1991 851 Restoration

hindsight

As mentioned elsewhere, I've taken on another 851 project. The last one is complete, and should be going off to a new home soon.

Mick Dixon posted on these forums last weekend about his 1991 851 that had a bit of an engine failure. We spoke that evening and a deal was agreed.

It'll probably be a few weeks before I really get started with this project properly (I've got my 916 Strada on the operating table at the moment, getting her recommissioned after a few years of being tucked at the back of the garage).

However - Mick has done an amazing job of packaging everything up (thanks Mick!) and I'm starting to organise the garage and have a look at the bits and pieces. Here's what Mick said:

Unfortunately last July my beloved 851 suffered an engine failure. The engine has been stripped by V Due Motor Cycles of Lincoln where it was found that front cylinder piston had failed….. The piston skirt had broken away resulting in a damaged barrel as well as piston.

Of course, curiosity got the better of me:

True enough the piston skirt is broken, and the oil control ring is missing:

Mick tells me that they didn't find the missing piece, nor fragments of the ring - I presume that it was quickly ground and I'll find it when I cut open the oil filter in due course.

There is some scratching on the interior faces of the piston, and a curious score around the circumference of the gudgeon pin hole - I can't immediately see any obvious damage to the gudgeon pin itself, and the face of the piston is just fine.

It's clear that the barrel is obviously now also very, very second hand...

Mick tells me that the crank was checked to be just fine - and that certainly looks to be the case:

I'd be interested in any opinions or insight as to what actually caused the piston failure. The break line on the piston looks like it shattered, though some of it has been worn to a slightly smooth feel (presumably from the ride home that Mick had with lots of debris in the engine). If it is a shatter break, then I'd have expected that to be caused from impact - but with what? - could it have been the oil control ring that shattered, and the fragments of that caused the skirt to break maybe?

I'll try giving the fella that tore down the engine a call next week to hear what his observations were when he opened it up.

Mike

RWG

O dear, looks a bit of a mess, what is your plans (spec) very interested in developments.

I have just had major service carried out on my 888 strada and it is sweet but after riding sp4 the strada is lacking in the emotive gain given by the sp4, considddering selling but may be engine works could change my mind.
Look forward to your future post's

hindsight

Unless someone reprimands me for missing an opportunity, I'll probably be keeping it relatively standard Paul. I've mulled over a number of scenarios, including a 907 upgrade and ST4s transplant. But where I think I want to be here is putting it back together with least risk and without it costing a fortune (most probably keeping the 851 displacement). Any serious engine work would lead on to brake and possibly suspension upgrades to keep it balanced.

As usual with these projects, I'll build it - have a little fun on it, then move it onto the next custodian to make a bit of space in the garage for the next project.

my 888 strada and it is sweet but after riding sp4 the strada is lacking in the emotive gain given by the sp4, considddering selling

Totally with you there. For a while I had a '93 888 Strada at the same time as my SP5. I quickly realised that I would never choose to take the strada out over the SP, and sold it.

hindsight

Starting to draw up a list of bearings and seals, with help from previous threads and discussions. Avoiding the Ducati tax whereever possible, it still looks like I'm in for a £280 bill for this lot...

Right Crankcase

Qty 2 : Swingarm                  HK20202RS
Qty 1 : Distribution countershaft RNU202ECP
Qty 1 : Crankshaft                RHP 7307X2ETN
Qty 1 : Mainshaft gearbox         6305/C3
Qty 1 : Layshaft gearbox          NJ 203 ECP/C3
Qty 1 : Primary Gear (inside)     6005
Qty 1 : Primary Gear (outside)    16005

Left Crankcase

Qty 2 : Swingarm                  HK20202RS
Qty 1 : Distribution countershaft 6004/C3
Qty 1 : Crankshaft                RHP 7207X2ETN
Qty 1 : Mainshaft gearbox         NJ 203 ECP/C3
Qty 1 : Layshaft gearbox          6305/C3
Qty 1 : C/Case Seal               18x30x7
Qty 1 : C/Case Seal               25x52x7

marvin

A good stock 851/888 engine should not be all that hard to find which would be less expensive!

Marvin

guy851

851 rebuild

Good to see that the 851 is going to be put back on the road, I was tempted myself but had a reality check with a number or projects including new workshop to build i decided not right now.

I have two sets of good pistons and cylinders in storage one pair standard and one pair for G cams if of interest

Guy851

marvin

I also have a new OEM original pair of 851 head gaskets if you need them. I believe I also have a set for an 888.

hindsight

I've already got a barrel/piston/ring set organised (thanks again guy) - but I'll definitely need a set of 851 head gaskets - PM me with details, and I'm sure we can do a deal - thanks Marvin!

hindsight

Are "NJ 203 ECP/C3" and "2nu03EC" bearings equivalent?

I've been out validating the list of bearings with what is actually currently installed, and there is several references in this forum to the former code, whereas I seem to have the latter installed..

BABA

2nu03EC is the the roller bearing without inner retaining ring (but it's the reference writes on the outer ring. When you want ordering this kind of rollerbearing, it's RNU203ECP)

You need to ask the NJ 203 ECP C3 for the gear box.

The "J" is the reference for the retaining inner ring.

With a "U", you will have a normal inner ring, without retaining (NU 203 ECP).

I hope I'm clear 😳
(if not, you only have to know that you need to order two roller bearing NJ203-ECP-C3 😉)

BABA

Another details.
If you want to respect the original mounting for the swing arm, with the two seals, the reference for the needle bearings is HK2016 (I suppose that it's for removing these two seals on each side that you want to buy HK2020-2RS ?)

hindsight

Excellent - thanks Baba for the clarification.

BABA wroteAnother details. If you want to respect the original mounting for the swing arm, with the two seals, the reference for the needle bearings is HK2016 (I suppose that it's for removing these two seals on each side that you want to buy HK2020-2RS ?)

Yes, exactly. I spotted the reference to HK2020-2RS in a thread on this site - seems like a reasonable approach.

hindsight

I now have a nice big box full of bearings and seals ready to go into the cases once I finish extracting all bearings and cleaning the cases. In the meantime though, I went to strip the rods off the crank last week, and realised to my surprise that all my 10mm sockets were six-point hex, no matter though - sorted now.

The big end bolts came off with a little gentle "persuasion" - the crank looks fine - 42.00mm +/- 0.2mm, and within spec.

(uber-high resolution versions of these pics available by clicking on the images below).

The shells are quite interesting. They show a bit of wear, but also some scores where some engine trauma has dragged debris through the oil. There are scores, particularly on the left hand (horizontal) one.

Current plan is to fit new shells, then pop the crank and rods back together as-is. Note that the horizontal rod appears to have had some of its' coating removed - again - probably debris. There doesn't appear to be any material damage there.

Opinions and advice sought on the suitability of this planned approach..

Thanks,
Mike

brad black

replace the bolts.

hindsight

Absolutely - thanks Brad - I'll also be replacing the oil gallery plugs while I'm at it.

hindsight

Some good progress. The bearings all came out easily enough: cooked the cases in the oven for a bit, and a combination of various sockets, hammers and a blind bearing puller saw them all out pretty quickly.

The bearing bush popped out also on one of the cases, so I'll need to pop that back in, in due course. It still looks to be an interference fit, but I'll secure it with loctite when the time comes.

I decided to take a look at the heads this week also. To my surprise, six of the eight closers were tighter than I like to see them, so spent an evening juggling shims, and the clearances are now looking good.

Now waiting on wifey going out, so I can pop the cases into the dishwasher for a final, thorough clean before I start installing bearings again.

BARONROJO

If one of the main bearings bush has gone out, check it hasn't been turning in its housing, a bad sign for this kind of engines. If it has (signs of light scores in the rotation direction) you should have a machinist make a tighter fit one (+0,1 mm) as there's no spare for that.
Loctite may work for a road engine but not for a track bike.

hindsight

That's a fair point, yes. I've not inspected it in detail yet - the components are still sitting where I left them to cool.

Out of interest - if the bush bearing had spun in the case, could that resultant vibration have contributed to the piston failure?

hindsight

Hmm - now that I take a look, seems pretty clear to me that it almost certainly has spun (unless anyone can tell me differently from these photos.

+0.1mm you say? what material should be used?

hindsight

Hmm - that's a surprise - having recently had a delivery of a few parts, including a job lot of 92mm cylinders and pistons, I was having a close look at them.

First I noticed Gia.Ca.Moto in the casting on the side of the broken barrel that came off the bike, and thought that to be a little strange, but with them side-by-side : it dawned on me - the pistons that I was looking at were blatently different.

This bike had a 94mm kit fitted - I wish I'd measured it earlier!

How can I quickly and accurately check the crank stroke, with the crank out of the cases, and no rods on?

94mm 888 kit