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Yamaha Tech Originally the Yamaha XT600 Tech Forum, due to demand it now includes all Yamaha's technical / mechanical / repair / preparation questions.
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  #1  
Old 2 Jun 2009
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Top End rebuild
I've got a loverly rebored barrell and new piston for my '85 XT.

just putting it on and have a query on the sealant for the cover on the cylinder head.

i've got some Threebond 1104 (same as Yamabond?) which says is OK up to 150c. is that suitable or does it get hotter than that?

also, anyone got any top tips on the easiest way to clean off corrosion & baked on crud from the cooling fins?


cheers
andy
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  #2  
Old 2 Jun 2009
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Yes, wire brush and sandpaper...
that's what I did to my XT's engine, than degreased it and painted it with spray paint... (the paint is just for short term until I get back to Azores)


Vando
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  #3  
Old 2 Jun 2009
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the sealant you have should be fine just don't use too much, the most important thing is that the surfaces are clean and flat the sealant is just there to fill in minor imperfections.

one of the best cleaners is caustic soda but its not the safest stuff to use, wire brushes and sand paper are very slow but effective.

what make piston did you use?
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Old 3 Jun 2009
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Quote:
Originally Posted by wolfzero View Post
what make piston did you use?
the new + .75 piston is from the israeli chap on ebay, ( 9 euro's + shipping, he starts his auctions at a higher price now!) can't remeber the make but my man that done the rebore recognised the make and said yes they are japanese and make a lot of good stuff for karts.

here's the old piston, a wiseco?




and the new one


found the box
Last edited by Lamin Sambou; 3 Jun 2009 at 13:49. Reason: add picture
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Old 3 Jun 2009
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Your old piston has a lot of carbon build up. Looks like you are running very rich or your old rings were letting oil through.
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Old 3 Jun 2009
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the old piston is def a high comp not sure if its a wiseco tho as i've used a wossner high comp one in mine.

the new piston is an oe spec part so it should be fine, but it wont be as good as the old one for performance.
did it damage the barrel cos if i took the head of an engine and saw a high comp piston i think i'd have just got a set of rings for it.
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  #7  
Old 3 Jun 2009
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Originally Posted by tedmagnum View Post
Your old piston has a lot of carbon build up. Looks like you are running very rich or your old rings were letting oil through.
yes, plenty of oil was getting through
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Old 3 Jun 2009
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If a high Comp piston has been in, make sure you check the ring gap with the new one at top, middle and bottom of the bore.
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  #9  
Old 3 Jun 2009
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Quote:
Originally Posted by wolfzero View Post
the old piston is def a high comp not sure if its a wiseco tho as i've used a wossner high comp one in mine.

the new piston is an oe spec part so it should be fine, but it wont be as good as the old one for performance.
did it damage the barrel cos if i took the head of an engine and saw a high comp piston i think i'd have just got a set of rings for it.
I think it was too far gone for new rings. a rough measurement gives me about 25 thou clearance.
the piston skirts show a lot of wear also

I'm looking forward to reduced oil consumption...
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Old 3 Jun 2009
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Originally Posted by tedmagnum View Post
If a high Comp piston has been in, make sure you check the ring gap with the new one at top, middle and bottom of the bore.
Hi Ted, I got a second hand barrel and got it rebored to fit the new piston so all should be good.....
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