Backfiring can be caused by a lot of things, exhaust leaks, valve lash, running lean, bad shutoff off valve and the list goes on and on.. In the last 1872 I purchase the M18 seem to starve for fuel like your if I push the throttle up, I did the K.I.S.S things first AKA Air filter/spark plug/gas filter/ clean the carb and adjust the mixture and the idle screw by the book. Better but still struggle to go up in the RPM, I swap a gas pump from a spare M18 I have and adjust the mixture and the idle screw again, Problem solved! Since that M18 never backfire I didn't look further but you may have to. :Huh:

I'm surprise no one shim in to help you, maybe you get better result if you post that question in the engine section?

Thanks Skull. Well this thread is all over the place so once I get serious into troubleshooting I will repost in engine.

The interesting thing (to me) is it seems to run great for a while and also when starting. So at first glance at least, seems to only come on after about 30mins of use. BUT - I need to repeat that pattern a few times and see.

I did just have the engine down to put in a new fuel pump and had the heads off and manifold/carb off and cleaned carb. So lots of potential screwups... :bigthink:

Do you have all metal tin on that engine? Since you remove the head I suppose you clean both cylinders "Jug". I remember reading about one of those Magnum with very severe overheating problem, the gas was literally boiling in his gas filter after few minutes of use! I hope you didn't need to deal with the valves because they are rare and expensive ..:bigeyes:

btw - decals on order.

They do have the tunnel cover sticker separately (said they dont make 1812 tunnel sticker but I just got an 1811 sticker)

I procrastinated on this long enough that it is now running great. Maybe a piece of dirt in the fuel cleared, but have not had the surging issues lately.

Starts when below 10F, with ease. Remarkable.

Picked up decals from Maple. Tins are painted (see pics), doesnt suck too bad.

I gotta prep and spray yeller.

The 45 degree flare on the hydraulics are leaking going into the hydro. More work on those. For now I put a piece of cardboard under it to catch the drips but when the fenders come off will re-eval those flared fittings. May make an adapter for my flaring tool, or borrow one, or buy a cheapie. Cant live with drippy leaks, always annoying.

In the meantime a foot of snow due today so it is going to get another workout.

:beerchug:

On the leaking fittin's
Been my long time experience, that while *45 and *37 are not recommended together, it works in the real world.
I mostly just snug them a bit tighter, sometimes back them off and re tighten.
Possibly the tubing flair is a bit short when you flared it, or it split?
( I don't know your expertise/experience):bigthink:
Don't accept failure too easily.

Regarding my 'expertise', it is a real possibility that I simply forgot to tighten them when it went back together and they are only started. So expertise wise, it could be even the most basic of problems (like forgetting to plug in an electrical appliance then wondering why it doesnt work!)

:)

Just saying anything is possible. I will get them to stop leaking. I work slow, but get there eventually. And do appreciate all the great inputs and encouragement from this site.

:beerchug:

Paint job look "georgeous" from where I sit! :beerchug:

I just did the same with hydraulic lines on my 1864. I used my 45 degree tool and used 3/8 sleeves and nuts for 37. So far everything seems good. Sorry for the poor pictures, just got a new phone so im learning

Paint looks real good there yeeter.:ThumbsUp: