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 Dropped a cylinder

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beetle
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PostSubject: Re: Dropped a cylinder    Wed Mar 21, 2018 7:06 pm

Timing chain jumping a tooth won't stop it running.

Check there's 12V at the injector. If so, it's not the relay.


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Pete Roper
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PostSubject: Re: Dropped a cylinder    Wed Mar 21, 2018 10:03 pm

Is the pin lined up with the hole in the flinger plate? If so you've gotta fix that or it's gunna work its way out and then there be trubble!

On TDC compression the peg should be at 6 O'Clock in relation to the bore as it were. Essentially 180* from its current position. I'm assuming the valves are on the rock in that pic.

If the cam timing was off a tooth you w ou'll either of bent a valve and compression would be shit on that side or it would run out of puff at 6,000rpm.

Pete
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racepics
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PostSubject: Re: Dropped a cylinder    Wed Mar 21, 2018 10:43 pm

Pete - in the pic above the piston is at tdc compression stroke - all tappets have clearance at this point

I've looked in the pdf manual for a timing diagram but there doesn't seem to be one.
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PostSubject: Re: Dropped a cylinder    Thu Mar 22, 2018 12:37 am

If that's the case then there is something rotten in the state of Denmark.

Gimme a few hours and I'll go through it.

Pete
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PostSubject: Re: Dropped a cylinder    Thu Mar 22, 2018 10:42 am

I will strip the top off the good side and post a pic of that today to compare.

As an aside, I'm going fishing for a week as of Sunday so will resume hostilities with the Guzzi upon my return Smile
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paulbrice
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PostSubject: Re: Dropped a cylinder    Thu Mar 22, 2018 1:46 pm

Presume the valve clearances are moving up and down normally as you turn it to get to TDC & they are not 'free' when the cam is at the normal TDC position ?
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PostSubject: Re: Dropped a cylinder    Thu Mar 22, 2018 2:23 pm

The timing set up is very simple.

On the end of each camshaft there is a locator peg. This slips into a hole in the sprocket. Each sprocket has two holes markets L and R for obvious reasons.

When the piston is at TDC compression the peg and its hole should be at 6 O'Clock in relation to the axis of the bore. On TDC exhaust the peg should be at 12 O'Clock and the valves will be on the rock.

On the end of the camshaft there is a flinger plate. This is the wavy item visible in the pics and its purpose is to fling the blow-by gasses and their particulate content outward as the cam spins so the oil particulates stick to the surrounding castings by surface tension lessening the amount of oil that gets passed into the condensor and re-breathing system.

The flinger plate and the sprocket behind it are retained on the camshaft by a central bolt. When this is done up it retains the rocket on its locator peg BUT for some bizarre reason the flinger plate has two holes in it which have the potential to align with the ends of the locator peg if care is not taken to avoid this when tightening the nut. If that happens the peg has the potential to pop out of the camshaft meaning that the only thing retaining the integrity of the timing will be the friction between the back of the sprocket and the flange on the camshaft. While this is the main driving force it is possible to overcome the static friction with enough force and cam timing will be lost.

I can't really make out whether there is something amiss in the photo. The first thing to do is ensure the piston is at TDC compression and undo and remove the bolt and flinger plate from the end of the cam. UNDER NO CIRCUMSTANCES ATTEMPT TO REMOVE THE SPROCKET FROM THE CAM AT THIS POINT AS THE TENSIONER PLUNGER WILL FILL WITH OIL MAKING IT VIRTUALLY IMPOSSIBLE TO REPLACE THE SPROCKET!. Once this is done you will be able to see the position of the locator peg and its hole and confirm if the timing is correct.

From this remove I suspect it is. If the timing had slipped the compression on that side would be either far too low or far too high, (I can explain the latter later after we've fixed the current problem if people would like.). I'm still suspecting this is spark related. The fact the machine was rattling along happily and suddenly went on to one and it seemingly has good fuel delivery and compression while not throwing an error code makes my crystal ball say spark.

Pete
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PostSubject: Re: Dropped a cylinder    Thu Mar 22, 2018 5:34 pm

Ok I think we're on to something. The pic below shows the right side cylinder at TDC compression stroke, and as you say the lock pin is at the bottom. You will also notice the pin is in WAY further than the pin on the left side cylinder.
I'm thinking the left side pin has worked its way out far enough to slip?

So the next question... is it safe to remove the centre bolt and plate without the sprocket dropping off the cam and releasing the tensioner?
Right - firing ok
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Left - not firing
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racepics
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PostSubject: Re: Dropped a cylinder    Thu Mar 22, 2018 6:34 pm

Something amiss here for sure


So I removed the bolt and plate (and put the bolt back in just so the sprocket doesn't fall off)
Rotated the crank a few degrees and there is a second hole (R) that lines up with a hole in the cam.
Does the cam only have one hole in it? Or L and R holes like the sprocket?
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PostSubject: Re: Dropped a cylinder    Thu Mar 22, 2018 7:30 pm

Yup, well there's the issue!

Now the whole point of the holes in the flinger plate is that they are totally bloody functionless! Why they are there God alone knows! The plate is supposed to hold the pins in place but for some reason they are made with those two bloody holes that line up perfectly with the pin and one can only assume that some dipshit thought that they should giving the pin the opportunity to work its way out. The only weird thing is why is it still pumping 150 PSI? If the valves are bent it wouldn't, nor would it if they were shut the whole time!

Anyway, the long and the short of it is you have to get it right. First up loosen the bolt on the working side and then turn the flinger plate so a solid bit of it is over the pin and then re-tighten it.

On the non running side it is going to be best if you first unload the cam chain tensioner. On the left hand side you do this by removing the small dome headed Allen screw, (4mm) in the back wall of the camchain tunnel. Then using a long, thin screwdriver slipped between the chain and tensioner blade lever the blade back. Make sure you get the screwdriver down as far as the tensioner plunger before you increase pressure as you don't want to fracture the tensioner blade. If you do it's an engine out job! Once the tensioner blade is pushed back and the tensioner plunger bled down a small thin rod, something like a 3mm Allen key or an old carburettor needle, can be pushed into the hole the dome head bolt was blocking, through the tensioner blade and into the recess in the inner wall of the cam chain tunnel. The screwdriver used to depress the tensioner blade can then be removed and the rod will hold the tension off the camchain

Make sure the pin can't drop down the camchain tunnel as when you loosen the flinger plate it will probably just fall out. Set it aside and remove first the flinger plate and bolt and then gently pull the sprocket and chain off the end of the camshaft.

At this point the sprocket will still be timed correctly but who knows where the cam will be! Once the sprocket is off you'll be able to see the peg hole in the cam flange though and if you are careful you should, (Providing it isn't damaged.) be able to re-insert the pin into the cam flange.

Look carefully at the sprocket and identify which of the two peg holes in the sprocket has an 'L' stamped next to it and then keeping tension on the chain and sprocket turn the crank until that hole slips over the peg and the sprocket can be re-mounted on the cam. Once this is done, providing the camchain hasn't had the opportunity to jump a tooth either on the sprocket or the idler shaft, the cam timing should be correct again. Turn the crank again until the peg is at the 6 O'Clock position and make sure the piston is at TDC and then check the valve clearances. If either pair are drastically out of whack then the valves are bent. If by some miracle they aren't then double check you are at TDC and that the peg is at 6 O'Clock and if it looks good reinstall the flinger plate with a SOLID part over the peg, remove the rod that is holding back the tensioner blade and put the dome head screw back in the 'ole. Tighten the cam bolt with some Loctite 243 on the threads and then turn the motor over by hand through 720 degrees at least to make sure nothing is tangling and feel the rockers from time to time to make sure the clearances don't get huge at any point.

If that all checks out? Disconnect the coils and run another compression test. If comp is good? Put H the lids on, reinstall the plugs, reconnect the coils. Pray to any or all the gods you may or may not believe in and hit the go button.........

Pete
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PostSubject: Re: Dropped a cylinder    Thu Mar 22, 2018 9:32 pm

She's a runner!!!
Bloody amazing. Many thanks for all your help Pete, owe you many beers and bbq.

Will chat more about the rollers thing when I get back from my holidays.

Cheers Team.
Chris
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PostSubject: Re: Dropped a cylinder    Thu Mar 22, 2018 9:43 pm

I strongly advise rollerising ASAP.

Glad it all turned out OK. Normally in that sort of situation it will turn to shit! Thumbs Up

Pete
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PostSubject: Re: Dropped a cylinder    Fri Mar 23, 2018 1:10 am

cheers
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paulbrice
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PostSubject: Re: Dropped a cylinder    Fri Mar 23, 2018 1:27 am

Fantastic stuff....Looks like you were saved by fact the valve springs force default to 'off cam' when the pin moves out but still amazing !. At 1500 km unlikely anyone has dug that deep before so probably came out the factory like that.
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diedel
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PostSubject: Re: Dropped a cylinder    Fri Mar 23, 2018 5:34 am

Shocked Holy shit! A real thriller!
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PostSubject: Re: Dropped a cylinder    Fri Mar 23, 2018 10:09 am

And the fact that I rode it some 10km home on one cylinder thinking it was probably an electrical issue....

It seems to me that the locating pins should be about 4mm longer than they are. When seated in as far as they can go, they are only driving on half the thickness of the cam gear. So when they move outwards and hit the flinger plate, they are only just still located in the cam flange by a small amount.
Might look at getting/making longer ones when I do the rollers job.
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PostSubject: Re: Dropped a cylinder    Fri Mar 23, 2018 12:18 pm

That might of been an idiocyncracy of very early bikes. The pegs are usually almost full sprocket depth long.

As for worrying about it when you rollerise there is no need. When you do the swap the camboxes come complete including cams with the pegs inserted. I can send you any number if you wish from dead cams in the workshop but I'd just rollerise and be done with it!

Pete
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GuzziSteve
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PostSubject: Re: Dropped a cylinder    Fri Mar 23, 2018 1:07 pm

WOW, I have never seen the big hole lined up w/pin from the factory.
Did the shops over there replace the original flats w/new & improved flats they had made up.
In USA we swapped out all new on floor and sold.
I always put one of the small holes in front of pin so I knew where it was, then the pin can't come out. This was just in case the chain came off and I was off a tooth.
The Guzzi God sure looks out for those down under!
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PostSubject: Re: Dropped a cylinder    Fri Mar 23, 2018 1:35 pm

A 2008 model would have been a pretty early build. One thing people tend to forget is that bikes aren't built by mechanics or engineers, they are put together by poorly paid, often bored and disinterested, assembly line workers. Generally they will be tasked with one or two jobs that they are swapped between. They are shown, probably once, how to perform it by someone who just might have half a clue and then they're just told to get on with it!

My guess is when they first started building the 8V whoever was given the job of assembling the top ends looked at the parts, saw the holes and how they corresponded with the peg and thought "Well that hole has to be there for a reason and it lines up with that bit so I reckon that must be how it should be."

After a few of them had spat their cam timing word probably got back to the factory and someone put the stick about and it stopped. Just a guess but if I remember rightly the arrival of the 8V was delayed for quite a while in the US while the rest of us in Europe and the antipodes crash-test-dummied the design. They may well of had that particular screw up sorted by the time they started shipping to the US.

Pete
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GHTE
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PostSubject: Re: Dropped a cylinder    Fri Mar 23, 2018 2:50 pm

Loved reading this post and understood at least 25% of it. Great outcome and it seems that luck played a fair bit in this process-go buy a lotto ticket.
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PostSubject: Re: Dropped a cylinder    Fri Mar 23, 2018 4:02 pm

affraid  A fine example why it's best to avoid the first year of any new model! Don't be Luigi's guinea pig!
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PostSubject: Re: Dropped a cylinder    Fri Mar 23, 2018 5:47 pm

For those who were having a tough time grasping the thread fine points, if I may.  What Paul was describing was the reason the compression was still good. IE the valves were both closed due to the cam being able to rotate from the pressure of the valve springs on the lobes.  This was possible as the cam was no longer pinned (doweled) to the chain and crank driven sprocket. Since Vv's were closed they didn't suffer any piston strike, consequently that cylinder maintained good compression as crank was rotated. Yeah, luck played a big part in this one.

Another good reason to keep slippery oil in em.
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PostSubject: Re: Dropped a cylinder    Fri Mar 23, 2018 6:32 pm

Ahh thanks Kel recon I am approaching a 50% pass mark now. Appreciate the effort.
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PostSubject: Re: Dropped a cylinder    Fri Mar 23, 2018 8:23 pm

Kel wrote:
For those who were having a tough time grasping the thread fine points, if I may.  What Paul was describing was the reason the compression was still good. IE the valves were both closed due to the cam being able to rotate from the pressure of the valve springs on the lobes.  This was possible as the cam was no longer pinned (doweled) to the chain and crank driven sprocket. Since Vv's were closed they didn't suffer any piston strike, consequently that cylinder maintained good compression as crank was rotated. Yeah, luck played a big part in this one.

Another good reason to keep slippery oil in em.

That's where the argument falls down. If the valves are closed there is no way for air to get into the cylinder and be compressed. At the piston descends it creates a low pressure area in the bore but without some opening through which air can enter all you'll get is a pressure drop. When the piston rises again it will just, more or less, restore the original pressure.
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PostSubject: Re: Dropped a cylinder    Fri Mar 23, 2018 9:17 pm

The cam was still turning with the engine - its was just slipped 180 degrees out because the pin wasn't locking it in position -Thats why the pin was showing at the top instead of the bottom in my photos - only the friction (tightness) of the bolt was enough to make it turn.
The cam sprocket didn't spin freely (without the cam) until I cracked the bolt open a little.
It was pretty much 180 degrees out so even though the cam was in true TDC position (not on the rock) and the piston was still at TDC - it was on the wrong stroke as far as injection and ignition was concerned.
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