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I F’d up! 🤬(cylinder o-rings)

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breakbeatz69

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So I finally, for the second time, reassembled the jugs, cylinder head/valve train, and valve cover. The first time I reassembled it I caught myself after I put on the cylinder head/valves back on that I forgot the front cam chain guide that goes down to the crank. So I took it ALL APART, got the chain guide in, and now I’ve reassembled everything including the valve cover. When I did all that, I also injected 10w40 oil into the cam reservoirs like they say to do when you reassemble the engine so there’s oil in the top end by the cams when you first start the engine again.

Recently I’ve been knocking out the electrical (which is always a pain in the ass) I’ve almost finished the new wiring loom for the new electronic ignition and PMA system.

As I’m walking through my shop today, I see the rebuild gasket kit I have and see these big o-rings sitting there. Yup, you guessed it, after fighting with the pistons and rings getting them into the cylinders right, and taking the top end apart twice, I REALIZED I NEVER PUT IN THOSE STUPID O-RINGS THAT GO ON THE BOTTOM OF THE JUGS!!🤬
These ones…..
IMG_6257.jpeg

Now I always use copper coat on all my gaskets on both sides which leaves a tacky film that seals the gaskets to the mating surfaces.

My question is, I know some of these models didn’t have those cylinder o-rings (I think they didn’t anyways?) and I’m absolutely DREADING tearing this engine down for a third time because I fucked up again to put in these o-rings. Considering I used copper coat on all my gaskets, are the O-rings really necessary??? I mean, the jugs are sealed to the crankcase with the main gasket and copper coat so what is the chances I can leave these o-rings off?

I’m so pissed off right now I could punch a baby…in the throat. I’m just irritated I fucked up again and this engine rebuild has given me nothing but problems and I really don’t want to remove the pistons from the jugs again but, if I have to, I’ll grit my fucking teeth and do it I guess. I just can’t believe I forgot those o-rings considering I worked hard on getting the old ones out and prepped the jugs so they were ready for the new ones.

Please, someone help. Thanks in advance.
 
You would be best to slow down a little and don't rush. Start over. Yes you need them. Also you have compressed that base gasket twice so I would recommend you replace it too. Go easy on the silicone too.
 
Honestly, I take my time and don’t rush. This engine is just new to me and has components on it I’m not used to on other engines. And I don’t use silicone on the gaskets except on the valve cover gasket on the few places it specifies. I use copper coating which is just a tacky gasket coating for paper gaskets and nothing more. You really think I need to replace the gaskets? I mean they’ve been compressed but are brand new and again, I use copper coat that fills in any irregularities and mates the surfaces nice. And I really need those o-rings huh? I’m assuming my compression will suffer without them or something or are they just o-rings to keep oil out?
 
Ok. Damn it. I just took the valve cover off and I’m going for round 3 I guess. It just makes me mad that I had a bitch of a time cleaning those old o-rings out and you would think that would be enough of a reminder to put the new ones in. I’m just irritated but at this point I’ve taken it down to the crank case so many times that I’ll at least be quick with the disassembly and reassembly. Who knows, maybe I’ll find my piston rings out of position and this will give me a chance to fix them. (Me trying to be optimistic)
 
As far as new gaskets, you really think I need them and can’t reuse the new ones I just put in? That’s just another $70 for the base and head gaskets that I’d rather not spend if I don’t absolutely need to.
 
I feel for ya, man. Take deep breath. It will be done soon!
Yeah I know, it’s just like a “fuck me” moment when I saw those o-rings sitting there. Like I KNEW I had to replace those o-rings and I still forgot and it’s just frustrating thinking you’re finally DONE with the engine only to see that shit laying there looking at me like, “you fucking idiot, remember us???”
 
I’m just going to order new gaskets because that copper coat is sometimes too tacky and it’ll tear the gaskets when you peel the head and jug base apart. So I’m not taking any chances and I’m just going to eat the cost of more new gaskets. I’m just so mad at myself. 🤦‍♂️
 
So just an update, everything did happen for a reason. So I took the engine apart again and when I pulled the cylinders off of the pistons, low and behold one of the oil scraper rings (the bottom one) on my number 2 cylinder had came out of the groove at the gap (about a 1/4” of it) and it was folded smashed between the piston skirt and cylinder wall. Luckily it barely did any damage to the cylinder sleeve so I re-honed that cylinder to be safe, put a new oil ring on the piston, and installed those cylinder sleeve base o-rings. Talk about a lucky thing that I forgot those fucking o-rings and didn’t start the engine like that.
 
Like I said, slow down a little. Mistakes are happening.
In my defense, the mistake with the ring was more of a cylinder lube issue when sliding on the jugs and not using the proper tools than a rushing issue. I decided against my better judgment to try this Total Seal Quick Seat which is a “dry” assembly lube for the first time and it worked like shit. This time I went back to my old tried and true Lubriplate No. 105 assembly grease and the jugs slid right on over the rings. This time I also used the actual Honda piston ring compressor tools specified in the original CB750 service manual to compress the rings into the cylinders instead of my fingers and popsicle sticks. The jugs went on great now. Then I had a compression issue on cylinder one with everything timed perfectly. So I smoke tested the cylinder through the spark plug hole and found I had an exhaust valve leaking a little bit. I exercised those valves a little and my compression issue went away. I think a piece of debris or something was caught in one of the cylinder 1 exhaust valve seats holding it open a little and stealing my compression.
 
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Glad you found that! Is she put back together now?
I know right. I really got lucky that I forgot those o-rings.

And almost. I just have to put the valve cover back on and then the engine should be all buttoned up.

In the meantime I sorted out all the new electrical and re-did the wiring harness for how I need it. I got the new electronic ignition system installed with a control module that allows me to advance or retard the timing on the fly (also has a rev limiter feature) and got that statically timed. Then I got the Permanent Magnet Alternator on with a reg/rec to run a small lithium ion battery.

My hardtail supplies should be coming this week hopefully. Once I get that fabricated and welded to the front section of the original frame, I’ll be in business to put the engine back in and then I’ll be finishing up the wiring harness once I figure out where I want to mount everything.

All in all I’ve had a couple hiccups, but nothing major and every chopper/bobber I’ve ever built, whether it be a sportster or xs650, there’s always some hiccups along the way. It’s all just part of bike building.
 
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That is not a good thing to use on piston rings.
I’ve been using that for years on motorcycles and never had a problem. It’s also used pretty widely on cars as well. You seem to know some stuff about motorcycles, myself as well. I’m curious why you say that? Is it just you’re stuck in your ways, same as me? Or is there actually a good reason why it shouldn’t be used on rings? Because I know a ton of lifelong mechanics that would absolutely disagree with that statement. It’s a light assembly “grease”. It’s not slimy stringy assembly lube.
 
It sounds to me that you need to start hanging around with better mechanics. I wouldn't use that crap to lube the hinges of my house, let alone an engine. I have built many hundreds of engines over my time. I'm retired now but still do a couple of dozen engines a year. And I don't mean motorcycles. I have engines that have raced from Daytona to the Nurburgring so I know a little about building an engine. For me motorcycles have been a hobby since I was a kid. I always liked the CB750 bikes and that is why I hang around here, hoping to help others. So if you think I'm stuck in my ways at least I have the credentials to back it up. It is clear to me you don't know what the hell you are doing so please don't pass your experience on to others.
 
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