Topic: Help with K0 motor assessment

[Ujeni]

What is the compression like? It its less than great, then now is the time to do a top end. I hate taking engines in and out of these frames, so I tend to do everything in one go instead of needing to take it back out again in a year.

If your compression is good, then I would replace the head gasket and pucks.

[WideAWAKE]

I did test compression when I had it in the bike

Don’t remember the numbers off the top of my head, but they were all within a few pounds.

When kicking it over compression “felt good”.

No reason to think it’s an issue, if I did, I’d just take it apart now.

[WideAWAKE]

Did a little cleaning,

Anyone know what this stamp is ??

Maybe a line bore ID of some sort?? To keep the bottom and top half together? I didn’t see another stamp but I also didn’t look too hard.

[MauiK3]

Pretty dirty.

[WideAWAKE]

Haha!!!

Pic was taken while cleaning when I found the stamp, not once I was done cleaning.

 I’m still not done cleaning, just looking to gain some info on the case stamp.

[Ujeni]

If your compression is indeed good, then I still think you have strong evidence of pucks leaking and maybe a head gasket leak. I would do both.

Personally, I would double check the compression. "Feels good" might be way below Honda's 170 lbs spec! I only bring this up again to save you from needing to pull the engine out again in the near future.

[WideAWAKE]

Pucks seems to be a need so those will get done along with anything else that needs doing while it’s open.

And note taken : I’ll double check the compression to get some actual numbers.

[PeWe]

You will regret if not lifting the head when engine is out.
I should lift cylinder too replacing cam chan tensioner, Honda stock, no afternarket.

Open the cases and replace primary chain tensioner too.
The rubber tensioners can be hard as bakelite falling into small pieces found in oil pan.

[WideAWAKE]

I should hopefully have room cleared to open it up in the next week or so.

I’ll be sure to take pictures and ask questions along the way. I don’t have a problem pulling it apart if need be.

[HondaMan]

If you remove the head, PM me for some O-rings to seal the oil ports in the head gasket, or else it WILL leak after reassembly.

Those stamp marks: those are characteristic of the early engines, especially the K0 types and into the K1 era. They seem to be inspector's initials and/or datecodes, and there isn't much rhyme nor reason to them. They show up all over, even inside the engines. The heads often have them in the center, on the top fin, on either the front or back of the head where the rider can't see them unless the engine is out. They are also found inside the oiled areas, like next to a valve guide or in the bottom end. I suspect they were indicating that 'someone' found a defect somewhere during inspection and fixed it.

[newday777]

If you remove the head, PM me for some O-rings to seal the oil ports in the head gasket, or else it WILL leak after reassembly.

Are the o-rings the same on up to K6? I have a couple motors I'm working on. K5 and a K6.

[WideAWAKE]

If you remove the head, PM me for some O-rings to seal the oil ports in the head gasket, or else it WILL leak after reassembly.

Those stamp marks: those are characteristic of the early engines, especially the K0 types and into the K1 era. They seem to be inspector's initials and/or datecodes, and there isn't much rhyme nor reason to them. They show up all over, even inside the engines. The heads often have them in the center, on the top fin, on either the front or back of the head where the rider can't see them unless the engine is out. They are also found inside the oiled areas, like next to a valve guide or in the bottom end. I suspect they were indicating that 'someone' found a defect somewhere during inspection and fixed it.

Thank you for that kind offer. I will be in touch I’m sure.

Also, thanks for the info about the stamp.

I was hunting pics online of engine cases and could see a few that had similar stamps.

From your info it definitely seems they are quite random.

I also have a stamp on my swingarm, although not as clear, I think it just says “ 6 S”  - it’s on the underside and doesn’t quite look factory, but I could be wrong. - these early frames seem quite crude in terms of workmanship. I don’t think I’ve seen worse welds on a 70s frame before. Mine is late in the K0 production so maybe they gave up some quality to crank em out. Bubblegum, splatter all over, even got part of a rod still stuck to the frame.

[PeWe]

You can have a look inside and check the status by removing oil pan, clutch cover, alternator cover and shifter cover.

The 2 first can show most.

Eventual debris in oil pan. Here measure the primary chain slack.
New chains 65mm, service limit 70mm.
Condition of tensioner might be seen too.
Clutch plates with steel basket that hopefully is not rusty.
Not good to start the engine if it has rust that can fall off and torture the bearings. If deeply rusty, another reason to take ut apart and clean all steel inside.

[WideAWAKE]

Noted!

Hope to have it on the bench early next week

[PeWe]

Forgot to mention the importance to remove oil pan and inspect the oil pump strainer. It can be blocked by various goo.

Good idea short after break-in when restored and around every 10.000 km or every 3rd oil change or so.

I use Honda stock gasket (light green) that does not need to be replace that often.
If very old and hard another thing.

[WideAWAKE]

Well it looks like I’ll be gettin into it.

Primary chain measure well within spec at 66mm but my tensioner is toast. Lots of crunches in the oil pan.

Nothing metallic or magnetic.

From what I understand, I’ll need to crack the bottom, to replace with a nice rubber one.

Does it make sense to split the bottom, change the tensioner, button it up, and then get into the top end?

I’d prefer to tackle one at a time.

[WideAWAKE]

Anyone have experience with the tensioners and Cryo chains from cycle x?

Was looking at their upgraded oem primary tensioner, cam chain roller, front slide and their Cryo chains for both.

[PeWe]

I used car timing chains as primary chains in my K2.
Correct lenght. 68 links.
http://forums.sohc4.net/index.php/topic,168243.msg1964931.html#msg1964931

This made me curious about those chains my K2 has.
Need to remember to measure slack next time I lift the oil pan that can take some time.
Maybe next oil change.

[ekpent]

Some of those "crunches" in the oil pan may be from the rubber cam chain wheel also.If and or when you go there don't buy a cheap China aftermarket one because people were having problems with them falling apart quickly.

[WideAWAKE]

Some of those "crunches" in the oil pan may be from the rubber cam chain wheel also.If and or when you go there don't buy a cheap China aftermarket one because people were having problems with them falling apart quickly.

I figured that would be the case. Even if it looked good I was still gonna replace, just cause I’m in there.

Cycle x has oem ones I was gonna use.

[WideAWAKE]

Got the top end all pulled apart, separated, labeled and sorted.

Here is what I’m working with.

I’m not quite sure what is excessive wear for these motors but if the rocker arms were in other motors I’ve been in, I would run em but one give me a little concern. The exhaust arm on cylinder 2. The others I think will polish up and the cam itself doesn’t show any real damage or excessive wear.

I’m thinking I may get a new arm for number 2 and run the rest.

There is a little score on the cam lobe of 2 but I think it will clean and polish up ok.

Thoughts??

Barrels are clean, still show cross hatching.

Head got some carbon build up haha but it should soda blast off. Same with the pistons.

Cam chain wheel is toast haha.

Clean the head and cylinders, fresh hone, rings, seals, gaskets, cam guide, roller, chain, replace rocker arms 2. - seems to be my plan, granted everything measures within spec. 

[WideAWAKE]

Started cleaning up the head.

Will try to keep all the info contained in one place at this point.

http://forums.sohc4.net/index.php/topic,189641.50.html

I’ll keep all the info there.

[HondaMan]

I'd suggest that the valves be wire-wheeled clean and then lapped back into their original seats. The intakes show a little leakage, typical of engines being reawakened with some rust on the open-while-sitting valves.

That scratchup on the #2 cam lobe is odd, but if it is on the slack side of the cam it won't hurt anything. The 500/550 cams are frequently much worse than that one,with little effect on the rockers.

[PeWe]

I had to let a shop refurbish my K6 head after sitting 19 years in a barn.
Kicked around  engine every year, but forgot the valves and seats that should have needed oil sprayed inside from the beginning.

Rust spots too dip to fix by lapping valves.
Cut the seats and new valves in.

I did not think 19 years when parked September 1990.