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Thread: dropping a cylinder

  1. #21
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    Quote Originally Posted by ron d View Post
    Cheers ferret i will get some sealant and hopefully fit them tomorrow.
    I think sealant is a waste of time as if you ever want into the the plugs again you will find the bond with silicone restricts you from refitting with a proper seal.
    I've used "corrosion block" grease a blue high temp waterproof dielectric grease.

    If you ever do a plug chop just wipe the grease again to reseal. Might not look nice but no one is going to see it.

    Silicone has it's place but not in coil sticks. Just like in the building game it depends on cleanliness for a perfect seal.

    Just grease the coil very lightly to aid pushing past the valve cover coil grommet and then when all bolted down a smear round the coil sticks at valve cover level.

    If the coil pushes back out due to air pressure it will just be the small drain weep in the cylinder head behind the radiator gunged up. Nothing much you can do about it except push the grommet up the coil before fitting and then once the coil stick is down use a blunt tool (large allen key) to locate the grommet in the head.

    Or carry a small tube of sealant with you if you go for the silicone type version

  2. #22
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    Quote Originally Posted by ron d View Post
    Cheers ferret i will get some sealant and hopefully fit them tomorrow.
    This is what you want. Silicone grease, NOT silicone sealant
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    Don't use petroleum based grease as it will swell the rubber seal at the tip of the coil.
    To expel the air in the cavity as you slip the stick into position, slide some thin copper wire (0.6mm?) into the cavity before installing the stick, then slide it out once the coil is seated.
    hooroo, Errol www.engenia.com.au [136,351 km - and counting .....]

  3. #23
    Senior Member Trevor68's Avatar
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    And join us on bookface, we have a few members from tassie now. One day I will even trick Engenia into joining.

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  5. #24
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    Sorry Trevor, I don't do Facebook.

    Being something of a Laverda tragic, my main participation in social media is the Laverda forum.

    One of the reasons I bought the Benelli triple is that it's the next generation of the Laverda triple. (Benelli engine had its design genesis in the Laverda factory).

    The Tre-K shares the garage with a Laverda Jota amongst other things, including a Benelli 900 Sei.

    I’m a handy enough mechanic with old bikes, but I’m more used to things that have carbies, proper sized spark plugs (14mm thread) and separate coils.
    These pissy little spark plugs with stick coils buried in the cylinder head seem like a bad idea to me. Jamming a coil down a hole in the cylinder head is asking for trouble because cylinder heads get damn hot and coils don’t like heat. My Tre-K has only done 23,000 km and the coils are failing already, so it seems to me the stick-type coils are pretty much a consumable item.

    If there’s room to mount them somewhere, I’d be tempted to go back to old-school design practice of separate coils and HT leads.
    Last edited by Sprocket; 02-03-2019 at 05:39 PM.

  6. #25
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    Quote Originally Posted by Sprocket View Post
    Sorry Trevor, I don't do Facebook.

    Being something of a Laverda tragic, my main participation in social media is the Laverda forum.

    One of the reasons I bought the Benelli triple is that it's the next generation of the Laverda triple. (Benelli engine had its design genesis in the Laverda factory).

    The Tre-K shares the garage with a Laverda Jota amongst other things, including a Benelli 900 Sei.

    Iím a handy enough mechanic with old bikes, but Iím more used to things that have carbies, proper sized spark plugs (14mm thread) and separate coils.
    These pissy little spark plugs with stick coils buried in the cylinder head seem like a bad idea to me. Jamming a coil down a hole in the cylinder head is asking for trouble because cylinder heads get damn hot and coils donít like heat. My Tre-K has only done 23,000 km and the coils are failing already, so it seems to me the stick-type coils are pretty much a consumable item.

    If thereís room to mount them somewhere, Iíd be tempted to go back to old-school design practice of separate coils and HT leads.
    Where in Tassie are you Sprocket? I am down the Huon.

  7. #26
    Wyn
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    Sprocket says the design genesis for the Tornado Tre 900 engine was at Laverda. I'm curious where this comes from, as all the references say that Dr Riccardo Rosa was recruited to design the engine, and was an ex Cagiva 500GP designer - he doesn't seem to have worked at Laverda. I have read that the engine also had input from Ferrari - a triple is half a V6? I've always thought that Rosa designed what he knew as a race engine designer and the problems experienced were because he wasn't a production bike engine designer.
    Love to know more about the Laverda link as I was a frequent visitor to Slater Laverda many years ago.

  8. #27
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    Wyn - I read somewhere about the stillborn Laverda triple engine design ending up at Benelli. I'll see if I can dig up a reference. In the meantime here's some photos of the Laverda engine Moto Laverda's New Triple

    Tractorman - I live in Bellerive. The problem with my bike dropping a cylinder happened in Huonville. Can't have been far from your place!

  9. #28
    Senior Member Engenia's Avatar
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    Quote Originally Posted by Sprocket View Post
    ... stick coils buried in the cylinder head seem like a bad idea to me. Jamming a coil down a hole in the cylinder head is asking for trouble because cylinder heads get damn hot and coils donít like heat
    It's not the heat that does the damage (generally < 120C in a water cooled engine), it's the humidity. If the coil is not sealed, air is pumped in as the engine cools. If the conditions are right, the moisture will condense on the wires. Moisture and electricity are a bad mix if there are any free ions available to conduct. Once you have conduction you have current flowing where it won't do any good, and the coil fails, until the conduction path clears, but eventually the damage is too great and failure is permanent.

    The reason stick coils are preferred in a modern engine is that the voltages they generate can be higher because there is no chance that an ignition lead can break down - there is none. A higher voltage means a fatter spark with more likelihood of healthy ignition. 20,000 Volts is way better than 3,000. Touch it! You'll get the idea. ............. Actually, don't touch it. That's a bad idea.
    RobShed likes this.
    hooroo, Errol www.engenia.com.au [136,351 km - and counting .....]

  10. #29
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    The possible Laverda connection came from comments made by Piero Laverda (the surviving brother of the original Laverda motorcycle dynasty). Piero said that when Aprilia bought the Laverda factory, they didn’t buy the 3-Cylinder concept as it seems they thought it had no future and they were not willing to pay for it. Although oddly enough, they went on to design their own in-line 990cc triple for MotoGP, which they called the “RS Cube”.

    Anyway, the story goes that some of the personnel from the Laverda design team for the 3-cylinder engine had connections with Benelli, and to quote Piero: "You could argue that the Benelli Engine is based on the concept of the engine that was under construction in the 90's at Laverda."

    So, I don't know whether Laverda's design drawings found their way to Benelli, but Piero seems to indicate that there was some kind of technology transfer.

    On the other hand, it may all be rumour and wild speculation. Next time I see Piero, I’ll ask him.

    RobShed likes this.

  11. #30
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    OK. I got the coils out. What a pain in the arse they are to get at. You wouldn't wanna have to change a spark plug on the side of the road.

    This is the only vehicle of any sort I’ve come across where the cylinders are numbered from right to left. It must have been builtby Arabs (Arabic writing goes right to left).
    Anyway, the dodgy cylinder was the right one (#1 according to Benelli, #3 according to normal convention). I’ll stick with R, C & L for Right, Centre and Left to avoid confusion.

    Primary resistances measured: R 1.0 Ω; C 0.7 Ω; L 0.6 Ω. They’re supposed to be 0.6 Ohms, with 1.0 max, so the R coil is at the limit of acceptable spec. Perhaps it gets worse when hot.

    As for secondary resistances, the workshop manual says 10 KΩ, which is a typical figure that I’d expect for an ignition coil. Mine all measure around 15 MΩ, so they’re either way out of range (by a factor of 1500) or the book is wrong, or I've done something stupid with my meter (although it's a self-ranging meter so not easy to stuff up). I’d be interested to know if anyone else has measured secondary resistances and what values they got.

    Cheers,
    Cam



    PS: Found this replacement coil out of China
    https://www.aliexpress.com/item/Igni...f6296c75ESaB22

    For $25 US it's almost worth a punt! Although I've been stung with cheapo Chinese coils before.
    Last edited by Sprocket; 02-06-2019 at 08:49 PM.

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