Can I reuse my piston on my 102?(pictures attached)

[pat777]

Thanks Jerseyman. I'll have to look into whats available and prices when I'm ordering more parts again. Does anyone else have a century piston running in a 102 block? Also I'm a bit reluctant to go honing the cylinder as it doesn't look too bad. I don't own a hone and If I was to buy one I would only be buying a cheap one and I don't imagine a £15 hone is going to leave a great finish on the cylinder. Has anybody tried one of the cheap cylinder hones on a seagull cylinder?

[Charles uk]

Pat I would suggest before you spend any money, that you carefully remove the piston rings & clean them & their grooves in the piston.
Give the bore a light flexi hone, clean carefully & then reassemble the powerhead with a light oiling, only stick the crankcase / cylinder gasket on the cylinder side with RTV silicon, & then check the compression with a screw in the plug hole compression gauge, if you can get 50 lbs just use it.

Less than 45 lbs would indicate you will need a replacement piston, your cylinder has a bridged transfer port, which means using a late model piston with the narrow deflector which will shroud some of the transfer ports restricting it's ability to scavenge properly, so you will have to find yourself an early piston with the wider deflector & new rings.

Much of the carbon inside the cylinder could well have been caused by the use of 30 weight oil before modern two-stroke was in common use.

Your local motor cycle shop would probably hone it for a packet of Smarties.

[pat777]

Thanks for the reply Charles uk. Thanks for confirming that I need an earlier model piston. That sounds like a plan alright. I'll have to go to the newsagents and buy a packet of smarties. I'll tell the motorcycle repair shop guy that charles uk sent me! Seriously though, I'm sure somebody I know will have one I could borrow. My brother is in to motorbikes so perhaps he will know someone with a decent hone.

Thanks for the information on the carbon build up. I'm now using tcw3 outboard two stroke oil, however I know the previous owner to me was using Stihl chainsaw two stroke oil.

Cheers Pat

[headdownarseup]

CHAINSAW OIL!!!!!
that could be half the trouble? chainsaws are aircooled, seagulls are watercooled (depending on waterflow through the waterjacket)
chainsaw oil will be totally different to outboard oil and will burn differently. what ratio of fuel to oil are you using. (hopefully 10:1)

as charles said, if its got reasonable compression of about 50psi or so, then try it. you've got nothing to loose at this stage.
if it becomes a right PITA to start and run, then swap the piston with new rings and a light hone to the bore and all will be good i'm sure.
let us know what happens.

jon

ps i might have a spare piston (early type) if you get stuck.
pm me if you need it

[Hugz]

A honing tool is pretty basic and cheap to acquire and a must for us.

Very easy to use with a variable speed drill. 1200rpm max.

Whoops, a cracked cylinder bore. I thought it was running rough! And the crack backs on to the inaccessible water chamber adjacent exhaust port (century block).

I would finish it with a fine wet and dry. Though it feels a lot smoother than it looks.

I have also been advised to to drip feed brasso to the fuel when first running to bed in the new rings but do have some trepidation re bearings. Might give the brasso a miss.

[pat777]

CHAINSAW OIL!!!!!
that could be half the trouble? chainsaws are aircooled, seagulls are watercooled (depending on waterflow through the waterjacket)
chainsaw oil will be totally different to outboard oil and will burn differently. what ratio of fuel to oil are you using. (hopefully 10:1)

I'm on a 10:1 mix, although if you look up my engine number on the engine identifier "AD338**L" (I've left out a few numbers there,if you type that in it will bring up all the details)(Paranoid or what!!). It says I should be running on 8:1. When I told the guy I bought it off that I'd looked up the number on sos before coming to look at it and that it should be running on 10:1. His reply was roughly along the lines of "no, no I've been running on 25:1 for years". I really should have walked away at this stage probably but I'd driven to far to collect it to walk away empty handed and of course I wasn't as knowledgeable then as I am now about seagulls, so I was more easily convinced with the "sure it will be grand" reply. I won't tell you how much I paid for it, lets just say I paid too much.

ps i might have a spare piston (early type) if you get stuck.
pm me if you need it

Thanks for the offer of selling me the spare piston Jon, sure we'll see how I get on with this one first.

Cheers Pat

[phil]

About carbon build up, avoid any oil except TCW 3. Or if you must use an oil like SAE 30 motor oil, use Seafoam or OMC engine tuner to clean out carbon deposits regularly.

[Charles uk]

Your 102 Seagull was built to run on 30 weight motor oil during the early to mid 50's, 30 weight oil burns more readily than modern 2-stroke oils hence the carbon build up, many early Seagulls were run using waste engine oil to save money.

Stihl chainsaw oil is a very high quality lube, I bought a box (10 litres?) of it at a boat jumble many years ago (it was very cheap) it's all gone now, used in my race engines, very little carbon deposits, at around 20:1, I really liked it.
If your flywheel doesn't rattle sideways, you don't have scarey main bearing wear.

[pat777]

Thanks for the reply Hugz about the honing tools.This is type I had been looking at on ebay and amazon although I had seen the type you have pictured as well. How long roughly would you be running it in the cylinder for? I can appreciate that it's going to vary cylinder to cylinder depending on condition but is like a 10 second spin or what?




Also is there a particular size I should look out for? Would you be concerned about taking to much off the bore with the honing tool or are they fairly gentle in operation?

Anyway I'll let you know how I get on with it, well when I say "I", I mean that in the loosest possible sense of the word. My Dad likes taking engines apart and putting them back together again, so he's doing most of the work on them with occasional comments from me about what we should or shouldn't do. Now I just need to convince him that you lads are all experts when it comes to seagulls and we should be taking your advise on board. I'll let you know how we get on with it. It might be a while as there are a couple of centuries taken apart also that I've already ordered new parts for (gaskets, rings etc)

Thanks for all the advice,

Cheers Pat

[pat777]

Yes phil, I'll be sticking with the tcw3 all the way and it's good to know that Charles Uk has been using the stihl 2 stroke on his race engines, so maybe the previous owner knew what he was doing after all. He did seem fairly convincing at the time when I remember back. He even offered me a money back guarantee with it. I'd say he's forgotten all about that at this stage nearly three years on.

[Charles uk]

Don't use that type of hone, use the flexi one, there are plenty of threads on here explaining why.

[pat777]

Okay thanks, If I can't get a loan of one, then I'll look out for one with the beads. Here's a bit more info. on the subject for any other newbies reading.

Cylinder honing hugz; viewtopic.php?f=2&t=4081

Cylinder honing Stelios_Rjk; viewtopic.php?f=2&t=4217&hilit=cylinder+hone

[headdownarseup]

charles

i stand corrected about chainsaw oil. i had always believed that using oil from an air cooled motor in an outboard that tends to run cooler would produce more carbon build up, and that the lubricating properties were different with extremes of temperature.

incedentally, i use ROCK semi synthetic tcw3 in my seagulls and it seems to be quite good with very little smoke even at 10:1

jon

[Charles uk]

Very little tcw 3 type oil burns in a Seagull with such low compression & low combustion temperature, at the low temperatures inside a Seagull only the petrol can vaporise.

[Collector Inspector]

New piston/rings and kit from john. It is dead what you have. No hope.................it is stuffed!

Bore..... flex hone.

Do it right, not expensive.

End of problem.

B