JP2 woes

[Proper Job]

Me mates JP started to develop a knock of the last cruising season. It didn’t sound big end and he had done the big ends a few years back.

 

The sound was bottom end though, so off came the crank case doors and the big ends checked – no discernable movement, but took them apart anyway just to check. All fine.

 

The noise was at the rear of the engine, so the gearbox/gearbox interface was regarded with suspicion. Maybe a loose key? Off with the top of the gearbox and all was found to be well. Time to split the gearbox from the engine! Gearbox out (bloody heck they’re heavy!), but couldn’t find anything amiss.

 

Back to the engine – It didn’t sound like main bearings as it was a distinctive ‘knock’ rather than a ‘rumble’, but we put a bar under one of the crank balance weights just to see if we could discern any crank movement.

 

Bugger! The balance weight moved! It had come loose on the crank web!

 

Now……. We don’t know if there’s any damage to the threads on the holding stud and…… how does the locking dowel that goes into the side of the balance weight come in to play? Especially as you can’t get to it with the crank sat in the engine.

 

Is the crank going to have to come out?

 

Help………

[mrsmelly]

Me mates JP started to develop a knock of the last cruising season. It didn’t sound big end and he had done the big ends a few years back.

 

The sound was bottom end though, so off came the crank case doors and the big ends checked – no discernable movement, but took them apart anyway just to check. All fine.

 

The noise was at the rear of the engine, so the gearbox/gearbox interface was regarded with suspicion. Maybe a loose key? Off with the top of the gearbox and all was found to be well. Time to split the gearbox from the engine! Gearbox out (bloody heck they’re heavy!), but couldn’t find anything amiss.

 

Back to the engine – It didn’t sound like main bearings as it was a distinctive ‘knock’ rather than a ‘rumble’, but we put a bar under one of the crank balance weights just to see if we could discern any crank movement.

 

Bugger! The balance weight moved! It had come loose on the crank web!

 

Now……. We don’t know if there’s any damage to the threads on the holding stud and…… how does the locking dowel that goes into the side of the balance weight come in to play? Especially as you can’t get to it with the crank sat in the engine.

 

Is the crank going to have to come out?

 

Help………

 

Take it to a foundry and have the antiquated piece of scrap melted down and turned into a PROPER engine......

[RLWP]

Not to worry you of course

 

My mate's A35 managed to break the crank between the flywheel and number four cylinder. Somehow it broken diagonally across the journal so that it still worked, just wobbled and knocked a bit...

 

Richard

[Timleech]

Me mates JP started to develop a knock of the last cruising season. It didn’t sound big end and he had done the big ends a few years back.

 

The sound was bottom end though, so off came the crank case doors and the big ends checked – no discernable movement, but took them apart anyway just to check. All fine.

 

The noise was at the rear of the engine, so the gearbox/gearbox interface was regarded with suspicion. Maybe a loose key? Off with the top of the gearbox and all was found to be well. Time to split the gearbox from the engine! Gearbox out (bloody heck they’re heavy!), but couldn’t find anything amiss.

 

Back to the engine – It didn’t sound like main bearings as it was a distinctive ‘knock’ rather than a ‘rumble’, but we put a bar under one of the crank balance weights just to see if we could discern any crank movement.

 

Bugger! The balance weight moved! It had come loose on the crank web!

 

Now……. We don’t know if there’s any damage to the threads on the holding stud and…… how does the locking dowel that goes into the side of the balance weight come in to play? Especially as you can’t get to it with the crank sat in the engine.

 

Is the crank going to have to come out?

 

Help………

 

Yes the crank will have to come out to do anything properly. The weights as you probably know are held in with tubular nuts with a slot across the top, it might be possible to make up a key that you can use in situ to tighten them temporarily. The dowel is from what I remember to lock this nut, but it's a while since I took any JP weights off. Martyn or Steamraiser can probably give chapter & verse.

 

Tim

[ditchcrawler]

Not to worry you of course

 

My mate's A35 managed to break the crank between the flywheel and number four cylinder. Somehow it broken diagonally across the journal so that it still worked, just wobbled and knocked a bit...

 

Richard

I've seen that on a car engine as well.

[zenataomm]

I hope you get it right without developing hernias.

 

The most impressive reason for an engine knock I saw was a Lister SR2 that sounded like a bag of spanners under load but only on just above tick over, otherwise it was fine.

 

After a couple of years of it not getting any worse my friend decided to check the big ends at the end of that season. Having undone the big end caps on number two he discovered the crank was split into two pieces across the journal and only held together by the big end caps. As he removed them it fell apart.

[steamraiser2]

Oh dear!, The pins lock the whole thing together as Tim says. They are a pig to get out. We cut through them with a cut down hacksaw blade and a small reciprocating air saw once the crank is out. Not our favourite job..especially when some numpty has used roll pins instead of mild steel pins! There is a bigger issue though. If the pins are in place how has the weight come loose? It can only be poor assembly or a failure of the stud/ thread in the crank. It has got to come to bits. Before you strip it check for end play on the crank. If it is more than a thou or two you can be assured that the bearings/crank are well worn. Don't ignore it.Worn JP cranks can fail quite readily. Geoff

[Proper Job]

It had a new crank 20 years ago after the exisitng one bust!

 

That was it's last major, major rebuild, so it's taken that long to come loose.

 

It had new big ends, liners and rings last year. Maybe it was the increase in power after replacing all of these worn bits that weakened the nut.

 

Flywheel off time then and then out with the crank

 

Happy days

[steamraiser2]

We have just restored a JP3M that has been running around for a year or two on standard bearings on a -020" crank. No oil pressure of course and must have been clattering somewhat! No loose weights though! Best of luck with that, it is not a fun job.!

[frangar]

Great....something else to worry about that might go wrong with my JP.....As if I wasnt paranoid enough...I will now worry about cranks snapping and balance weights coming loose.....

 

Cheers

 

Gareth

[martyn 1]

Oh dear!, The pins lock the whole thing together as Tim says. They are a pig to get out. We cut through them with a cut down hacksaw blade and a small reciprocating air saw once the crank is out. Not our favourite job..especially when some numpty has used roll pins instead of mild steel pins! There is a bigger issue though. If the pins are in place how has the weight come loose? It can only be poor assembly or a failure of the stud/ thread in the crank. It has got to come to bits. Before you strip it check for end play on the crank. If it is more than a thou or two you can be assured that the bearings/crank are well worn. Don't ignore it.Worn JP cranks can fail quite readily. Geoff

 

Ha ha, my father(steamraiser2) has beaten me to it, when it comes to replying to this. Edited as it is useful if I dont miss a line of the Original posters comments. Crank out it is then as the pin that goes through the weight is from the outside face of the weight and should go through the weight, nut and stud and out the other side back into the weight. Unfortunatly not a nice job but better that than another broken crank.

Edited February 2, 2012 by martyn 1

[Proper Job]

Well.........

 

It's out and off to the have a polish and new bearings:

 

 

The journals are all good but the mains were showing a bit of cracking in the white metal.

 

Jesus..... it's heavy!

[by'eck]

Notice you have the balance weights off.

 

Were there any signs as to why they came loose, given that they are normally firmly locked in place with the pinned nuts?

[Proper Job]

Nothing obvious. We were also expecting the overlap interface on the balance weight/crank web to be shiney, but that wasn't the case (as you can see in the photo).

 

Various theories now abound.

 

The nuts bottomed out on the thread before the balance weight was fully tight to the web?

Stud has stretched?

There was originally something between the mating surfaces which eventually came out?

 

It may also have been a slightly loose flywheel! Apparently this has happened before and required re-tightening.

 

Either way...... it's out now and may take up to a couple of months to get back from the grinders (they've got a large back log)

 

It'll give us time to do press ups and other exercises ( ) to get in trim for putting it back

[Timleech]

Nothing obvious. We were also expecting the overlap interface on the balance weight/crank web to be shiney, but that wasn't the case (as you can see in the photo).

 

Various theories now abound.

 

The nuts bottomed out on the thread before the balance weight was fully tight to the web?

Stud has stretched?

There was originally something between the mating surfaces which eventually came out?

 

It may also have been a slightly loose flywheel! Apparently this has happened before and required re-tightening.

 

Either way...... it's out now and may take up to a couple of months to get back from the grinders (they've got a large back log)

 

It'll give us time to do press ups and other exercises ( ) to get in trim for putting it back

 

Looking at the taper for the flywheel it does look as though it hasn't been seating properly. Best to check that they still fit together properly before putting the crank back in the engine.

 

Tim

[RLWP]

<snip>

 

It may also have been a slightly loose flywheel! Apparently this has happened before and required re-tightening.

 

<snip>

 

That would tie in with the appearance of the flywheel taper

 

Richard

 

MORE: SNAP!

Edited February 22, 2012 by RLWP

[Proper Job]

Looking at the taper for the flywheel it does look as though it hasn't been seating properly. Best to check that they still fit together properly before putting the crank back in the engine.

 

Tim

That's what we thought when the flywheel came off.

 

No looking forward to lifting that back on either

[mrsmelly]

That's what we thought when the flywheel came off.

 

No looking forward to lifting that back on either

 

 

Young Mark can lift that single handed !! I remember him lifting your rudder single handed !!!

[Proper Job]

Young Mark can lift that single handed !! I remember him lifting your rudder single handed !!!

It's not so much the lifting. It's the threading it in to the engine block in situ that's the problem.

 

But you're right, once out he lifted it into the barrow.

 

Mind you.... he did go a funny colour

 

It made the Polo sit quite low on its suspension when it was dropped in to the boot

[Redeye]

Nothing obvious. We were also expecting the overlap interface on the balance weight/crank web to be shiney, but that wasn't the case (as you can see in the photo).

 

Various theories now abound.

 

The nuts bottomed out on the thread before the balance weight was fully tight to the web?

Stud has stretched?

There was originally something between the mating surfaces which eventually came out?

 

It may also have been a slightly loose flywheel! Apparently this has happened before and required re-tightening.

 

Either way...... it's out now and may take up to a couple of months to get back from the grinders (they've got a large back log)

 

It'll give us time to do press ups and other exercises ( ) to get in trim for putting it back

 

Hi Steve,

 

If you are struggling on the grinding it might be worth trying Billcar Engineering in Shrewsbury. They did a great job on a K2 crank for me and were pretty quick.

 

Cheers

 

Andy

[Proper Job]

Hi Steve,

 

If you are struggling on the grinding it might be worth trying Billcar Engineering in Shrewsbury. They did a great job on a K2 crank for me and were pretty quick.

 

Cheers

 

Andy

Andy

 

Thanks for the contact.

 

It's not my crank to worry about. I'm just helping a mate out. He's got a good relationship with the engineering company that it's gone to (he also owns a 650 Panther and a Triton - enough said )

 

He also has the luxury of electrical hook up so doesn't need the engine for battery charging.

 

He now plans to spend the intermediate time checking and tarting up the rest of the engine. I'll be back in to the fray as an extra pare of hands when the rebuild proper starts.

[BEngo]

Looking at the picture I see the JP2 has only two main bearings- I would have expected there to be one between the two cranks. You learn something every day!

 

Are there any other common vintage engines like this?

 

N

[Timleech]

Looking at the picture I see the JP2 has only two main bearings- I would have expected there to be one between the two cranks. You learn something every day!

 

Are there any other common vintage engines like this?

 

N

 

It actually has three, but you are quite right there isn't one between the cylinders. Fairly unusual for a diesel.

Austin Seven engines originally only had two mains for a 4-cylinder engine, I believe!

 

Tim

[RLWP]

Looking at the picture I see the JP2 has only two main bearings- I would have expected there to be one between the two cranks. You learn something every day!

 

Are there any other common vintage engines like this?

 

N

 

Quite a lot I would guess. It may seem odd, but less bearings meant that the machining requirements were easier (less cylinders and holes to get correctly lined up), and more chance for the crank to flex if you got the calculations wrong or if the crank had bent when it de-stressed itself

 

Shorter engine too

 

Richard

Edited February 26, 2012 by RLWP

[Springer Skipper]

Ive got a lister D type as a battery charger genny ,it has only ONE bearing.Thats at the flywheel end.The other end is in free air and drives the magneto.Its a parrafin engine so not highly stressed!

Amazing innit what our forerunners did

R.

Edited February 26, 2012 by Springer Skipper