Hi
My bike sometimes suffers detonation at low revs which is at worst dangerous in a tight bend or very bad for the motor.I've put this down to over advanced ignition or poor fuel as it only happens when I've forgotten about it.My neighbour drove a petrol tanker and told me that all the different brands fill up at the same terminal at Imingham .But I am suspicious of super market petrol as I have had pre ignition problems with old bikes that stopped when filled up elsewhere.Apparently they can call all sorts of different stuff "Petrol" and sell it .Buying the "Super" doesn't guarantee a cure because it is usually old stock and stale.I shall now check the throttle pot and also take note of where I fill up.I am surprised by this as a flat top piston four valve head is usually quite resistant to Knocking and is anyone else having this problem.
Detonation
Re: Detonation
Sure it's not just lugging if at low revs in a high gear? Twins don't like that and it could be damaging to the engine.
If you think it's fuel drain or use it up and replace with fresh. Maybe try a fuel system cleaner additive that cleans the carbs and combustion chamber?
No idea about Supermarket fuel but I've pretty much only used Sainsburys in mine since new (Nearly 25K miles) Never had a problem and my tank and carbs are spotlessly clean.
The one good thing about supermarkets is they shift so much fuel it never has a chance to go 'stale'
Might be worth balancing the carbs and I've recently done the TPS mod (search for it) which definitely smoothed mine out a bit.
Other than that no idea. Timing is fixed, not like it has a distributor, although I think the base setting of the TPS (Throttle position sensor) can affect the timing if I understood correctly the discussions on here about it.
If you think it's fuel drain or use it up and replace with fresh. Maybe try a fuel system cleaner additive that cleans the carbs and combustion chamber?
No idea about Supermarket fuel but I've pretty much only used Sainsburys in mine since new (Nearly 25K miles) Never had a problem and my tank and carbs are spotlessly clean.
The one good thing about supermarkets is they shift so much fuel it never has a chance to go 'stale'
Might be worth balancing the carbs and I've recently done the TPS mod (search for it) which definitely smoothed mine out a bit.
Other than that no idea. Timing is fixed, not like it has a distributor, although I think the base setting of the TPS (Throttle position sensor) can affect the timing if I understood correctly the discussions on here about it.
'02 VTR1000-FY Yellow.
'12 Moto Guzzi Griso 8V SE Tenni.
'12 Moto Guzzi Griso 8V SE Tenni.
Re: Detonation
Timing isn't fixed, there's an advance curve pre-programmed into the ignition module which is dependent on revs and the tps sensor.Rob wrote:Sure it's not just lugging if at low revs in a high gear? Twins don't like that and it could be damaging to the engine.
If you think it's fuel drain or use it up and replace with fresh. Maybe try a fuel system cleaner additive that cleans the carbs and combustion chamber?
No idea about Supermarket fuel but I've pretty much only used Sainsburys in mine since new (Nearly 25K miles) Never had a problem and my tank and carbs are spotlessly clean.
The one good thing about supermarkets is they shift so much fuel it never has a chance to go 'stale'
Might be worth balancing the carbs and I've recently done the TPS mod (search for it) which definitely smoothed mine out a bit.
Other than that no idea. Timing is fixed, not like it has a distributor, although I think the base setting of the TPS (Throttle position sensor) can affect the timing if I understood correctly the discussions on here about it.
But there's no advance plate behind a points plate, like on old bikes, if that's what you mean, it's an electronic ignition system.
Oldbikeman, it isn't likely that you're getting pinking (predetonation), as the compression ratio isn't high enough, unless for some reason the ignition trigger (sort of oddly spoked wheel on the RH end of the crank) has been moved on the crankshaft.
Even with a 4 degree advancer and high compression pistons mine only occasionally does this on std 95 RON petrol, and not at all on 98.
I think your problem is something else, maybe running very lean?
But pull the plugs and see, there's a useful colour chart in every Haynes manual that should give you some corroboration if it's that.
It's not falling off, it's an upgrade opportunity.
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oldbikeman
- Posts: 280
- Joined: Sun Jul 25, 2010 3:32 pm
Re: Detonation
Hello
When it does happen it is at off or very low throttle under light load (2nd gear tight S bend)and occurs as one violent bang inside one of the combustion chambers.Classic detonation.When balancing through a difficult tight S bend it makes the bike react as though you had run over something with the rear wheel.You cannot just make it happen at will .The super market here is very busy so it would be down to bought quality as they really squeeze the suppliers.If it's not gas then I would guess it's over advanced ignition from a out of range TPS.If I just leave it then serious damage will happen.In every other aspect the engine is very nice ,runs like a watch.
I would be surprised if it is not happening to other bikes but you must be able to recognise the symptoms which is not easy .
When it does happen it is at off or very low throttle under light load (2nd gear tight S bend)and occurs as one violent bang inside one of the combustion chambers.Classic detonation.When balancing through a difficult tight S bend it makes the bike react as though you had run over something with the rear wheel.You cannot just make it happen at will .The super market here is very busy so it would be down to bought quality as they really squeeze the suppliers.If it's not gas then I would guess it's over advanced ignition from a out of range TPS.If I just leave it then serious damage will happen.In every other aspect the engine is very nice ,runs like a watch.
I would be surprised if it is not happening to other bikes but you must be able to recognise the symptoms which is not easy .
Re: Detonation
That's what is known on these as a carb cough, or on Superhawk forum as a carb fart.
It's where part of the incoming charge through the carburettor detonates inside the airbox- possibly a tiny bit of glowing carbon blown back through the inlet valve or exhaust valve into the airbox. The valves are actually open as the piston starts to rise in the bore, and the incoming charge starts to fill the chamber due to the incoming fresh charge gas intertia in the stack and airbox. If the outgoing charge is still burning, or a small glowing bit of carbon is able to ignite the incoming charge early, it burns back into the airbox.
You can feel it as a single bang through the tank, as well as hear it, and sometimes it causes a stall.
Usually when the bike is warming up, at low revs, as the throttle is opened.
It can be improved by balancing the carbs, as has been suggested, by setting the tickover a little higher than would be normal, around 13-1400 rpm, and also by fitting an ignition advancer.
It's not fuel-related; it's a result of huge carbs and the cam timing/ignition timing.
Detonation is a light ticking noise when the throttle is opened hard at low to medium revs, when the engine is under load, uphill or in too high a gear.
The compression ignites the charge inside the chamber, due to pressure and conditions rather than the spark plug starting the burn.
It can cause damage to valve seats, and if ignored, can also burn a hole in the piston crown, but I've never known it to be a problem in Storms due to the low state of engine tune.
It's where part of the incoming charge through the carburettor detonates inside the airbox- possibly a tiny bit of glowing carbon blown back through the inlet valve or exhaust valve into the airbox. The valves are actually open as the piston starts to rise in the bore, and the incoming charge starts to fill the chamber due to the incoming fresh charge gas intertia in the stack and airbox. If the outgoing charge is still burning, or a small glowing bit of carbon is able to ignite the incoming charge early, it burns back into the airbox.
You can feel it as a single bang through the tank, as well as hear it, and sometimes it causes a stall.
Usually when the bike is warming up, at low revs, as the throttle is opened.
It can be improved by balancing the carbs, as has been suggested, by setting the tickover a little higher than would be normal, around 13-1400 rpm, and also by fitting an ignition advancer.
It's not fuel-related; it's a result of huge carbs and the cam timing/ignition timing.
Detonation is a light ticking noise when the throttle is opened hard at low to medium revs, when the engine is under load, uphill or in too high a gear.
The compression ignites the charge inside the chamber, due to pressure and conditions rather than the spark plug starting the burn.
It can cause damage to valve seats, and if ignored, can also burn a hole in the piston crown, but I've never known it to be a problem in Storms due to the low state of engine tune.
It's not falling off, it's an upgrade opportunity.
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oldbikeman
- Posts: 280
- Joined: Sun Jul 25, 2010 3:32 pm
Re: Detonation
Hi
You are maybe describing pre ignition which it is not and also any twin making 100 hp per litre is pretty highly tuned.A vtr runs slipper pistons has huge ports and fairly sporty cams and massive carbs in fact it is ahead of a rc51 in some areas. Detonation is not light as it cracks nearly anything inside the cylinder-pistons,valves,plugs,heads etc. It may be happening to some but they recognise it as backfires .I have been using a Esso garage this week and so far no problems but different weather conditions also can have effect as the air is now colder so I cannot be certain.
You are maybe describing pre ignition which it is not and also any twin making 100 hp per litre is pretty highly tuned.A vtr runs slipper pistons has huge ports and fairly sporty cams and massive carbs in fact it is ahead of a rc51 in some areas. Detonation is not light as it cracks nearly anything inside the cylinder-pistons,valves,plugs,heads etc. It may be happening to some but they recognise it as backfires .I have been using a Esso garage this week and so far no problems but different weather conditions also can have effect as the air is now colder so I cannot be certain.