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Offline Soos

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Re: My piston project(s).
« on: February 06, 2010, 03:33:49 PM »
Ok, lets try posting this again....



side by side pics of the cb750 and cb750 auto pistons cut as per the "gentlemans express" instructions.
The auto pistons are 0.5mm taller.(and have not had valve pockets cut yet)




l8r
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Offline Soos

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Re: My piston project(s).
« Reply #1 on: February 06, 2010, 03:35:21 PM »
Nor the skirts shortened either.... yet.




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Just think to yourself what would Alowishus Devander Abercrombie do?
"Brix will be shat by your neighbors." - schwebel
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Offline Soos

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Re: My piston project(s).
« Reply #2 on: February 09, 2010, 05:03:42 PM »
Well....


Found out something interesting today.


CB750/650/550 pistons I have seen so far are ALL 0.020(0.5mm) off center for the wrist pin.
HOWEVER, KZ650 and 750 pistons are in the neighborhood of 0.040(1mm) off center!!

I'll do some double checking to be sure...
At least I can make my piston fixtures work for both offsets for a particular OD of piston.





l8r
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Just think to yourself what would Alowishus Devander Abercrombie do?
"Brix will be shat by your neighbors." - schwebel
(61mm)652cc 1979 cb650

Offline Soos

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Re: My piston project(s).
« Reply #3 on: February 10, 2010, 06:52:07 PM »
Pictures, pictures, I know you all want pics...


here you go.

Closest, un-machined high domed 66mm pistons, next machined low domed 66mm pistons, then a stocker 59.8mm cb650 piston, and lastly a KZ650 piston.

Note the dome heights.




Been able to do my lathe work, but the mill has ben tied up the past few days.





Another new mod I will be doing when I get mill time is deepening the valve pockets on the cb750/cb550 modded pistons.
The buyer wants clearance for a .330('ish) lift cam.





And reports on CR's.
Forgot if I have added those lately.

Pinhead firstly, your pistons are about 10.7:1 WITHOUT a base gasket.
And Yes, there IS valve clearances for you if you choose to run without a base gasket.


Next, the 66mm LOW domed KZ750 pistons.
I was thinking they would not have enough dome to give enough CR.
:) I WAS WRONG.
10.6:1
 ;D ;D ;D ;D ;D ;D ;D ;D ;D ;D ;D ;D ;D ;D ;D ;D ;D ;D ;D


That means those high domed ones are looking good for REALLY high CR pistons!!!

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Just think to yourself what would Alowishus Devander Abercrombie do?
"Brix will be shat by your neighbors." - schwebel
(61mm)652cc 1979 cb650

Offline Soos

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Re: My piston project(s).
« Reply #4 on: February 10, 2010, 06:55:55 PM »
Sorry, no reports on the 62mm pistons yet.

I still need to bore out one of the cylinders in the tester block for testing a 62mm piston.
I wonder if a motor with 4 different sized pistons would run? 59.8, 61, 62, 66...
Not long I bet.
haha..


Just giddy from the piston luck :)
Who would have thought a 66mm kz750 piston would be a possible overbore for a cb650?






l8r


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-=≡ Soos ≡=-
Just think to yourself what would Alowishus Devander Abercrombie do?
"Brix will be shat by your neighbors." - schwebel
(61mm)652cc 1979 cb650

Offline Soos

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Re: My piston project(s).
« Reply #5 on: February 12, 2010, 04:41:52 PM »
Well, yet again a good omen for these pistons.

There is ALREADY enough valve clearances.
A good 0.090 for the exhaust valves, and a good 0.120 on the intake valves.
:)

I heated the cylinders to drop one of the sleeves today, on monday I'm going to bore it out, and then install it that night(hopefully!)
I am really, REALLY interested in the KZ650 pistons potential CR!!!
Looks like it will need machined to be in the street riding range.
I might offer those in a kit with bored/honed cyl's, and a head and base gasket.
Found a fairly cost effective replacement ring set as well.

The cb750 and the KZ650 pistons share the same top 2 ring lands.
I keep seeing 1mm over cb750 piston ring sets go on ebay for as cheap as $30 for a set of four.
And the third ring(the 3 piece ring) can be widened to accomodate the cb750 rings.

:)







l8r
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-=≡ Soos ≡=-
Just think to yourself what would Alowishus Devander Abercrombie do?
"Brix will be shat by your neighbors." - schwebel
(61mm)652cc 1979 cb650

Offline MRieck

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Re: My piston project(s).
« Reply #6 on: February 12, 2010, 07:50:09 PM »
 You are doing a great job here. Very nice, methodical work.
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Offline Soos

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Re: My piston project(s).
« Reply #7 on: February 12, 2010, 11:07:34 PM »
 ;D
Just wished I had a cb550 motor to toy with as well...






l8r
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Just think to yourself what would Alowishus Devander Abercrombie do?
"Brix will be shat by your neighbors." - schwebel
(61mm)652cc 1979 cb650

Offline Soos

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Re: My piston project(s).
« Reply #8 on: February 17, 2010, 05:15:19 PM »
Well, not all is well in fantasia today.



I was cutting the exhaust pockets on a set of gentlemens express pistons...
All 4 exhaust valve pockets went fine.... however when I went to do the intake side, that's when the #$%* hit the fan.
I knew immediately when I had done when I saw the cutter careening WAY too close to the ring land.
Forgot to use the correct offset...
You can now see through the valve pocket INTO the top ring land  >:(



So after correcting the error(and doublechecking... twice), I cut the other 3 pistons.


Before tearing the setup off the mill, I got a wild hair and thought that to top off a bad move, I would find out something that MIGHT be able to save my arse.(the piston I fubar'ed is a customers piston!)
Or possibly trash yet another useful piston.

I set up a CB750 Auto piston up in there.
hit go, and stood back.



Well, the dome thickness at the thinnest point is still in the usable range.
0.100 to 0.110.
Gotta love widgets at work.
We have a thickness "caliper" for checking into recesses and cavities of the pump bowls we repair at work, it has deep fingers. Worked great for checking wall thicknesses on these pistons.

(Gotta make me a set one day.
Extremely simple design as well.)




Anyways....
I went ahead and cut the auto pistons all for the intake and exhaust valve pockets, and all is VERY well.
Just hope my customer is willing to accept these pistons in trade.  :-[




Anyone got a single stock cb750 piston to sell/donate?



l8r

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Just think to yourself what would Alowishus Devander Abercrombie do?
"Brix will be shat by your neighbors." - schwebel
(61mm)652cc 1979 cb650

Offline jwl41085

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Re: My piston project(s).
« Reply #9 on: February 17, 2010, 05:33:08 PM »
i have one you can have if you pay shipping
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Offline Soos

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Re: My piston project(s).
« Reply #10 on: February 22, 2010, 06:49:02 PM »
Well, I got the Surface Turbulence pistons and bores back today.



not too bad.
They even blasted the outside of crud. :)








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Just think to yourself what would Alowishus Devander Abercrombie do?
"Brix will be shat by your neighbors." - schwebel
(61mm)652cc 1979 cb650

Offline Pinhead

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Re: Re: My piston project(s).
« Reply #11 on: February 22, 2010, 08:16:39 PM »
I finally got back to an internet connection and I see THIS post. :D 10.7:1 ain't bad. Now I'll just have to figure out how to make sure it won't leak without the gasket. :)
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Offline Soos

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Re: My piston project(s).
« Reply #12 on: February 23, 2010, 03:22:36 AM »
checked the valve clearances on the KZ650 pistons...
SWEET!!!

Runnable. :)
A little trimming needed, I think the cb650 uses a larger intake, or it is in a different position than the KZ650.

Not sure, but a small amount removed(even by hand is easily possible here) , and no more question on clearances.
And they have one helluva CR.



:)
have to post a pic later.





l8r
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-=≡ Soos ≡=-
Just think to yourself what would Alowishus Devander Abercrombie do?
"Brix will be shat by your neighbors." - schwebel
(61mm)652cc 1979 cb650

Offline Kemp

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Re: My piston project(s).
« Reply #13 on: March 01, 2010, 08:24:54 PM »
Need those pictures!! What is compression ratio? You say only moderate piston relief required, is that on both int & exh?
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Offline Soos

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Re: My piston project(s).
« Reply #14 on: March 02, 2010, 05:32:22 PM »
That is with how I did my set.

With a 45 degree tool, I establish the deck height(leaving a land at 60mm)
After that, if you were to flatten out the ridges left by the old valve pockets there, you would get great clearances.

The intake side is nearly located perfectly, the exhaust pretty much is.


My guess, the KZ650 has either a smaller intake valve, or a slightly different position to the valve.





l8r
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Just think to yourself what would Alowishus Devander Abercrombie do?
"Brix will be shat by your neighbors." - schwebel
(61mm)652cc 1979 cb650

Offline Soos

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Re: My piston project(s).
« Reply #15 on: March 02, 2010, 05:33:23 PM »
And the pics are coming soon, I just recently finished doing a complete valve clearance claying to the kz650, kz750, and stock cb650 pistons.


l8r
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Just think to yourself what would Alowishus Devander Abercrombie do?
"Brix will be shat by your neighbors." - schwebel
(61mm)652cc 1979 cb650

Offline Soos

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Re: My piston project(s).
« Reply #16 on: March 07, 2010, 12:48:22 PM »
ARGH!!!!!!!!!!!!!!!


Figured the wife is away on her girls day out, so I would use the camera to get some pics of the finished Gentleman's Express pistons I have finished and ready for a customer.(W/.330 lift valve pockets!)
That and the slay on the KZ pistons from checking valve clearances...


And the camera has a dead battery.... Can't find the charger, and the other battery is dead also...
:(




Soon I'll get some pics, I swear guys!




l8r
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-=≡ Soos ≡=-
Just think to yourself what would Alowishus Devander Abercrombie do?
"Brix will be shat by your neighbors." - schwebel
(61mm)652cc 1979 cb650

Offline Pinhead

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Re: Re: My piston project(s).
« Reply #17 on: March 07, 2010, 05:58:56 PM »
I've got a question for all of you overbore guys... Concerning the head gasket, since the pistons "pop up" out of the cylinders into the chamber, what needs to be done to the "holes" in the head gasket to let the pistons through?
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Offline Soos

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Re: Re: My piston project(s).
« Reply #18 on: March 08, 2010, 05:15:08 PM »
Quote from: Pinhead on March 07, 2010, 05:58:56 PM
I've got a question for all of you overbore guys... Concerning the head gasket, since the pistons "pop up" out of the cylinders into the chamber, what needs to be done to the "holes" in the head gasket to let the pistons through?



Pinhead you are in luck with your overbore.
The stock cb650 head gasket will run 61mm pistons no problem.

:)


As to options(if you want anything thinner or thicker, or a bigger bore) Cometic seems to be the ticket there.



l8r
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Just think to yourself what would Alowishus Devander Abercrombie do?
"Brix will be shat by your neighbors." - schwebel
(61mm)652cc 1979 cb650

Offline Pinhead

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Re: Re: My piston project(s).
« Reply #19 on: March 08, 2010, 10:33:19 PM »
Good deal, one more thing to check off the list! :)
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Doug

Click --> Cheap Regulator/Rectifier for any of Honda's 3-phase charging systems (all SOHC4's).

GM HEI Ignition Conversion

Quote from: TwoTired
By the way, I'm going for the tinfoil pants...so they can't read my private thoughts.
:D
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