I recently was lucky enough to buy a 1975 forty plus with only 30 use since new. When I looked at my 2 stroke measure and realised how much oil 10:1 was going to be fitting the needle for 25:1 suddenly seemed to be a good idea. (not really to save the environment but to make it easier to dispose of fuel before it gets stale by putting into my main boat gas tanks where it will get diluted to a suitable level more easily)
My question concerns the height of the adjusting screw. On my slide there is a larger diameter section with no thread and then the thread starts. Should the screw head be level with the top of the slide or the top of the thread?. The orinial 10:1 needle was set to the top of the thread.
Villiers needle height
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needle adjustment
Thanks for the response, I'm going to try 2 1/4 turns down as a starting point. I will have to wait to get my boat on the water, the behaviour in a test tank is very different from that under load when attached to the boat.
I agree you need to run it on the boat but I think you should start with the needle flush not 2 turns down but be prepared to lower it to get it to run properly.
What i found was that the engine four stroked (ie only fired every second revolution) except when really working hard. That, as far as I am concerned is a sign of a rich fuel air mixture, so I kept lowereing the needle a bit at a time until it ran without four stroking except maybe when very lightly loaded. The final result is between 2 and 2¼ turns down.
Nobody has satisfactorily explained why I have had to do that. (I have btw checked the float level)
I am a little concerned because it means that after reducing the oil from 10% to 4% I am reducing the lubrication even further by reducing the amount of fuel it is using.
What i found was that the engine four stroked (ie only fired every second revolution) except when really working hard. That, as far as I am concerned is a sign of a rich fuel air mixture, so I kept lowereing the needle a bit at a time until it ran without four stroking except maybe when very lightly loaded. The final result is between 2 and 2¼ turns down.
Nobody has satisfactorily explained why I have had to do that. (I have btw checked the float level)
I am a little concerned because it means that after reducing the oil from 10% to 4% I am reducing the lubrication even further by reducing the amount of fuel it is using.
Needle Height
Probably should have explained that I tried the needle flush, and then flush with top of recess in slide where original needle was adjusted. Motor ran OK on either but was not revving to maximum. Seemed too rich with needle flush and from looking at the plug too weak the other way. So I thought about 2 turns was in the middle so I would start from there next time. I think the altitude here of 5,000 feet above sea level could be attributing to the situation as most carb fed motors are jetted down to allow for the "thinner air" seee my other topic "effect of altitude, I 'm still interested in theories or anyones practical experience of these conditions. When I have driven my trucks to lower altitudes the increase in power is quite noticeable.
Regarding the lubrication on your motor, yes having less oil is a concern but 25:1 is still a pretty rich mix. Because you are having to run a little leaner in theory doesn't mean you are in practice so I would say if the mixture is right for your motor based on smooth running etc. and a plug chop to double check you aren't running lean, then you should have adequate oil.
Regarding the lubrication on your motor, yes having less oil is a concern but 25:1 is still a pretty rich mix. Because you are having to run a little leaner in theory doesn't mean you are in practice so I would say if the mixture is right for your motor based on smooth running etc. and a plug chop to double check you aren't running lean, then you should have adequate oil.
Interesting question about the altitude. As far as i know there are no alternative jets for the Villiers carb so the only solution, I guess, is to lower the needle. The end result will be the same, less fuel drawn up. Carbs with fixed jets need re-jetting. Because the volume of fuel and the amount of air will be reduced the power will be reduced. I don't think there is anything you can do about that. (Never seen a turbo charged Seagull!) Maybe engines with alternative props would benefit from a different one (finer pitch) that will allow the engine to rev higher and so develop more power.
Worth trying it without the air intake compensator but it will probably affect the carb tuning so you'll have to readjust it to run without the compensator. (The same carb when fitted to small motorcycle engines back in the 1950s had an air cleaner so I guess the compensator compensates for the absence of the air filter)
A question on the iBoats forums might get some further advice on running at high altitude. No lake in the Uk at anything like that height! The highest that i can think of is a little lake below the summit of Mount Snowdon about 1900 feet up and I should not think it attracts any boaters.
I am sure you are right about the lubrication of my engine. It's that logic that has let me run it like that for 20 years or more!
Worth trying it without the air intake compensator but it will probably affect the carb tuning so you'll have to readjust it to run without the compensator. (The same carb when fitted to small motorcycle engines back in the 1950s had an air cleaner so I guess the compensator compensates for the absence of the air filter)
A question on the iBoats forums might get some further advice on running at high altitude. No lake in the Uk at anything like that height! The highest that i can think of is a little lake below the summit of Mount Snowdon about 1900 feet up and I should not think it attracts any boaters.
I am sure you are right about the lubrication of my engine. It's that logic that has let me run it like that for 20 years or more!
Hi Vic, regarding propellors, that is quite usual here to use a different propellor with less pitch at the even higher lakes to allow the motor to still pull full rpm. There are lakes here I could go up a further 2,500 feet to. I guess Seagulls were designed for the sea so were always at sea level, so any variations in altitude were not a consideration. I'm sure the altitude is responsible for the slight lack of power I'm suffering so I am going to double check everything else, points, float height etc, try removing the air compensator to see if that really makes any difference, and then just play with the needle height until I get the best balance with plug chops to ensure adequate fuel. I know that a number of the Japanese two stroke motorcycles from my youth could be made to rev higher and go faster by using smaller jets, they actually over fuelled them to make them more reliable by reducing the maximum rpm and presumably the running temp. I aim to err slightly toward the rich side for safety and longevity of the motor.
By the way Vic, never seen a turbocharged Seagull - Hmmm that's got me thinking, I'm seeing a supercharger belt driven from a modified flywheel!!
By the way Vic, never seen a turbocharged Seagull - Hmmm that's got me thinking, I'm seeing a supercharger belt driven from a modified flywheel!!