I tried to order Madeira 50 head via Engine Marine Part, the part number is 2020306 (Testa Madeira 50 / Head Madeira 50). The price was 174 EUR, unfortunately Selva was not able to provide the spare part although I waited for five months 😒
So how Selva 40 head is different from Selva 50 head ? I don't have the service manual so I can't say for sure but I bet the compression is different. I have measured my Selva 40 compression and it is around 130-132 PSI.
I decided to increase the compression by cutting (i.e. shaving) the Selva 40 engine head.
The guys at Screamandfly.com suggested that I should cut 0.5 millimeters (~ 20 thousand of an inch, aka thou) from the engine head and that is what I did. I took the head to GT Motor and they milled the head and the cost was 70 EUR.
I bought new head gaskets and assembled the head and did a new compression test.
The compression test now showed 150 PSI in both cylinders which is a quite good reading and still not too high for regular gasoline, I'm using always 98 octane gasoline.
The actual effect of the increased compression will be evaluated in a later post.
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| The compression with stock cylinder head is a little above 130 PSI. |
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| Selva 40 engine head removed. |
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| Selva 40 engine head opened. |
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| Selva 40 stock head thickness is 39.72mm. |
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| Head thickness after shaving is 39.27 mm. |
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| Compression after engine head shaving is about 150 PSI. |
Hi
ReplyDeleteYou have a great blog with very good description of your work.
I have two problems with my selva 40 hp 2004.
I have a problem with the main fuse 20 ah blowing once in a while when i am starting the engine. When i change the fuse it will work for two or three starts and then the fuse is blown again. Have you any experiance of this?
The second problem that i have occures most often when i drive the engine slow at low rpm for a while and then hit the throttle the engine wont rev up and is choking. When i leave the engine to the next day it will work as normal again. Have you had this problem?
Thank you very much!
Thank you for your feedback! :)
DeleteI haven't had any problems with the main fuse, please check all the cables leading from battery to the engine (all the way to the starter), there might be a cut somewhere or maybe the starter motor is about to fail.
I have had the problem that when opening throttle the motor does not rev, the root cause was dirty carburetors, most 2 stroke engine problems are related to carburetors.
When you are experiencing the problem you could try to manually pump fuel, if that helps then the problem might be in the fuel pump. If not you can put some carb cleaning fuel additive, or try choking trick (https://www.youtube.com/watch?v=iWqhJVdLcfk), last option is to open the carburetors and clean them properly, I have done this many times, it's quite easy and seals can quite often be reused http://selvatuning.blogspot.com/2018/05/carburetor-cleaning.html
Hope this helps!
hi there... nice Blog.i have a question.
ReplyDeletethe caburators have a tube for syncronisation. is is right that this tubes are allways open??? because i Think ist sucking wrong wir if.or is must these tubes closed whis a srew???
hope you know what i mean..greetz. cat
Hi, do you mean this tube ?
ReplyDeletehttps://3.bp.blogspot.com/-iLyQlUWmJJI/XOZccjmnr6I/AAAAAAAAWGk/-XAudUvZpbEOsZIz9KB-msn22gK7ZCOdgCKgBGAs/s640/IMG_20190522_202413.jpg
I think it's always open, I don't see any screws to adjust it.
hi no... thats Not in the caburator!@
ReplyDeleteHi, great and clear blog!
ReplyDeleteJust owned my first boat and it's equipped with a 1988 Selva 1000 with 80hp.
Do you have any experience with this type of engine?
Currently it does not run as it doesn't have a spark on the plugs.
Thanks!
Hello. Any help on removing cylinder head bolts? They don't want to come out. One is cracked already.
ReplyDeleteYou can try heating the bolt using a torch and then apply penetrating oil (non-flammable).
DeleteYou are right. They need Very much heating where the bolt screws. I still need to unbolt the four inner bolts. I cannot reach the coils of them, but I will try to remove the side covers first. I own a portofino 80 1998. Thank you!
ReplyDelete