another engine rebuild thread
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Senior Member
SuperBike
Joined: Feb 2007
Posts: 1,252
From: boston
another engine rebuild thread
I know I have been discussing a stage I engine rebuild for the past year or two but this fall my VTR is going under the knife...
Anyways there has been something that ive tried searching for that I cant seem to find the answer to...
Why dont people buy the factory 0.5mm oversized pistons?
they are made by Honda, they dont have to be custom ordered, and they cost about 1/3 to about 1/2 as much as the JE's or other aftermarket brands.
I'm thinking it might be because they might be heavier but I have no idea on what the weight difference is...
Anyways there has been something that ive tried searching for that I cant seem to find the answer to...
Why dont people buy the factory 0.5mm oversized pistons?
they are made by Honda, they dont have to be custom ordered, and they cost about 1/3 to about 1/2 as much as the JE's or other aftermarket brands.
I'm thinking it might be because they might be heavier but I have no idea on what the weight difference is...
Senior Member
SuperBike
Joined: Oct 2007
Posts: 1,082
From: Menifee, CA
The OEM piston would have the same compression as stock so why bother! The aftermarket JE are 12.4 or 12.5:1 a big difference although there is some machining to be done with the deck height to get all of that increase.
Senior Member
MotoGP
Joined: Apr 2005
Posts: 5,631
From: Montreal
The JE are 11.5:1 (maybe 11.6:1, have seen both numbers thrown around). The upped comp ratio was my reason for picking the JEs (and I can only surmise is the reason for others doing so as well, the stock being a very conservative 9.4:1). Together with a decked head, I calculated that my compression ratio is now at about 12.2:1 (my pistons are 0.5mm OS btw.....)
Thread Starter
Senior Member
SuperBike
Joined: Feb 2007
Posts: 1,252
From: boston
that thought came accross my head too but if Im going to have my head machined cant I make up the compression difference in deck height?
or would that require too much off the head and cause problems elsewhere?
has anyone calculated how much would have to be removed from the deck height in order to compensate?
or would that require too much off the head and cause problems elsewhere?
has anyone calculated how much would have to be removed from the deck height in order to compensate?
Senior Member
Superstock
Joined: Mar 2009
Posts: 277
From: south nj (philly area)
Considering the stock pistons are flat and the je ones have a pyramid on top id say you would cut through the combustion chamber trying... if youre gonna do it and want more power you want the je or other pistons there are a few others that make them... if you have these questions after 2 years of talking about a rebuild you may want to think twice about tackling it yourself...
Thread Starter
Senior Member
SuperBike
Joined: Feb 2007
Posts: 1,252
From: boston
dont worry im not new to building engines and the only reason I havent rebuilt mine yet is because of money... I just want to get a finalized parts list within the next few months so I can start sourcing parts and getting money together.
the only reason I question this is because I dont have a picture or specs on the factory oversized piston except for the diameter and I know people have milled down there heads as well...
I know Im going to buy aftermarket hi-comp but I was just wondering why know one has discussed this, or atleast I cant find a thread on it
the only reason I question this is because I dont have a picture or specs on the factory oversized piston except for the diameter and I know people have milled down there heads as well...
I know Im going to buy aftermarket hi-comp but I was just wondering why know one has discussed this, or atleast I cant find a thread on it
Thread Starter
Senior Member
SuperBike
Joined: Feb 2007
Posts: 1,252
From: boston
and by the way the rebuild would have happened this past winter but my son was born in december and I had too much going on...
now that we've gotten settled in and will be moving to a new townhouse next week I will have the space and time to get the parts and get it done.
now that we've gotten settled in and will be moving to a new townhouse next week I will have the space and time to get the parts and get it done.
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