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  #971  
Old 08-07-2018
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Quote:
Originally Posted by Jakobi View Post
Is the difference in piston dome height only on the 250's or the 300's as well? Is it just the new models or the old as well?

I have a new Vertex (OEM) slug in a box here, and an older used Wossner I could compare if that helps.
Jake, I donít know. The story was that the other fella ordered an oem piston & what came had a higher crown than the one he was taking out, as measured on the TSP bench.

It may be just Ď18 - it appears both myself & the other 250 owner that have used TSP have different pistons fitted from the factory. Me - the larger, he - the smaller.

The 2018ís have higher compression stock than previous years, which could be both piston &/or head design-derived.
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  #972  
Old 09-07-2018
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Quote:
Originally Posted by gibnut View Post
The 2018ís have higher compression stock than previous years, which could be both piston &/or head design-derived.
That's news. The 250's in particular have always been way up on the compression ratio (compared to the 300's) and even more so if you attempted to close the squish just using base gaskets.
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  #973  
Old 09-07-2018
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The EC & GP have the same piston, according to the fiche. Different head, though.

Jake, if you can, a crown height measurement of your new Vertex oem would be handy, including a part #.

Thanks in advance.
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  #974  
Old 09-07-2018
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Quote:
Originally Posted by gibnut View Post
The EC & GP have the same piston, according to the fiche. Different head, though.

Jake, if you can, a crown height measurement of your new Vertex oem would be handy, including a part #.

Thanks in advance.
I'll see if I can get out the shed tomorrow some time and rough up a measurement for you. I might as well do both while I'm out there.. I like my Wossners.. Only bought the Vertex when previous importer was clearing stock.
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  #975  
Old 10-07-2018
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Ok, so UMI just measured all their 250 pistons & theyíre all exactly the same dimensions as mine.

Looks like TSP had a Gas Gas owner with a random mini-piston, then!

My heads gone back down to be re-machined for a crown height of 4.15mm, not 3.77mm.

Hopefully all good now.
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  #976  
Old 11-07-2018
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Good news mate! I've been in and out of the shed loads the last couple days but flat stick so haven't had a chance to measure a piston. Was on the list for tomorrow! I'll still do it for peace of mind.

I think from memory the dome height on the 300 is different to the 250.. I probably have one of those slugs laying around too (I know I do; hoarder).. so I'll measure that as well.
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  #977  
Old 11-07-2018
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In what may be a record for the slowest first top end ever Iíve finally clocked up enough hours on the Ď14 300 to freshen the top end.
This top end has seen a lot of different jetting specs, some very rich and one way lean. The head was machined by TSP at 30 hours, comp ratio is around 12.5:1. For the past 50 hours or so I have run the following jetting:
Main jet = 175
Pilot jet = 42
Leak jet = 85
Needle = N3EJ #2
And been really happy with it, awesome power and great economy.
So after 113 hours and 3300kms this is what the top end looked like:

My finger is the front of the head.



Front:


Back:


Right side:


Left side:



Again my finger is the front.

Top ring end gap was .559mm,
Bottom end gap was .508mm.

The new rings are .279mm and .254mm.

Pretty happy with that. Next top end can be stretched to 125hours. So Iíll change that in about 5 years.
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  #978  
Old 11-07-2018
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Can someone remind me what the min ring end gap is?
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  #979  
Old 11-07-2018
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I always set them up around 4-5 thou per inch of bore size with 12 thousands being the minimum so 0.30mm should do nicely mate.
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  #980  
Old 12-07-2018
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Next Thursday for '19 model reveals!
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