Author Topic: Decarbonising my engine  (Read 1581 times)

Offline Greybeard

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Decarbonising my engine
« 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?

Online metalflake11

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Re: Decarbonising my engine
« Reply #1 on: 04.04. 2016 19:25 »
Fuel additive for me, after only 10,000 miles the engine shouldn't be coked up.
England N.W
1960 A10
England

Online morris

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Re: Decarbonising my engine
« Reply #2 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.
'58 BSA A 10 SA
'52 BSA A 10 Plunger
'55 MORRIS ISIS
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Online muskrat

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Re: Decarbonising my engine
« Reply #3 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
'51 A7 plunger, '57 A7SS now A10CR,  '83 CB1100F, 88 FXST .
Australia
Muskys Plunger A7

Online chaterlea25

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Re: Decarbonising my engine
« Reply #4 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
1961 Super Rocket
1963 RGS (ongoing)

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Re: Decarbonising my engine
« Reply #5 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.
A good rider periodically checks all nuts and bolts with a spanner to see that they are tight - Instruction Manual for BSA B series, p46, para 2.
New Zealand

Offline Greybeard

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Re: Decarbonising my engine
« Reply #6 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*

Online morris

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Re: Decarbonising my engine
« Reply #7 on: 10.04. 2016 22:33 »
'58 BSA A 10 SA
'52 BSA A 10 Plunger
'55 MORRIS ISIS
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Belgium

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Re: Decarbonising my engine
« Reply #8 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.
'51 A7 plunger, '57 A7SS now A10CR,  '83 CB1100F, 88 FXST .
Australia
Muskys Plunger A7

Offline Greybeard

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Re: Decarbonising my engine
« Reply #9 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.

Online metalflake11

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Re: Decarbonising my engine
« Reply #10 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!!!
England N.W
1960 A10
England

Offline shabashow

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Re: Decarbonising my engine
« Reply #11 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.

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Re: Decarbonising my engine
« Reply #12 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
'51 A7 plunger, '57 A7SS now A10CR,  '83 CB1100F, 88 FXST .
Australia
Muskys Plunger A7

Offline coater87

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Re: Decarbonising my engine
« Reply #13 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*

Central Wisconsin in the U.S.

Offline Greybeard

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Re: Decarbonising my engine
« Reply #14 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