The BSA A7-A10 Forum

Technical => A7 & A10 Engine => Topic started by: Greybeard on 04.04. 2016 18:59

Title: Decarbonising my engine
Post by: Greybeard on 04.04. 2016 18:59
I have finally managed to stop prevaricating and made a start on getting my '55 Plunger A10 sorted out for this years riding season. If I do nothing else I want to fit a longer legged gearbox sprocket to allow more comfortable cruising speeds. As has been recently discussed I need to take the lump out and unbolt the gearbox from the engine before I can change the sprocket.
 
I put the machine back on the road three years ago after being stored for over thirty years. I've not done a huge mileage since then; I'd guess less than 10k miles. Today I took off the head. Thankfully the bores are good. What surprised me was the amount of carbon. The head and piston tops are thick with carbon and in the combustion chamber there were some chunks of soft carbon build up. The exhaust valve heads are a nice beige but the inlets are black.
Now, I don't usually drive the old girl hard, preferring to potter.  In normal UK weather the engine starts without needing choke. The engine ticks over sweetly and pulls really nicely without any flat spots when making progress. I have an air filter. I use a fuel additive. I have the original Amal 276 carb with a new slide and needle fitted.
What do you think of all this? Is it a case of needing to flog these engines often to keep them clean? Is my carburetor too rich? If so what should I be adjusting?
Title: Re: Decarbonising my engine
Post by: metalflake11 on 04.04. 2016 19:25
Fuel additive for me, after only 10,000 miles the engine shouldn't be coked up.
Title: Re: Decarbonising my engine
Post by: morris on 04.04. 2016 20:34
Hi GB,
I would experiment with some smaller main jets.
They are easy to change on a monobloc and they do have an influence through the range.
My plunger ran to weak (concentric carb). Went up 2 sizes main jet and now the plugs have a healthy brown colour.
Title: Re: Decarbonising my engine
Post by: muskrat on 04.04. 2016 21:16
I'd be looking at fitting a hotter plug, say a B6HS.
Too much lugging in a high gear will carb'em up.
Cheers
Title: Re: Decarbonising my engine
Post by: chaterlea25 on 04.04. 2016 21:35
HI All,
If the bike is only pottered about no point on changing main jets
Start off by fitting a new needle jet and needle
Its surprising how much they wear !!

John
Title: Re: Decarbonising my engine
Post by: Rocket Racer on 04.04. 2016 23:44
If its carboning up, the previous posts are all good recommendations.
The worry I have with engines that potter is that apart from not getting hot enough so that carbon builds up, they can also glaze rings, which can encourage the carbon build up.
So I'd be looking to give it a deglaze and fit fresh rings.

Rings need to do hard work early in their life. They don't appreciate gentle running. plenty of revs, not laboured.

Fully understand wanting a cruising top gear, but it does mean the engine is further encouraged to labour and any hills or passing require down changes, so can be counterproductive - lower oil pressures, more load on the bearings...

As a counterpoint; not that I'm recommending it, Eddie Dow noted a safe continuous max rpm of 6800 for a sound engine and my race engine routinely pulls into the sevens in top gear. Just watch you don't over gear is all I'm saying.

While the box is out, it might be a good opportunity to review the gearbox bushes and layshaft for wear.
Title: Re: Decarbonising my engine
Post by: Greybeard on 10.04. 2016 17:45
Ok, thanks guys. Sorry I haven't replied until now.

I've just been for a short ride on my black beauty! It's the first ride since last autumn and it felt GREAT! She fired up on the first kick! I've fitted a 20 tooth gearbox sprocket and was a bit worried that the old girl might not like pulling a longer legged ratio but she still pulls like a train. I need to check the speedo readings when I've charged up my old tablet that has a speedo app installed.

I decoked the combustion chamber, valve faces and piston tops, (remembering to leave the bores alone). I've decided to stop using fuel additive as I think that almost two-stroke Petroil mixture was contributing to the carbon buildup. I've also decided to use Super Unleaded, (RON 98) rather than Standard Unleaded (RON 95?).

Chaterlea25: I've lowered the carb needle by one groove. Needle and jet were replaced during rebuild
Rocket Racer: I'll try to make sure the engine gets a good burn-up every now and then.
Muskrat: I'll keep an eye on plug colour and go hotter if it's still needed.
Morris: 276 carb
Metalflake11: See above

Thank you for all your input.  *smile*
Title: Re: Decarbonising my engine
Post by: morris on 10.04. 2016 22:33
Morris: 276 carb

Ooops... *red*
Title: Re: Decarbonising my engine
Post by: muskrat on 11.04. 2016 09:31
Now it's done I'll tell you the old fashioned way to do a decoke. Bring motor up to operating temp, remove the air filter. Find a squrty bottle and fill with water. Start the motor and hold it WOT (wide open throttle) now squirt water into carb mouth. Watch the s&it fly out the exhaust pipe. You can also use this method to deglaze a bore by changing the water for bonami/ajax. *eek* *bash* *evil* *whistle*
Now I'll run for cover.
Cheers
Disclaimer. That's how the old mechanic did my grandfathers EH Holden in 1966.
Title: Re: Decarbonising my engine
Post by: Greybeard on 11.04. 2016 14:12
Now it's done I'll tell you the old fashioned way to do a decoke. Bring motor up to operating temp, remove the air filter. Find a squrty bottle and fill with water. Start the motor and hold it WOT (wide open throttle) now squirt water into carb mouth. Watch the s&it fly out the exhaust pipe. You can also use this method to deglaze a bore by changing the water for bonami/ajax. *eek* *bash* *evil* *whistle*
Now I'll run for cover.
Cheers
Disclaimer. That's how the old mechanic did my grandfathers EH Holden in 1966.

Ok Musky, you do it first and let me know if you are happy about it.

I've noticed that a little water sprinkled on flames makes a big display. I guess the Hydrogen in the water is being released. I know that old tractors injected water into the combustion chamber to aid the burning of their fuel, (paraffin?). I have also often noticed that my old banger motor cars have gone better in the rain.
Title: Re: Decarbonising my engine
Post by: metalflake11 on 11.04. 2016 18:19
Now it's done I'll tell you the old fashioned way to do a decoke. Bring motor up to operating temp, remove the air filter. Find a squrty bottle and fill with water. Start the motor and hold it WOT (wide open throttle) now squirt water into carb mouth. Watch the s&it fly out the exhaust pipe. You can also use this method to deglaze a bore by changing the water for bonami/ajax. *eek* *bash* *evil* *whistle*
Now I'll run for cover.
Cheers
Disclaimer. That's how the old mechanic did my grandfathers EH Holden in 1966.

I've heard about the water one, there's even a modern product on You-Tube that claims to de-coke an engine by squirting it into the air filter housing................................But Ajax for a deglaze *eek* *eek* *eek*.......Wow!!!
Title: Re: Decarbonising my engine
Post by: shabashow on 11.04. 2016 19:19
I think water injection such as for extra power in military aircraft piston (and some early jet) engines was more to do with the cooling effect allowing more fuel and air to be burned because cooler gasses are denser and contain more 'stuff' than warmer gasses. I doubt that conditions will be right in our engines to break the hydrogen-oxygen bond in water. Remember water as well as CO2 are the end products from our combustion chambers. I think it was a purely physical effect (depending upon how much water is squirted in) that got the muck out of your old holdens.
Title: Re: Decarbonising my engine
Post by: muskrat on 11.04. 2016 20:34
I decarboned the old XT500 that way about 25 years ago. She's still going.
I have used the Ajax method to bed in new rings in the A7SS at the races. Quick rebuild o/night, the only spare rings were next o/size. A couple of puffs within 30 seconds of start up, a quick oil change (a little will get past the rings into the oil), out to race with full (14:1) compression. Even did it to a Chev 350 sprint car motor that went out and won 3 out of 4 races. I'd be a bit shy doing it to a road motor.
Cheers
Title: Re: Decarbonising my engine
Post by: coater87 on 11.04. 2016 23:50
 Ive never heard of using ajax, but Bon-Ami on the other hand- yes.

 It has a baby chick on the can and the slogan is "hasn't scratched yet!" , so how could it be bad for the motor? *eek*

 You think back to all the things we have seen and done to engines, its amazing anything still runs and that we are still alive.

 Like the spray can of either cobbled to the choke cable on an old Pontiac Boneville just to give some extra ooomph while passing....she went pretty good for a short while. *ex* *smile*

Title: Re: Decarbonising my engine
Post by: Greybeard on 12.04. 2016 09:20
I needed to research Bon-Ami; I've never seen the product in the UK.

https://en.wikipedia.org/wiki/Bon_Ami
Title: Re: Decarbonising my engine
Post by: BSA_54A10 on 12.04. 2016 11:04
Now it's done I'll tell you the old fashioned way to do a decoke. Bring motor up to operating temp, remove the air filter. Find a squrty bottle and fill with water. Start the motor and hold it WOT (wide open throttle) now squirt water into carb mouth. Watch the s&it fly out the exhaust pipe. You can also use this method to deglaze a bore by changing the water for bonami/ajax. *eek* *bash* *evil* *whistle*
Now I'll run for cover.
Cheers
Disclaimer. That's how the old mechanic did my grandfathers EH Holden in 1966.

Ok Musky, you do it first and let me know if you are happy about it.

No the hydrogen is not being released and burned.
Hydrogen burns wih an intense white flame, bloody quickly.

It is pure physics.
16 mils of water ( 1/2 teaspoon ) turns into 22.7 liters of steam at 100 deg C , 1 atmosphere of pressure at sea level.
However it is 1600 deg C in the cylinder so you get a 16 time volume expansion due to the heat.
But at those temperatures the normal steam turns into super steam , then dry steam, then dissasociated dry steam.
At each phase change there is a massive volume increase and this is what cleans off the carbon deposits, and all the oil off the cylinder walls so you don't do it for very long.

When I was running the foundry we did the calculations ( don't ask me to do them now ) but what we told the new furnace men was a 2 liter milk carton od water in the copper furnace turns into an 8 lane 50 meter long swiming pool of steam in less the 1/5 a second.
Most of them could visualise that and then noting that the furnace was about 4 vans in volume would ask where the metal goes when this happens .
I used to point to the dags of metal hanging from the rafters, 100 foot away at the other end of the building.
They got the message and made sure every thing that went nto the furnaces was dry.

Back in the blue smaoke days it was SOP every month or so, just had to make sure mums washing was not on the cloths line.

I've noticed that a little water sprinkled on flames makes a big display. I guess the Hydrogen in the water is being released. I know that old tractors injected water into the combustion chamber to aid the burning of their fuel, (paraffin?). I have also often noticed that my old banger motor cars have gone better in the rain.
Title: Re: Decarbonising my engine
Post by: Greybeard on 12.04. 2016 11:15
Quote
I know that old tractors injected water into the combustion chamber to aid the burning of their fuel, (paraffin?). I have also often noticed that my old banger motor cars have gone better in the rain.
So, what's going on when water aids combustion?  *conf2*
Title: Re: Decarbonising my engine
Post by: bsa-bill on 12.04. 2016 18:18
Quote
So, what's going on when water aids combustion?

Is it not related to the density of the mixture, sort of like an increase in compression, bot an expert in physics though
Title: Re: Decarbonising my engine
Post by: BSA_54A10 on 13.04. 2016 11:32
Quote
So, what's going on when water aids combustion? 

It does not aid combustion in any way shape or form.
It simply acts as a steam engine and robs some heat from the flame front

The amount of energy that it takes away from the combustion is substantially less than the energy available from the expanding steam.
Thus the engine runs a lot cooler because you are actually using some of the 70 to 80 % of the energy from combustion that would normally go out the exhause as waste heat.
The auto industry played with it for years but gave up for exactly the same reason you old Kero tractor got replaced.
You have to start up on petrol to heat the engine.
When it is up to operation temperature you then have to get the water into the cylinder plus a little oil to stop scouring on the rings .
You also need to run the engine a bit leaner so you have to change the air fuel ratio.
When you shut down you have to finish back on fuel so as to leace oil on the cylinder wall or the engine & valves will rust between uses.

I knocked around with a bloke who set up an old Holden 138 Cu" grey engine with a deisel fuel injected head and two carburettors.
HE started the car on petrol then switched over to water and the second carb jetted very very lean.
The car got around 120 MPG on a run and had tons of torque, enough to strip all the teeth off several gears on more than one occasion.
Back in the 60's it was a difficult car to drive as all this had to be done manually and if you switched carbs too earlly you got detonation & a holed piston and if you switched too late you got water wet plugs.
So it was a set up that never would have worked with Joe Public.
However now days with computer controlled engines it will be a doddle you would just need 2 injectors per cylinder and when you get home the engine would go through the run down proceedure after you switched it off, A problem for people with small garages but I can see it making a come back as car makers get stretched to compete with "clean" electric vehicles.
After all I have an LPG vehicle that does the first bit quite well, you just need to program a run down into the computer.
Title: Re: Decarbonising my engine
Post by: Greybeard on 13.04. 2016 13:23
Quote
So, what's going on when water aids combustion? 

It does not aid combustion in any way shape or form...

It simply acts as a steam engine and robs some heat from the flame front

---- SNIP ----

Really fascinating information, thanks!
Title: Re: Decarbonising my engine
Post by: duTch on 14.04. 2016 09:43

 Interesting stuff, have ta love the old grey motors, and can live without Joe Pubelick anyway, but I have to ask in a maybe dyslexic moment, if you mean 'less' or 'more' (underlined);
 
Quote
The amount of energy that it takes away from the combustion is substantially less than the energy available from the expanding steam.

 The Cat D4 we had on the farm had a kero starter motor, then ran on distillate (which reminds me, a guy I did a job with the other day told me the local BeePee factory is being dismantled-as discussed elsewhere)

 My Ma's hubby (he hated being called that) used to talk about running old Fords with a water drip feed into the carb  *dunno*
Title: Re: Decarbonising my engine
Post by: Greybeard on 17.04. 2016 17:22
As I had dropped the carb needle one groove I wanted to check the plug colour. So today from a fast speed I selected neutral, hit the kill button, stopped the engine and rolled to a halt so tick-over didn't soot the plugs up as advised in tuning manuals. Both plugs were a mid brown/mushroom colour so I am pleased with the running mixture. While checking the plugs beside the road a very nice chap pulled up in his car to ask if I needed any assistance. How good is that?  *smile*
Title: Re: Decarbonising my engine
Post by: muskrat on 17.04. 2016 18:35
While checking the plugs beside the road a very nice chap pulled up in his car to ask if I needed any assistance. How good is that?  *smile*
Exactly the same for me the other week. I always do the same.
To do a plug chop for best reading of the needle clip position. Riding at 1/2 throttle (mark the twist grip before you start) up a gentle slope for a few hundred yards, pull the clutch and hit the kill button, coast to a stop. Even just a few revs at any other throttle position will mask the reading. I also use an endoscope camera to look at the piston crown.
Cheers
Title: Re: Decarbonising my engine
Post by: BSA_54A10 on 19.04. 2016 13:12
Because you arre using heat from the combustion of the fuel to turn the water into steam, it robs the energy from the combustion thus the amount of work the fuel air buring does is reduced.
However the small amount of heat "stolen" from the combustion is a lot less than the massive amount of energy released due to the formation of steam.
If it was not this way it would go slower when you turned the water on.
It is just the conversion of heat into pressure energy raising the steam is substantially better ( more efficient) than the conversion of heat into pressure from the burning of the fuel.
Because the water turning inot steam is taking energy from the burning fuel it actually cools it down so you can run a much more lean air:fuel ratio.

 have been hearing rumbles of this being applied to truck engine in te near future again in order to pretend to meet exhaust gas EPA requirements.
Title: Re: Decarbonising my engine
Post by: cyclobutch on 19.04. 2016 13:19
While checking the plugs beside the road a very nice chap pulled up in his car to ask if I needed any assistance. How good is that?  *smile*
Exactly the same for me the other week. I always do the same.
Cheers

When my T3 ground to a halt Sunday I soon had two other Guzzi mounted riders pull up, but all they did was take the p155. But then they had just been at the same pub as me on a branch meeting. Turned out my RH plug lead had popped off at the same time I had to switch the tank to reserve (LH tap) - what are the chances of that happening?
Title: Re: Decarbonising my engine
Post by: Greybeard on 19.04. 2016 13:57
When my T3 ground to a halt Sunday I soon had two other Guzzi mounted riders pull up, but all they did was take the p155. But then they had just been at the same pub as me on a branch meeting.
Maybe they overheard you bulling up the virtues of a T3!
Title: Re: Decarbonising my engine
Post by: metalflake11 on 19.04. 2016 14:49
Interesting this water/steam business. On a warm summers evening going through a mist due to crossing a river has always made mine improve noticeably. Good theories as to why.

However, I can confirm without any contradiction, that filling your tank with diesel does not have a good effect though, so don't do it!
Title: Re: Decarbonising my engine
Post by: kiwipom on 19.04. 2016 22:20
hi guys, when water turns to steam it expands 1600 times its own volume, cheers