2 stroke crank seals

[HughF]

The mighty midget I have, with the early pattern 4 bolt head JLO won't pull more than 115 amps without going really lean and dying.

Carb stripped and cleaned, fuel system checked, governor checked, needle moved up a notch to ritchen things up a bit, marginally better (managed to get it up from 100a)... Compression feels good, does this sound like bad crank seals?

 

[dobbslc]

Has it been sat unused for a long time?

 

[HughF]

Ummmmm, probably...I honestly don't know. I only picked it up a few months back. Came with a spare engine though.

 

[dobbslc]

Not sure if you can reach the seals with it assembled but you could try spraying some oil or wd40 on the outside of the seals to see if it temporarily runs better.
I don't know what a mighty midget is, any pics? Most seals can be bought from wholesalers easily enough if you have the diamentions.

 

[Rig Pig]

Your not using old petrol are you? It doesn't seem to keep well.

 

[HughF]

Good news everyone! If I shut the choke plate down to a little over a 3rd open, she runs perfectly and will push a red hot 4mm rutile through a piece of 1/2 inch plate at 200 amps without dying at all... needs a bigger jet then I guess?

 

[CRB]

The power of the stroker.

 

[HughF]

It's got so much arc force it's unreal. Definitely my go-to stick machine now, given I'm off-grid and have to run some sort of engine to weld, might as well run the one that works the best.

 

[Ian X]

Good news everyone! If I shut the choke plate down to a little over a 3rd open, she runs perfectly and will push a red hot 4mm rutile through a piece of 1/2 inch plate at 200 amps without dying at all... needs a bigger jet then I guess?

I feel envy, how much did that set you back? I like 2 stroke, no mystery and very few moving parts, loud though.

 

[HughF]

could be dirty jets...carb might need stripped and rebuilt

First thing I did when I got it home, carb is a single jet Jobby and looks okay. I can't remember if I checked the holes in the emulsion tube though.

I gave 180 for the machine. It came with a spare engine and 30 meters of 70mm welding cables.

 

[normspanners]

I can't see it suddenly needing a larger jet has the carb got pumping diaphrams in it ? coz they are the prime suspect as they get older on small engines.

 

[HughF]

Nope, it has no diaphragms at all. It's as simple as they come, slider with a needle attached going into a jet.

 

[normspanners]

Needle adjuster clip dropped off?

I can't remember if I checked the holes in the emulsion tube though.

Thinking about that statement they can be a pain to get out so I would think you would have remembered checking that.

Mind you I had an aprillia 50 that I had allkinds of problems with, and ended up going to nearly twice the main jet size but that had been messed with/ tuned ? previously

 

[Wendelspanswick]

Air leak on carb to cylinder gasket?

 

[normspanners]

It might have a rubber inlet /carb anti vibe coupler tubey thing they sometimes split.

 

[normspanners]

I am thinking back to many years ago of using one of those, they had the jlo engine with an amal type carb didnt they with a big round air filter with the choke on the back ?
have you checked the colour off the plug when it was running without choke that will tell you if it is running weak.
A bad plug can give a similar problem you are allowing it to run by limiting the air, that limits compression a bad plug can fail under high compression.

 

[HughF]

Mine is a bing carb. When it was running lean the plug indicated this was the case. After shutting the choke down and running it for an hour, I checked the plug, a nice mushroom/light brown colour. Plug looks new (ish), NGK I think.

 

[DanielW]

Compression feels good

How manyt times have i heard that.....only a compression meter/dial will tell you if the compression is up to scratch,using the hand over the plug socket is fruitless.