Jon, I had to pulled my FVP out of the shed, I found a compression gauge, I removed the plastic screen to see it better.
With a handful of pulls, note the engine hasn't run since May and it has no fuel in it and it's pretty awkward to do as well, it may have been better if I didn't have to hold the tester and motor one handed, it was averaging 45psi.
I could have used a drill, but I wouldn't and never will.
This motor is 51-2 era and has never been apart since new, I can guarantee that, I tried once, even ran it with no head bolts fitted, didn't make any difference.
Sorry for rubbish picture, I haven't got three hands, but you get the idea, as I would rather prove the point, than just write BS.
Coolie ignition timing
Moderators: John@sos, charlesp, Charles uk, RickUK, Petergalileo
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Charles uk
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Re: Coolie ignition timing
Are you sure you've got which is the lower compression size the right way round Jon?
Apart from Keith's most 40 series run higher than the 102s/century's by about 10 lbs!
Apart from Keith's most 40 series run higher than the 102s/century's by about 10 lbs!
Make it idiot proof and someone will make a better idiot.
Re: Coolie ignition timing
Yes, l can confirm that when I measured the ignition timing on some FVs with the points set correctly at 0.020 and the baseplate locking screw in its location spot on the crankcase the results were all between 45 deg and 64 deg. This was on 7 off FVs. The variation is surprisingly large. I reset them all to an advance of 45 deg. I have no evidence that this is the optimum advance, but its a nice round number and they seem to start very easily and run well at this setting.
Jeremy
Jeremy
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seagull101
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Re: Coolie ignition timing
Over the weekend i will find out the exact timing of the new motor.
Here are some pics of where it is on the SD then OP.
Also a Link of the OP running:
https://www.youtube.com/watch?v=KKiyj1L7nZU
Jacob
Here are some pics of where it is on the SD then OP.
Also a Link of the OP running:
https://www.youtube.com/watch?v=KKiyj1L7nZU
Jacob
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headdownarseup
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Re: Coolie ignition timing
That looks about right Jacob.
I'm looking at the locking screw and its proximity to the closest crankcase bolt directly below it. This is roughly where i set a coolie magneto and should (fingers crossed) be in the ball park of 40 ish degrees BTDC.About 4 o'clock for the HT lead as well by the looks of it. Measure things carefully Jacob. Check and double check everything.
Jon
I'm looking at the locking screw and its proximity to the closest crankcase bolt directly below it. This is roughly where i set a coolie magneto and should (fingers crossed) be in the ball park of 40 ish degrees BTDC.About 4 o'clock for the HT lead as well by the looks of it. Measure things carefully Jacob. Check and double check everything.
Jon
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headdownarseup
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Re: Coolie ignition timing
Yes Charles, i do know how to read a compression gauge! Mine has psi on the outer ring of numbers and BAR on the inner ring of numbers. As we're talking "old skool" here we'll keep things simple with numbers we can all relate to and that's psi. Things didn't come across very well in my last post so i'll have another go here.
If we're talking STRICTLY about "little model 40's" here, of the 4 examples i can lay my hands on right now the compression values are as follows.
FV11716 71psi and 55cc displacement(dry, and hasn't been run in over 2 years) This one hasn't been apart in my ownership.Runs fairly well all things considered.
LS35744 110psi and 64cc displacement(dry, and hasn't been run in over 2 years) This one has been apart as when i first bought it the thing was seized solid. Careful application of "gloop" where it counts i believe has helped things here.Original piston rings from when i bought it as a wreck, and in "barn found" condition.
LS18849 100psi and 64cc displacement (dry, and hasn't been run in over 2 1/2 years) This was an utter wreck when i first bought it. Incomplete with a very knackered and rotten gearbox. Still has its original piston rings from when i bought it, just carefully rebuilt and a little "gloop" where it matters. Apart from needing the lower leg re-chroming, this one is what i call "finished". Runs like a clock.
LS36688 80psi and 64cc displacement(dry,and hasn't been run in over a year) This one is something of a long term "resto" job for me. Originally bought from Jeremy as a project and when it's finished will go to my buddy in sussex as a gift. This might benefit from a new set of rings just to keep things on par with the other LS's in my possession, but as it is it runs pretty good and starts easy enough.
Keith's FVP i think is a 55cc engine, and for this particular motor i think 40 odd psi sounds like it's somewhere in the right ballpark for one of these.
It would be good to see if Jeremy could do some simple compression measurements of some of his 55cc FV's to see if Keith's FVP falls into a similar ballpark. The only 55cc displacement engine i currently own is FV11716 as shown above, and this still manages to squeeze out a fair bit more than Keith's FVP.Whether this is down to variances between different pressure gauges or something else between 2 different engines remains to be seen. I strongly suspect that the squish band will have something to do with it though.
As a comparison i measured EGF221GG1 and found 91psi. This engine was used only a few weeks ago at Cholsey by my eldest son and was run pretty hard all day with little or no regard to the engine's well being. This engine was put together from second hand spare parts i had lying about the place and has been the centre of some heated debates recently!
When we talk about compression we can attribute this to a few things in an old seagull engine. The interface between the piston crown at TDC and its proximity with the cylinder head/combustion chamber (in many 2stroke engines known as a squish band) will vary quite a bit with a lot of these smaller 40 series engines. Over time some of this compression is lost by a worn cylinder or rings, heaven forbid cutting back on oil in the fuel mix as i don't believe this will do the engine any favours in the long run, not to mention it could lead to further losses of compression. All of the square block engines have the benefit of a removable cylinder head,(even though in a lot of them it says DONT REMOVE) should the need ever arise and you're brave enough,with some careful machining some of this lost compression can be regained if you know what you're doing and not necessarily from replacing the rings or honing the bore either. Some parts are just not available any more so you have to do what you can elsewhere to bring things back to where they were when new.(or for those of you that don't have access to a local machine shop, or are on a limited budget like me then some of this re-machining could be done by careful rubbing with emery paper over a flat surface) I think it's a very good exercise to measure compression both before and after a rebuild and by this i'm talking about using a compression gauge in the spark plug hole. Now, although i haven't "re-machined" the heads on any of my 40 series motors to date, with some of these engines i think that how some of the components were manufactured in the first place could be better, and as a result some engines will run happier than others probably because there's a tad more compression than some of its flock mates.
It's probably worth mentioning that within the 40 series motors there are 3 different sizes. 40cc,55cc and the later 64cc variants. Each of these specific types will probably have their own sets of values when it comes to compression. Some will be appear quite low, and some will be noticeably higher than others, and i believe this has a lot to do with how good the manufacturing of the cylinder head and piston crown proximity actually is.(squish)
Ignition timing can to some degree depend on how high or low this compression is in the first place with some of these gull engines. For some engines with a higher compression value a smaller advance angle could be used, where as an engine with lower compression a bigger advance angle might be more beneficial.
For those that might still be interested my OA measures 55psi of compression, which (for me anyway) is in the same ballpark as a typical 102.
Many of the 102 blocks i've pulled apart haven't really had any appreciable signs of wear in them aside from a few light scratches and scuffs in the bore, and this is probably due to most of them having been run on 10:1 fuel mix. Everything i can lay my hands on in a round block 102 format falls within 48-60 psi.
As i'm not really into century's that much, the 2 specimens i have in my possession measure 48psi for a silver century plus (dry and hasn't been run for a long time and never been apart since i've owned it) or my other century "play thing" built from spare parts with a so called "high compression" head measures 65psi. This one though still has some machining work left to do before i'm happy with it so who knows where this one will end up when it's finished!
Although Charles is right about 40 series motors having a slightly higher compression over their larger cousins, it's quite a bit higher than 10lbs with some of them and that's just from the ones i have to hand. Some engines will have quite a big "squish" gap compared to others and i feel that this is where some of the discrepancies occur with some of these older so called "little model 40's" and probably with some of the bigger century engines as well.
With any of the dear old round block 102 engines, whatever the compression has to offer that's all there is to play with. Very difficult to do anything with them in this respect apart from fitting new rings to try and perk things up a bit.
Aside from anything to do with racing or going fast, having enough compression inside your cylinder is pretty important if your engine has any chance of running reasonably well, but how much is enough? Is there a positive answer to this question?
Hopefully this will spur some of you to go out and measure compression on your gull engine, and if you're a good sport will share the findings on here.
Jon
If we're talking STRICTLY about "little model 40's" here, of the 4 examples i can lay my hands on right now the compression values are as follows.
FV11716 71psi and 55cc displacement(dry, and hasn't been run in over 2 years) This one hasn't been apart in my ownership.Runs fairly well all things considered.
LS35744 110psi and 64cc displacement(dry, and hasn't been run in over 2 years) This one has been apart as when i first bought it the thing was seized solid. Careful application of "gloop" where it counts i believe has helped things here.Original piston rings from when i bought it as a wreck, and in "barn found" condition.
LS18849 100psi and 64cc displacement (dry, and hasn't been run in over 2 1/2 years) This was an utter wreck when i first bought it. Incomplete with a very knackered and rotten gearbox. Still has its original piston rings from when i bought it, just carefully rebuilt and a little "gloop" where it matters. Apart from needing the lower leg re-chroming, this one is what i call "finished". Runs like a clock.
LS36688 80psi and 64cc displacement(dry,and hasn't been run in over a year) This one is something of a long term "resto" job for me. Originally bought from Jeremy as a project and when it's finished will go to my buddy in sussex as a gift. This might benefit from a new set of rings just to keep things on par with the other LS's in my possession, but as it is it runs pretty good and starts easy enough.
Keith's FVP i think is a 55cc engine, and for this particular motor i think 40 odd psi sounds like it's somewhere in the right ballpark for one of these.
It would be good to see if Jeremy could do some simple compression measurements of some of his 55cc FV's to see if Keith's FVP falls into a similar ballpark. The only 55cc displacement engine i currently own is FV11716 as shown above, and this still manages to squeeze out a fair bit more than Keith's FVP.Whether this is down to variances between different pressure gauges or something else between 2 different engines remains to be seen. I strongly suspect that the squish band will have something to do with it though.
As a comparison i measured EGF221GG1 and found 91psi. This engine was used only a few weeks ago at Cholsey by my eldest son and was run pretty hard all day with little or no regard to the engine's well being. This engine was put together from second hand spare parts i had lying about the place and has been the centre of some heated debates recently!
When we talk about compression we can attribute this to a few things in an old seagull engine. The interface between the piston crown at TDC and its proximity with the cylinder head/combustion chamber (in many 2stroke engines known as a squish band) will vary quite a bit with a lot of these smaller 40 series engines. Over time some of this compression is lost by a worn cylinder or rings, heaven forbid cutting back on oil in the fuel mix as i don't believe this will do the engine any favours in the long run, not to mention it could lead to further losses of compression. All of the square block engines have the benefit of a removable cylinder head,(even though in a lot of them it says DONT REMOVE) should the need ever arise and you're brave enough,with some careful machining some of this lost compression can be regained if you know what you're doing and not necessarily from replacing the rings or honing the bore either. Some parts are just not available any more so you have to do what you can elsewhere to bring things back to where they were when new.(or for those of you that don't have access to a local machine shop, or are on a limited budget like me then some of this re-machining could be done by careful rubbing with emery paper over a flat surface) I think it's a very good exercise to measure compression both before and after a rebuild and by this i'm talking about using a compression gauge in the spark plug hole. Now, although i haven't "re-machined" the heads on any of my 40 series motors to date, with some of these engines i think that how some of the components were manufactured in the first place could be better, and as a result some engines will run happier than others probably because there's a tad more compression than some of its flock mates.
It's probably worth mentioning that within the 40 series motors there are 3 different sizes. 40cc,55cc and the later 64cc variants. Each of these specific types will probably have their own sets of values when it comes to compression. Some will be appear quite low, and some will be noticeably higher than others, and i believe this has a lot to do with how good the manufacturing of the cylinder head and piston crown proximity actually is.(squish)
Ignition timing can to some degree depend on how high or low this compression is in the first place with some of these gull engines. For some engines with a higher compression value a smaller advance angle could be used, where as an engine with lower compression a bigger advance angle might be more beneficial.
For those that might still be interested my OA measures 55psi of compression, which (for me anyway) is in the same ballpark as a typical 102.
Many of the 102 blocks i've pulled apart haven't really had any appreciable signs of wear in them aside from a few light scratches and scuffs in the bore, and this is probably due to most of them having been run on 10:1 fuel mix. Everything i can lay my hands on in a round block 102 format falls within 48-60 psi.
As i'm not really into century's that much, the 2 specimens i have in my possession measure 48psi for a silver century plus (dry and hasn't been run for a long time and never been apart since i've owned it) or my other century "play thing" built from spare parts with a so called "high compression" head measures 65psi. This one though still has some machining work left to do before i'm happy with it so who knows where this one will end up when it's finished!
Although Charles is right about 40 series motors having a slightly higher compression over their larger cousins, it's quite a bit higher than 10lbs with some of them and that's just from the ones i have to hand. Some engines will have quite a big "squish" gap compared to others and i feel that this is where some of the discrepancies occur with some of these older so called "little model 40's" and probably with some of the bigger century engines as well.
With any of the dear old round block 102 engines, whatever the compression has to offer that's all there is to play with. Very difficult to do anything with them in this respect apart from fitting new rings to try and perk things up a bit.
Aside from anything to do with racing or going fast, having enough compression inside your cylinder is pretty important if your engine has any chance of running reasonably well, but how much is enough? Is there a positive answer to this question?
Hopefully this will spur some of you to go out and measure compression on your gull engine, and if you're a good sport will share the findings on here.
Jon
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Collector Inspector
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Re: Coolie ignition timing
This topic and similar re SDs "anything" is...
A work in progress still.
More and I like it aye.
BnC
A work in progress still.
More and I like it aye.
BnC
A chicken is one egg's way of becoming others
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Charles uk
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Re: Coolie ignition timing
Lookup "Squish" to see if it relates in anyway to a classic Seagull design!
Make it idiot proof and someone will make a better idiot.
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Collector Inspector
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Re: Coolie ignition timing
Charles uk wrote:Lookup "Squish" to see if it relates in anyway to a classic Seagull design!
Was that for me?
BnC
A chicken is one egg's way of becoming others
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Charles uk
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Re: Coolie ignition timing
No Bruce I don't think you used the word.
Just trying to bring the thread back to the poor chaps original question that was answered with another model's details.
Just trying to bring the thread back to the poor chaps original question that was answered with another model's details.
Make it idiot proof and someone will make a better idiot.
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seagull101
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- Location: Scottish islands
Re: Coolie ignition timing
Today i tested some of my motors compression.
OP626=67psi and hasn't run for 4 days.
SD10588.L4=62psi and hasn't run for 4 months
EDL53AA3=65psi and hasn't run for 2 months
SJP51611=114psi and hasn't run for 3 months
FPL790KK5=110 psi and hasn't run for 2 weeks
FPC911AA6=90psi and hasn't run in 3 weeks (this is my regular use motor on the dinghy)
EFNR1029EE9=43psi and hasn't run in my ownership of a year, it has a badly scored block from a circlip coming out of place (only did this one to show what compression a knacked motor gives)
Jacob
OP626=67psi and hasn't run for 4 days.
SD10588.L4=62psi and hasn't run for 4 months
EDL53AA3=65psi and hasn't run for 2 months
SJP51611=114psi and hasn't run for 3 months
FPL790KK5=110 psi and hasn't run for 2 weeks
FPC911AA6=90psi and hasn't run in 3 weeks (this is my regular use motor on the dinghy)
EFNR1029EE9=43psi and hasn't run in my ownership of a year, it has a badly scored block from a circlip coming out of place (only did this one to show what compression a knacked motor gives)
Jacob
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Charles uk
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Re: Coolie ignition timing
That looks more like they should Jacob, Keith's use of a push in compression gauge usually requires at least 3 hands, that might be why his FV comes up so low, when we measured the timing on it, I got the impression it was a strong example with crisp compression.
Make it idiot proof and someone will make a better idiot.
Re: Coolie ignition timing
I tried. 
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headdownarseup
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Re: Coolie ignition timing
I know that the term "squish" when used in a seagull isn't quite correct as a gull has a deflector shape to its piston rather than a flat or domed top as you'd normally see in a lot of other 2 stroke engines.
But, what i was trying to get across with a "little 40" is there's sometimes quite a big gap when measured across the width of the piston crown.From what i've looked at when rebuilding a few is that with some of these 40 series with a bigger gap they've sometimes had little overall use, probably because the thing was a pain in the **** to start due to low (ish) compression and nothing to do with ignition timing at all. I've noticed in later 64cc models that this gap can sometimes be a little bit smaller with the resulting slightly higher overall compression and indeed some more wear.
Hopefully Jeremy will be along to add his bit on this.
Probably better coming from him anyway with anything to do with little 40's
I tried as well.....
might find another less stressful hobby after all this, but going by Jacobs results they're on par with mine wouldn't you say?
Century's by and large have lower compression than 40's.
For the record when i was measuring compression (on my own i might add with only 2 hands) 3 pulls of the cord,throttle wide open, choke off and no electric drill.
But, what i was trying to get across with a "little 40" is there's sometimes quite a big gap when measured across the width of the piston crown.From what i've looked at when rebuilding a few is that with some of these 40 series with a bigger gap they've sometimes had little overall use, probably because the thing was a pain in the **** to start due to low (ish) compression and nothing to do with ignition timing at all. I've noticed in later 64cc models that this gap can sometimes be a little bit smaller with the resulting slightly higher overall compression and indeed some more wear.
Hopefully Jeremy will be along to add his bit on this.
Probably better coming from him anyway with anything to do with little 40's
I tried as well.....
might find another less stressful hobby after all this, but going by Jacobs results they're on par with mine wouldn't you say?
Century's by and large have lower compression than 40's.
For the record when i was measuring compression (on my own i might add with only 2 hands) 3 pulls of the cord,throttle wide open, choke off and no electric drill.
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Charles uk
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- Joined: Wed Feb 27, 2008 4:38 pm
- Location: Maidenhead Berks UK
Re: Coolie ignition timing
That's why you tend to get a more accurate answer with a screw in compression gauge.
102's will start & run with around a minimum of 45 lbs compression, I've never seen any of the 40s as low as that & the scavenging ability of the forty head style fairs well against a century, in fact this year the Bermudian dingy class was won by a forty plus I believe, beating identical boats with centurys.
Naughty Bits can you confirm that?
102's will start & run with around a minimum of 45 lbs compression, I've never seen any of the 40s as low as that & the scavenging ability of the forty head style fairs well against a century, in fact this year the Bermudian dingy class was won by a forty plus I believe, beating identical boats with centurys.
Naughty Bits can you confirm that?
Make it idiot proof and someone will make a better idiot.