Brand new engine low compression (50 psi)

[Daveinfl33777]

I got a new engine that was fully assembled...I put it on bike and got it to start and idle but then it stopped idling...it's very hard to start...I have to pedal as fast as I can to get it to start and when it does it will just die out...doesn't want to idle either...if I disengage clutch it dies abruptly...

I don't know how good my compression gauge is but I got 50 psi when I pedaled and tested....it feels like compression is fine because it really slows me down when I try to start it...

I tested spark by removing it and grounding it to the engine and spinning the back tire....well I don't know if that is a good test or not as I'm not testing it while it's inside the engine under normal operating conditions...but I did get a blue spark...maybe I should get one of those spark gap testers and see if it will jump a bigger gap? To really see if the spark is good enough? Or should I look more into compression...my compression gauge maybe is bad and I should test it on other known good equipment

 

[ImpulseRocket]

When you tested the compression did you make sure to open the throttle all the way? If not your compression reading will be low.

If you have spark and do actually have compression then your issue is going to be air/fuel. Make sure to check and set the float height on the carb and make sure the carb is seated all the way on the intake as that can be a common source of air leaks which can also cause hard starts.

New engines are just hard to get started to begin with. I will often use the magneto nut with a socket on a drill to get a new engine started on the first run because they can be a pain sometimes.

 

[Daveinfl33777]

When you tested the compression did you make sure to open the throttle all the way? If not your compression reading will be low.

If you have spark and do actually have compression then your issue is going to be air/fuel. Make sure to check and set the float height on the carb and make sure the carb is seated all the way on the intake as that can be a common source of air leaks which can also cause hard starts.

New engines are just hard to get started to begin with. I will often use the magneto nut with a socket on a drill to get a new engine started on the first run because they can be a pain sometimes.

Yeah I had throttle wide open...I am starting to think I messed this up by not properly breaking it in....since I had such trouble getting it to stay running it seemed I needed to give it a lot of throttle just to stay running....so I probably went WOT for too long....

Also add the fact that I used the premixed fuel from Lowes...now I realize that synthetic oil is a big no no in breaking in an engine and you want to use conventional oil instead....

I just want confirmation...maybe I can take it to a machine shop where they have the tools to tell me if the cylinder wall is egg shaped or not

 

[Gordy]

Re torque the head bolts to 144 inch lbs

 

[ImpulseRocket]

Yeah I had throttle wide open...I am starting to think I messed this up by not properly breaking it in....since I had such trouble getting it to stay running it seemed I needed to give it a lot of throttle just to stay running....so I probably went WOT for too long....

Also add the fact that I used the premixed fuel from Lowes...now I realize that synthetic oil is a big no no in breaking in an engine and you want to use conventional oil instead....

I just want confirmation...maybe I can take it to a machine shop where they have the tools to tell me if the cylinder wall is egg shaped or not

Try as Gordy suggested. Otherwise, pull the head and see if you still have any cylinder plating.

 

[Johnny_]

Yeah I had throttle wide open...I am starting to think I messed this up by not properly breaking it in....since I had such trouble getting it to stay running it seemed I needed to give it a lot of throttle just to stay running....so I probably went WOT for too long....

Also add the fact that I used the premixed fuel from Lowes...now I realize that synthetic oil is a big no no in breaking in an engine and you want to use conventional oil instead....

I doubt either of those caused the problem you are dealing with. How long did you run it for?

 

[Daveinfl33777]

Re torque the head bolts to 144 inch lbs

I did it to 12 ft lbs last night

 

[Daveinfl33777]

I doubt either of those caused the problem you are dealing with. How long did you run it for?

I dont even think i ran a full tank in yet because it never starts...I would guess I put about 2 or 3 miles on it to be honest. I got it sometime last week...had it up and running for about a week now...

 

[Johnny_]

I dont even think i ran a full tank in yet because it never starts...I would guess I put about 2 or 3 miles on it to be honest. I got it sometime last week...had it up and running for about a week now...

You should pull the head and take a peek inside.

 

[Daveinfl33777]

You should pull the head and take a peek inside.

I kind of did but with these things even being out of round by thousands of an inch can cause loss of compression...I can't tell much with the naked eye..
Maybe if I had ZERO compression I might be able to...but I will attempt it right now...I'll snap some pics for you guys