Problem with a Norwest!

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ChrisB998
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Problem with a Norwest!

Post by ChrisB998 » Tue Jul 31, 2018 9:32 am

Folks,

Had a little problem with my Nordwest a couple of weeks ago, I lost oil pressure on the motorway!

So having stripped the engine I now need to get new big end shells and possibly main bearings. Does anyone know where they might be for sale, as Bob Wright in the UK doesn't have any.

Most worrying thing is that we haven't found any reason for the loss of oil pressure having stripped the engine and the pump appears to be fine.

The main worrying thing was that the big end bolts appeared to be over tightened.

Chris

garagien
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Re: Problem with a Norwest!

Post by garagien » Wed Aug 01, 2018 6:24 am

Hi Chris,
your problem is strange to understand, normally from mechanical side the engine has absolutely no problems with the oil system.
What´s the milage of the bike?
Did you ever cleaned the 3 oil channels drilled by factory and closed with allen screws on bottom of engine (hard to find). If you not change the oil regulary these dead ends can be filled up with oil sludge and may block a main oil path.
Do you use external oil filter with bypass valve or not? Normally the oil filter is with bypass valve which opens if filter is blocked. But there are filter available without bypass valve (cheaper) and when these filter are blocked engine will not get oil.
Is the filter at the oil drain plug clean?
Was your engine opened shortly ago. Using silicone at the sealing surface? Silicone particels can block very quick the small oil drills inside engine.
In cylinder at bottom there is a drilled allen screw inside oil path to top. This is a kind of orifice balancing the oil pressures between bottom end and camshafts. If this little screw is missing oil pressure is too low for crank causing the defect what you described.

To make it more clear please prepare a copy out of the manual showing the parts you need.
1. For the Main crank bearings I can provide you contact for procurement
2. For big end bearings normally specialists for engine overhaul can help. Indeed you will not get, but parts from cars may suit. Nevertheless somebody must grind the surfaces and prepare oversize bearing parts.
This is a big cost impact. Normally it´s seems cheaper to find a engine block for 250 € and you mix the best of all parts.
Regards
HP

lambs
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Re: Problem with a Norwest!

Post by lambs » Wed Aug 01, 2018 7:24 am

ChrisB998 wrote:
Tue Jul 31, 2018 9:32 am
The main worrying thing was that the big end bolts appeared to be over tightened.
Curious about this. Big end bolts/nuts are high tensile strength items, so over-tightening results in one of two things;

- stripped threads
- bolt failure - either complete failure (fracture) or yielding, which is effectively the same thing but the bolt 'appears' intact

Either way, big end (conrod) failure is inevitable.

ChrisB998
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Re: Problem with a Nordwest!

Post by ChrisB998 » Wed Aug 01, 2018 3:56 pm

Guys,

Well I have been able to make some good progress over the last couple of days.

In the 1st instance it looks like i have been able to find a source for big end shells to fit these engines. My bearing supplier has a set of std and -0.5mm in stock, but other sizes are available. I am going over on Friday to collect a set with a view to checking the width of the locating tang on the shells and that they are a good fit inside the conrod eye - my internal micrometer says they are but I wont know till I try.

If this all works out then the shells will be available from Bob Wright motorcycles in a couple of weeks (bob@bobwrightmotorcycles.co.uk).

To answer some of the questions raised by HP & Lambs:

The bike was bought off ebay May of last year as an unfinished project, out back on the road and run around for a bit, then I had a problem of leaky inlet valves, which meant that we had to take the head off, cut the seats and grind the valves in. It had obviously been stored in a damp garage with the valves open and the seats were corroded.

As we have stripped it this time, it is apparent that someone has been in there before and when putting it back together had no idea of using a torque wrench, they were more like a gorilla with a rattle gun! Everything was way over tightened.

The inside of the engine is clean, but I haven't cleaned the oil ways through yet or had a look inside the oil filter to check for blockage. My blow up was almost certainly due to oil starvation to the big end, I just need to find the blockage.

HP could you give me the details of where I might be able to get replacement main bearing/bushes from please. If I am going this far then I want to do everything properly.

If you want a more detailed information, please e-mail on chris.bushell@nourishengineering.co.uk

garagien
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Re: Problem with a Norwest!

Post by garagien » Wed Aug 01, 2018 9:29 pm

Hi Chris,
sent you separate mail.
Seems that somebody worked on the engine before with air compressor wrench, that´s pussy hardcore *deibel* :kacke: *durchdreh*
Good luck
HP

lambs
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Re: Problem with a Nordwest!

Post by lambs » Thu Aug 02, 2018 11:58 pm

ChrisB998 wrote:
Wed Aug 01, 2018 3:56 pm
As we have stripped it this time, it is apparent that someone has been in there before and when putting it back together had no idea of using a torque wrench, they were more like a gorilla with a rattle gun! Everything was way over tightened.
I'd regard the conrod bolts (and nuts, if it has them) as suspect and replace them as a matter of course. Not worth the risk. If the bolts thread into the conrod, there's also a question mark over the conrods themselves.

ChrisB998
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Re: Problem with a Norwest!

Post by ChrisB998 » Thu Aug 16, 2018 12:25 pm

Well a bit of an update so the information gets shared.

We were checking the eye of the conrod last week to check for ovality and noticed that the slots for the tangs for the big end shells were both on the same side of the rod - which is not correct. This meant that the shells were tight on the crankshaft, hence leading to the signs of heat and eventual bearing failure.

There are no markings on the rod to show which way round the cap should be put back, so the Gorilla with the rattle gun had a choice of two ways and got it wrong! This would make sense as to why this all happened and why there are no problems with pump/main bearings, etc.

This is something that would be very easy to get wrong and worth watching out for, I will mark the rod before it goes back together now.

In the short term I have got hold of another engine bottom end that I have stripped, cleaned and will get back together this weekend. I am looking to refurbish the original engine over the winter as a spare, once I have got another barrel and piston.

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Joachim
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Re: Problem with a Norwest!

Post by Joachim » Thu Aug 16, 2018 7:43 pm

congrats... serious, no smilie!
You now know what happend (bad part) and *why* it happend (good part)
Perfect for a new beginning ;)
Bring it back to the road.

*thumb* Joachim
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