Cylinder clearance numbers for 400f big bore kit.

ronnie

ronnie

Calm down and sail on
I just finally found a mechanic that can bore my jugs out to size. I left him my jugs yesterday and today I'm going offshore for two weeks. My pops is brining him my cylinders and head(resurfacing) tomorrow or today.

The only thing I need is the piston clearance numbers for heat expansion. If anyone knows any of this or has used the 466 kit before please let me know. I would love for it to be done when I get home. Hurricane Isaac screwed my last time home up so it's been months since I worked on the bike.

Thanks guys

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First, you don't mention having the pistons. Your machinist should be insisting on having the actual pistons you plan on using with the cylinders, as there sometimes slight differences from one piston to the next. They match them to the cylinders and measure / bore each one specifically.

They should also know what the clearances should be, and should be asking you if you're racing the bike (bigger clearances typically) or just riding it on the street.

If they're not doing this, then find another shop. There have got to be other places. If not, ship your parts somewhere else. I'm sure another member here can recommend a good place.
 
I have the pistons and my pops will be bringing them this week to the guy. The reason he doesn't really know is because he is a outboard motor guy not a motorcycle guy. I looked for other shops, even out of town. I have waited 2 months for Golden age in virginia to email/call me back but nothing so I'm going to just get them done. I'm just tired of waiting..
 
I'll start calling around.. If i have to I'll send it across the country to LA Sleeve... Time will tell.
 
Skirt clearance should be .0012" - .0016" for the 466 bigbore kit. I just got mine done, shoot for the lower number.
 
I was just looking at 400f piston clearances.
Numbers are good for road motor, if your racing go about 0.0002" ~ 0.0004" bigger (0.0018"~0.0020")
 
Cylinder clearance numbers for 400f big bore kit.

crazypj said:
I was just looking at 400f piston clearances.
Numbers are good for road motor, if your racing go about 0.0002" ~ 0.0004" bigger (0.0018"~0.0020")
Click to expand...

0.0018" is 0.0457mm

Good to know for when I put the 466 kit on my bike.
 
.002" is a number I've used with success, outboard motor guys are often very good, the engine machinist I use in town builds high performance outboards and he does really great work
 
I use 0.0016"~0.0017" in my 378 motors and 0.002"~0.0022" in the 390 or bigger, but, as they are twins, it doesn't really apply to 400f (just something to throw out there ;D )
 
Re: Cylinder clearance numbers for 400f big bore kit.

So I can pretty much tell the guy anywhere from .0012 to .0020? And I should tell him to shoot for the .0012 if he can?

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I would probably go 0.0015", you never know when you'll decide to 'see what it woill do'
A tighter clearance will need a lot more break in time/miles
 
I just got my 1977 400f turn 466 back together last month. I sent my jugs to la sleeve. I tried to do it locally but if someone doesn't have a borring bar that is perfect your gunna have trouble on a 4 cylinder machine. I'm assuming your using cruzin - images 466 kit? I did and I went between 2 and 3 thousandths clearance between the piston and the jugs. I gotta go back to work ill write more later
 
Only use 'wide' clearance if you have forged pistons, they expand more when hot.
Cast pistons are harder and lower expansion (but tend to break rather than bend if over stressed)
 
@Wilber, yea that's the ones I'm using. Those are forged right? They defintely aren't cast. I didn't ask the guy if he had a boring bar but he hasn't started yet as I haven't given him the number yet, or the pistons really. You said you went between 2 to 3 thousandths, as in .0020-.0030? And I'm assuming that is total clearance, as in .0015 on each side?

@PJ, I'm pretty sure they are forged, if not then billet(is that used?), but they are definitely not cast, as when I looked at them it didnt appear to be casting marks and such. The listing for the kit doesn't specify but I emailed the seller last week so hopefully I get a response.

I just don't really want to send it out to LA Sleeve cause they are more expensive and I still have to pay for the shipping.. That will add up fast.
 
It will add up fast but you get what you pay for with them. Plus they are the best. No mistakes and top notch work. If your machinest is a thousandth off on one jug your crank is hammered. I understand taking a twin or a single to the Joe machinest but the reason I'm pushing la sleeve is because when they do the bore for this kit it leaves very little skirt meat left, less then 50 thousands which is sketchy but works because the diameter of the sleeves is thicker inside the cylinder block. Hope this helps.
 
Post a pic looking inside pistons, it's easy to tell if cast or forged.
Surface finish doesn't actually have much to do with it, particularly if precision die cast or investment cast
 
I got ya, man this sucks. Hate having to make a decision like this. Cause I know what you're saying Wilber.

@PJ, I don't have a pic of the inside with me.. just the sides and top on my phone. And i'm offshore.

This is a drag, I was hoping this would go smoothly and I would have bored jugs when I got home next week. I'm looking at $50 a hole local or $75 a hole at LA sleeve +shipping. That's a considerable amount. I'll have a chat with my dad, he used to do all that machine work, see what he thinks about the risks.
 
Ya I was in your shoes about 2 months ago. I ate fuckin off brand cherrios for along time to afford the bore job. Funny how these bikes cost 400 bucks for the whole thing but end up costing 3 times to fix em! I love my Cb though. Wouldn't trade if for anything. Building her has taught me tons.
 



466 installed, they are cast pistons

Just to let you know , my machinist screwed up and these ended up at .0025 clearance and it runs great, in fact it screams.
He offered to do them over and I got another set of jugs but I think I'll just see how long these last.
 
How long does one of these motors take to wear in typicialy? Mine has about 300 after rebuild and its just now getting smooth
 
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