Stop end in a pistons gudgeon pin

You can talk about almost anything here

Moderators: John@sos, charlesp, Charles uk, RickUK, Petergalileo

Post Reply
african imp
Posts: 395
Joined: Thu Jan 03, 2019 5:44 am
Location: Hout Bay

Stop end in a pistons gudgeon pin

Post by african imp »

Why does one end of the gudgeon pin have a stop end?

Does it have something to do with how a 2 stroke engine runs its cycle?

I have a spare piston here and with pin, the piston from my 102 series motor is still fitted with its gudgeon pin, so I can see which way it should be fitted, or can it go either way in the piston?
You do not have the required permissions to view the files attached to this post.
blokewithaboat
Posts: 66
Joined: Tue May 15, 2018 9:05 pm
Location: uk

Re: Stop end in a pistons gudgeon pin

Post by blokewithaboat »

I fit all of my seagulls gudgeon pins with the blocked end towards the top and away from the exhaust port. Stops any oil filling the hollow tube of the pin over time and adding extra weight to the reciprocating assembly.

Some early 102's had a slightly different design of pin where both ends had an aluminium plug at either end resembling a solid pin and no circlips either. Essentially a free floating pin.

Not all 2 stroke engines have a blocked end either. Perhaps this is just a seagull thing.
User avatar
Charles uk
Posts: 4784
Joined: Wed Feb 27, 2008 4:38 pm
Location: Maidenhead Berks UK

Re: Stop end in a pistons gudgeon pin

Post by Charles uk »

If you remove the gudgeon from a piston & slide the piston into the cylinder while looking up the exhaust port you will understand why they have a blanked off end.
Make it idiot proof and someone will make a better idiot.
african imp
Posts: 395
Joined: Thu Jan 03, 2019 5:44 am
Location: Hout Bay

Re: Stop end in a pistons gudgeon pin

Post by african imp »

Guys, thanks on your advice.

I will refit the gudgeon pin back in the same way that it came out :P
You do not have the required permissions to view the files attached to this post.
Journeyman
Posts: 107
Joined: Thu Aug 16, 2018 6:26 pm
Location: Pembrokeshire

Re: Stop end in a pistons gudgeon pin

Post by Journeyman »

Yes Charles uk is right.
The gudgeon pin on my LLS is fitted with the open end facing down towards the exhaust port and the blank end facing the transfer port. This way there is less turbulence and interference with the incoming charge.
african imp
Posts: 395
Joined: Thu Jan 03, 2019 5:44 am
Location: Hout Bay

Re: Stop end in a pistons gudgeon pin

Post by african imp »

Journeyman wrote:Yes Charles uk is right.
The gudgeon pin on my LLS is fitted with the open end facing down towards the exhaust port and the blank end facing the transfer port. This way there is less turbulence and interference with the incoming charge.

Thanks,

Your saying not the way it was as in my picture?

I ask as that was the factory build ( i think ) and as it is again now that I have stripped the crank case and reassembled it all.

I used a power drill to spin up the 2 stroke lubricated engine, the compression is very good and the suction at the inlet port is very stong.


I used some 600 wet & dry paper on the bore to de glaze it before fitting the piston.
Journeyman
Posts: 107
Joined: Thu Aug 16, 2018 6:26 pm
Location: Pembrokeshire

Re: Stop end in a pistons gudgeon pin

Post by Journeyman »

Crankcase compression is very important on a two-stroke.
Seagulls like most two-strokes have the transfer port and the exhaust port opposite each other cross the bore, so they can’t have a hollow gudgeon pin or they would lose crankcase compression as the pin passed the transfer port.
If you have the blank end towards the exhaust you will lose some of the compression, that’s why blokewithaboat is correct in fitting the blocked end towards the top.
They will run with the pin the way you have it but it will be better the other way round.
african imp
Posts: 395
Joined: Thu Jan 03, 2019 5:44 am
Location: Hout Bay

Re: Stop end in a pistons gudgeon pin

Post by african imp »

Journeyman wrote:Crankcase compression is very important on a two-stroke.
Seagulls like most two-strokes have the transfer port and the exhaust port opposite each other cross the bore, so they can’t have a hollow gudgeon pin or they would lose crankcase compression as the pin passed the transfer port.
If you have the blank end towards the exhaust you will lose some of the compression, that’s why blokewithaboat is correct in fitting the blocked end towards the top.
They will run with the pin the way you have it but it will be better the other way round.
A question, why was it fitted the other way round when I opened the motor ?
african imp
Posts: 395
Joined: Thu Jan 03, 2019 5:44 am
Location: Hout Bay

Re: Stop end in a pistons gudgeon pin

Post by african imp »

Charles uk wrote:If you remove the gudgeon from a piston & slide the piston into the cylinder while looking up the exhaust port you will understand why they have a blanked off end.
Question, should the blanked off end be as I found it when the motor was opened, or should it be the other way around as has been suggested?

I ask as the motor is now re asembled and the blanked off end is fitted as I found it when the motor was opened.
User avatar
Nudge
Posts: 794
Joined: Sun Feb 15, 2015 2:43 am
Location: Auckland, New Zealand

Re: Stop end in a pistons gudgeon pin

Post by Nudge »

Just leave it be as it is. The motor will still work!
"THE KING OF BLING"!
Is it better to over think, than not think at all?
african imp
Posts: 395
Joined: Thu Jan 03, 2019 5:44 am
Location: Hout Bay

Re: Stop end in a pistons gudgeon pin

Post by african imp »

Nudge wrote:Just leave it be as it is. The motor will still work!
Thanks, yes even with the Seagull Villiers carb fitted, the motor fired on the second pull and then started on the third pull of the pull cord and now starts a runs really well :P
You do not have the required permissions to view the files attached to this post.
Post Reply