SC52 2stroke issue.

[Snorbitz]

Hi Guys, I've just refitted an SC52 2stroke after a 3 year layup and its also has a brand new carb from JE. Old one was missing a part. Started just fine, idled perfect and mid range ok but it will not run at WOT. Just cuts out....this happened a few times and now it won't run at all. It's a new model with the plumbing checked and double checked. Scratching my head a bit. I've gone to 2,5 out on the needle, tried a new plug but still nothing. Very odd.Any ideas?.

[Denis Watkins]

From the layup, has got to be some particle or goop blocking the fuel flow

So, even with new pipe, and cab, some debris

Edited By Denis Watkins on 27/12/2018 20:19:15

[Snorbitz]

I didn't think 2str engines had these...or am I missing something?.

[Paul Marsh]

Posted by Denis Watkins on 27/12/2018 19:55:45:

Tappets,

Clearance, or sticking or stuck, or broken valve spring Snorb

Its a 2 Stroke...

Is your Glo starter still ok? Check the obvious: Fuel, supply, Glow and if they are ok then its something else...

Also, even new plugs are known to blow - check that with your glo stick..

Edited By Paul Marsh on 27/12/2018 20:12:34

[Shaunie]

Are you using exhaust pressure and is the nipple clear? As it is not the original carb are you sure the Venturi is not too large? Try opening up the main needle even more, hard to tell without listening to it but I suspect it’s too lean.

Shaunie

[Paul C.]

Do you have much compression , after 3 three year lay up the piston ring may be gummed up expecially if you have been using castor based fuel. Also is the fuel new or three year old ?

Paul.

[Snorbitz]

Mmm I've wondered about the fuel as that is also a few years old. It's been in its sealed bottle but it is a little old.

[Steve Hargreaves - Moderator]

I think these are ABC motors Paul so no ring to gum up....

How does it stop.....? Just cuts dead once the throttle barrel get close to full open or does it gurgle & spit fuel back from the carb.before grinding to a halt? If the former (& I suspect it will be) then it's not getting enough (liquid) fuel & is simply too lean....this means insufficient fuel flow which indicates a blockage somewhere.....work through the fuel system until you find it....can you blow through the fuel feed pipe into the carb (with the throttle & NVA open)? Is there a blockage or a kink in the tank lines? Don't forget to check the clunk...I've seen clunks weights where the central hole is almost obscured by the bright nickel plating (& indeed one where the hole wasn't drilled at all!!). Do you have a fuel filter on the model? Is it clear? (if you do have one then personally I'd throw it away...filter the fuel going into the tank...you won't need to filter it coming out again)

Let us know how you get on

[Jon H]

^ what he said

Also, if you can shoot a video and post it on youtube. post the link here so we can all have a gander.

I recommend this to my customers all the time and its helped sort out many an engine. Just keep the camera out of the propwash

[Peter Miller]

That sounds as too lean. Start it treally rich and see if it runs slobbering rich. If it does start closing the needle down to until it is running lean at full throttle.

Just becausex you are running 2 1/2 turns open doesn't mean that it isn't too lean.

[Paul C.]

Your right Steve I had forgotten about them being ABC, if I remember correctly the SC needle has a O ring that tends to crack quite frequently but as this is a new carb it should be ok.

Paul.

[cymaz]

Try this,

Take off the main needle retaining clip and slip over some fuel tube so that it completely covers the needle and body. This will stop any air if you have a leaking o ring.

[SIMON CRAGG]

As its been laid up for three years, its probably the bearings corroded. The rear one is especially prone to this. The ball bearings get rusty and "drag" on the cage. Virtually impossible to tune for reliable running. Have seen this happen many times. Straightforward job and parts a tenner. Hope this helps.

[Snorbitz]

Lots to work through. I'm going to try another Glo system too as the plug does not glow overly well when out even though the little needle swings right over. On my glow panel which I'm about to try how much current should I dial up for a No3 plug?

[alex nicol]

Check the tank to make sure the clunk hasn't travelled forward and kinked the tubing.

it sounds as if it may be to lean or drawing air. if you open the throttle wide and do a few choke turns can you see the fuel being drawn through the pipe?

if you prime and choke it until its slobberingly rich do you get the 'bump' when you turn the prop over with the glow start on?

[Jon H]

Posted by Snorbitz on 27/12/2018 21:52:48:
On my glow panel which I'm about to try how much current should I dial up for a No3 plug?

Ignore the amp reading, its totally meaningless. Just put the plug in the glow thing and turn the amps up until its glowing nicely. Pop it in the engine and never touch the dial again. If you use different types of plug, say a 4 stroke plug, repeat the procedure and see if you need more juice. If so, make two marks on the face plate so you know where to turn the knob to for each plug. Its unlikely you will need more than one position to be honest, but that is the best way to set up power panels.

One final thing is that when the engine is cranking on the starter make sure the amps have not fallen through the floor as this will put the glow out.

[Snorbitz]

I'm using a separate battery for the starter so it shouldn't drag the voltage down under load. I've had a coffee and a read so time to try again with some of these suggestions and with the new glo driver.

[Snorbitz]

I've uploaded some pics of the engine install in the Extra. I wondered if the exhaust being above the engine is effecting things.

Edited By Snorbitz on 27/12/2018 22:04:23

[Steve Hargreaves - Moderator]

As I understood it the engine is starting & running OK at low speed/throttle settings it's only when you open up to full throttle there is a problem.....this means it's unlikely to be an issue with the glow plug battery...

Or have I missed something?

[Steve Hargreaves - Moderator]

Just had a look at the two pictures in your album.....the engine is mounted sidewinder on the left side meaning the exhaust muffler exits through the top of the cowl......that is unusual..... in fact I don't think I've ever seen an installation like that. It is more usual to mount the engine so the muffler exits through the bottom of the cowl.

That said it shouldn't affect the running of the engine particularly.......

But I am intrigued...why did you fit the engine like that?

[cymaz]

I would have put the exhaust out of the bottom myself.

[Snorbitz]

Trust me it wasn't through choice....it would've taken some major reconstruction of the firewall to get it to fit even without the extra peice in the silencer. The glow plug access is on the right. If I have to remove the cowel which I'm a little loathed to do now I'll take a picture of it too just so you can see what I've done.

[Snorbitz]

Here's a video of the cutting out at full throttle. I think the starting issue is just glow driver related.
https://youtu.be/8vOd7x87lHk

[Jon H]

Having the exhaust poke out of the top of the cowl will not be good for idle performance and will be a nightmare for hydraulic locking. Be very careful turning the engine with an electric starter. In future i would recommend the firewall be modified. its only wood!

For the engine itself, my suspicion is fuel starvation as the other guys have said as the engine seems to pick up to a certain point and then suffers a lean cut.

However, if i am hearing what i think i am hearing the bearings sound as though they are totally finished and need to be replaced. i recommend you check these out before going any further as a damaged bearing can fail and destroy the engine.

Stripping a 2 stroke is easy and there are only likely to be 8 or 10 screws holding the whole thing together. I suggest you whip it apart and see what the story is inside.

[Paul Marsh]

How weird! The pilot will get the full lot in his face!!!

Edited By Paul Marsh on 28/12/2018 09:15:01