Topic: FFJMOORE CB550 BIG bore engine build.

[Flying J]

Well after spending the entire day measuring, checking, swapping pistons around and measuring some more i have found almost nothing conclusive. I was trying to figure out if the cylinder is not flat. By moving the same piston from hole to hole and checking the deck height I thought the cylinder was sloped from one side to the other by about .010. but using my calipers im not sure it is. I think im going to take it to a machine shop and have them check it out.
I did measure the thickness from the top ring gap and the top of the piston. There was a differance of .010 from one side to the other. That looks so small on the calipers but i guess its a pretty big deal. So for sure the pistons are a little out of whack. I feel like i would be ok running these pistons with no detriment to the motor but Im not satisfied with the quality for this particular build. I think i will save these pistons for a different rebuild that i dont care so much about. So ill have to talk to dynoman about his piston.

Couple of questions
1) What are the possabilites causing the piston height problems? So far possibilities are Pistons & cylinder. Any other thing i should scrutinize?
2) if im going with the dynoman pistons and a cb650 cam should i get the KPMI valve springs and titanium retainers?

[LesterPiglet]

Sorry for your rough luck ffJ. It should be obvious even looking by eye at the sleeve base thickness or flange top if it was bored out of square.

You can see a 1 or 2 thou difference with your eye?

[bwaller]

Sorry for your rough luck ffJ. It should be obvious even looking by eye at the sleeve base thickness or flange top if it was bored out of square.

You can see a 1 or 2 thou difference with your eye?

Why...you can't?  I suppose it sounds off base alright, but I was thinking about that piston picture and the difference side to side.

[RAFster122s]

Sorry for your rough luck ffJ. It should be obvious even looking by eye at the sleeve base thickness or flange top if it was bored out of square.

You can see a 1 or 2 thou difference with your eye?

Why...you can't?  I suppose it sounds off base alright, but I was thinking about that piston picture and the difference side to side.

What? Your Mark 1 eyeball needs calibrated, Son?

Seriously when i was between jobs i worked in an electronics remanufacter of CRT and LCD monitors for a big name...well i ended up in QC after time on the line and i could detect variations of .001 in vertical lines and usually equal in horizontal.  I had to let lots of stuff through that i could see had a tilt that wasnt adjustable and was within specification. I was tougher on the line than the head QC who ran sampling on my 100% check after they came off the line.
So it is measurable and detectible for the eye to see variations that are very very small.

[Flying J]

Very cool. Well have a look at some of the pictures i posted and let me know if you see anything wrong. 

[Flying J]

I should have never got it in my head that i was building a big bore for this bike!    Now i cant go back and Im going to have to drop some serious coin to stick with the plan. On the list to buy now is 61mm dynoman pistons, web cam 358b, adjustable cam gear, race valve springs, barnett clutch kit, and a dyna 2000 with mini coils. HOLY CRAP! Im never getting my money out of this bike. I keep telling my self that its just money and you cant take it with you.

[dave500]

yeah it can be a bummer,,depending how you look at it,plan A often becomes plan B once you overbore past the factory offered oversizes,youll be keeping this bike forever anyway?itll be so much better once its all dialled in and your riding though.

[ivanhoew]

could the pistons be lathed down to give the .021 clearance across the board, fairly cheaply ?

[Flying J]

 i don't want to sink any more money into these pistons.  if you would like to mess with them id sell them for the cost of the ring set.

[Gman]

FFJ,
    Just wandered onto your thread and didn't read all the way through it, so please excuse if this is NOT helpful.  BUT, I saw you're building a big bore and there seems to be some issues and things you still need to buy.  I came across this ad from my local CL that has some of the same things you mentioned - here's the gist of it.  Might be worth looking at??  He was asking $700.  I can send you the link, or if you go to Mpls CL and search 'action honda' or similar, it will pop up.  Good luck regardless!
Cheers,
G

'Action Fours' Stage 2 Street/Strip 12.5-1 compression 590cc Big Bore Kit out of a '75 CB550 Super Sport up for sale. The kit was removed from an engine with 7000 documented miles, complete with original receipts for the installation/machine work from back in '77 at McNamera Cycle Sales in Saint Paul, MN. The kit is complete and includes re-sleeved and freshly honed 61mm cylinders, 12.5:1 polished and relief-cut ART domed pistons with wrist pins, rings (one piece oil control), Stage 2 K&H cam, Titanium valve retainers/keepers and racing valve springs, all loaded in the head, (which is included in the sale, along with the required post '76 pinned rocker arm cam cover) ***There was absolutely nothing wrong with the engine at the time of dis-assembly. All numbers mic'd to the high end of spec, IE: No Measurable Wear. It had 170-plus psi across the board, with less than 5% leak-down on each hole, done with a 100psi test*** This top end kit is a straight forward 'plug-and-play' swap, just supply the top end gasket set and you're good to go.

[Flying J]

Very cool. I did already order all the parts i will be needing. That set up, to me, is not worth $700. For 1 its used. also those one piece oil rings are said to be total crap, so you would want to machine all the pistons to accept 3 piece rings. I also dont want to be running 12.5:1. you can buy a pretty decent setup from dynoman. He has kits from $900-$1500. But unlike buying from dynoman you could point out some of the problems and talk him down a couple hundred. I kinda gave up on finding cheap parts for a  high performance motor and bit the bullet and bought the real stuff. I had a stash of cash from my last bike sale that i was holding onto to buy a triumph. OH well.

So my pistons and other goodies should be in on Monday. Ill post pictures.

[Flying J]

Well I took the cylinder to a motorcycle shop. It was closed for a while cause the guy was in jail i guess. But he is back now and know how to build bikes. He checked the cylinders and said they are off .005 from one side to the other. I also brought in my new pistons and he said just using a gap gauge that they were .004 bigger bore then the piston already. These need .0028. So Im going to try and find a new cylinder to start fresh. So the last cylinder is a $400 paper weight. 

[Greggo]

So the last cylinder is a $400 paper weight. 

I'm seriously bummed for you man.  Is that one of the Dynoman pistons??  It looks nice!!

[lucky]

First off here is a list of parts I will need or possibly need for the rebuild. Am i missing anything?

Pistons
Rings
Head gasket
Base gasket
Engine gaskets
Oil seals
clutch
Clutch springs
HD cylinder studs
Camcahin
Cam chain tensioner
Crank bearings
Rod bearings
Cylider bore
Valve Job
Primary Chain

A can of Gaskacinch for the cases and other gaskets.

[Flying J]

does anybody else think gaskasinch is a good idea?

[fastbroshi]

  I think it's good for head/intake gaskets, don't think I'd use it in place of Hondabond though.  Come to think of it, I don't know what Honda used for stock head/intake gaskets but it's always a bear taking off the originals.  I think the Gaskacinch can help here, I think it keeps the gaskets from ever really bonding with the metal and tearing upon disassembly.

[Flying J]

So does anybody have a set of cylinders they want to sell? Local junk yard wants $75 if they have em. 

[Raef]

are we talking 550 jugs? if so, I think I have a set you can have for shipping and packing, not sure if that will save you much $$ though, coming from Indiana. 47383

Mark

[Flying J]

Thanks to Raef for a nice price on a set of cylinders. Had them bored out , checked the height and now they are back at the machine shop being decked. Should have them back home in a few days.

[Tintop]

Sounds like things have started to move in the right direction again. Those Dynoman pistons look very nice.

[Flying J]

OK, so the cylinders are decked. Pistons came in level to .004 below. Im happy with that. The machinist (my new one) said that when he set the cylinders in the mill and cranked it down he found that the cylinders flex a little bit. This explains a lot of the issues I had with the previous set of cylinders. To keep it level he said he had to back off a hair and it was fine. So i may have the old cylinders for the 750 pistons decked again and run them on a different motor.

So now I need to assemble the top end to check for valve clearance issues. I also picked up a NOS cam chain slipper tensioner. Mine was cracked. They are not cheap.

10772

[SF]

glad to see your still at it, lookin good man

[Flying J]

A member on another forum suggested to

"counter-bore oil feeds in block and head and fit hollow dowels, then use slightly larger diameter 'o' ring.It cures all the oil leak problems when 'o' rings get hard"

Has anybody done this or have any reason why it would be a bad idea?

[dave500]

i chamfer the oil hole feeding into the head only.

[crazypj]

Just skimmed through the entire thing, will check it out properly later.
Jeeze, don't think I've ever seen anyone have so many problems with various things and be so calm about it
Kudos for your patience