Engine Rebuild.

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Serlant
Posts: 111
Joined: Fri Apr 22, 2011 9:02 am

Engine Rebuild.

Post by Serlant »

Well the de(con)struction of the old engine has begun (has around 70k on it) after retrieving it from my friends on monday.
this is the first thing i noticed awry after taking the cams out (this is the head bolt closest the cam chain tunnel)
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front piston
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rear piston
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the pistons are pretty clean for the mileage its done.
one head
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other head
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the heads are going to be cleaned up and the valves and seat re-cut with 3 angle I think.

big end main bearings
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as it stands at the moment.
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just awaiting a clutch holding tool so that I can get the clutch centre nut off then i'll split the cases.

rear piston after a whipe with a piece of kitchen roll
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front as it came out of the lump
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its pretty easy to get the pistons out of the lump with the cases not split but I wouldn't fancy getting a torque wrench in there on re-assembly!
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VTRDark
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Joined: Sun Mar 18, 2012 9:24 pm

Re: Engine Rebuild.

Post by VTRDark »

Good work. Those pistons and valves are very clean considering the mileage. The big end bearings need changing for sure. There's quite a bit of scoring and the outer coating has worn.
I can't see what your seeing there with the bolt or is it not torqued up. It's hard to see on the pic.

(:-})
==============================Enter the Darkside
Serlant
Posts: 111
Joined: Fri Apr 22, 2011 9:02 am

Re: Engine Rebuild.

Post by Serlant »

with the bolt the shiny bit below it is the bit the bolt should be seated against, its undone about 50mm or so, must have not been torqued up properly.
tony.mon
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Joined: Wed Jul 25, 2007 10:46 pm
Location: Norf Kent

Re: Engine Rebuild.

Post by tony.mon »

Serlant wrote:with the bolt the shiny bit below it is the bit the bolt should be seated against, its undone about 50mm or so, must have not been torqued up properly.
or tightened at all.......let's hope it's not because the thread has stripped.
It's not falling off, it's an upgrade opportunity.
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lloydie
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Joined: Mon Jan 17, 2011 11:16 pm
Location: In the garage somewhere in Coventry

Re: Engine Rebuild.

Post by lloydie »

I'll be doing mine soon so it's good to read your .
Keep us updated on the progress
Serlant
Posts: 111
Joined: Fri Apr 22, 2011 9:02 am

Re: Engine Rebuild.

Post by Serlant »

Well the clutch holding tool arrived today, so I set at the clutch centre nut again but was un-successful in removing the nut still, It would seem I just don't have the minerals as I hung off it with my breaker bar with another 12" extension ontop of that and it didn't budge, so I put that on the back burner for the moment and continued with the the bits I otherwise had access too. I removed and labelled up all the buckets and shims, put some plugs in and filled the combustion chamber with paraffin to try and loosen up some of the carbon.

some scoring on the rear barrel, the middle left one seems major but the others seem minor, the big score seems to have been cause by some damage to the piston?
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this is the corresponding mark on the piston which lines up with the big score, it looks like something has hit the piston or it was dropped before assembly, as it has pushed the piston material upwards into the crown area and judging by the size of the nick in the piston if it was something in the cylinder that caused it it would probably has caused a lot more damage.

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gudgeon pin looks to have taken some abuse on the rear pot.

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there is a corresponding black mark on the con rod on the bottom of the small end bearing.

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Am i looking at replacement rods, pistons and boring the cylinders at a minimum? I can try and take some better pictures when its light outside!

also any ideas for the clutch centre nut (yes I unstaked it! :lol: )

I worry about the cam bearings aswell as I did do the rear camchain tensioner up to tight then did 40 miles or so before I was able to slacken it. I will get some more photos of the cam bearings for an opinion?
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AMCQ46
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Location: Worcestershire / Warwickshire border

Re: Engine Rebuild.

Post by AMCQ46 »

I used a ratchet strap to pull the breaker bar and the clutch holding tool towards each other and that has worked every time

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AMcQ
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lloydie
Posts: 20920
Joined: Mon Jan 17, 2011 11:16 pm
Location: In the garage somewhere in Coventry

Re: Engine Rebuild.

Post by lloydie »

AMCQ46 wrote:I used a ratchet strap to pull the breaker bar and the clutch holding tool towards each other and that has worked every time

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worked for me twice too :thumbup:
Serlant
Posts: 111
Joined: Fri Apr 22, 2011 9:02 am

Re: Engine Rebuild.

Post by Serlant »

Well after reading this this morning hope was restored so I dug out my ratchet strap and headed into the shed, that sicker came off first time! Thanks for the advice :)
tony.mon
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Joined: Wed Jul 25, 2007 10:46 pm
Location: Norf Kent

Re: Engine Rebuild.

Post by tony.mon »

I'm more old-school- a length of scaffold tube works fine.
Use a long enough length and its own weight undoes it for you! (make sure it's undoing downwards.

You need a new centre nut, but if you have lots of different spare ones try another, and see if an undamaged section of the knock-over security tab lines up.
The old one will always line up at the same place, so can't be re-used.

Re your little ends, all you can do is to measure them carefully- Haynes has the wear limits.
New gudgeon pins every time, though. AND CIRCLIPS!
It's not falling off, it's an upgrade opportunity.
Serlant
Posts: 111
Joined: Fri Apr 22, 2011 9:02 am

Re: Engine Rebuild.

Post by Serlant »

measure them carefully vernier or dial gauge? got the bottom end apart last night after getting the clutch nut off. took me a little while to split the cases until I realised there was a sneaky little 10 mil bolt hidden behind the clutch below the rear cyclinder still done up. came apart easily once I removed that bolt! I must have checked 10 times to make sure I didn't miss any!

the crank journals don't look too bad.
clutch side
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flywheel side
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crank looks alright although there is a strange mark on the big end surface, looks like something in the metal (impurity?)
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how the bench looks by the time I was finished last night (photo was taken at 11:45! Dedication!)
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Next is to remove the valves and springs and see about getting the valves and seats re-cut, I did a leak down test with parrafin in the combustion chambers and one cylinder lost about half the parrafin over the course of 2 days, one either didn't loose any or an imperceptable amount, so they're both ok (last time I did a compression check was 179 and 183psi on the cylinders) so that was ok but might aswell get a fresh cut while its all out(anyone recommend somewhere to get the head and valves done? possibly in or aorund plymouth? (tony?)).

then its just waiting while I buy parts and decide what to do next.
tony.mon
Posts: 15943
Joined: Wed Jul 25, 2007 10:46 pm
Location: Norf Kent

Re: Engine Rebuild.

Post by tony.mon »

With those numbers and the leakdown test I wouldn't bother getting the seats recut, just lap the valve seats in.
Have a look at the seat widths, if they're less that 3mm wide and even just a light lap with fine paste will be all you need.

Plus you probably get away with using the same shims that came out :thumbup:

You really wouldn't notice a difference getting them cut. But if you want to get them done, I don't know anyone near you, check out anyone offering engine tuning services for bikes, but it's a straightforward job if you have the kit. Otherwise, try HM Racing or Roger at Revolution, or this bunch:
http://www.bobfarnhamtuning.co.uk/whoarewe.asp
It's not falling off, it's an upgrade opportunity.
Serlant
Posts: 111
Joined: Fri Apr 22, 2011 9:02 am

Re: Engine Rebuild.

Post by Serlant »

Thanks for all the help so far tony mon :thumbup:
I got some more work done this evening, removed the gearbox and got the bearings out which is pretty easy, the design is very simple! the clutch and output shaft both have some discernable play, the clutch bearing was easy to remove but for the output shaft do I need to remove all the gears first? or does it come off the sprocket side??

you can tell which cylinder was burning oil! the rear was covered in coke! the rear exhaust valves were in a bad way one had a little bit missing off the sealing face. this is the worst one, the front valves were are ok, there is a small amount of pitting on the valve seats front and rear,
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how do the cam bearings look? I plastiguaged the oil clearances and they all came in as over 0.038 and below 0.050 service limit is 0.048.

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tony.mon
Posts: 15943
Joined: Wed Jul 25, 2007 10:46 pm
Location: Norf Kent

Re: Engine Rebuild.

Post by tony.mon »

Can't remember re the shaft, but lay everything out on clean cloth or paper or it'll be a nightmare to get back together in the right order.
It's not falling off, it's an upgrade opportunity.
Serlant
Posts: 111
Joined: Fri Apr 22, 2011 9:02 am

Re: Engine Rebuild.

Post by Serlant »

ok, i'll take it apart and see if I can get the bearing off that way, Would you say the cam bearings look worn? or ok? should they be shiney? :) (sounds retarded?)
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