Lies Mother Told You

AndyW said:
Sounds like a Viccy bodge to me.. :D
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Ken Oath.... you keep running that soft motor on 91 just don't open the throttle  :'(
Only plus side to runnin that shit is the xtra coin in ya pocket at the end of a day.... gotta be change for at least 3 sherberts  :LOL:
 
Curious about continuing spark plug issues reported here. I used to have trouble with fouling plugs when had original ignition, but once upgraded to modern version have never had an issue since ???. (be very few still on original you would think)
My current plugs (NGKs) have done 20,000+kms, starts at hit of the button and good as gold..........
 
I thought his take on cams/shapes and valve clearances was also very interesting and went some way to explaining the physical differences between the A11 and 4C cams and why some regard the A11 as a superior cam profile..


cam5.jpg
The cam lobe profile layed out linearly, allowing a more intuitive view of the transitional nature of the clearance ramps.
 
True Andy. I'm sure many think valve clearance is to accommodate heat and stretch at high revs ... conrods will stretch close to a mm at high revs, which is why a piston to head clearance is nec. But valves, and the hammering of seats and the valve face is another thing entirely.

Interesting to note the comments on better ignition coils in light of his remarks about poor carburation. Wonder if the Mikuni brigade have fewer issues due to better fuel metering at low throttle openings? I'm guessing riders who upgrade to Miks or Keihins also upgrade ignition sys.

I've never fouled a plug on the SF, regardless of the many states of tune it's been through. It has always been a very forgiving motor.
 
Spark plug life has been an issue with my Jota since I first bought the bike. It had Dellortos and a DMC 1 when I bought it. Some years later the DMC got replaced with an Ignitech. Then another couple of years later, the carbs got replaced with Mikunis. The bike has been dyno tuned several times to make sure carburettor and ignition settings are OK. But the plug issues remained through all the upgrades and tuning.

I suppose the root cause could be mechanical, such as sucking a bit of oil into the cylinders. The engine has done around 100,000 km. It runs well and doesn't blow any visible smoke. But maybe the rings and valve guides are past their prime.

Interestingly, when I pull a misfiring plug, there's no obvious fouling on it. The colour always looks OK and it's the same as the plug in the next cylinder that's working OK. In fact, I can't tell which cylinder is misfiring just by looking at the plugs. But replacing it with a new plug always clears the misfire. Occasionally, when I haven't had a new plug to hand, I've restored a misfiring plug to working condition by heating it with a propane torch to burn off any residue that might be on it. But the burn-off fix doesn't tend to last very long. A couple of tankfuls of fuel later and it starts to misfire again. Can get a bit tedious on a long trip.

 
Get a water testing kit - and use it. Local marina may carry a kit.
On the current fuels it's my experience that the old sandblasting won't restore a fouled plug. There's some kind of surface chemical reaction occurs - which seems to be irreversible.
Also check plug cap resistances...
 
I experienced the hard starting and misfiring after 2-3000km on my RGA when it had the original BTZ, but it was something that set in at a certain point.  It seemed to be an age related issue of the ignition system in some way.  It was cured with an IIS and later the Autronic EMS and it has never come back.  I've never experienced it on a bike with any of the aftermarket digital ignitions DMC/IIS/Sachse/Ignitech.
Interestingly, the original BTZ system on my 79 Jota was still working fine until last year when I replaced it with an Ignitech (still using original pickups).  It would very occasionally foul one plug if I was dithering with my gloves and left the choke on, but that was operator error.  Other than that it ran fine other than the hunt at ~2800rpm which is a feature of the system.  It would never develop that same hard starting/misfire, neither before the engine rebuild when it was totally knackered and using heaps of oil and fuel, nor after.  And the system was then more than 20 years older than the BTZ on the RGA which seemed to 'go off'.  Weird.
These days I only change plugs when I can't recall how long it's been since I last did it and feel guilty.
 
When I first built the Mongrel RGS it was fitted with the original BTZ system & dellorto carbs. I experienced cold fouling almost weekly. I did however run the bike on Avgas while on the isle of man for three weeks & never had to touch the plugs.
Go figure!

When I rebuilt the engine after crankcase repairs I modified & fitted a set of Keihin CVK's from a Triumph. Ran that set up for near 3 years, never fouling a plug. 2 years ago I upgraded to DMC ignition & rejetted the Keihin carbs & that transformed the bike. I had never come across the issue of cold fouling until I ran my Laverda &  tried restoring fouled plugs without much success so gave up trying( didn't throw them out tho. Box of them in the workshop waiting for a method of fixing ::))

TT1 rep runs BTZ & 36mm Dells. Cold fouls on regular basis. I'm going to do the opposite this time & upgrade the ignition first. Hopefully that will cure the fouling.


I don't remember my mates with Laverdas back in the day complaining of fouling plugs. Has it always been an issue with these bikes or is it a recent phenomina(doo doo, doo doo, doo) with modern fuels?


Graham
 
It's a very interesting article isn't it. Most of it was of passing interest but I sat up was regarding what he said about K&N filters and petrol. I have found that using the expensive premium grade of fuel - Shell V power for example seems to makes my bike go like a rocket. No pinking at all which I have found can happen on tesco type fuel.  Also with the K&N filters something marvellous happened in that my middle plug ceased fouling immediately (had always been an issue). Also the fuel consumption improved a a bit along with the engine feeling very lively indeed.

Its a very happy bike now, and I can't remember when I last had to replace a plug because there was something wrong with it.
 
TheWrongTrousers said:
It's a very interesting article isn't it. Most of it was of passing interest but I sat up was regarding what he said about K&N filters and petrol. I have found that using the expensive premium grade of fuel - Shell V power for example seems to makes my bike go like a rocket. No pinking at all which I have found can happen on tesco type fuel.  Also with the K&N filters something marvellous happened in that my middle plug ceased fouling immediately (had always been an issue). Also the fuel consumption improved a a bit along with the engine feeling very lively indeed.

Its a very happy bike now, and I can't remember when I last had to replace a plug because there was something wrong with it.
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Proof it was set up far too rich beforehand... properly set up, it would not have required any mods at all and the bike would have been happy a lot earlier. :D

piet
 
I agree Piet. By the way its a standard Jota in almost all other respects. It used to have an empty airbox so I once thought I was being very clever and purchased an air filter and installed it. The bike became totally sick so I threw it away.  Then I read the laverda twins and triples bible by Ian Fallon. By reference to my frame number I discovered (if memory serves) that my model was up jetted as standard and was supposed to run with just an empty airbox. I guess this must explain it.
 
Don't like the no-air-filter thing one bit on a road bike - my SF destroyed its bores (which i discovered when I pulled the top end off with 65,00 miles on it, so may have had some wear anyway  :D) after running on long highway trips including dirt roads in the north of OZ for several years. Rings in several pieces, ditch sized ridges at the top of the bores ... straight to 80.6mm from 80.0mm std. Oh boy, did it feel like a rocket after that rebuild!

I reckon it's possible to give clean air to the motor without having to sacrifice much of anything - if you find the right filters (for me that equals BIG filters).
 
Quentin,

My triple hasn't seen an air filter since 1980!

Bores and pistons were still servicable after 60000km when I tore the engine down to fit 78mm pistons with the lightened crank.  Apart from the normal top groove wear, the forged Asso pistons that I had fitted in 1991 could be re-used without issue.  Bore wear was as expected, traces of the original hone pattern were still visible with no ridges at top nor bottom of ring travel.

Guess it has a lot to do with the environment the engine is run in.  Lots of dust in dry conditions might wreck an engine quickly, but we have no un-surfaced roads and it's mostly wet here... at least moist. :D

piet
 
sfcpiet said:
it's mostly wet here... at least moist. :D

piet
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That?s music to my ears ........ so much fun can be had in those conditions  :P
Oh, you mean weather?

My Jota had no air filters for a few years, no bad outcomes. But rarely rode it on anything but tar, at a snails pace ::)

I saw the inside of a 1200 after it did a trip the The centre of Australia, with air filter in place ..... fine red dust everywhere.

 
Yep, I'm sure thousands of ks on dusty dirt did the damage - especially between Darwin and perth, bulldust (read talcum powder like dust) aplenty. Even on 100% sealed roads I still won't run my motor without filters tho. Figure filters can't hurt if they're done well.
 
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