48 cub will not fire

Thu Aug 22, 2013 10:25 pm

I am new here, hope someone can help. I came across a cub in the process of "restoration" that wasn't assembled, so not running. After my engine overhaul. reassembled being careful to time crank, cam, and magneto drive gears (at least I think I did). It came with a new carb and I purchased a different mag as the original was not all there. I timed the rotor to the rotor drive gear, timed the mag to the engine as the tech manual and other posts on the internet indicate. The mag drive with the drive slots line up with the mark on the housing as the should (2 and 8 ), so in theory the mag drive is timed correctly. I have spark to all spark plugs and in the correct firing order. I have been through the timing process several times to be sure I am right and I have never gotten the engine to fire even once, I am getting fuel to the cylinders. I also pulled the valve cover to check valve lash and verify no. 1 TDC ( an aftermarket crank shaft pully had been installed and it had no TDC mark). Any ideas on what I am missing?

Lee

Re: 48 cub will not fire

Fri Aug 23, 2013 3:45 am

Welcome to the forum Lee!

Compression? Come visit us on the weekend of the 6th and 7th of September in Longmont and we'll see if we can get you going!

viewtopic.php?f=8&t=76433

Re: 48 cub will not fire

Fri Aug 23, 2013 4:40 am

You didn't say whether the mag you bought was an exact replacement or not (J4). If an H4, the internal advance is not correct for a cub; however, it would probably run (others have) even with an H4, just not as well. I would dress the points with either a points file, or a piece of brown paper, they may be glazed over from lack of use. Also be sure the grounding post and kill switch are not making constant ground (post on side of mag, should have single wire to a kill switch). Lastly make sure points and or condenser aren't grounding to mag housing internally, where they connect to the inside of the grounding post. An ohm-meter that checks continuity is helpful for those last checks. Finally, what guarantee came with the replacement magnet? Are you sure it was operating, or just an ebay purchase with no guarantee?

Re: 48 cub will not fire

Fri Aug 23, 2013 4:51 am

Seems odd to me that if you have fire to the plugs and gasoline to the cylinder that it would not fire at all, even if incorrectly....Unless its flooded all to heck... I've had engines backfire run backwards etc etc from collapsed lifters and whatever....But usually something happens if you've got spark and fuel....Check your compression???? :D Dave
Last edited by pickerandsinger on Fri Aug 23, 2013 4:54 am, edited 1 time in total.

Re: 48 cub will not fire

Fri Aug 23, 2013 4:54 am

Welcome to the forum from Arkansas. Is the switch a one wire or two wire switch? Take Raymond up on the invitation to the CubFest that is being held in Longmont. A good place to get your cub checked out.

Re: 48 cub will not fire

Fri Aug 23, 2013 7:34 am

What was done on the engine rebuild? Bore? Rings? I don't know why, but every time I had my tractor open, I ended up needing to pull start it the first time. After that initial start, it would start perfectly with the starter or the crank.

If you are SURE that everything is right, try pull starting the first time around...

Re: 48 cub will not fire

Fri Aug 23, 2013 7:36 am

Lee:

G'day and congrats to you on getting your 1st new to you Cub reassembled.

Remember that once you are on #1 TDC you then have to time the governor - make sure the marks are aligned and then time the mag to the governor. If that is correct then you should have fire. Course are you assuming that the new mag was rebuilt correctly? Did you get it off of :eBay: :?:

Spark, fuel and air along with compression will give you a start situation. Did you prime the engine before turning it over? What are the compression numbers like?

Those are a few ideas. Let us know if you get this resolved. Also, Rocky Mountain CubFest would be a great idea.

I have kinda of been through this with my '47 Granny. Finally had to pull start her to get her to pop off .. not sure why but sometimes it has to be pull started.

Since you have been lurking a bit, this may be redundant but usually it is a good reminder. We have tons of resources available to our members and I strongly suggest that some time is spent reading some of the material below:

Image to Farmallcub.com :big smile: Forum Family. And you have come to the right place for all things Cub related. If you click on the Site Rules, Regulations, & Important Information, it will point you to :arrow: the Welcome Wagon wherein you will find links to many useful sites and topics. One of the most important resources are Owner's Manuals, Parts Catalogs and Service Manuals. The Cub Manual Server is the home of the jpg versions and the PDF Manuals -- well the pdf's of course :wink: Enjoy!.

Re: 48 cub will not fire

Fri Aug 23, 2013 7:53 am

Hello Lee and welcome to the best Cub site on the web! Since you are getting spark (that's a good thing) is it a bright bluish spark or a yellow anemic spark? Sounds like it's timed right, double check you firing order. If all is described as above and still a no go then I'd try a fresh set of plugs. It seems a fresh rebuild fouls the plugs during the initial start up attempts. Sometimes it the simplest things. Let us know how it goes.

Re: 48 cub will not fire

Fri Aug 23, 2013 8:42 am

Thanks for the responses. To answer questions: it is a J4 Mag, it does have spark to all sparkplugs when plugs resting on manifold for ground, there is continuity between plugs and head, the ground port is not connected, and it is not flooded. I do not know what the compression is, I will get a tester and check, but I did hone the cylinders and put in new rings. It has never fired or backfired once. Could I also have more specifics about Longmont next month? Location, time etc.
Thanks

Re: 48 cub will not fire

Fri Aug 23, 2013 8:51 am

I have a 48 cub that over last weekend it would run for a while but guit. then it refused to run since. I replaced the mag with another mag with new points and coil.. Would start but not run properly. replaced that mag with another , still would start but would not run properly, found to have irratic spark in both mags.. I installed a battery ignition . It fired right up and runs like it should. Im thinking the magnets in the mags are too weak to produce a steady spark.

Re: 48 cub will not fire

Fri Aug 23, 2013 8:59 am

Lee:

CO old iron wrote:Could I also have more specifics about Longmont next month? Location, time etc.
Thanks


PM Bob McCarty - he is the Host. Click on his name here and then Send a PM in his profile or simply hit the PM button in any of his posts.

Re: 48 cub will not fire

Fri Aug 23, 2013 4:51 pm

One last tidbit with the mag, the rotor and pinion gear must be timed properly. There is a cast line on the rotor, that lines up with a dot/triangle on the pinion gear. You have to remove the bakelite cover under the distributor cap, usually brown or black. That is the last step in timing, and is not covered in all timing instructions since it is internal to the mag, and not typically messed with. Check that it is correct. That will likely involve removing your mag and timing it one more time.

Re: 48 cub will not fire

Fri Aug 23, 2013 6:21 pm

CO old iron wrote: Could I also have more specifics about Longmont next month? Location, time etc.
Thanks

Lee, not sure if you've gotten ahold of Bob McCarty, so I'll throw out the specifics here.

Bob McCarty wrote:... It's 2104 Ladera Road, Longmont, CO. Your directions should have you exit I-25 at Hwy 66 (exit 243). Then west 7 miles to Hwy 287 (Longmont's Main St.). There is a Walmart on the NE corner and the Super 8 on the SE corner of that intersection. Then north on 287 4 miles to Horseshoe Circle. Left or west on Horseshoe to Ladera where you will see a Cub parked on the corner. Home # is 303-772-2566, my cell is 303-330-3692.

Bob

Times will be around 8 am to late afternoon-ish both days. No need to bring any tools, we'll have everything covered. Just bring the Cub! If you need talk some more, send me a PM by way of the "PM" box to the right of this text and we can talk offline. Hope to see you there!

Re: 48 cub will not fire

Fri Aug 23, 2013 7:23 pm

Lee, Just got home from the tractor show and sent you a PM which repeats Raymond's post.

Bob

Re: 48 cub will not fire

Sat Aug 24, 2013 11:22 am

Forgive me if it was mentioned already, but I haven't seen it, valve timing is very important. If you haven't checked them, they could be off.