Topic: Seized 550 Engine

[Smudgemo]

I couldn't find what I was looking for, so new thread.  I have a '74 or '75 550 engine that is seized up.  Got it a few years ago off CL and not sure what the background was, but the guy clipped the cam chain trying to do something so I'm going to dig into things by splitting the cases.  I want to do a thorough check for debris and so I can install a new endless chain.  The bolt on the rotor is already loose, the head is off, but it won't turn with hand pressure.  I don't have any sort of stand at the moment, but could build one (and probably will shortly.)

I suppose I could rig up some sort of strap wrench for the rotor to try and work it back/forth, but I'm thinking instead of breaking the cases to disconnect the connecting rods so the jugs/pistons come free and I can see about pushing the pistons out 1x1 and not potentially damage anything else.

I got this engine I wanna say a few years ago and there's red oil in 3/4 of the bores from when I stuck it in storage.  I don't recall if it's ATF or Marvel, but one seems to have drained so I assume it's not stuck and the others potentially are.  So it has been sitting with oil before anyone says that's step 1.

Thoughts?  Suggestions?  I can't think of any reason I can't disassemble it this way, but I've never rebuilt a 550 before and don't really want to learn the hard way. 

[bryanj]

Cant remember if the big ends will come out of the top case but i know the pistons will not go down through but your idea is about the best possible.
Remember to note where each half shell goes when you take them out as there is no way of id ing them when mixed in a bag

[Smudgemo]

I started stripping it down and it looks like most of the bolts are gone from the lower case, cam chain is cut and the #2 or #3 (forgot which) exhaust valve is stuck open.  However, the gears all look unharmed, they spin freely, and the shifting appears to work smoothly.  The remaining oil was pretty black, but the bottom of the oil pan wasn't too badly gunked up.

Wrapping up day 1, I propped up the front to level the pistons and dropped in some PB Blaster to see what happens.  Seems like one cylinder might be draining, not sure about the others.  Just for giggles, I'm going to make a lever tool that will fit the slots of the rotor so I can give it a little bit of gentle persuasion before I split the cases.  I tried the bolt holding the rotor a bit, but that wasn't promising.

Good call bryanj, definitely planning to document bearings and their locations.

[calj737]

I had a 500 engine that had stuck pistons. After removing the head, I filled each cylinder with kerosene and lit them afire. Had to fill them a few times as piston height limited how much fluid could be poured in. After a good 45’ of playing CB BBQ, I was finally able to get the pistons to rotate, but the stuck pistons began to push up the cylinders while letting the others slide down.

A bit of trickery and more heat, and finally got the whole thing apart. Heat, patience, and hatred are your friend. Force, not so much.

[newday777]

I had a 500 engine that had stuck pistons. After removing the head, I filled each cylinder with kerosene and lit them afire. Had to fill them a few times as piston height limited how much fluid could be poured in. After a good 45’ of playing CB BBQ, I was finally able to get the pistons to rotate, but the stuck pistons began to push up the cylinders while letting the others slide down.

A bit of trickery and more heat, and finally got the whole thing apart. Heat, patience, and hatred are your friend. Force, not so much.

I didn't know of the fire route 9 years ago (a couple years before finding this forum!) when my trying to disassemble my dad's K6 750, mice pee had frozen the rings to the cylinders. I had used MMO and PB Blaster penetrating oil to try to free the rings to no avail, ended up cutting a 2x4 ripped to fit in the cylinders and beat on the pistons until they freed up. I still haven't gotten funds to build the motor into a 900+ big bore. I'll be going through the bottom end too and replacing what all needs done in there.

[Smudgemo]

This one is stuck pretty good, three cylinders it appears as they don't drain.  I grabbed the O/A torch set up with LP and a fat, soft flame to heat things up this afternoon.  The tool I made worked okay to safely grab the rotor and not cause damage, but the rotor started moving so that's not going to break things free just yet. 

This evening I hit it again with heat but I used a heat gun this time.  I'm not sure if the PB Blaster is soaking in or cooking off, but I left it to soak again and will have a better idea tomorrow.  I guess I'd like to take every opportunity to pull the jugs before splitting the cases, and it's not like I'm in a rush.

[Smudgemo]

I guess I can end this thread with a yay-me!  I heated the jugs a number of times  with soaks between of PB Blaster, and grabbed some scrap steel to braze a simple wrench to turn the rotor without damaging it too much.  It worked well enough that the #2 piston came loose, so now 2/3 were moving, but 1/4 were not. 

But that movement also lifted the jugs out of the case, so one less thing stuck.  After some heat cycles I finally got #1 moving a little, but #4 was steadfast in its refusal to budge.  I didn't like applying all the torque to the rotor side, so I grabbed some more scrap and fashioned up a driver with a bit of drill rod for the points side that wouldn't damage the threads.  I don't have a way to hold this size in a hex block for milling and I wasn't planning to go gorilla on it, so I just set it vertically and took off four sides for use with a 19mm open-end wrench.

I finally got a little movement and from there it was just a matter of time working 1 and 4 out of the bore.  There is some corrosion in one or two of the cylinders, but I'm not sure yet whether boring will be required so I'll let next-week me worry about cleanup and measurements.  The crank turns as smooth as can be, and the gears all look a feel good.  The only problem I found was the stuck exhaust valve, and maybe that's what took it off the road only to sit and seize up.  I wish the guy I got it from didn't cut the cam chain, but whatever, it was free.

[RAFster122s]

Isn't their a cheap Kawa chain that is high quality and better cam chain? Seem to remember something like that...
The 550 doesn't have as many options as many more shops cater to the 750 and the 550 just piggybacks along on some stuff...

[calj737]

Expect a rebore if the pistons were that stuck.

[bryanj]

The kawa chain is for the primary not the cam

[Smudgemo]

Expect a rebore if the pistons were that stuck.

I kinda went into this thinking it was likely.  I found a bag of case bolts in the attic that I got with the engine, so I could possibly buy a master link for the cam chain as someone just clipped the side plates.  I'm less concerned about debris getting in the lower end, but I also found a nut down there from the head so I'd need to be careful. 

It also looks like the cases were never actually separated, but I'm not sure how to verify that.  Suggestions would be appreciated.  Maybe I can skip the bottom and just do a top-end rebuild.  So far everything down low looks and feels great, and I keep thinking of my dad's advice of not fixing things that ain't broke.

[PeWe]

If bores have rust, it can be rather deep.
I had a stock CB750 stock cylinder with some rust in 2-3. Thought that +0.50 pistons should be enough. Almost 0.25mm to remove.
Hell no, there were pitting in bores. Pistons were bought, so replaced the sleeves. Bought 2 old from a friend.

The shop replaced the 2 sleeves and rebored and honed. Nice guy that did not charge much extra. He had made some jobs for me.

If I knew I should have ordered the next size of pistons. Cheap Cruzinimage, +1.0mm.

[Stev-o]

Expect a rebore if the pistons were that stuck.

Maybe I can skip the bottom and just do a top-end rebuild. 

Pull the oil pan and see what she looks like.  The bottom ends of there Hondas are nearly bulletproof...

[calj737]

Expect a rebore if the pistons were that stuck.

Maybe I can skip the bottom and just do a top-end rebuild. 

Pull the oil pan and see what she looks like.  The bottom ends of there Hondas are nearly bulletproof...

Yup, pulling the pan exposes it’s tonsils…

[HondaMan]

The only way I know 'for sure' to detect if the lower cases were opened before is: open the cases and look for the fully-silkscreened layout of the Hondabond (-like) sealant used to seal them. If every single parting surface has teh light-grey bond on it, that was factory. It also didn't 'drool' much toward the upper case, as they applied it with the silkscreen, let it 'flash off' the solvent (with fans nearby) and then closed the cases, so it was very even everywhere. Most of us aren't that careful, nor have a silkscreener.

[bryanj]

If its very rusty Honda go up to 1mm oversize and i have had a lot that did not clean at 0.5mm.
Cruzinimage do a "kit" that takes it out by 3mm and yes they will take it, 600cc ish i believe but dont expect cheap machining as that is about 12 passes of the bar for each hole!

[Smudgemo]

The pan is off, and everything looks and feels great.  I'll do a closer eval on the bonding of the cases now that I have an idea what to look for.

I'll also see what some careful cleaning of the cylinders reveals.  So far I didn't notice pitting, just residual corrosion that hopefully isn't hiding pits as I'd prefer to go .25 over if I have to do a bore.  It's fast enough for a nearly 50 YO bike.

[Smudgemo]

The case sealer looks more black than gray, but nothing looks obvious as having been apart.  I also forgot that the shift mechanisms are still in place as was the clutch before I removed it.  I don't think a guy who'd cut the cam chain and leave everything in the state I got it would have made any effort to put all of that back together and still leave out most of the case bolts, but I'll keep checking when I have more time.

I'll need someone with some experience to decide how big to bore things, but the pistons are Honda and measure 2.303" on my imperial mic, so it appears they are stock size.  That'll hopefully give me plenty of room because there is some rust on the #2 cylinder as 2/3 were stuck low.  Doesn't look that bad, but what do I know?

Next question is where to send the cylinders for boring.  I'd rather ship than drive very far, and I'd like it be someone with the right experience.

[Stev-o]

I'll need someone with some experience to decide how big to bore things.

Next question is where to send the cylinders for boring. 

I always let my machinist measure the cylinders and order proper size pistons [if needed].

Your in California, right? Don may have a contact for you.

[Smudgemo]

I always let my machinist measure the cylinders and order proper size pistons [if needed].

Your in California, right? Don may have a contact for you.

Yeah, near SF but I hate driving so shipping is fine by me. 
That's what I'm thinking, let the machinist bore until the surfaces are clean, and then stop at the next available piston size.  No need to go any further.  I just don't want to be forced to interview a shop and would rather hire a proven outfit.

[calj737]

If you are up for shipping it, ship it to Stuart Hyder at Ballos Machine in Richmond, VA. Outstanding results for very reasonable prices. Decades of experience.

[HondaMan]

I have them done locally, too, at Ridge Reamer in Arvada, CO. I 'trained' them years ago, and they have been faithful to do my parts right (and others who brought their Honda parts to them, by inference).

[Smudgemo]

Thanks, fellas.  Maybe this work isn't difficult for a competent shop, but I like knowing a place is familiar with it and has a record of doing good work. 

I'm presently scrubbing off the years of oil/dirt that should have been removed prior to disassembly, but I guess not everyone thinks that far ahead.  I still need about three bolts for the cases to torque them up and be sure all is still smooth, then I can start taking apart the head and looking for damage.  One valve for sure has issues.