Subaru ex17 issues/Manco Spitfire

[auswag]

Hello,

I picked up a Manco go kart with a 6..5 hp Subaru ex17 that is not running. I have cleaned the carb and have spark but the engine will not start no matter how much starter fluid I put in it. I put a compression tester on it today and only got about 40 psi (2.8 kpa) after about 6 pulls.

Any suggestions? Is this compression too low to get it to start? The cord pulls smoothly and the engine sounds like it wants to start but will never completely turn over and start. I have adjusted the choke as well.

Kind of lost and frustrated so appreciate any help!
Swag

 

[infernisdiem]

Does your kart have a key switch? if so is there something wrong with the switch/wiring to the switch

Is the kill switch(s) working properly, could be causing the issue.

I haven't really gotten a chance to tinker with my Mano "funkart" with the subaru engine, but plan on doing it soon.

 

[auswag]

There is a kill switch on the motor and the steering wheel. When they are both in the correct direction I get spark on the plug. If one or both are not in the correct direction I don't get spark. I am assuming they are both working because of this.

 

[infernisdiem]

I think I found a booklet on the maintance of the engine, it says that it should be 4.0 for a compression... assuming that I read it right. Here's the link: it is on the bottom of page 79 (82 is you use the pdf viewer)

http://www.subarupower.com/wp-conte...x17-ex21-ex27-sp170-sp210-ex21efi-service.pdf

 

[auswag]

Thanks for the link! I thought the compression was low. What can I do to increase the compression? I have found a link on how to adjust the valves but don't know if that will help. Suggestions?

 

[infernisdiem]

that's where my mechanical knowledge is limited, but I would think head gasket/heads would be the issue, I know on my wife's blazer, we blew the headers and it has a hard time to start, and very little power.

 

[auswag]

I was thinking the head gasket as well but wasn't sure what else it could be. Thanks.

 

[Poboy kartman]

I was almost tempted to just sit back and watch the show....because I don't care much for people that don't fill out profile locations...and even less for those that start spewing out advice before doing so.

Yes....blown head gaskets happen....(on cars)....nearly unheard of on small engines.

I have no clue whats on page 79...maybe spring height or spring pressure? IDK.. But I suggest you have a look at page 56.

 

[auswag]

Thanks for the suggestion on of 56. I have read it and I guess it is a little over my head. Not sure exactly what it was telling me and not sure how I would adjust/make a change to it to increase my compression. I will keep reading.

 

[OzFab]

Low compression is a result of one of three issues; either
1. valve issues
2. blown head gasket or
3. worn piston rings

1. If the valves are burnt (damaged) or incorrectly adjusted, obviously, they will leak

2. As previously stated, a blown head gasket on a small air cooled engine is not common but, not unheard of

3. As an engine ages, the piston rings start to wear &, eventually, they wear out; piston rings are designed to hold compression but, as they wear, they don't perform as they should; unfortunately, if the rings are worn out, the only solution is to replace them, which involves an engine rebuild...

Here's what I'd do... in order:
1. place about a teaspoon of oil directly into the spark plug hole &, if possible, move the engine around so the oil covers the entire piston; then, repeat the compression test...

The oil acts as a seal between the piston & the cylinder, therefore, if the rings are worn out, this should increase compression...

2. If this yields no positive results, perform a "leak down test"; this involves applying compressed air into the spark plug hole & listening to where it escapes, which will be one of 4 places:
1. Crankcase. If air can be heard escaping into the crankcase, this indicates worn rings
2. Carb. If air can be heard escaping through the carb, this indicates a worn or maladjusted inlet valve.
3. Exhaust. If air can be heard escaping through the exhaust, this indicates a worn or maladjusted exhaust valve.
4. Around the head. If air can be heard escaping around where the head meets the block, this indicates a blown head gasket...

 

[auswag]

Thank you! I will try all of these.

 

[Poboy kartman]

Well page 56 talks about compression release on the cam. In simple terms, it's a device that keeps the exhaust valve from closing when cranking the engine, making it easier to pull the cord.

So...the short answer is it keeps the engine from building much compression at cranking speed...so low compression is normal. IIRC, You may have to spin the engine backwards...but I really don't know what is necessary for sure. Also, the spec for compression is going to be a low number.

Maybe someone else can help more ....but a leakdown is going to loose air through the exhaust.

 

[OzFab]

Thanks Doug I forgot about the compression release...

 

[auswag]

That makes a lot more sense now, thanks. So maybe compression is not the problem. I have spark and I have fuel, seems like it should turn over. I will still try the list of things this week. Would like to get this going for my son. Thanks everyone for the help/suggestions so far!!

 

[QaaUz]

Plug Wet? or no fuel

Wet? Maybe a Bad plug... Not necessarily visible

Fuel block to the carb. Or
- jets blocked.

Typical can be..

Old fuel.

Water in base of float chamber.

Timing wrong.

Valve clearances. At TDC (Top dead centre) both valves (Valve to rocker - called tappet) have clearance every other revolution.

Remotely, you could have a blocked breather hole in the fuel tank.!!

All the best.

I read your situation and the replies. Thought you may benefit from this note so joined to post you.
LOL