Author Topic: Engine Rebuild: What should I do next? (Read 8604 times)

Dave-and-his-550 · « **on:** June 20, 2009, 07:29:10 PM »

I'm rebuilding the top end of my '76 550F due to a leaking gasket. And I've read a few threads on here about what else should be done while you're in there. What needs to be replaced...And I have a few questions of my own. I'll start with an easy one:

I've read those little rubber pucks that cover the bolts that mount the head on should be replaced. Mine are in perfect condition, so is it really needed?

Also, I've read you must replace the piston rings? And have the cylinders honed? Are we talking about the metal rings that sit in the piston, or the rubber o-rings for the cylinder head?

And I'm curious about what whaleman said in this post:

Quote from: WHALEMAN on December 28, 2008, 08:28:26 PM

I think one thing to keep in mind is how much the rings float around the piston. Everything I have read says they do not move around and that is why you space the gaps. We agree the rings have seated at 33000 miles and I hope we can agree that the odds of getting the rings in the exact same positions they all were is zero. We also can agree with the cylinder glazed that the rings will not seat to the cylinder again.

Are the piston rings suppose to sit in a certain manner? Are they suppose to be nice and tight so they don't spin around? All the rings moved freely with a bit of resistance.

754 said this about it:

Quote from: 754 on December 28, 2008, 08:56:01 PM

The key here is cylindrical bore, should not matter where the ring is in it, just stagger on assembly & put the top gap 180 deg from midpoint between ex valve and spark plug..

What does he mean by stagger regarding the two piston rings?

My bike ran good, and had good compression before, so must I mess around with anything else other then just replacing the gaskets?

Here are a few pictures of the pistons; They're still a little dirty around the ends, I'll scrub that off.

To break it down: I'm just looking to know what would be absolutely critical at this stage. Thanks for any help!

1timduke · « **Reply #1 on:** June 20, 2009, 10:43:14 PM »

Hmmm...personally, I'd hone the cylinders, new rings, pucks, and so on. I'd be a real bummer to put it back together and find a cylinder w/ lower compression, or a leaky puck or gasket. A little more wrenching now may save you down the road. On the other hand, I'm sure they're are folks who have been at the same stage as you and not replaced those items and the bike ran fine.

As far as the staggering of the rings quote, the gaps should not be near one another so as to allow combustion gases to escape, resulting in lower compression. The top ring goes in the position he described and the next ring goes 180 degrees off of that (I think...don't worry, someone will correct me if I'm wrong

)

-Tim

HondaMan · « **Reply #2 on:** June 21, 2009, 09:26:11 AM »

Hone the cylinders if you replace the rings.
If you reuse the exisiting rings (less than 20,000 miles on them?), and if the bore has ovalled itself, the gaps will spin until they find the widest radius of the oval shape, and park there. This is what often causes blowby on reused rings: the gaps line up to this wide spot, which then slowly becomes a groove of sorts, and eventually oil and blowby will migrate through the area.

On the performance side: if you bore it even one step oversize, you will pick up 10% HP for your efforts. This is because the metals Honda (almost all engines, actually) uses is uncured when built, and cured after thousands of miles of riding: now the bores are anything but round. Boring restores the round holes and a perfect ring seal results, which will be the first time in that engine.

Honing with a typical hone will not restore the roundness (a large adjustable reamer could), but at least it would make some new rings reseal the bores pretty well. The new rings will then not rotate much, as they will wear themselves into the bore's shape in about 2000 miles or so: you will probably burn a little oil until that happens. You will not regain that initial lost HP, though, with just new rings.

Dave-and-his-550 · « **Reply #3 on:** June 22, 2009, 02:21:15 PM »

Thanks for the information!

So what exactly is 'Honing'? Is it a way of measuring the roundness of the cylinders? If this is the case, why must I replace the rings?

And what exactly is 'Boring'? Makes the cylinders larger and round?

If I had the cylinders bored just one step oversized like you said, will I be able to use the same pistons and gaskets? Would I need to order different sized piston rings? Would I need to do any tweaking of the carbs? Timing? Does it affect any other system components?

So if I have them bored, my cylinders will finally be round, I would get a nice seal between the rings, I wont get any blowby, AND I'll gain 10% HP?

Or, if I use a large adjustable reamer to round up the cylinders, I wont gain any HP, but they'll be round so I will also get a perfect ring seal, and no blowby etc? And would I be able to use the same piston rings?

I'm full of questions regarding the topic

HondaMan · « **Reply #4 on:** June 22, 2009, 04:13:14 PM »

Quote from: Dave-and-his-550 on June 22, 2009, 02:21:15 PM

Thanks for the information!

So what exactly is 'Honing'? Is it a way of measuring the roundness of the cylinders? If this is the case, why must I replace the rings?

And what exactly is 'Boring'? Makes the cylinders larger and round?

If I had the cylinders bored just one step oversized like you said, will I be able to use the same pistons and gaskets? Would I need to order different sized piston rings? Would I need to do any tweaking of the carbs? Timing? Does it affect any other system components?

So if I have them bored, my cylinders will finally be round, I would get a nice seal between the rings, I wont get any blowby, AND I'll gain 10% HP?

Or, if I use a large adjustable reamer to round up the cylinders, I wont gain any HP, but they'll be round so I will also get a perfect ring seal, and no blowby etc? And would I be able to use the same piston rings?

I'm full of questions regarding the topic

Umm...I think that if you're new at this, you probably should not attempt a reamer...

Oversizes: Honda sells oversize pistons and rings in steps of 0.25mm/0.5mm/0.75mm and 1.00mm. You can also choose from a wide variety of oversized piston kits, which I think go all the way up to 650cc (or something like that) for the 550 engine. You then take those pistons and your cylinders to an automotive machine shop (like NAPA or many others) and tell them to bore the cylinders to match your pistons, with .001" clearance for these engines. They do the work, you just have to pay the bill.

Honing is done with a cylinder hone. These can be bought at a typical auto parts store, and a 3" hone would be fine for these engines. You oil up the cylinders and chuck the hone into a drill or drill press, then spin the hone while running it up and down in the cylinder until all of the cylinder is evenly "sanded" from the stones on the hone (typically 1-3 minutes per cylinder). This will restore the roughed-up surface needed to seat the surface of the rings. The rings will later polish it to look like they do now, with a near-perfect seal.

Dave-and-his-550 · « **Reply #5 on:** June 22, 2009, 04:31:41 PM »

Oh cool. So I don't have the money for a rebore, I think honing sounds more like my option. I did a pressure test not to long ago, and I believe I was getting standard readings, but if I got the cylinders honed and got new rings, I assume pressure would go up a bit more, making my engine run even better? If so, then I'll definitely consider doing it, and buying new rings. I imagine honda still sells the rings? Hopefully reasonably priced.

Any special tools needed to remove/put on the rings?

I'll see if I can look up what my engine pressure readings were and post them. Maybe then you can give me an opinion if a honing is truly needed.

clarkjh · « **Reply #6 on:** June 22, 2009, 04:31:58 PM »

I had my 550 bored to 1st over size two years ago or so. The bore, hone, head and cylinders flattened was about $400/$450CND. Now the piston kit at the time was the only one I could find and it was on E-bay, I think it was $250CND by the time I got it. Even if you only hone the cylinders, go with new rings.

James

Dave-and-his-550 · « **Reply #7 on:** June 22, 2009, 04:56:28 PM »

Thanks James.

I'm curious what you guys think of the mating surface of the cylinder block, I got as much residue from the previous gasket off, the surface is pretty smooth, I think whats there is mostly discoloring, if not its a very thin layer of residue. Would it be ok to install new gaskets over this? I absolutley do NOT want oil leaks this time!

Maybe I should just sand down the whole surface with 200-400 grit to bare metal?

clarkjh · « **Reply #8 on:** June 22, 2009, 05:07:42 PM »

With mine, the head and top of the cylinders where warped, so I had to have them flattened. Test yours, or if you are unable to, then a machine shop should be able to do it, shouldn't be too much. I just had the head and cylinders cleaned honed and checked for flatness, as well as the crank checked and polished for my GL1100 and it was only $118CND for it all.

Hope this helps.
James

HondaMan · « **Reply #9 on:** June 23, 2009, 06:46:30 AM »

A razor blade (not a utility knife blade, they are too strong) and some gasket softener, or oil, or lacquer thinner, will usually lift off any remaining residues. A flat grind, one pass on the grinder, costs about $10 here, plus a "setup charge" (which consists of turning the knob to the height you want

on the table) of about $10-$30, depending on where I go. A "setup" of removing, say, .005" from both the cylinders and the head, would then cost about $30-$60. It is not often necessary, unless the engine was leaking oil at this gasket earlier. The grinding pass will also remove all of the residue, so some builders just do that as a matter of course. It raises the compression ratio slightly, too, which isn't a bad thing for performance.

Dave-and-his-550 · « **Reply #10 on:** June 23, 2009, 03:17:10 PM »

Ya, I did have a slight leak between the block and the head...When I pulled them though, the gasket was in shambles. I took a flat metal ruler and put it upright along the block and head, wasn't a gap anywhere, so I don't think anything is warped.

I did use denatured alcohol on the remaining residue and it came off great

If only I wouldn't fret over the little remaining paint still on them...I would probably have them repainted by now

Dave-and-his-550 · « **Reply #11 on:** June 29, 2009, 02:42:03 PM »

Quote from: HondaMan on June 21, 2009, 09:26:11 AM

Hone the cylinders if you replace the rings.
If you reuse the exisiting rings (less than 20,000 miles on them?), and if the bore has ovalled itself, the gaps will spin until they find the widest radius of the oval shape, and park there. This is what often causes blowby on reused rings: the gaps line up to this wide spot, which then slowly becomes a groove of sorts, and eventually oil and blowby will migrate through the area.

The bike has 24,000 miles. I have noticed my #4 intake boot making popping noises, and oil leaking from it towards the carbs...I guess this is a sign of this blowby you're talking about?

Each piston ring set is $36.95 I was told. I seem to remember a website that sold genuine honda parts pretty cheap but I can't remember it, anybody know?

Should I have the cylinders checked for roundness? I can't see why if there is really no fix other then boring it, I guess it would help to know though.

One more question about honing. If I get it done, and replace the rings with new ones, they'll seal much better, this I know. But how many miles can I expect out of the machine until they start to wear again, and begin to move in the cylinder, causing the loss of compression and blowby?

OldSchool_IsCool · « **Reply #12 on:** June 29, 2009, 03:01:17 PM »

When I overhauled my top-end this winter ('77 550K), I took the cylinders to a local mechanic and had him hone and measure the bores. He has the tools and the knowledge and only charged me $30. I didn't order rings until I got the measurements back in case they were out of spec for STD rings. since I was also changing my cam chain and didn't want to split my cases, I also had him break the old chain, feed on a new and rivet it back up for me. If it werent for the soft link being a slightly different color, I wouldn't be able to tell which rivets were machined and which were his!

Dave-and-his-550 · « **Reply #13 on:** July 01, 2009, 02:07:47 PM »

Ya, I was just talking to a parts guy about the standard ring sets, and the next size up. I'll talk to my machinist tomorrow and ask him just how much he'll be taking out, or maybe he can give me a measurement.

If I do need the .25 ring set (The next size up from standard) will I need to replace the pistons also? Or can I stick with the standard pistons that are in there and just install the larger ring set over it?

clarkjh · « **Reply #14 on:** July 01, 2009, 02:38:30 PM »

You will need the oversize pistons to fit oversize rings.

James

Dave-and-his-550 · « **Reply #15 on:** July 01, 2009, 03:08:22 PM »

Well, I don't want to spend the money for new pistons, so I guess I'll have to tell him not to hone them, unless he can do it in a way that'll keep it in spec for standard rings/pistons.

razor02097 · « **Reply #16 on:** July 01, 2009, 03:25:46 PM »

Well since you have the jugs off already its best to replace the rings and hone the cylinders but first you need to determine if your pistons will work or if you need to bore 1 size.

Easiest thing to do is to pick up a good shop manual for the bike to get all the measurements cause you will need to find what the ring gap sould be and such.

link below explains blowby...
http://www.misterfixit.com/blow-by.htm

Oh and staggering the rings means to stagger the ring gaps I.E. they should not line up you put one to the right and the other to the left. In two strokes they actually have locating pins on 2 ring model pistons like this...

that is a 2 stoke piston there is no oil rings on your 4 stroke piston the oil control ring would be below the compression rings.

Dave-and-his-550 · « **Reply #17 on:** July 02, 2009, 09:11:25 AM »

I was reading through the parts manual regarding installing the cylinder block over new pistons and rings, and they mentioned two specialty tools that are needed:

-Piston ring compressor
-Piston base.

Now, I don't know HOW necessary they are...But I am in that situation where I will have to install the head over the pistons soon. The shop manual said to use the piston base to rest the wo pistons on while you have the piston ring compressor to compress the rings down so you can slide them and the piston into the cylinders...

Should I try and order these parts? Should I try at the local auto parts store for a universal type piston ring compressor? Or can I just do the above steps with an extra hand?

razor02097 · « **Reply #18 on:** July 02, 2009, 10:47:43 AM »

Quote from: Dave-and-his-550 on July 02, 2009, 09:11:25 AM

I was reading through the parts manual regarding installing the cylinder block over new pistons and rings, and they mentioned two specialty tools that are needed:

-Piston ring compressor
-Piston base.

Now, I don't know HOW necessary they are...But I am in that situation where I will have to install the head over the pistons soon. The shop manual said to use the piston base to rest the wo pistons on while you have the piston ring compressor to compress the rings down so you can slide them and the piston into the cylinders...

Should I try and order these parts? Should I try at the local auto parts store for a universal type piston ring compressor? Or can I just do the above steps with an extra hand?

Both tools would make installing the jugs much easier. Make sure if you do get a ring compressor that you get one that will separate so you can get them off the rods. It is possible to do the job with neither tool but it would be more difficult. Plus the rings are sharp and will cut skin easy.

OldSchool_IsCool · « **Reply #19 on:** July 02, 2009, 12:49:03 PM »

I used hose clamps for ring compressors and square tubing for piston bottoms. The idea with the piston bottoms is you want the pistons to be held firm and square as the cylinder block slides down. Allowing the pistons to rock back and forth on the wrist pin is a good way to snap a ring.

the bottoms of the bores on the 550's is beveled which makes the rings slide in easier. But the bevels also make the bore bottoms sharper so do take care!

Dave-and-his-550 · « **Reply #20 on:** July 02, 2009, 02:31:50 PM »

Thanks guys. Now if I can just pry off that right side case cover, and get it polished up, i'll be happy camper. I know when I get it off, that gasket is gonna be torn up pretty bad...

razor02097 · « **Reply #21 on:** July 02, 2009, 07:23:39 PM »

If you don't already have one... get a rubber mallet. It will save you headachs and damage to engine covers.

Dave-and-his-550 · « **Reply #22 on:** July 02, 2009, 08:59:55 PM »

Got one. Either I need a BIGGER rubber mallet, or larger muscles.

razor02097 · « **Reply #23 on:** July 03, 2009, 04:47:28 AM »

penetrating oil helps also. If the covers are painted though you will need to repaint them

OldSchool_IsCool · « **Reply #24 on:** July 03, 2009, 05:01:40 AM »

Check a parts fiche, then inventory the bolts you took out just to make sure you got them all.

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Author Topic: Engine Rebuild: What should I do next? (Read 8604 times)