CB350 Twin Pistons/Engine rebuild

whynot

~~~If it ain't raining, I'm riding~~{iii}?~~prost~
First time I've ever torn into an engine this deep by myself.

Just wondering what the consensus is on these pistons.
 

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irk miller

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Skirt looks pretty rough on the piston to the left. I don't like that valve damage either.
 

whynot

~~~If it ain't raining, I'm riding~~{iii}?~~prost~
irk miller said:
Skirt looks pretty rough on the piston to the left. I don't like that valve damage either.

Yea, I kind of feel the same way, just wanted to ease my mind some........ordering a piston set is in my future.

Thanks Eric
 

Hurco550

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does the 378 piston dealio work on the 350 lumps too, or just 360's?
 

whynot

~~~If it ain't raining, I'm riding~~{iii}?~~prost~
Hurco550 said:
does the 378 piston dealio work on the 350 lumps too, or just 360's?

I'm no expert, but I think I read on one of the 360 builds that they don't.
 

Spoonz

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Those pistons are best used for paperweights. That one looks like someone tried to put a longer plug in it and failed.
 

teazer

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Let me think: Bad seizure. Excessive blow by. Yep. They are junk. There are a few choices in 66mm plus pistons available and I suspect they are all forged by Wiseco. Todd Henning Racing were the first - after HRC and Yoshimura back in the day, but there are others now.
 

whynot

~~~If it ain't raining, I'm riding~~{iii}?~~prost~
I just want to replace them with a regular stock set. I read a post not too too long ago where to buy a set w/o having to cut the kids arm off for them.

Just can't find it.
 

Hurco550

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WhyNot said:
I just want to replace them with a regular stock set. I read a post not too too long ago where to buy a set w/o having to cut the kids arm off for them.

Just can't find it.

You may want to take a good look at the bore. If the pistons looked like that, there is a chance that the cylinders need bored out anyhow, in which case youd need oversize pistons. Not a terribly spendy proposition. MototechUSA in Mansfield Ohio still bores (and does a fantastic job) for $35 per cylinder. so youd be looking at $70 + s&h for a fresh bore + whatever for a set of oversized pistons rings. oversize shouldn't cost much more than stock size, and are likely a bit easier to find than stock size pistons. Its that way at times anyhow, but not sure if its the case on 350's or not.
 

irk miller

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Bore-tech sells overbore piston kits (rings, piston, pin, clips) for $130. That plus the bore through Mototech is only $200. That's a great price for the results. I love Mototech. I don't use anyone else.
 

whynot

~~~If it ain't raining, I'm riding~~{iii}?~~prost~
Hurco550 said:
You may want to take a good look at the bore. If the pistons looked like that, there is a chance that the cylinders need bored out anyhow, in which case youd need oversize pistons. Not a terribly spendy proposition. MototechUSA in Mansfield Ohio still bores (and does a fantastic job) for $35 per cylinder. so youd be looking at $70 + s&h for a fresh bore + whatever for a set of oversized pistons rings. oversize shouldn't cost much more than stock size, and are likely a bit easier to find than stock size pistons. Its that way at times anyhow, but not sure if its the case on 350's or not.

I don't have the original jug or head, so this was gonna be a hone/bore anyways.

I really had intended to do a .50 oversize, but I was trying to see if these pistons had anything left in them.

I actually have two complete bottom half engines......CL350 and CB350.
 

whynot

~~~If it ain't raining, I'm riding~~{iii}?~~prost~
irk miller said:
Bore-tech sells overbore piston kits (rings, piston, pin, clips) for $130. That plus the bore through Mototech is only $200. That's a great price for the results. I love Mototech. I don't use anyone else.


Care to elaborate a little more on this?

Found the pistons, but Mototech?

What's your take on these?:

https://www.ebay.com/itm/68-73-HONDA-CB350K-0-5mm-OVERSIZE-PISTONS-SET-2PISTONS-INCLUDE-10-CB350KPS-1/162215405000?hash=item25c4caa5c8:g:0n8AAOSwAuZX5gbw


Thanks for your help Eric.
 

Hurco550

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MototechUSA is a shop in Mansfield ohio. One man operation, but he has been doing powersport engine machine work for years, and his prices are still outta the 80's. His name is Chris and his phone # is 1 419 512 3588. Leave a message if he doesn't answer. He is still old school and doesn't have a website.
 

crazypj

Split personality, I fake being smart
Hurco550 said:
MototechUSA is a shop in Mansfield ohio. One man operation, but he has been doing powersport engine machine work for years, and his prices are still outta the 80's. His name is Chris and his phone # is 1 419 512 3588. Leave a message if he doesn't answer. He is still old school and doesn't have a website.

Sounds like someone I could get along with ;)
That's a cheap price for complete piston kit, even from China. Pretty sure I've bought stuff from them but quite a long time ago. The fact they are still going says a lot about a Chinese company
I used to have a lot of stuff for CB350's but got rid of just about everything a few years ago. Piston pin is 1mm smaller than 360 but think I may have some Suzuki stuff that fits?
 

ex119x

Been Around the Block
I think KZ750 or GPZ750 pistons work as CB350 big bore. I am thinking to get a set off e-bay and go with new rings. I'll probably have Bill Bune do the boring.
 

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