checks. 

 

Get intouch with me if you want to measure that bore. 

 

Kind regards 

 

Geoff.

Edited by GEOF

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So I've been away for the last week or so but before I went, Geoff was kind enough to measure up my piston and cylinder.

 

The cylinder was well within spec and was in good condition other than the alluminium pickup it measured 54mm if I remember right.

 

The piston on the other hand measured 53.97mm even though the Wossner box had it labeled as a 53.95mm. The clearances were too tight, so even though the top of the piston was stamped "A" it sized closer to a "C" which Wossner sell. Not sure whether that's a machining fault of Wossner's but either way the piston was too big.

 

The plan now is to buy a new piston to suit my cylinder size and Geoff will measure it before I put it in just to check clearances. I need to get around to cleaning up the alluminium off the cylinder for now so will have to have a play with that.

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When I had a sleeve installed in my 98cr 250 the guy matched the piston as well. I'll never forget when I handed over the $500 for the job and I was about to walk out and he says"if it doesn't seize in the first minute you are good to go".

I couldn't believe he said that. It scared the crap out of me, after spending all that money. I didn't want to start the bike. Luckily it all turned out good tho. That motor was scary fast. Ridiculous amounts of power.

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Hey HP.....Here are the measuremets taken from last night. 

It looks like, and if my measurements are correct, that you require a piston that would be 53.942 to get the desired clearance of 0.043mm as per the manual. It still looks to be a bit small on the clearance if you take into account the old rule of thumb of 1 thou for every inch of bore size. I would recommend the cast piston in the plated bore and not the forged as the clearances could also be a bit tight for thermal expansion. Pro X do a 53.94 piston. 

I am no expert as I mentioned yesterday and as I have just siezed the KX engine due to poor jetting but the theory certainly stacks up at least that it would be a clearance issue even on a cast piston. The four corner siezure certianly points in that direction. It does not look like a lean mix siezure. This is all also assuming that your jetting is correct and there are no air leaks in the engine. But judging by the condition you keep this bike in I would say it is well looked after. Post a pic because it is a nice looking bike.

This would be the best advice I could offer anyway. 

I would like to measure that other Woosner piston when you get a chance. 

Marlborough trials center can get those Pro x pistons.

 

 

CR 125 2004

1 THOU = 0.0254 MM

0.0254

ALL IN MM

 

CYLINDER A = 53.976

                         53.983

                           0.007

 

CYLINDER B = 53.968

                         53.976

                           0.008

 

CYLINDER STAMP = B

 

CYLINDER ACTUAL = 53.985

 

PISTON A = 53.933

                    53.940

                      0.007

 

PISTON B = 53.925

                    53.933

                      0.008

 

PISTON STAMP = A

 

PISTON ACTUAL = 53.97

 

 

CYLINDER ACTUAL = 53.985

PISTON ACTUAL =      53.970

CLEARANCE =              0.015

 

CLEARANCE THOU = 0.59

 

MANUALS CLEARANCE = 0.043

MANUALS CLEARANCE  THOU = 1.69

 

 

FOR PLATED BORE & CAST PISTON

Edited by GEOF

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That doesn't look like the normal kind of wear you'd see, even for a seized piston.....it looks like something got stuck in there.

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Thanks for the info Geoff. I have contacted the shop I got the piston off and they will exchange the Wossner for a Pro X in a 53.94mm so that should sort out the clearance issue, That will probably arrive early next week.

 

He did tell me this info about the Wossner coatings which I didn't know though:

 

"Wossner pistons already have the recommended clearance built in. Skirt diameter is smaller than the recommended bore size (see sizing on box). Some applications: Nitrous, supercharged, turbo, and cold water marine engines may need more than the recommended clearance. Wossner clearances are set before coating. Coatings are 0.012mm (0.00047") thick and should be deducted when measuring for piston to bore clearance."

 

Interesting to know but I'll go back to a cast piston for now anyway and see how that goes.

 

I'll post up some pics of my bike when she's all back together, I think it still looks quite nice for the hours I have done on it!

Itching to get back out riding, it's been too long. :ride:

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Interesting......even deducting the coating thats just over one thou.....still not enough as you need nearly two thou. Good info though and thanks.

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