180 triple knock and ignition timing

L

laverda180

Junior member
Location
Amberley, New Zealand
I am hearing the occasional knock at relatively low engine speeds upon accelerating, to less than half throttle, on even relatively gentle gradients. Change down or throttle back and all ok. Is more noticeable on hot and / or dry days and seems to be less common when I am running 100RON fuel (AGIP super+). Any thoughts? Engine has done approx 3500km since full rebuild with new Ross pistons, rebuilt gearbox, new starter clutch, etc.. Series 2 with 4C cams, CR head and original 32mm Dellorto’s opened to 36mm. Crank was determined to be good. Sachse ignition originally on curve 4, 34 degree max advance, since last 700km running curve 1 with lowest max advance, 31degree from 6000rpm with gentle curve from 7degree at 1000rpm. Static timing, valve clearances, primary (duplex) and cam chain tensions checked and found ok. Should I be worried? Engine has been run for the first 3000km at speeds upto 4000rpm, recently with the odd run to 5000rpm. Carbs were also rebuilt, float levels good, balanced, standard air box, etc.. Engine oil is Motul 3000 20w50 non synthetic.

Plugs always look good, doesn’t appear to burn oil and at 1st and 2nd oil changes (500 and 1500km) nothing untoward noticed in oil strainer. At last oil change fitted a magnetic sump plug.

My research so far suggests that low speed knock is not usual for engine designs such as this. Is that true? Perhaps I should use lower gears, but it is a knock that I hear and not any sort of lurch from the drive train, new 530 non o-ring chain and sprocket, good cush drive rubbers, etc.

Separately I am interested in thoughts re ignition timing for this engine spec. Reading earlier posts it would seem that 31 max advance may anyway be excessive for this state of tune and likely result in pinging. Some posts seem to suggest a steep advance to max 28 degree, but what is steep? From what engine speed should max advance start? What about idle advance? I think it is not too critical and recall advice ranging from 2-8 degrees, but little comment about over which rev range. From 400rpm seems good, but to 1000, 1200, 1500? Have noticed on curve 1 that idle, 1100-1200 rpm, seems more stable / reliable with a better throttle response on pulling away.

Sachse have offered to reprogramme curves when I know what I want. Currently I am thinking to specify 26, 28 and 31 max advance options each with two options for idle advance and different advance gradients (9 curves available). Current curves 1 and 4 attached.
 

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buy an Ignitech box, throw the Sachse box in the bin but keep the Trigger plate

Specify Hall Effect triggers when you buy the Ignitech box from them, once arrived install it
Plug in your Laptop and start programming your own ignition curves
Or send me a PM with your email address and I'll email you an Ignition map that you can load into the Ignitech box to get started
 
It sounds to me like you may have a worn out small end bush on one cylinder. The classic sign is, as you crest a hill on a small amount of throttle, the noise goes away.
 
FWIW, nice work on the engine, doing a lot correctly, all the makings of a good Laverda Man. Curve 1 is useless, Curve 4 is sort of ok, any HC engine has a variable fuel load, the more dense the incoming air/fuel the longer the flame front takes to consume the fuel load in a burn, ie more advance required, takes some skill to adjust a curve matched to a particular engine setup. Redax has been doing more work on this over last many years. Seen some shocker curves for various ignitions over the last 28 years... not a skill for the unskilled.

Did proffer to the few "advance the ignition for better power".... increase the advance to when the engine blows/fails, then back it off 1 degree.... not sure even then these diy had a clue.... j.
 
I have an 81 Jota with a Sachse as well it knocks and this bike is in the queue to have an ignitech module put in, those pre programmed curves in the Sachse box don't work that well on a high compression engine.
 
redax5 said:
buy an Ignitech box, throw the Sachse box in the bin but keep the Trigger plate

Specify Hall Effect triggers when you buy the Ignitech box from them, once arrived install it
Plug in your Laptop and start programming your own ignition curves
Or send me a PM with your email address and I'll email you an Ignition map that you can load into the Ignitech box to get started
Click to expand...
Hi Red, thanks, the TCIP4 unit, correct?
mauricejota7604 said:
I have an 81 Jota with a Sachse as well it knocks and this bike is in the queue to have an ignitech module put in, those pre programmed curves in the Sachse box don't work that well on a high compression engine.
Click to expand...
Hi Maurice, which curves have you tried? I guess being in Australia it is more economical / practical for you to install a programmable ignitech than to return the Sachse for reprogramming. I live in Germany so still weighing up if for me reprogramming Sachse is the way to go. Being able to define and set my own curves is though very tempting, so Ignitech probably now on the cards.

Patrick
 
iis_iis said:
FWIW, nice work on the engine, doing a lot correctly, all the makings of a good Laverda Man. Curve 1 is useless, Curve 4 is sort of ok, any HC engine has a variable fuel load, the more dense the incoming air/fuel the longer the flame front takes to consume the fuel load in a burn, ie more advance required, takes some skill to adjust a curve matched to a particular engine setup. Redax has been doing more work on this over last many years. Seen some shocker curves for various ignitions over the last 28 years... not a skill for the unskilled.

Did proffer to the few "advance the ignition for better power".... increase the advance to when the engine blows/fails, then back it off 1 degree.... not sure even then these diy had a clue.... j.
Click to expand...
thanks, engine development is more down to input of others in our community over years, my role has been more break it to give them opportunity to fix and improve it! My approach these days is more sympathetic, grew up a bit whilst bike was in storage for 18 years. Ignition timing is for me a black art, for example I had so far understood that less advance was required for higher tune!! Install a programmable Ignitech and then hand over to someone who knows what they are doing is probably way to go.

Patrick
 
I tried setting 1 as it has the least full advance but the problem is its not just full advance its the settings around 3000 rpm that's the problem in my opinion. None of the settings are ideal, the engine will run but there is quite a compromise, in saying that they are far superior to the original Bosch unit.
 
I will leave the knock diagnostics to the ignition experts. But most common wisdom ( unless I am not aware of something) in breaking in a rebuilt Laverda motor is not to limit rpms to 4000. You should confirm this for the rest of your break in. A search should do it.
 
laverda180 said:
thanks, engine development is more down to input of others in our community over years, my role has been more break it to give them opportunity to fix and improve it! My approach these days is more sympathetic, grew up a bit whilst bike was in storage for 18 years. Ignition timing is for me a black art, for example I had so far understood that less advance was required for higher tune!! Install a programmable Ignitech and then hand over to someone who knows what they are doing is probably way to go.

Patrick
Click to expand...
Hello Patrick, nice to meet you. Ducati race engines were in the day ( about 20 years ago ), running upwards of 45DBTDC ignition timing. Posted here a reference to an excellent practical research, based around air cooled light aircraft engines, much of which pertains to the air cooled engines we ride, or did ride.

Use the curve from others to begin with, modify a curve for your engine, soon become apparent how long this can actually take to have a well balanced riding curve, not a fan of dyno tuning as a sole arbiter of best road ride curves, and matching fuel load delivery... we all learn as we go... even the older hands, and minds that age with difficulty, a smile here. j
 
1200ts said:
It sounds to me like you may have a worn out small end bush on one cylinder. The classic sign is, as you crest a hill on a small amount of throttle, the noise goes away.
Click to expand...
Thanks. I have taken it out for a couple of runs but found no change in noise on cresting hills, only the occasional knock on loading engine (gentle acceleration) at around 2-3000rpm on a hill with high ambient temp (27c here yesterday, 36 C in Breganze last week) seem to be the factors. New pistons, pins installed by experts leads me to think this is unlikely. Any other way to check without stripping down? Will try curve 2 or 3 as these have slightly less advance than 1 at these revs having an idle advance of only 2 degrees.
 
OK if we are assuming the motor is detonating from the ignition providing too much spark advance and the motor has no mechanical issues to cause the noise, then I would move the carb needle up so the bike is running very rich. I would also try moving the ignition trigger plate so the bike is running with a very retarded spark.

At that point detonation should be impossible. The bike won't run very well in this condition but it will indicate if too much spark advance is the problem. If running like this you still have the noise, you are going to have to open the motor.
 
With a warm to hot ( normal road riding, engine loaded ), lower rev range, wide open the throttle, this will provoke severe pinking, for a given advance in ignition. Not certain what we are talking about here, "Knocking" is a broad term, could be a clunk, a pinking issue sounds like a bunch or marbles being rattled in the cylinder chamber ( been suggested it is the high frequency rattling of the piston in the bore ) it does not sound like a mechanical "knock" at all. As i read your ride report, loading a slow rev and opening the throttle induces the pinking, if we are discussing the same sound from the engine.

As Bruce 1200ts indicates, reducing timing is one easy method to ascertain the actual root cause of the issue. The installed ignition may well not respond to minor adjustments in timing, or have a technical problem with its curves. Dial back timing light may be a useful test tool for maping the advance curve selected. HTH j
 
"like a bunch or marbles being rattled in the cylinder chamber"

John, it sounds like you are describing a Kawasaki 500 two stroke triple. My brother had a first year model, 1969 I think? You would turn on the ignition key, a buzzing noise would appear from under the saddle from the CDI ignition. Once the bike was running it did really sound like there were marbles in the cylinders.

Bruce
 
That marbles in a can sound is exactly what I once heard on my 64 Bonnie. Being young and dumb back then I swapped a twin carb head to a single carb head and used one of the twin head carbs on it with obviously now but not to me back then way way too small jets installed. So off I go trying to keep up with much faster bikes on one of the long sweeping uphill bends on the Sydney side of The Putty Rd, now known by me as Triumph Killer Hill when that sound happened, I was wondering what it was till the bike suddenly slowed. Yep, a nice 20c coin-sized hole was melted in a piston top and a very expensive and time-consuming engine rebuild happened. That's a very expensive sound best responded to. On the 2 occasions I smashed ring lands off the inlet side of pistons in my 3c I heard NOTHING odd, zero pinging and contrary to lots of comments back then I was in 2nd gear at 3000rpms and just about to accelerate out of a 35k bend, zero lugging was happening when it either suddenly lost power or suddenly resembled a WW2 Destroyer hiding from a Submarine, massive smoke. Those 2 were put down to Detonation. The silent engine killer. Apparently fixed through a tune change but never did get the full story.
https://www.speedperf6rmanc3.com/content/Engine Basics Detonation and Pre-Ignition.pdf
 
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