Low compression.

[george2490]

Sounds like a lifter had drained down.

[bigbadbob76]

Interesting thought George.
This is the first engine I've worked on an engine with hydraulic lifters, I'm more used to old oil cooled bike engines etc.
Am I right in thinking the valves lift more as oil pressure rises?
Or more importantly... fail to lift high enough when oil pressure is low?
I'm away to the wiki for a read.

[itchyfeet]

Should lift the same with different oil pressure becausd it takes time to drain down, if it's been stood a while they often do drain, if your engine was not hot then it may have drained down.

could also have been rings I think , when hot they are oiled and so more likely to increase compression.

looking forward to your rebuild thread

[george2490]

I had an issue when I rebuilt my air cooled CT. Tried to do compression test while out of vehicle. Three cylinders were round ninety when hand cranked. One was zero. Stripped and rebuilt heads and examined everything several times. Eventually stuck it in van and ran it. Clattered a lot then smooth idle after fifteen mins or so. Checked compression. All equal. I had pre-filled the lifters but I guess that one cylinder either one or both lifters had drained down. Happy days. Still going strong and I had the added benefit of practice with stripping and building. Could do it in quarter of the time now.

[bigbadbob76]

Good to hear your experiances George, I've been using the van regularly so if one is draining down that fast it needs replaced, one more thing to check when I strip it down.
Do drained down ones feel spongy when you push the push-rod in? can you feel the spring?
Aye, i'll be doing a rebuild thread with pics Paul, got a mate (with a supercharged 1600 beetle engined trike)coming over in a couple of weeks or so to give me a hand so I'm stocking up on parts and beg/borrow/stealing tools I havn't allready got.
I'll resist his urging to supercharge the DG engine.
It's good to know what to look out for before I start rather than find out later I should have checked something and didn't.

[itchyfeet]

yes hydraulics feel spongy you can push them in with a pushrod when drained down, they are solid when full of oil.

If you had one that was a bit faulty it would show as a clatter when you left it a few day or a week.
If you didn-t have that then don't bother replacing, the point was it may have drained a bit giving odd readings, thats normal not faulty.

Personally if you are keeping it I'd fit telescopic tubes far easier for future maintenance and inspection.

[bigbadbob76]

Cheers. I'll leave it a couple of days and pop the rocker cover off and give em a push.
She's never clattered, more of a tappety rattle that never fully goes away., hope it's not the piston bouncing off the head.

[sarran1955]

Hello,

Just my little contribution...

As you are prepared to get your hands dirty..

Setting valve clearances on hydraulic tappets can be done cold or warm..

When I set cold on an engine rebuild, I assume that the lifter is empty, and so go to 'contact plus 1/2 turn'..

But the trick is to hold the pushrod up to the rocker with thumb and fore fingers..like smoking a cigar..
and have the adjustment screw and locknut really smooth to get a micrometer like touch.

Also, you will get a 'sharper' setting if you do the valve timing counter clockwise, (less play), on a CT there
is a handy 24 mm bolt for this..
on the CU/T4..a measly..(usually rounded off)..14 mm head..

I then reset twice.. once when the engine has run for a couple of minutes..

and then again when the engine is cooling down after a test run..

if the engine is level and not over oiled..there will be no oil gush when you remove the rocker boxes

and reset to (IMHO)1 1/2 turns..


Those wasserboxer blocks look sooooo CT...

I wonder if......

Cordialement,

[bigbadbob76]

Thanks Sarran.
I did wonder about rocker cover "gush".
Sounds like it would be worth popping the covers off and checking things over.
Thanks for the tip on doing it in CCW order.

[sarran1955]

Hello,

Thanks for the tip on doing it in CCW order.

as easy as 1 2 3 4 ..

Cordialement,

[bigbadbob76]

or 4 3 2 1 if we're going ccw.

[itchyfeet]

1432 or 1234 always start at 1 because thats where the tdc marks are

[bigbadbob76]

Ok, the saga continues......
I popped the rocker covers off and found the rockers were ratting, a quick feel with a feeler guage showed 0.2mm between adjuster and valve stem on all valves.
No.2 inlet was spongy, all the rest were firm. I suspect someone might have "done the tappets" at some point in the past. hmmmm....
At least all the thread lengths were pretty much the same so no dropped valve seats.
So I set them up as reccomended with 1/2 turn in from just barely touching when cold, with a plan to re-do it to 1.5 turns when warm.
I did it CCW, 1234.
While the plugs were out I did another cold compression check and found No.2 was low this time so that ties in with what George was saying about drained down tappets.
That's me happy that while compression is low on all cylinders it's not drastically low on No.3 as first thought.
One happy BBB at this point.

While I had the covers off I cleaned off all the blue hylomar that was caked in there and fitted new cork gaskets as the rubber ones seemed to be not quite the right shape.
So i fired it up and noticed that the cork gaskets were leaking. Grrrrr.... where's me hylomar.
I also noticed No. 4 exhaust header gasket was blowing, so I gently eased out the bolts (yes bolts, not studs for some reason) without shearing them and fitted a new gasket and shiney new bolts. I had to pull the oil filter off to get at the lower one so drained the oil and did an oil change while I was at it.
Fired it up again and it's still blowing so I nipped up the lower bolt a smidgeon and ping!!!! I stripped the thread.
"oh dear" I shouted, "what a shame" (or something like that anyway).
The lower bolt did look in pretty bad shape when it came out so maybe it wrecked the thread on the way out but now I'll have to pull No.2 header off too to get that section of pipe off and helicoil or 10/8 stud it. not the end of the world, but the end of driving the bus for a while.
Again, the top nut (yes, nut this time) came off the stud no bother with a bit of to-ing and fro-ing so I didn't shear it, but the bottom one is proving stubborn so I called it a night.
No photo's as I was up to my wrists in oil but you guys know what this stuff looks like anyway so nothing new to show.
Time for a cold one.

[itchyfeet]

Engine is coming out anyway as it smokes and leaks oil and water from both ends but I was just curious about the bad cylinder being better when hot and/or cranking faster, but the others being the same.

why bother with exhaust if it's coming out anyway, just stick some exhaust paste in for the compression test.

[bigbadbob76]

I've never had much luck with exhaust paste that close to the head TBH, but could give it a try.
Then if compression is good when hot, there's no rush to take the engine out.
Think the problem's been there for a while as the exhaust flange is not parallel with the head (it's an aftermarket stainless one. ) and trying to pull it in with a bolt has stripped the thread, that's why there should be a stud in there not a bolt. ho-hum.
I'll probably have to grind the flange flat to the head so get it to seal properly.
I was planning on taking the exhaust off to make it easier to get the engine out, so that reluctant nut will have to come out anyway.
I've just made up a couple of M10/M8 stepped studs at work as I think I'll be needing them.