In the next couple of weeks I'm going to put some ex MOD, BSF obstruction spanner based tool kits on Ebay.co.uk, seems silly having a small fortune sitting in a drawer, I'll put a note on here when I do.
John still has some still in stock.
Loss of power in Century
Moderators: John@sos, charlesp, Charles uk, RickUK, Petergalileo
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Charles uk
- Posts: 4971
- Joined: Wed Feb 27, 2008 4:38 pm
- Location: Maidenhead Berks UK
Re: Loss of power in Century
Make it idiot proof and someone will make a better idiot.
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Stelios_Rjk
- Posts: 1458
- Joined: Sun Jun 17, 2012 10:15 pm
- Location: Athens - Greece
Re: Loss of power in Century
Sure you don't have to remove the cyl head to fit new piston rings.
But since you remove the cylinder from the crankcase consider using a flexhone.
In case you decide to remove the head, heat is you friend. Heat the bolts to get red hot. Then attempt to undo them.
But since you remove the cylinder from the crankcase consider using a flexhone.
In case you decide to remove the head, heat is you friend. Heat the bolts to get red hot. Then attempt to undo them.
I love the 10600/145 turns!!!
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OverseasSoul
- Posts: 24
- Joined: Tue Aug 05, 2014 3:21 am
- Location: Charleston,SC
Re: Loss of power in Century
Thank you.
The nuts holding the powerhead onto the crankcase have all yielded very easily to a 7/16" US 6 point socket which had a very tight fit, so that has given me some confidence. As has the screw holding on the clamp to the exhaust tube. So I'm going to try to remove the powerhead today with my existing tools. I'm a bit confused about which to remove first - do I need to remove the exhaust tube first and undo the water pipe nut inside it? How do I do that? Do I need to remove the gear casing down below so I can mobilize the exhaust tube? It seems a very snug fit and I don't see how I can lower the exhaust tube to get at the water tube nut. All the fittings seem in good condition so far.
Iain
The nuts holding the powerhead onto the crankcase have all yielded very easily to a 7/16" US 6 point socket which had a very tight fit, so that has given me some confidence. As has the screw holding on the clamp to the exhaust tube. So I'm going to try to remove the powerhead today with my existing tools. I'm a bit confused about which to remove first - do I need to remove the exhaust tube first and undo the water pipe nut inside it? How do I do that? Do I need to remove the gear casing down below so I can mobilize the exhaust tube? It seems a very snug fit and I don't see how I can lower the exhaust tube to get at the water tube nut. All the fittings seem in good condition so far.
Iain
Re: Loss of power in Century
You can either loosen the pinch bolt that holds the waterpump housing to the driveshaft and then try to wiggle/pound/whatever that down off the driveshaft tube. then the cylinder should slide off the crankcase with the exhaust tube attached to it.
Or you can undo the 2 nuts holding the crankcase to the top of the drive shaft tube. Then life the whole powerhead off.
This all assumes that corrosion/rust etc is not holding things together
Or you can undo the 2 nuts holding the crankcase to the top of the drive shaft tube. Then life the whole powerhead off.
This all assumes that corrosion/rust etc is not holding things together
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OverseasSoul
- Posts: 24
- Joined: Tue Aug 05, 2014 3:21 am
- Location: Charleston,SC
Re: Loss of power in Century
Thanks Michael,
Trying both of those now
Neither has yielded easily - I can't work out what's holding it together. Loosening the two bolts under the crankcase was easy and the whole power assembly lifts a couple of millimeters, but the exhaust axis is preventing further movement. Likewise, loosening the crimp bolt on the lower drive shaft was easy, but nothing else can be encouraged to move. I will try more force..
iain
Trying both of those now
Neither has yielded easily - I can't work out what's holding it together. Loosening the two bolts under the crankcase was easy and the whole power assembly lifts a couple of millimeters, but the exhaust axis is preventing further movement. Likewise, loosening the crimp bolt on the lower drive shaft was easy, but nothing else can be encouraged to move. I will try more force..
iain
Re: Loss of power in Century
Re trying to lift lowerhead off, it is probably the water tube the is sticking. Try to pry upwards between bottom of crankcase and top of driveshaft tube.
Re waterpump housing -try to twist the housing sideways a little bit with a rubber or dead blow hammer to try to free up where it clamps around the driveshaft. Heat might help. If it twists sideways, then you should be able to hit it down and off with a block of wood bewteen the driveshaft and the exhaust tubes. Hit wood with hammer.
Re waterpump housing -try to twist the housing sideways a little bit with a rubber or dead blow hammer to try to free up where it clamps around the driveshaft. Heat might help. If it twists sideways, then you should be able to hit it down and off with a block of wood bewteen the driveshaft and the exhaust tubes. Hit wood with hammer.
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Charles uk
- Posts: 4971
- Joined: Wed Feb 27, 2008 4:38 pm
- Location: Maidenhead Berks UK
Re: Loss of power in Century
Avoid the hammer if possible!
Remove the 5/16 bolt that clenches the drive shaft tube into the water pump housing & replace from the other side, when it starts to project into the split, place the maximum thickness that will fit coin under the end of the bolt & wind in a little further, gently, this will open the clench until it fractures, so don't go mad!
Some bottom main bearings project into the drive shaft tube & can be a tight fit & some drive shafts grip the pinion & crankshaft really well after the application of water.
Treat it like a women, only hit it when it responds to nothing else, but be prepared to spend heaps of money repairing the situation you've just created!
Remove the 5/16 bolt that clenches the drive shaft tube into the water pump housing & replace from the other side, when it starts to project into the split, place the maximum thickness that will fit coin under the end of the bolt & wind in a little further, gently, this will open the clench until it fractures, so don't go mad!
Some bottom main bearings project into the drive shaft tube & can be a tight fit & some drive shafts grip the pinion & crankshaft really well after the application of water.
Treat it like a women, only hit it when it responds to nothing else, but be prepared to spend heaps of money repairing the situation you've just created!
Make it idiot proof and someone will make a better idiot.
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OverseasSoul
- Posts: 24
- Joined: Tue Aug 05, 2014 3:21 am
- Location: Charleston,SC
Re: Loss of power in Century
Thanks Michael,
Prying the driveshaft off the crankcase is the most promising, but I'm stuck. I can get a big screwdriver between the two and pry upwards about a centimeter, but the exhaust is pivoting wrt the block on the forward indentation of the exhaust tube, so the whole power block is tilting forward.... i'm concerned the angular nature of this will put strain on the driveshaft... Whats happening to the driveshaft in any case as I pry upward? So I'm concerned about prying harder, and don't knee how I can release the exhaust tube on that little indentation without damaging it. I've noticed there are three linear cuts at the top of the exhaust tube - are those factory made?
iain.
Prying the driveshaft off the crankcase is the most promising, but I'm stuck. I can get a big screwdriver between the two and pry upwards about a centimeter, but the exhaust is pivoting wrt the block on the forward indentation of the exhaust tube, so the whole power block is tilting forward.... i'm concerned the angular nature of this will put strain on the driveshaft... Whats happening to the driveshaft in any case as I pry upward? So I'm concerned about prying harder, and don't knee how I can release the exhaust tube on that little indentation without damaging it. I've noticed there are three linear cuts at the top of the exhaust tube - are those factory made?
iain.
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OverseasSoul
- Posts: 24
- Joined: Tue Aug 05, 2014 3:21 am
- Location: Charleston,SC
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Charles uk
- Posts: 4971
- Joined: Wed Feb 27, 2008 4:38 pm
- Location: Maidenhead Berks UK
Re: Loss of power in Century
Remove the clutch rod from the lever, then remove rod & connector nut, the exhaust should slide up, off the water pump housing, some times the water delivery tube gets stuck in the water pump housing, where it should be a slide fit.
Make it idiot proof and someone will make a better idiot.
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OverseasSoul
- Posts: 24
- Joined: Tue Aug 05, 2014 3:21 am
- Location: Charleston,SC
Re: Loss of power in Century
Charles and Michael,
It'll take me a week to get back to work on my Seagull and be able to follow your sage advice. I had to leave it partially dismantled with the exhaust not yet released. This weekend I delivered one of my sons to College, so it will have to wait for next weekend.
Iain.
It'll take me a week to get back to work on my Seagull and be able to follow your sage advice. I had to leave it partially dismantled with the exhaust not yet released. This weekend I delivered one of my sons to College, so it will have to wait for next weekend.
Iain.
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headdownarseup
- Posts: 2484
- Joined: Thu Apr 04, 2013 2:26 pm
- Location: bristol
Re: Loss of power in Century
iain
all fairly normal stuff so far with your gull.
arm yourself with a blowtorch, you'll find that the application of heat on certain parts will often help to release stiff or seized components.
something else you could try, seperate the pump housing from the gearbox lower section. (trust me you will need a fair bit of heat on the screws that connect the top and bottom sections of the gearbox together)
once you've got the gearbox in 2 bits, turn the whole lot upside down so you can see the underside of the pump housing. what you're looking for is the small water delivery pipe that runs inside the exhaust tube. give this area a lick with the blowtorch and maybe the bottom of the exhaust tube as well where it attaches to the pump housing. A tap or two with a hide or rubber hammer and block of wood on the bottom of the cylinder will hopefully get things moving. (carefull though, dont go too mad or heavy with the hammer)
as per STELIOS's suggestion, HEAT IS YOUR FREIND. especially with old and rusty fasteners. bsf spanners are a must. nothing else will do.
cylinder head is easy peasy to get off, just use HEAT on the nuts, heat em up red hot and away you go. clear out the water jacket (i bet its clogged up with rust somewhere, you'll be glad you did)
do the whole job properly and this motor should last for decades yet.
i normally strip everything right down and clean absolutely EVERYTHING. unless you can trust the guy that you bought the motor from initially, dont believe everything you see on an advert.Appearences can be deceiving, i've been stung a couple of times before.
plenty of help on here
just ask
regards jon
all fairly normal stuff so far with your gull.
arm yourself with a blowtorch, you'll find that the application of heat on certain parts will often help to release stiff or seized components.
something else you could try, seperate the pump housing from the gearbox lower section. (trust me you will need a fair bit of heat on the screws that connect the top and bottom sections of the gearbox together)
once you've got the gearbox in 2 bits, turn the whole lot upside down so you can see the underside of the pump housing. what you're looking for is the small water delivery pipe that runs inside the exhaust tube. give this area a lick with the blowtorch and maybe the bottom of the exhaust tube as well where it attaches to the pump housing. A tap or two with a hide or rubber hammer and block of wood on the bottom of the cylinder will hopefully get things moving. (carefull though, dont go too mad or heavy with the hammer)
as per STELIOS's suggestion, HEAT IS YOUR FREIND. especially with old and rusty fasteners. bsf spanners are a must. nothing else will do.
cylinder head is easy peasy to get off, just use HEAT on the nuts, heat em up red hot and away you go. clear out the water jacket (i bet its clogged up with rust somewhere, you'll be glad you did)
do the whole job properly and this motor should last for decades yet.
i normally strip everything right down and clean absolutely EVERYTHING. unless you can trust the guy that you bought the motor from initially, dont believe everything you see on an advert.Appearences can be deceiving, i've been stung a couple of times before.
plenty of help on here
just ask
regards jon
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OverseasSoul
- Posts: 24
- Joined: Tue Aug 05, 2014 3:21 am
- Location: Charleston,SC
Re: Loss of power in Century
Hello everyone,
Thanks to your help I was able to break down my Gull, with judicious use of heat, WD40 and a few taps with a wooden block( we have a heatwave here in Charleston - 100 degrees F and 100% humidity- so it was hot work). All the fasteners yielded quite easily and I used regular US sockets ( 17/32 was good for removing the bolt on the lower unit). Taking off the lower unit, clutch shaft, and drive shaft did the trick. I now have everything in a couple of white buckets. There was a lot of gunk in the exhaust. I am amazed at the condition of the parts and think that some previous owner really loved this motor, now 49 years old. I get the impression some of the parts have been taken off many times before, and that anti-seize compound has been used on the bolts.
I do have a definite diagnosis for the low compression - the piston head is eroded around the rings and I will need a new one. I have attached a few pics. The block and crankcase look in excellent condition and the bore of the block seems very smooth to touch all round without any kind of indentation. I wonder if the erosion is a consequence of the PO using the engine at 1:25 mix when it should have been 1:10?
So I will be back in correspondence with Jon for some more parts and will spend the next two weeks cleaning the bits I have. Is there supposed to be a part covering the hole in the piston head? I will also be purchasing the shop manual
Thank you so much -
Iain.
Thanks to your help I was able to break down my Gull, with judicious use of heat, WD40 and a few taps with a wooden block( we have a heatwave here in Charleston - 100 degrees F and 100% humidity- so it was hot work). All the fasteners yielded quite easily and I used regular US sockets ( 17/32 was good for removing the bolt on the lower unit). Taking off the lower unit, clutch shaft, and drive shaft did the trick. I now have everything in a couple of white buckets. There was a lot of gunk in the exhaust. I am amazed at the condition of the parts and think that some previous owner really loved this motor, now 49 years old. I get the impression some of the parts have been taken off many times before, and that anti-seize compound has been used on the bolts.
I do have a definite diagnosis for the low compression - the piston head is eroded around the rings and I will need a new one. I have attached a few pics. The block and crankcase look in excellent condition and the bore of the block seems very smooth to touch all round without any kind of indentation. I wonder if the erosion is a consequence of the PO using the engine at 1:25 mix when it should have been 1:10?
So I will be back in correspondence with Jon for some more parts and will spend the next two weeks cleaning the bits I have. Is there supposed to be a part covering the hole in the piston head? I will also be purchasing the shop manual
Thank you so much -
Iain.
Re: Loss of power in Century
It could well be the 25:1 mix, it normally shows around the exhaust port.
If you mean the gudgeon pin, as this has a hole only on one side, that's how it should be, the hole goes at the bottom, exhaust side.Is there supposed to be a part covering the hole in the piston head?
Re: Loss of power in Century
You were very lucky if the cylinder did not get damaged. Looks to me like a piece of ring broke originally, started to dig a hole other pieces broke off, and it continued being run for quite a long time afte that. Maybe the previous owner was deaf. 
Need different piston and rings. Think I could supply them used if you want.
Need different piston and rings. Think I could supply them used if you want.