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Digit

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As in engines. Is there anyone on here that could advise me on a crankshft rebuild problem please?

Roy.
 

Digit

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Thank you gentlemen. Over the years I have re-built numerous engines, but to date i have never had to rebuild a crankshaft with shell bearings.
The job may turn out to be impossible as I have yet to find a supplier of the necessary shells. But that's for the future.
I have the worshop manual, I have read up about Plastigauge, I have mentally followed the instructions there in, but i don't understand a word!
The crank journal nominal size is stamped on the crank, there should only be one journal as it is a 'V' twin, shells in four different sizes and colour coded.
Where I am currently stumped is the use of Plastigauge, as I read in the manual I strip the rods off, clean everything, put a strip of Plastigauge on the journal and rebuild the crank. Next I strip the rods off again and measure the width of the Plastigauge.
Ok, I get all that, I fully understand the principle of using Plastigauge as well, but how does knowing the gap between journal and a worn set of shells help me find the replacement size!?
All this of course is assuming that the crank is ok.

Roy.
 

Dibs-h

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Roy

I would expect the shells to wear and not the crank. There should be published spec relating to the maximum allowable clearance between crank and shells. You use the Plastigauge to check this.

Or mic the crank if you now what the journal size should be - I've always viewed it as either or. The only real difference being in that the Plastigauge can be used in-situ (at least with car engines) whereas to mic a journal properly means the crank has to come out.

In the case of an engine already in bits - I can't see the value of Plastigauge, when you can mic it far easier.

HIH

Dibs
 

Digit

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The journal size is a code letter stamped on the crank web Dibs, the manual will tell me what that size should be, I have mics of various sizes and the shaft will come out once I take the caps off, that way i can leave the pistons in situ, unless I have to remove them for some reason of course.
So if I understand you, and my own experience correctly, if the journal is to spec I simply replace the shells with the same size as those already in situ, correct?

Roy.
 

Spindle

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Hi

I'm afraid I'm going to have to question the statement that only the shells will wear - this is not the case. The relatively soft material of the shells pick up and reatain harder particles which in turn cause the journals to wear. Measure the ovality of the journals, (use a micrometer), and from that identify the minimum regrind to return to cylindrical, then compare to the available shell diameters and get the crank ground to suit, install with new shells - jobs a good un.

Regards Mick
 

Dibs-h

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Digit":191cv35p said:
The journal size is a code letter stamped on the crank web Dibs, the manual will tell me what that size should be, I have mics of various sizes and the shaft will come out once I take the caps off, that way i can leave the pistons in situ, unless I have to remove them for some reason of course.
So if I understand you, and my own experience correctly, if the journal is to spec I simply replace the shells with the same size as those already in situ, correct?

Roy.
Yes - if the crank journals are to spec, replace with the same (hopefully std) size shells.

Spindle":191cv35p said:
Hi

I'm afraid I'm going to have to question the statement that only the shells will wear - this is not the case. The relatively soft material of the shells pick up and reatain harder particles which in turn cause the journals to wear. Measure the ovality of the journals, (use a micrometer), and from that identify the minimum regrind to return to cylindrical, then compare to the available shell diameters and get the crank ground to suit, install with new shells - jobs a good un.

Regards Mick
Mick - that's why I said, I would expect the shells to wear rather than the crank. Most cranks have been treated to harden the surface of the journals and it usually takes a "dead-engine" event to introduce harder particles to score and damage the journals. Thus requiring a regrind. But as you say - if you are going to mic a journal - makes sense to check for ovality, be daft taking a single measurement.

Obviously for plastigauge - you need to turn the engine to get the journal to rotate. Much easier with the plugs\injectors out mind you.

HIH

Dibs
 

Digit

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I appreciate the possibilty of crank wear/damage etc and will be checking all round, which is why I will be pulling the crank out of the casing.
Meantime fingers crossed, it's about time I had some luck with this bike, believe me. If I find the previouse owner, (Pr**t) has left the oil pump out I wouldn't be too surprised!

Roy.
 

MickCheese

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When I replaced the crank shells on a VFR400 I got the stamped in number off the shaft and if I remember correctly there was a stamped in number on the crank case then, in the manual, there was a colour code for the correct shells.

The Plastigauge is to check for oil clearance. With new shells they should be within tolerance but if the crankshaft is worn then the plastigauge will be too thick and so you will need a new shaft, I don't know if you can regrind and get smaller shells for these bikes?

So, with new shells the Plastigauge is only telling you if the crankshaft is worn or not.

Mick
 

Digit

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That basically confirms what I reasoned to be the case Mick. As for regrinding, I doubt it. In the magazines a company called SEP reckon to repair or service exchange any crank, though God knows what that would cost.
David Silver is advertising ONE shell????
As it stands even if the crank is ok shells are gonna be a problem, I don't know if they can be produced to order by some one and if so, the cost.
The bike is still big in Oz so there may be a source there.
Out of curiosity Mick, what is the nominal diameter on the VFR, any idea?

Roy.
 

Dibs-h

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MickCheese":33rtk36g said:
When I replaced the crank shells on a VFR400 I got the stamped in number off the shaft and if I remember correctly there was a stamped in number on the crank case then, in the manual, there was a colour code for the correct shells.

The Plastigauge is to check for oil clearance. With new shells they should be within tolerance but if the crankshaft is worn then the plastigauge will be too thick and so you will need a new shaft, I don't know if you can regrind and get smaller shells for these bikes?

So, with new shells the Plastigauge is only telling you if the crankshaft is worn or not.

Mick
But surely mic'ing the crank journals would tell you if any of them were worn?

Dibs
 

MickCheese

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Digit":272yt33u said:
That basically confirms what I reasoned to be the case Mick. As for regrinding, I doubt it. In the magazines a company called SEP reckon to repair or service exchange any crank, though God knows what that would cost.
David Silver is advertising ONE shell????
As it stands even if the crank is ok shells are gonna be a problem, I don't know if they can be produced to order by some one and if so, the cost.
The bike is still big in Oz so there may be a source there.
Out of curiosity Mick, what is the nominal diameter on the VFR, any idea?

Roy.
I want to sat 30mm. I have looked in my workshop manual and it looks like the shells have a tolerance either side of that so I assume as a guide it is 30mm.

I have a spare VFR400 NC30 engine that has new, never run shells in it but the engine will not run, it has sat in my garage for a few years cluttering up the place. If you think the shells may be the same you are welcome to the engine to get it out from under my feet. Just got to collect it! :roll:

Mick
 

Digit

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Dibs, I'll hazard a guess that you are an old 'un like me. I know of a vehicle engineer who now travels the world lecturing on vehicle maintenance, if he can read a mic I'll eat me hat!
He has diplomas enough the paper his lounge wall and boasted to me one day about his knowledge, I put up with it for a while then told him he knew only about SOHC 4 strokes. I went on to point out that he knew nothing of De Saxe cylinder arrangements, nothing about 5 strokes or 6 strokes, nothing of sleeve valves or rotary engines.
He stood open mouthed, and having put my foot in it I had to spend the next few hours in lecture mode! :oops:

Mick, thanks for the offer, I may well take you up on it, first thing is to obtain info. As you will be aware Honda have used the same parts on more than one machine, nobody designs a brand new L/H Wotsit if they already have a suitable unit in production. It's getting the info!
For example, the rubber inlet stubs were unavailable, but if I recall correctly it was you that led me to suitable ones from an NC30.
If needs must! This bike has gone from being fun to a challenge!!!

Roy.
 

Digit

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My son uses digital tools, he was surprised when I told him that they were normally accurate only to plus/minus one digit.
Having said that I use them for most things but if I want better I use a mic. I gave my lad an old vernier caliper to try one day! :lol:

Roy.
 

CHJ

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Try explaing to most folks that they can't measure anything accurately, any hand tool and most readily available measuring tools are only comparrators.
If you are lucky enough to have a metrology lab at hand who can check them against an even better comparitor then you get closer to the truth.
I was once sent in to sort out why an aircraft repair facility was having so many failures of rotary convertors after a few flight hours, only to find the guys were using two different mic's to measure housings and bearings without actually checking if the two agreed or unstand the difference that can be influenced by the hand pressure on a mic let alone the different feel between an internal and external.

(Interference fit bearings, all older generation brit. units always had clamped bearings)

An immediate improvement was to just use a micrometer to compare an internal mic 'reading' with the spare bearings to find one that matched by feel. Taking no notice whatsoever what the finite dimension was.

Went back to basics and had a set of plug guages and matching gap guages made that met the zone tollerance for fitting and took away the need to 'measure', problem solved.
 

Digit

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The hand pressure, the 'feel' when using old fashioned spring calipers and so on is one of the most difficult tasks to learn.
I recall an instant when a drawing gave a diameter as 'to fit part B'.
When I checked the drawing for part B it stated the diameter as 'to fit part A.'

Roy.
 

Dibs-h

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Digit":35xay66e said:
I recall an instant when a drawing gave a diameter as 'to fit part B'.
When I checked the drawing for part B it stated the diameter as 'to fit part A.'

Roy.
I'll have to remember that one if ever doing some kind of spec, where I feel like having some amusement! :D
 

Eric The Viking

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Roy, if you have access to Usenet, try uk.rec.motorcycles.classic: you might do worse than ask there if anyone knows a supplier of shells. It's the usual motorcycle gang, er, group of enthusiasts, but they're not anti-Jap (nor anti-BMW :) ), and in my experience are pretty helpful, if a bit rude sometimes!

If you haven't got a News server, you can post via Google Groups.

Cheers,

E.
(now only an R80RT, temporarily mothballed)
 
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