Topic: CAFE Folks-CB350 twin pistons;I want O.E. 66-67mm & 10.5:1 compression...

[grcamna2]

Not a sohc4,I know  ;I tried on hondatwins.net but, no action on that site...,but still hoping to research this question here on my favorite forum.
I want to find a pr. of stock O.E. pistons from any of the Big Four(Honda,Kaw.,Yam.,Suz.)that'll let me simply bore out my cylinder liners to accept either 66-67mm,up from the stock 64mm & 9.5:1 of the CB350 twin.
I'm asking if anyone here has ever done the research to find the correct pistons to achieve that 10.5:1 compression ratio(no higher)and w/o having to do lots of extra machine work other than just boring out the cylinder liners,etc.I don't plan on ever using a high lift cam(maybe a slight .020-.030 lift mod. only w/ a custom grind to my stock CB350 twin camshaft) as this will be a street use bike only.I want a little more grunt for climbing,etc. for when I load the bike up w/ more weight.I like this little bike and don't want to keep it parked.
I know there aren't too many folks who may have thought of using an O.E. piston from another manufacturer to accomplish this but,I think O.E. pistons & rings are very satisfactory & will make her work Best for me.

If any of you members have thoughts or experience on this that'll help,please feel free to PM me or just post here so I can get some help with this research.
I was told a pr. of KZ440 pistons may work... Any thoughts ?
                                                                    Thanks, grcamna2 

[grcamna2]

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[grcamna2]

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[madScientist]

I have a CL350 but I think the pistons are the same. I know folks used the 350 pistons to make 836 kits in the 4's but not vice versa. The 350 pistons were high dome pistons whereas the 750 pistons were not. It is possible to use 750 pistons but I think you're going to have to dome some surgery to get the compression ratio high enough to add any benefit. As to other makes I'm not sure either. The KZ pistons would likely be no good as they were flat top or slight domed. Suz's and Yami's i've never seen.

I've done a little research on the 440 pistons but not enough to warrant me speaking towards them. You might be better off going to bore-tech and picking up a set of their pistons. That is what I will be doing for mine.

[grcamna2]

Hi there you madScientist,
      I have a pr. of Boretech's 65mm cast pistons(cheap Chinese cast pistons w/ cheap rings)that come w/ wrist pins,clips,rings..,etc. but haven't installed them just yet.I've been on the phone w/ Kelly about a pair of chrome replacement rings that Bill can get that I would rather use to install these pistons for longer ring life.
I've had my cylinders bored out to fit these pistons by an Excellent machine shop in CO. and they used such a nice,fine finish hone that I look forward to installing the "O.E. style" chrome rings from Boretech once I purchase them.The finish of the bore job being done w/ fine stones is essential for proper break-in w/ chrome O.E. type rings.These Chinese pistons are only 9.5:1(same as stock) and I want just a little more..;but not as much as 12:1 such as that great set of forged Boretech 67.5mm racing pistons. I want a "street only" set up.
I'm still interested to do more research about the larger bore O.E. pistons that I can swap from another make/model to achieve my desired 10.5:1 compression ratio.
I'll just keep researching and possibly speaking to a few Café racers who've built different CB350 twins...

Thank You for your feedback madScientist     Bill grcamna2

[grcamna2]

Has anyone ever installed a pair of Kawasaki KZ440 67.5mm O.E. Std. pistons into a Honda CB350 twin that you know of ??
I'm wondering if the piston pin is the same size ?

[grcamna2]

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[FuZZie]

Wish I could help, your not getting any replies. Someone must have done something like this.

[BAchvytrk]

i have 4 or 5 old kz 400 and kz440 motors here. i don;t have any tore down but i could and get you the pin measurement.  pm me tomorrow to remind me, i'll be workin in the shop all day.

[grcamna2]

PM sent

[bj]

I just got Wiseco 66mm forged pistons for my 350. Compression ratio is 10.5 to 1. Haven't got them installed yet though. It another one of my many winter projects.

You might try posting a question on caferacer.net. Lots of real 350 knowledge there.

[grcamna2]

thanks bj !

[grcamna2]

i have 4 or 5 old kz 400 and kz440 motors here. i don;t have any tore down but i could and get you the pin measurement.  pm me tomorrow to remind me, i'll be workin in the shop all day.

Terry,
     I appreciate your PM & email  I hope you and Yours have a Great Thanksgiving !

[grcamna2]

Have any of you given this piston swap a go w/ your CB350 twin

                                            PM's Welcome 

[grcamna2]

I just learned that the KZ440 pistons won't work because of the height of the piston dome in relation to the wrist pin.

[grcamna2]

Anyone have any other idea's on O.E. Japanese motorcycle pistons that'll swap in to my CB350 twin ?? 

[grcamna2]

Anyone  

[kpier883]

What size wrist pin holes are in the stock CB350 pistons?

[kpier883]

Yamaha XS400 has a 69mm bore...  I don't know anything more about them though...

[grcamna2]

What size wrist pin holes are in the stock CB350 pistons?

kpier,
   They're 15mm. 

                Thanks

[grcamna2]

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[kpier883]

A little searching turned up these specs for KZ400 pistons.

Cylinder Diameter: 64.0 mm
Piston Length: 61.5 mm
Compression Height: 25.3 m
Dome Height: 9.7 mm
Wrist Pin Diameter: 15 mm
Wrist Pin Length: 53.5 mm

Fwiw...

[grcamna2]

THANK YOU VERY MUCH kpier883 ! I'm many steps closer now in research 

I wonder if KZ440 pistons have similar dimensions except for the 67.5mm bore ?

[grcamna2]

I just moved my storage/tools,etc. into this new area..,but when I can,I'm going to look at the 81-82' model year Kaw. KZ750 four piston and see if I can match it up to my CB350 twin piston...;from what I've been reading on other forums it could be a direct swap. I Hope so  !