Topic: 400/466 Big Bore...Please tell me I'm not screwed.

[Robbnc]

I just got my cylinders back from a machine shop that said they had done CB's before. Upon checking piston skirt clearance with a feeler gauge I'm getting a consistant
.0025,  002 is loose and .003 won't go. 

Is this too much ?
I don't care if it limits cylinder life as long as it runs a season or two, I can get new cylinders later,but I don't want to be screwed right off the bat if this thing won' cool right or bangs all to hell.

Am I screwed or did I just learn another lesson ?

[jessezm]

That's a lot of clearance for cast pistons!  I am having mine done right now and .0012-.0016  is what I told the machinist, which sounded right to him, and I asked him to shoot for the smaller number.  Now I am by no means an expert, but I did a whole bunch of reading and asked a lot of questions here before dropping them off...   Did you give your guy specific clearance numbers?

[Robbnc]

No I didn't , my first mistake.    But these guys do boring for every motorcycle shop in town, I assumed they knew but of course I shouldn't have assumed anything.
I guess my real worry is if this thing is going to just boil smoke from the get go with ungodly piston slap ?   Heck, if it make it to NEXT winter I can put new jugs in but I really hate to think
I have to start looking now , and of course have it out with the shop over whose fault it is.

[jessezm]

I may be able to help you if you end up needing to start over.  I have 3 good sleeves that I dropped from my block, and one bad one that had a pinched oil ring.  You could swap the three good ones out in your block and source an extra sleeve for the fourth.  In fact, if you send it to Advanced Sleeve, they'll do it all for you.   you can get them made for about $60-$80 dollars each--I looked into it... (see: http://forums.sohc4.net/index.php?topic=96453.msg1076355#msg1076355)

These sleeves were bored for the 466 kit and only have 1,500 miles since the bore.  They may just need a very light hone if anything.  Just let me know if you're interested.  I think Crazypj on the forums here may have one other good sleeve as well, may want to check with him.

[Robbnc]

I just looked at the manual and if I subtract the piston skirt service limits from the cylinder ID service limits I get something like .009 !!   I'm wondering how bad could this run
at .0025 ?    On the other hand if it cracks a skirt within 500  miles I will sure feel like a dumbass.

[Tim2005]

What make pistons are you using and what clearance does the manufacturer recommend?  You can get away with running Yoshimura 54mm high-comp 460 pistons at .003 clearance, but I can't vouch for other makes.

[Robbnc]

They are cast pistons from Japan (cruzinimage on e-bay) , I've seen several forum members use them.  And they came with no specs.

[scottly]

Since you are well within service limits, don't worry about it. Better a wee bit too loose than a wee bit too tight.

[crazypj]

I think you missed a zero in the first post, 0.025" is a lot bigger than 0.0025". 
 I fit 69mm pistons into CB360's with 0.0015~0.0018" clearance.
 If they are like stock with a long skirt, they will work fine but may need rings around 5,000 miles

[Robbnc]

You are correct .    I meant  .0025   
I corrected it.
thanks for the responses

[Robbnc]

thanks for the offer Jezzezm,  but the machine shop has agreed to rebore new cylinders if I want . They seem to think it will be fine and swear they have sent CB's out like this before.
And they said if I try it and see problems with it then they will rebore a new set then too.
So right now I am still trying to make up my mind , no rush anyway, it won't be ridden before next spring.