Topic: Flex or Ball hone for CB650 Top end Rebuild

[81cb650]

Hi All,

I've got a head gasket leak on my '81 CB650 and I'm getting ready to tear down and rebuild.  I have a claw shaped cylinder hone for 2-7 inch diameters, but I've heard flex and ball hones can be better for strictly breaking the glaze.  Does anyone know what size ball hone is best for the CB650 cylinders? 

A link would be much appreciated,
Cheers

[Yamahawk]

Here's a 320 grit hone...
https://www.ebay.com/itm/Flex-Hone-Cylinder-Ball-Hone-58-60mm-BC23832-KAWASAKI-KLX140-KLX140L-/362198336367?_trksid=p2349526.m4383.l4275.c10

Here's a 180 grit hone...
https://www.ebay.com/itm/1153-BALL-TYPE-FLEX-HONE-60MM-DIAMETER-180-GRIT-SILICONE-CARBIDE-USA-MADE/191115402306?epid=1654578240&hash=item2c7f5d9c42:g:PQcAAOxy4eJTMsCs

Charlie

[strynboen]

the hone process vill after a short run Wear the old rings aut of spec...so new rings is a must.

.or leave it as it is no hone..if you not vant to thange them..

[PeWe]

I ordered my flex hones from here if I remember correctly. http://www.enginehones.com/fl2to2.html
For 65 and 67 mm bores. Brush need to have bigger diam than the bore to apply grinding force.
240 grit worked fine. Check ring status before by measure end gap. You need to take off rings from pistons for that, and on again which is a risk.
Tech info about it: http://www.enginehones.com/technical.html

[Yamahawk]

Normally, the oversize is built into the hone, for the bore diameter ordered. So, if you have a 60mm bore, order a 60mm bore hone, it will already be a few mm oversize, according to the info at enginehones.com.
Charlie

[PeWe]

Yes, all bores have no perfect match of brush.

I used:
2 5/8" Flex-Hone® tool silicon carbide 240 grit (67mm) for 65mm bores. It did not feel like too big.
2 3/4" Flex-Hone tool silicon carbide 240 grit (70mm) for 67.5 mm bores
Stock CB750 need 64 mm brush since no 61mm brush

Remember that all tools are provided in over-sized, so do not add inches or mm's to the ID that you are machining.  If the bore size is between standard Flex-Hone® sizes, the next larger standard Flex-Hone should be selected.

[81cb650]

Thanks everyone

I went with: Performance Tool W80560 Piston Cylinder Hone 2"-7" 220 Grit

Seemed to work ok.  I did, of course, replace the rings.  Runs great, leaks like hell. I even doubled back and swapped the head gasket for a cometic, and it still leaks.  If anyone has suggestions for this let me know, it's driving me nuts.

[flybox1]

torque, retorque...or torque, run bike and retorque.

shell out $$$ to have it decked, or $15 for some copper gasket spray

[Bankerdanny]

torque, retorque...or torque, run bike and retorque.

shell out $$$ to have it decked, or $15 for some copper gasket spray

If I can hijack this thread a little bit. A friend of mine at Moto Guild where I work on my bikes is finishing a rebuild of a KZ400. He did a full rebuild with new oversize pistons and a valve job including new guides. It would appear that the machine shop that did the work didn't check the jugs and head for flatness as he now has a pretty obvious leak. Per some advice I gave him he put in a couple heat cycles and re-torqued (he hasn't ridden it yet though, something I also advised him to do). He is now thinking he will pull the head and have it checked for flatness, it is possible that his issue could be addressed by pulling the head and applying copper spray to the existing gasket and reassembling?

[flybox1]

That's a question I cannot answer, but from my F3 rebuild, the engine was apart and of unknown condition.
I didnt have the funds to have any machining done, but I prepped the surfaces as best I could, used HD studs, and copper-sprayed bottom and top end gaskets, and followed the torque/retorque sequence perfectly.
Thousands of miles and no leaks....

[RAFster122s]

Some wet dry on a 1/4" plate glass on a flat table has been used by backyard rebuilders to check a surface for flatness...
You have to manually slide it over the glass with the sandpaper attached and it be wet and then by checking the surface you can see where it is taking down any high spots or if it is abrading the surface evenly. It won't work for big variations.
Better to have a machine shop measure and then skim off enough material to flatten the surfaces (both) and then you will have to check your clearances by that reduction to see if you will be looking at valve and pistons kissing one another which could require you to flycut the valve recesses in the pistons deeper.

Copper gaskets by Cometic are often used by racers and they often will weep and "leak" a little. Nearly impossible to use the copper gaskets without some leaking I am told.

David

[dave500]

ive never had these heads or blocks decked,ive drawn a file over them,if you deck the head and block or either you can run into cam chain tension problems,you might not be able to tighten it enough?a couple of heat cycles is better for retorque,just over night doesent really do much on a cold motor I think,means you gotta redo tappets etc but so be it.

[dave500]

so long as the machinist whos never even seen one of these old bikes don't skim too much,just tell em to make it minimal at best.

[Bankerdanny]

Fair enough Cal. But I would think that a good machine shop would ask if the customer also wanted the deck surfaces checked and if necessary explain the benefit that comes with the expense.

In talking with Dan about his 400, he said the machine shop never said anything about it one way or the other.