Not turning crankshaft

[nms-georg]

Hi Guys!
Need again some help from you. Have changed my con rod bearings, everything looked fine. Till I tried to turn the crankshaft. I can turn it normally till the first piston comes close to the top. But it is not going over the "top dead end". Have opened the top valve case and realised that the valve from the first cylinder are not moving down any inch as long the piston is moved to the top. Looks like the valves are touching the piston and thats why I can't move it anymore.
- Is this possible?
- What happend that the valves are touching the piston?
- How can I check it if thi is the really problem or if the problem is somewhere else?

Thanks a lot,
Georgen

[Brian]

Are the valves stuck? Do any of the valves move as you rock the engine? Have you removed the valve rockers and got a push rod out of place on the side of the tappet?

[nms-georg]

Hi Brian!
Thanks for your first help. Here some further information:
- I didn't change the pistons
- didn't change the con rods
- didn't make any changes to the valves, to rockers and anything related
- while turning the crankshaft all valves are moving

What I'm wondering about: once the crankshaft is turned as far as it's not going further - I can press on the valves (from top) and they are moving downwards maybe 2 or 3mm. So there is still some space between the pistontop and the valves.

1) How can I check whats the problem?
2) Did I maybe broke something due to my turning the crankshaft in oposit direction?

Thanks you guys

[Brian]

Sorry I am muddling my Dextas and Majors, Dextas do not have push-rods.

There is nothing you can do by turning the engine backwards but I am wondering if it was something you did when you had the bearings off the crank or if the oil pump pick up tube got bent and is striking the crank.

[tom lad]

hi m8
did you take the crank out in the end ?
has the timing been altered ?

also did you figure out what broke in the first place ?

good job you noticed this problem before you tried to run it again i guess
tom

[nms-georg]

Hello Together!

- the tube from oilpump to the "sump" is in place and nothing is touching there
- the crank is in place as it was. didn't take it out and didn't touch the main bearings
- the probelm why I have opened it was a metal noise and this was coming due to the broken con rod bearing at the third cyl

The funny think is, that the crankshaft is moving quite smooth in both directions (as long as the first cyl is not coming to the top).

1) Do you think there is something sitting (something broken) on the piston-top`?
2) Does it have something to do with the clutch or the gearbox?
3) Someting else to check?

[Brian]

Dexta pistons do come to the very top of the bore and there is little room for anything to sit on the top of the piston but- The engine was running until the No 3 rod bearing was replaced. This would indicate something on the crank, I have seen a lock tab on a big end or main bearing give a similar problem when it struck the crank.

I have also seen big end bolts that are not fully home cause a problem, but luckily they have been noticed before completing assembly.

If the engine/crank turns freely without No 1 connected it must indicate there is something in No.1 that is stopping it. But how it got there and why now is a mystery.

If you try turning the engine with the clutch down that would eliminate a gearbox problem but not completely eliminate the clutch.

[nms-georg]

Guys, got it

Problem was: con rod have some play left and right to the crankshaft. During tightening they have been close to one side and not in the middle. Just this. Have loosen the screws, moved them correct to the middle and tighten them again. And now the crankshaft is moving...

Thanks for your help. Great job here...

Thanks and bye,
George

[Mervyn Spencer]

Well Done George. As the old Beatle song goes, "With a little help from your friends".

[60dexta]

Guys, got it

Problem was: con rod have some play left and right to the crankshaft. During tightening they have been close to one side and not in the middle. Just this. Have loosen the screws, moved them correct to the middle and tighten them again. And now the crankshaft is moving...

Thanks for your help. Great job here...

Thanks and bye,
George

Hi George,
I don't think I have ever taken an engine appart that did not have some location between the con rod and its bearing cap.
From the picture in the manual it looks like the bolts should be a good fit in the cap. Have you got the right bolts in there?
If that was the problem why did it only occur at the top of one cylinder?
Rob

[russelm]

I to am concerned as the hints that the big end bearing was not fitted correctly....is it still ok?

[nms-georg]

Morning!
Actually I don't have an correct idea why it was only at the first cylinder. I think that there is also a little play between the con rod and the piston. And if the play at the top and the to-one-side-fitted-con-rod made some funny angle so there was to much power needed to move it. And because it was almost at the top there was also the biggest compression. Maybe it would work also as it was an I have been to scary to use more power to crank it... But what I have learned - never work with "power" around the engine...

But finally the crankshaft is turning now and thats how it should be...

Thanks