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Discussion Starter · #21 ·
What do your cam and springs look like? Also is your cylinder bore scored beyond repair or could you bore it out and re-apply the Nikasil coating?
It



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will depend on if I can get parts and how long to arrive. Someone is selling a damaged F3 675 head and I may need to get it for replacement valves, same part numbers as F3 800. The piston I will have to order. I still need to remove clutch and gearbox then access the piston for removal the cams and valves springs appear oj
Fun times!
 

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Discussion Starter · #23 ·
Cost of one piston (complete) $745.60
Exhaust valve $390.00 each intake valves can only order upgrade kit at $1300.00 (unsure what is included)
All prices Australian dollars with no parts available in stock would need to order from Mv Italy.
Not sure if it's worth rebuilding now
 

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You shouldn't get OEM. If I were you I would find a good aftermarket company like Eagle, Wisco, JE, or Carrillo for Pistons and rods. (Or whatever the Australian equivalent company is)

For valve train I would look at Ferrera, Crane, Comp cams etc. You almost certainly are going to have to have them special ordered/made to order. But for what MV is charging you for one you can probably get the whole set! I wouldn't want to put it back to stock parts.

I'd upgrade valve guides, valves, springs and keepers. I think keeping the same cam profile would be fine if you upgrade the stock parts with stronger aftermarket ones.

Or if you don't want to mess with it buy that local RR used engine for $2 grand. Can't be sure how long that will last either I suppose that's the conundrum isn't it.....I'd build your existing motor with aftermarket parts that way you can be sure it's built to withstand way more power (not necessary but stronger parts that are less stressed last longer than adequate parts pushed to the limit) and be reliable.

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@Blinxnot Tighe Cams in Queensland custom made valves for my Honda CB750 F2 head from memory recommended by Rex Wolfenden from T Rex racing and cheaper than I could get them elsewhere and reasonable delivery. You may not need a full set if other valves are OK. They may also be able to help with your other head parts. Might be worth a call. Although I believe he is very busy you might want to talk to Brad “the bike boy” Black (on the forum) in Oakleigh about who to do the head work. I think C&C engineering in Thomastown does Rex Wolfendens head work for what it’s worth.
There is also Head Stud Development in Melbourne but I haven’t dealt with them. Ferracci in US has piston kits for $700USD. Google is your friend.
 

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Discussion Starter · #27 ·
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Managed to remove clutch and gearbox today. I think the bore in cylinder one look ok to my untrained eye. On starwin trading the have an inlet side package which is a new inlet cam and 6 new inlet valves for $700.00. I will also order a new complete piston set. Not sure if I would need to change rings on the other two cylinders
 

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The piston bore rule is: If you can feel it with a fingernail it's too rough. Looks good in the pic though🤞
 

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That piston is nasty. Looks worse than my old 2 stroke dirt bike that ingested it's own rings at high RPM.
 
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It's kind of hard to tell for sure from the picture but it looks like there is little gouges in the cylinder wall on the lower side of the picture. Those will eat your rings up. Your going to need to get an over sized piston and bore that cylinder out at the very least. Your case looks good though.

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No such thing as oversized pistons for MVs...and you can't bore out a plated cylinder. BUT, the plating can be repaired.
I think what you see is reflections. At any rate, once the cases are split and the piston is out the bore can be cleaned and inspected properly.

And on another note:
Contrary to popular belief and practice, you do NOT have to replace piston rings when a top end is disassembled.
Unless the bike has a lot of miles or some other concern that warrants it, you can reuse the rings that are happily bedded to the cylinders.
Some will say "as long as you are in there"....but it is really not necessary on low mileage engines.
 
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