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1975 400/4 project
Sprocket:
So I've popped the engine apart! I've discovered the head gasket was installed upside down, a whole load of gunge in one of the oil restrictors and two of the pistons' rings have broken. But, I consider this a bit of a 'win' as there doesn't appear to be any damage to the pistons, bores, valves etc.
I'm going to take the bits into a local motor engineering company, I called them up today and they said they'd give me some advice if I needed it, but bring the bits in to look at and stroke beards by.
All the pistons have 'Honda written on them, so I would guess they're original and thus I'd be getting the standard sized stuff from DS to replace the rings. Sound logic?
The bores are completely smooth, as you might expect in a 60k mile engine! Am I to expect the engineers to recommend a hone and just replace the broken piston rings, or does anyone think I'm being far too naive?
Nurse Julie:
At 60k, i would be expecting a lot of things to be beyond service limit now. Even if everything looks ok to the eye, everything needs to be measured, including the bores, to see if they are close to or beyond spec. A rebore is most likely at that mileage. Are your Honda pistons / rings standard size or oversize?. I'm assuming if the head gasket has been installed upside down, someone has been in there before.
And don't forget to fit new primary chain when you rebuild the bottom end and cam chain, totally false economy not to. And make sure your local engineering shop know about early Honda engines, the tolerances are very, very tight on these old girls.
Sprocket:
--- Quote from: Nurse Julie on February 11, 2019, 02:44:05 PM ---At 60k, i would be expecting a lot of things to be beyond service limit now. Even if everything looks ok to the eye, everything needs to be measured, including the bores, to see if they are close to or beyond spec. A rebore is most likely at that mileage. Are your Honda pistons / rings standard size or oversize?. I'm assuming if the head gasket has been installed upside down, someone has been in there before.
And don't forget to fit new primary chain when you rebuild the bottom end and cam chain, totally false economy not to. And make sure your local engineering shop know about early Honda engines, the tolerances are very, very tight on these old girls.
--- End quote ---
:) I was hoping you'd reply! I don't even know how to measure pistons to see if they're standard or oversize at the mo, so I expect I'll be leaving it with the engineers for a little while so they can measure stuff and advise. It certainly seemed like they were up for telling me what I needed to get, and letting them do the work I can't. I've previously experienced people getting a little testy when you say you just want them to do that. (Car stuff - "we can't give you a warranty, so don't come crying", etc)
I have used the engineers before for a couple little bits so I have a reasonable expectation they'll know what they're doing. I'm just keen to do as much as I can, and learn along the way. 8)
Nurse Julie:
Yes, it's great to DIY and learn but it can be a costly exercise as well. You will need to take the Haynes Manual with you to the engineers as it has the service limits in. Also, if you found crud in a restrictor jet, you need to strip the complete engine, thoroughly clean all oilways and the main oil gallery as that crud had come from somewhere and was travelling to somewhere else so anything or everything could be blocked or full of sludge.
Sprocket:
Yep, when I noted the positive stopper had broken, I made a mental note it's all coming apart anyway. I've been following the youtube videos and comparing to the book so far, and there's been relatively few show stoppers. Combine those two resources with you lot here and I reckon I'm laughing! :)
Costs wise, I reckoned a rebuild would set me back about £1000 but that wouldn't include any massive surprises. So I think we're still good at this point!
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