Cub No Start

[dterhaar2000]

I've been having issues with my cub not starting. I put it in time and replaced the points, condenser, rotor button, distributor cap, plugs, battery, battery cables, starter contact, and coil. I'm getting really good spark and fuel to the carb; its still a 6 volt system and there is good voltage at all contacts. I also have tried to put fuel into the head to see if it helps and still nothing. Is there something I'm missing or did wrong? I am very frustrated with this machine.
Thanks

[Eugene]

Is there something I'm missing ?

Compression

[Pwalker21]

Double check the firing order, compression could be your issue. Just rebuilt my cub because the compression was so low. Do you have a gauge to take your compression readings? Also check to make sure your valves aren’t stuck open. You can pull the spark plug out and turn the motor over by hand to watch each valve open and close through the spark plug hole.

[Don McCombs]

Spray a little carb cleaner in the carburetor throat while attempting a start. If it starts, runs for a few seconds and dies, your problem is most likely in the fuel delivery system.

[Pwalker21]

Also was it running before you did the tune up? Or did you just get the cub?

[dterhaar2000]

It feels like I have good compression, its hard to turn by hand. Ill get a compression gauge and check it. What should it be reading at? I have tried the carb cleaner and it still wont fire. I took the carb off and cleaned it also its a newer carb i got last year. I have owned this tractor for 3 years and it stopped running before the tune up

[Pwalker21]

Did you recheck the firing order to be safe? Also when you pull the plugs are they wet and gapped to .025? Compression should be 110-120 but I’ve realized when I check it with my 6V battery it reads 65psi but when I hook up a 12v battery only to check it again out of curiosity with a harder start I get 110. If you do the same just be sure to disconnect the coil so you don’t blow it. You could also have some buildup in the jets of the carb from bad gas. If it sat over the winter. Worth a double check Ive realized over the last couple years the gas is shit and was always gumming up my carbs while sitting over the winter. Now I always add fuel stabilizer to my gas for every equipment I use.

[ntrenn]

100 psi is considered normal low limit. Under 90 will really be hard to start.
I’ve had no luck on Cubs with carb cleaner, but if it won’t hit on starting fluid you are missing spark or compression.
Gas fouled spark plugs will act like you describe...not hit at all.

[Bill V in Md]

I'm confused, back in January you were considering an engine rebuild. Was that because of low compression? You also said that you got it to running after some carburetor work. What changed since then? You say the spark is good, and you have good fuel flow. How about the timing?

Do you have a magneto or battery ignition? Maybe you know this, but points are gapped differently for each of these systems.

[dterhaar2000]

I did a compression check and its reading 40 on cylinder 1,3,4 and 50 on cylinder 2.

I was going to do an engine rebuild but time and funds ran short lol. I still may look into a rebuild later on down the road

[SONNY]

Compression that low will never run! ----rebuild time! ---- one other thing----did you check the valve clearance? IF the valves are too tight it will lower compression a bunch!

[SamsFarm]

I did a compression check and its reading 40 on cylinder 1,3,4 and 50 on cylinder 2.

Sounds like your rings are worn out!

If your lucky your pistons and bores are still within specs!

[Nelson 634]

I did a compression check and its reading 40 on cylinder 1,3,4 and 50 on cylinder 2.

Was your compression check done correctly.

(Dry)Spark plugs removed, intake to carburetor open, use electrical starter.

(Wet)Spark plugs removed, intake to carburetor open, use electrical starter after squirting oil thru spark plug hole onto piston and give it time to get to the rings.

I've checked compression on all my cubs in the past. I did them wrong. The gentle people here taught me how to do it right. I hope I haven't left any thing out. If I did I'm sure someone will pitch in to help.

Hope this helps you.

[Glen]

Hi,
When doing a compression test, remove all the spark plugs from the engine before doing the test, so they are all out at the same time.

Open the throttle fully, so the engine can get air for the test.

Charge the battery fully before doing the test.

Use the starter, they have said on here that using the hand crank is too slow.

I write down the results, so I have a record.