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  #1  
Old 05-01-2019
Gibbit's Avatar
Gibbit Gibbit is offline
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Nikaseal worn around exhaust port. YZ250 and YZ85

I just wanted to pick the brains of the 2 banger gurus on here.
I have the top ends apart on my YZ250X (166hrs) and my sons YZ85 (178hrs). Both show the same signs of wear.
Iím wondering if I should be getting more out of my cylinders than I am.
Iím very anal about clean air filters and run Castrol TTS Racing at 40:1.

What is causing the Nikasil to prematurely wear like this!

Yz250x bore.


YZ85 bore


YZ85 head.
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Old 05-01-2019
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I have never been a fan of TTS. A mate children's bikes had repeated failures when their father switched to TTS due to sponsorship obligations (free oil). Went back to Motorex all good. I personally run ELF
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  #3  
Old 05-01-2019
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Gibbit Gibbit is offline
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Quote:
Originally Posted by oldboy View Post
I have never been a fan of TTS. A mate children's bikes had repeated failures when their father switched to TTS due to sponsorship obligations (free oil). Went back to Motorex all good. I personally run ELF


I like how the castrol burns so clean (as you can see from how clean the head on the 85 is).
I have done tests on motorex for 40hrs and castrol for 40hrs. The castrol piston was so much cleaner.
But maybe itís luberication properties are not good enough.
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Old 06-01-2019
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I run $5/litre 2T oil and my cylinders don't look like that!

Are you sure it is the nikasil wearing? Does the mark polish off? ie is it definitely worn or is there melted aluminium coating the cylinder there? What is the mark at the top of the 85 bore?

Aftermarket pistons too tight?

What do the pistons look like?

It all looks too clean to me....jetting too lean? Even then I would expect to see some carbon cooked on.

I have no idea what the issue is but I think it is more than brand of oil.
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Old 06-01-2019
Nutty Nutty is offline
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Classic lube-film failure, exacerbated by hot burn.

*Change to Motul 800T,
*Don't go any hotter than BR9EG in either bike,
*Don't use EIX plugs,
*Jet them a touch fatter on the MJ
*Change the PJ/needle-straight balance (PJ richer/NS leaner)
*Read the "Spooge ain't bad" thread.

http://www.dirtbikeworld.net/forum/s...ghlight=Spooge

Simple lubricant failure Gibbit, identical in both bikes...common demoninator? Oil. Not hard...

BTW, what premix ratio were you running?
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Old 06-01-2019
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I used to get the same wear on my YZ250s at around 200 hours, however not to that extent. Using Rock Oil K2, mostly trail riding at low revs.
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  #7  
Old 06-01-2019
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Quote:
Originally Posted by JJW View Post
I run $5/litre 2T oil and my cylinders don't look like that!

Are you sure it is the nikasil wearing? Does the mark polish off? ie is it definitely worn or is there melted aluminium coating the cylinder there? What is the mark at the top of the 85 bore? Definitely worn. The mark at the top of the bore is the ring mark

Aftermarket pistons too tight? Only use Oem pistons matched to the bore size. A,b or C ect.

What do the pistons look like? Clean but have been a little hot

It all looks too clean to me....jetting too lean? Even then I would expect to see some carbon cooked on.

I have no idea what the issue is but I think it is more than brand of oil.
See above in Red
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  #8  
Old 06-01-2019
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Weird Rooster Weird Rooster is offline
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@JJW. What oil do you run? pm if you prefer. Cheers
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  #9  
Old 06-01-2019
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Gibbit Gibbit is offline
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Quote:
Originally Posted by Nutty View Post
Lube film failure, exacerbated by hot burn.

*Change to Motul 800T,
*Don't go any hotter than BR9EG in either bike,
*Don't use EIX plugs,
*Jet them a touch fatter on the MJ
*Change the PJ/needle-straight balance (PJ richer/NS leaner)
*Read the "Spooge ain't bad" thread.

http://www.dirtbikeworld.net/forum/s...ghlight=Spooge

Simple lubricant failure Gibbit, identical in both bikes...common demoninator? Oil. Not hard...

BTW, what premix ratio were you running?
Cheers Nutty. Your always on the money. I'll give 800T a go. I already don't use EIX plugs. I usually just go with the recommended plug temp.
I run 40:1 in all my 2st (even the TC50 and TC65) but change to 32:1 for Finke and any fast enduro's.
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Present:2016 YZ250X
1990 YZ490
2014 YZ 125
Past:2016 KTM 300EXC
2010 YZ 250
2007 YZ 125
2011 YZ 450F SE
2009 YZ 450F SE
2001 YZ 426F
1998 RMX 250
1990 DT 200
1987 YZ 80
1984 DS 80
1980 PW 50
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  #10  
Old 06-01-2019
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Nikaseal worn around exhaust port. YZ250 and YZ85

Quote:
Originally Posted by Chewy View Post
I used to get the same wear on my YZ250s at around 200 hours, however not to that extent. Using Rock Oil K2, mostly trail riding at low revs.


The 250 piston had done 57hrs of finke prerunning, plus the race, a Transmoto 6hr and a few other pretty fast WOT enduros. I change from a 178mj to a 190mj for any fast WOT stuff.



The 85 piston had done about 90hrs of reasonably easy trailrides and MX. My son is no Pro but keeps it in the powerband pretty well.



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Present:2016 YZ250X
1990 YZ490
2014 YZ 125
Past:2016 KTM 300EXC
2010 YZ 250
2007 YZ 125
2011 YZ 450F SE
2009 YZ 450F SE
2001 YZ 426F
1998 RMX 250
1990 DT 200
1987 YZ 80
1984 DS 80
1980 PW 50
http://www.youtube.com/user/v8utes/videos
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