Polaris ATV Forum banner

1 - 20 of 22 Posts

·
Registered
Joined
·
12 Posts
Discussion Starter #1
i bought this used a few weeks ago. the guy i bought it from said previous owner put in new piston. and it ran when he got it but he couldn't get
it started. i checked compression 60 lbs. max. has anyone done a valve job or top end rebuild on one of these? any help would be appreciated.
i did adjust the valves to .002 no change. its getting fuel and has spark thanks
 

·
Premium Member
Joined
·
3,964 Posts
Get a repair manual if you don’t have one and five in. New piston doesn’t really mean anything. If the cylinder needed to be bored oversize but it wasn’t done then it was a waste of time and money. Pull the cylinder and have it measured. Then you will know how to proceed


Sent from my iPhone using Tapatalk
 

·
Registered
Joined
·
5,952 Posts
I would do a cylinder leak down to see where the compression is going - did you check the compression while holding the throttle wide open? Not opening the throttle will produce a low compression reading.
 

·
Registered
Joined
·
12 Posts
Discussion Starter #4
I would do a cylinder leak down to see where the compression is going - did you check the compression while holding the throttle wide open? Not opening the throttle will produce a low compression reading.
latebird no i didnt. i will try that next. it acts like it wants to start while the starter is spinning you let off the button it dies.
 

·
Registered
Joined
·
5,952 Posts
Make sure it has a good spark - use a timing light to verify spark - I have seen occurrences of spark while cranking but no spark when the starter button is released
 

·
Registered
Joined
·
5,952 Posts
It depends on the ignition system - if the ignition is DC CDI that's one thing - if it's AC CDI it's another - I'll be checking the wiring diagram and get back to you - in the mean time, check for spark while cranking
 

·
Registered
Joined
·
12 Posts
Discussion Starter #12
It depends on the ignition system - if the ignition is DC CDI that's one thing - if it's AC CDI it's another - I'll be checking the wiring diagram and get back to you - in the mean time, check for spark while cranking
i will
 

·
Registered
Joined
·
5,952 Posts
The vehicle has a DC CDI - if the battery voltage falls below about 10.5 volts while the starter motor is running, the spark may be intermittent - check the battery voltage while cranking the engine.

Have you tried starting with starting fluid?
 

·
Registered
Joined
·
12 Posts
Discussion Starter #15
The vehicle has a DC CDI - if the battery voltage falls below about 10.5 volts while the starter motor is running, the spark may be intermittent - check the battery voltage while cranking the engine.

Have you tried starting with starting fluid?
yes. it sounds like its running with the starter engaged. let off button it quits
 

·
Registered
Joined
·
5,952 Posts
Try compression again and cylinder leakdown if compression less than 100 - got to get compression up to about 110 to 130
 

·
Registered
Joined
·
5,952 Posts
I think there is a problem - I don't think piston first - I always suspect valves first - overhead cam engines tend to lose valve clearance, but I am a mechanic - I like to test to verify the cause, but valves are easy to check so I always just check the clearance automatically - for testing I just move the rocker arms to assure some free play - if there is none, I just loosen the tappet until there there is free play, then recheck the compression - if loosening the valves restores compression, then I see if it will start - if it does, then I set the valves correctly - if not, then move on to the other possibilities.
 

·
Registered
Joined
·
12 Posts
Discussion Starter #19
I think there is a problem - I don't think piston first - I always suspect valves first - overhead cam engines tend to lose valve clearance, but I am a mechanic - I like to test to verify the cause, but valves are easy to check so I always just check the clearance automatically - for testing I just move the rocker arms to assure some free play - if there is none, I just loosen the tappet until there there is free play, then recheck the compression - if loosening the valves restores compression, then I see if it will start - if it does, then I set the valves correctly - if not, then move on to the other possibilities.
i just wonder if the guy who put the piston in did something wrong? maybe wrong piston or head gasket. im going to tear it apart this weekend and will keep you posted. thanks for your help
 

·
Registered
Joined
·
5,952 Posts
OK - do you have a service manual?

I do not have a manual for the 08 Outlaw 50, but I have one for the Predator 50 - they use the same engine - if you want a copy message me an email address and I'll send you a PDF copy.
 
1 - 20 of 22 Posts
Top