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Old 08-09-2009, 12:56 AM   #1
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Default Does this look ok ? Need some thoughts pls

hi guys

this is my 8 month old OS 12TZ Spec II , I run 16% nitro (5% , 5% oils) and use P6 glow plug (OS).

it works very well but has wierd stuff on top of piston and above it ...

see photos :





is this normal ?

thanks
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Old 08-09-2009, 04:00 AM   #2
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that is pitting on the piston and head button. this is detonation
either not enough shims on head button, or the engine is too lean. or combination of both. either way its not looking good.
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Old 08-09-2009, 06:50 AM   #3
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most likely too lean as you're using 16% nitro already (unless <0.2mm shims). how much shims you got for the engine?
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Old 08-09-2009, 02:33 PM   #4
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was using 0.2 + 0.1 during break in ... using only 0.2mm now

I'll richen it a bit, thanks for the input guys
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Old 08-10-2009, 02:47 PM   #5
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Quote:
Originally Posted by Omarko View Post
was using 0.2 + 0.1 during break in ... using only 0.2mm now

I'll richen it a bit, thanks for the input guys

That's nasty. I would definetly add shims and richen. Also 5% oil is kinda low.
I would not go below 8% oil preferably 9%.


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Old 08-10-2009, 04:15 PM   #6
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this is one thing thats frustrating in this hobby ... everything you learn is the hard way ... every person says something different and I usually find the right solution by damaging something.

I searched these forums and found many posts saying that the 12TZ should have only 0.2mm shim if running 16% nitro and once it has been run in. Now , I am told to add more shims ? sorry, but its really confusing

Also, with regards to the oil, I could not find anything specific on the manufacturer website and the guys at local hobby shop recommended to run 5% and 5% ... yet I am told something different again.

I appreciate all the feedback and help from you guys ... but its just frustrating because I want to do the right thing, however, I get so many different opinions that its confusing
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Old 08-10-2009, 06:48 PM   #7
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Quote:
Originally Posted by Omarko View Post
this is one thing thats frustrating in this hobby ... everything you learn is the hard way ... every person says something different and I usually find the right solution by damaging something.

I searched these forums and found many posts saying that the 12TZ should have only 0.2mm shim if running 16% nitro and once it has been run in. Now , I am told to add more shims ? sorry, but its really confusing

Also, with regards to the oil, I could not find anything specific on the manufacturer website and the guys at local hobby shop recommended to run 5% and 5% ... yet I am told something different again.

I appreciate all the feedback and help from you guys ... but its just frustrating because I want to do the right thing, however, I get so many different opinions that its confusing
well...dont despair, different engines have got a different 'default' head clearance.
tz12 may have a default of 0.1mm head clearance, thus with 0.2mm shims the actual head clearance of 0.3mm is ok for 16%.

however the oil in the nitro is recommanded to be 8% minimum.
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Old 08-10-2009, 09:46 PM   #8
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Quote:
Originally Posted by Omarko View Post
this is one thing thats frustrating in this hobby ... everything you learn is the hard way ... every person says something different and I usually find the right solution by damaging something.

I searched these forums and found many posts saying that the 12TZ should have only 0.2mm shim if running 16% nitro and once it has been run in. Now , I am told to add more shims ? sorry, but its really confusing

Also, with regards to the oil, I could not find anything specific on the manufacturer website and the guys at local hobby shop recommended to run 5% and 5% ... yet I am told something different again.

I appreciate all the feedback and help from you guys ... but its just frustrating because I want to do the right thing, however, I get so many different opinions that its confusing
What he is saying that you are running 5% caster 5% synthetic so you are running 16% nitro 10% oil content
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Old 08-10-2009, 09:51 PM   #9
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Quote:
Originally Posted by Omarko View Post
hi guys

this is my 8 month old OS 12TZ Spec II , I run 16% nitro (5% , 5% oils) and use P6 glow plug (OS).

it works very well but has wierd stuff on top of piston and above it ...

see photos :

is this normal ?

thanks
Alex,

You may have dropped part of a plug element when running too lean.

Do you remember blowing a plug recently? If you did was the element intact or was it missing.

I would recommend pulling the piston out and checking the sides for any scratches.

If there is you may be up for a new Piston/Liner.

If not then the best course of action would be to polish up the top of the piston and the button.

Depending on the amount of pitting you can try autosol or if it is pretty bad then use a really fine wet and dry sandpaper first before polising with the Autsol.

Do you have another engine to run this sunday? If you do put that in and I will have a look at this one for you on sunday.
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Old 08-10-2009, 09:54 PM   #10
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Quote:
Originally Posted by chippy View Post
What he is saying that you are running 5% caster 5% synthetic so you are running 16% nitro 10% oil content
That sounds a little better. Never seen surface fuel at only 5% oil unless it's home made.
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Old 08-10-2009, 11:38 PM   #11
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u have pitted your button head and maybe piston head the good news is your engine didnt break any parts. easily done like what brag mention, get 1200 grid sand paper and smooth button head gently and polish top part of your piston. if the compression is still there, maybe need to remove 0.1mm shims.

what i've seen locally OS engines are really weak against lean bottom end settings. mostly end up breaking con rod and in 4 out of 5 cases its total loss. and get your conrod replaced.

just my humble opinion
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Old 08-10-2009, 11:46 PM   #12
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Originally Posted by barg View Post
Alex,

You may have dropped part of a plug element when running too lean.

Do you remember blowing a plug recently? If you did was the element intact or was it missing.

I would recommend pulling the piston out and checking the sides for any scratches.

If there is you may be up for a new Piston/Liner.

If not then the best course of action would be to polish up the top of the piston and the button.

Depending on the amount of pitting you can try autosol or if it is pretty bad then use a really fine wet and dry sandpaper first before polising with the Autsol.

Do you have another engine to run this sunday? If you do put that in and I will have a look at this one for you on sunday.
hi Andrew

hmmm ... I cant recall blowing a plug ... I did have a look on the liner and it seemed clean, but then again, I am no expert.

I'll try to give it a polish tonight ... is Brasso ok to use or do I have to use Autosol only ? I have a can of Brasso and plenty of super fine grit sandpaper that I used on my waterblocks and when I lapped my CPU.

if I get stuck, I'll just use the little Nova I have for the Sunday race and bring the 12TZ for you to have a look when you have a sec.
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Old 08-11-2009, 03:48 AM   #13
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just polished the piston...

before look :



after look :



the sleeve looks ok to me :





thoughts ?
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Old 08-11-2009, 04:43 AM   #14
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Quote:
Originally Posted by Omarko View Post
just polished the piston...

before look :



after look :



the sleeve looks ok to me :





thoughts ?

Alex

from my experience of OS spec II(3 of them), once you have pited the head and piston top even though you polish it will still blown plug and have irregular idling. But your one doesnt look too bad.

Head shims wise .2mm is fine for us with 16% and you should you use 7 plug. make sure you leave bottom end needle flush with the housing TZ dont like bottom end lean at all(leave it alone) depends on what pipe you are using top end needle is about 1.75-2 turns out from fully close.

1 last thing you are using Magnesium head so it take much longer time to warm up, so dont touch any needle until engine has some temp in it.

come and see me on Sunday I will try tune it for you. btw make sure clutch is set probably!

Tom
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Old 08-11-2009, 05:26 AM   #15
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also check you don't have a lot of play in the conrod at TDC. the only time i pitted a head is when i had excessive conrod play and this caused me to get the plug sucked in.
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