Topic: Big Bore Pistons (CB750 & CB400F) on Ebay

[Triffecpa]

Anyone else seen these before?

http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&item=130348723055&ssPageName=STRK:MEWAX:IT 

http://cgi.ebay.com/ebaymotors/HONDA-CB750K0-K5-PISTON-65mm-SET-OF-FOUR-WITH-GASKET_W0QQitemZ130348722699QQcmdZViewItemQQptZMotorcycles_Parts_Accessories?hash=item1e5963aa0b

Other than "there is no free lunch", "you get what you pay for" and "there is no Santa Claus" does anyone have an opinion about them?

The seller has minimal feedback and primarily as a buyer, not a seller.

Tracy

[mick7504]

Haven't seen those before.
The Honda 750 65mm pistons are an 836cc kit.
I noticed that they don't come with a warranty which is a good enough reason to stay away from them.
Mick

[Retro Rocket]

They look like they are made in Japan, they look ok but the lack of warranty could pose problems.

Mick

[754]

warranty  ?
 show me a big bore piston with warranty...

[Retro Rocket]

Yeah,i was thinking about that but i imagine if you got a new set of pistons of anyone that you weren't happy with before using them that they would have some sort of return policy.

Mick

[BLUE71TURBO]

The ad doesn't state if the pistons are forged or cast either. For that price i'll bet they are cast.

[SkyPilot]

It doesn't state what the piston compression ratio is?  What will be the new bore size, how many cc is 54.5mm?

[mick7504]

I sent these guys an email asking them about warranty and comp ratio for these pistons and here is their reply:

Dear mick7504,

Hellow, It don't have warranty. I don't check compression. These piston are reproductions of OEM parts . Thank you


- cruzinimage_co

[mick7504]

It doesn't state what the piston compression ratio is?  What will be the new bore size, how many cc is 54.5mm?

54.5mm will take your motor to 466cc (470cc)
Stock bore is 51mm

[SkyPilot]

Mick, thanx for the follow up on the 54.5mm / cc size (466cc) and the attempt to ascertain what the piston compression ratio is?  Wish they had an adequate answer, not a bad price, too bad they're so evasive!  Best, Rick

[Retro Rocket]

Mick, thanx for the follow up on the 54.5mm / cc size (466cc) and the attempt to ascertain what the piston compression ratio is?  Wish they had an adequate answer, not a bad price, too bad they're so evasive!  Best, Rick

There not so much evasive, its just that they are Japanese and it is very hard to get the answer you want from them as they are answering your questions as to what they "think" you are saying which is quite often a completely different thing. I buy and sell guitars out of Japan and used to have this problem a lot until i worked out how to ask specific questions...
It is just a communication breakdown....

Mick

[gsnorcal]

It doesn't state what the piston compression ratio is?  What will be the new bore size, how many cc is 54.5mm?

I asked him on eBay:

Dear cruzinimage_co,

What is the compression ratio? 9.4:1 like stock? Or higher? Thanks!

He answered within 8 hours:

Hello,
regarding some question. Just like same with OEM pistons.
Thank you

I've got a set on order. And he combines shipping if you want an extra head gasket or extra rings.

Dave

[Bodi]

I expect a slightly higher CR than stock. I don't know what's up with the Yoshimura 466 kits you can get through MC-Again: I don't think Yoshimura is involved with 70s bikes now, anyway. If these ebay kits are the same parts as in the "Yosh" kits or a copy of them (there are plenty of piston makers in Japan) then compression should be a bit higher. If I remember right the original Yoshimura 466 kits were 10:1? This is about right for a piston with the same deck height as stock and 3.5mm more diameter.
I would try this kit, it's about 1/5 the price of MC-Again's Yosh kit the last time I checked. Get an extra head gasket or two, they are hard to find for the 54.5mm bore.

[camelman]

I've seen three of these pistons sets now, and all three of them looked to be made well.  They are cast and machined.  The eBay seller is very easy to deal with and will quickly ship any replacement pistons rings you need for $17 total if you happen to break a ring.  Which, I did... and was really glad he was so easy to deal with.  Even the old-timey motorcycle racing shop I took the pistons and jug to thought the pistons were well made.  I respect this guy's products.

Camelman

[ummagawd]

sorry to bring up an old topic (I didn't want to start a new thread)...

but what should I expect with this big bore kit?

And what am i getting myself into (IE - do people that go this big bore route tend to experience more problems?)

I need to pull my engine apart for a cam chain tensioner issue, and figured i'd rebuild the engine while it's all apart.

[dave500]

just going one oversize will freshen it right up if its worn and has low compression now.