Topic: Boring top case for larger sleeves

[Turbogrimace]

I was told by a reputable engine builder that the top case does not have to be bored out exactly to fit larger sleeves (say for a 915 kit or 970, etc).  He said I could simply take my grinder and take off a little bit so that the sleeves will drop in. 

I just want to confirm this with a few other motorheads before I start hacking into my top case. 

Any suggestions? Tips?

Thanks!

[kos]

Might be able to do that, provided that the ony difference in new sleeves going in vs OEM ones coming out is O.D. But if the top lip of sleeve is thicker, then you have to mill out for proper deck height.  Anyway, a good machinist would be able to do the top cuts needed when he has the bore indexed for the larger sleeve O.D. that he owuld be cutting in. And a good machinest would also "deck" the top of cylinder when all sleeves are installed or you will have head gasket failures.

This is not a cheap inprovement...get ready to spend money, as Speed = $$$


KOS

[MCRider]

I was told by a reputable engine builder that the top case does not have to be bored out exactly to fit larger sleeves (say for a 915 kit or 970, etc).  He said I could simply take my grinder and take off a little bit so that the sleeves will drop in. 

I just want to confirm this with a few other motorheads before I start hacking into my top case. 

Any suggestions? Tips?

Thanks!

My first 888cc kit was from Powroll. They no longer make kits for CB750. It used sleeves with a taper on the bottom that fit into the cases without machine work.

The 888cc kit I have now is from ARIAS. The sleeves were sourced by my engine builder out of Texas. They too are tapered sleeves so no case machining required.

I don't know if the tapered sleeves can be used above 888cc as they are pretty thin. But the thinness is at a point in the sleeve where not much is going on. Getting them was not an issue, cost was the same, and once you have them in hand you or machinist can make the judgement as to how big to go in dispalcements. I'd bet that 900 and 915cc are doable. I'd have your guy look into it.

Above 915cc, my understanding is you must bore the crankcase. we discussed hacking it out with a grinder on a thread with Big Jay from APE. He thought it would be too big of a project for a hand grinder. Might as well do it right and bore the cases. You do have to remove the studs, but above stock displacement you'll want to replace the studs with HD anyway, IMO.

[NitroHunter]

I had an old Wiseco 915 kit that did drop in, no case boring required. I don't remember having to do any case clean up, so if there was, it was minimal at best. The block had to be bored out for the bigger sleeves, and I think they were smaller OD on the bottoms.
The larger OD sleeves for 970+cc do require case boring. I liked the 836 since it was just overbored stock sleeves, that one was easy!
Kos is right on about truing the case/sleeve deck, definitely zero deck if you have no dome / chamber / valve to pocket issues.

[Big Jay]

They don't have to be bored for a tight fit is that is the question. We usually bore them +.02".

[kos]

I was speaking to the issue of boring the block (cylinder) out to accept large bore sleeves. Sure you can get sleeves that don't have to have the top case bored out/enlarged but any sleeves used for bigger pistons need Cylinder block bored and deck cut. Zero deck is always the best. Honda typically have ther pistons down the bore .040" or 1mm in bikes of this era. Don' let the valve pocket depths determine your deck height..that is nuts. Get to zero deck and then clay the pistons to see what your valve pocket depth it. NEVER trust any piston maker about "bolt in" parts. You must check to see if everything fits and there is no interference with spark plug, valves hitting, etc. It is your responsibility not the piston company.

KOS

[MRieck]

Th last 915 kit I did required upper case boring.

[Turbogrimace]

Do you have to deck the cylinder block if you replace a sleeve with a stock one?  I have an 836 kit that came with a broken sleeve.  Seems ok, but not completely sure. 

I thought that the cyl block only had to mate with the top case surface well.  The bore on the top case didnt matter for alignment. 

So im a little stuck here.  I might be getting a 915 kit with cylinders already prepped, so it's not just a matter of having a machinist bore the cases at the same time.  I have the engine split for tranny cutting, crank polishing, new bearings, rods, etc. and I will be running the 836 kit for a bit and then later putting on the 915 kit.  I wanted to prep the top case for the 915 kit so I could simply replace the top end of the engine when I was able to finally install it.  Is this feasible?

[Jerry Rxman Griffin aka MuthaF'er]

OK boys, here we go. You do not always have to bore or enlarge the top case. Case in point (yeah, cheap pun) is my Henry Abe 900 kit. I just had to verify this for myself. Damn, I'm itching to do it!!



I sure wish Big Jay would get those 1000 kits done. I know that kit will have to have the case bored but I want to have this 900 kit installed and his 1000 in my "spare" at the same time.

Turbo,

you say "seems ok but not completely sure" but for the cash and effort you're investing there is no way in hell I would NOT deck the cylinder AND head if I replaced a liner. They need to match and the liner needs to be installed correctly and flush. Plus a little extra compression never hurt anyone.   
 

[Big Jay]

Do you have to deck the cylinder block if you replace a sleeve with a stock one?  I have an 836 kit that came with a broken sleeve.  Seems ok, but not completely sure. 

I thought that the cyl block only had to mate with the top case surface well.  The bore on the top case didnt matter for alignment. 

So im a little stuck here.  I might be getting a 915 kit with cylinders already prepped, so it's not just a matter of having a machinist bore the cases at the same time.  I have the engine split for tranny cutting, crank polishing, new bearings, rods, etc. and I will be running the 836 kit for a bit and then later putting on the 915 kit.  I wanted to prep the top case for the 915 kit so I could simply replace the top end of the engine when I was able to finally install it.  Is this feasible?

Boring the case out for a larger kit that you may run in the future, is a pretty common thing, so when the switch is made the top case will not need to be split again.

To answer the other poster, yes it is necessary to surface a block if a stock sleeve is installed. Remember, when the block is cooling off after the sleeves are installed, the area below the flange will pull away. So when the block has cooled, it is necessary to give the sleeves a push in a press to seat them before surfacing. If you fail to do this, the sleeve can drop when the block heats up when the engine is running.

We have a lot of blocks come through with this problem because that step was missed.

The machining labor to install those 890 Abe kits runs $299, ready to install

[Jerry Rxman Griffin aka MuthaF'er]

"The machining labor to install those 890 Abe kits runs $299, ready to install"

Yeah, but you know how big a pest I can be. You didn't mention the 1000 kit? Keep us informed when the time comes. Just as easy to do both at the same time. 

[Turbogrimace]

So when I dropped the new sleeve in, I pushed it down as far as it would go.  Can I simply get it decked now or should I have the machinist reheat it and make sure it's pressed in?

whats the typical cost to get a head and cylinder set decked?  Do I need to do the top and bottom of the cylinder block?

And so I'm clear, I can cut out some extra meat out of my top case and it doesnt have to be round, doesnt have to fit the new sleeves perfectly, it just has to be within moderation to maintain enough gasket, correct?

[crazypj]

I've done a lot of sleeves in various engines over last 20+yrs.
 When you heat block to shrink them in the alloy expands evenly, gets higher and wider
 The cast iron liner doesn't expand to the same level even if you get it hotter than the block. (liner is at room temp when you fit it)
 The block shrinks pretty evenly so the sleeve  'grows' out at top, unless you can chill top of block to shrink it back and grip top of liner.
 The chances of liner moving are actually pretty high, particularly if you haven't done this before.
 I use wood blocks to stand block off surface and give clearance for spigots and a 3/4" alloy plate on top plus a baking tray full of ice with weights to hold liners down and cool top first. Its worked prety good for me but is time consuming so couldn't realistically be done in a shop
 I'm in the process of making a 'press' plate with screw jacks to hold liners down so bottom of block stays hot longer.
 (for Yamaha XS650/CB350~360, I do a lot of twins))
 I heared the stories of how its possible to carve cases with a die grinder, tried it one time only, ( against my better judgment but thought I'd experiment)
 Not a pretty sight and never did it again, on XS its real easy to break through into oil passageway which is a pain to repair.
 If your going to do it, get it properly machined.
As Big Jay said, around 0.020" clearance for spigot is fine, I've tried tighter (0.010") didn't seem to make any) difference but there is less 'wiggle' room
 PJ