Skipping and Backfiring

[Larr991]

Well I went to start my 53 and I think or I know I have a stuck valve or two. Dumb question, any good ideas on freeing them? I really don't want to remove the head if I don't have to. Thoughts on this? I know sometimes its the only way, but I'm sure someone has a remedy that may help.

[Los_Control]

How long has it been since last started?

Mine sat for 20+ years and I soaked the cylinders with marvel mystery oil .... will help free up the rings and valves.

If it has been sitting for a long time, the old oil on the valve stems/guides gets gummed up and the springs are mot strong enough to pull them closed again.

MM will help free up the old gummy oil along with a few heat cycles to warm the oil up.

 

So after I got the engine running for the first time and warmed it up a few times, I would then use the mm oil on it while I worked on other things and then start it again and repeat.

I did the soaking at least 3-4 times after getting it started ... it runs pretty good (when not roasting marshmallows over the point fires) after all of that and compression returned.

 

Edit: I should add that is under the best conditions. If it got water in the cylinder and they are rusted or other mechanical failure, will need to tear it down for inspection.

Edited September 27 by Los_Control

[Larr991]

Ok thank! No, it never had water in the cylinders, had sat many years prior, but never outside. It ran fine, then just started this the last couple times I started it. It only has 11,000 miles on it. 

[JBNeal]

MMO in the crankcase oil could be a magical experience...follow the instructions, **abracadabra** problem solved

[Los_Control]

I was really amazed the first time I pulled the head on old Molly that sat for 30+ years ..... She had zero compression in any cylinder.

 

The real issue was gummed up valve stems .... I could use my little finger and simply push the valves back down ... rotate the engine and they were stuck again ..... the springs on these engines are really weak.

 

Just rotating the engine a few times and pushing the valves back down with my fingers  soaking the valves with mm oil .... they were all working within 1/2 hour.

 

You can do the same thing with adding mm oil and letting them soak and run a few heat cycles.

 

The springs work perfect, probably the best fit for a 90 HP engine .... they just will not pull down a gummed up valve stem.

 

Another edit ..... these engines use cast iron rings and some aluminum alloy for pistons.

We have two dissimilar metals and the rings like to stick to the pistons due to corrosion.

Rings need to expand and rotate freely on the pistons .... this is how they expand and seal against the cylinder.

 

MM oil also helps with this .... modern engines use different style of rings .... old engines do not.

The mm oil also drains down into the oil pan and gets mixed with the oil circulating through the crank and rod bearings ... cam, lifters .... it is a win win all the way around.

Edited September 27 by Los_Control

[Larr991]

Ok should I just add it to the oil or pull some plugs and put it in there> Thanks for the advice, much appreciated!

[JBNeal]

If ya let MMO sit in the combustion chamber long enough, it'll probably get into the crankcase...so whatever the instructions say to add to crankcase, put half in the engine oil and the other half in the combustion chambers, and let it sit for a couple of weeks...then spin the motor with ignition off to work whatever fluid remains along the cylinder walls, then see if engine will start.

[Merle Coggins]

I used to have this issue when my truck would sit for a month or so. It would fight me to get started and would run rough, due to the sticking valves. Once the engine warmed up they would free up again and be fine. I haven’t experienced that in several years now. I would occasionally add Marvel Mystery Oil to the gas back then in an attempt to remedy the situation. Maybe that’s why it’s not an issue anymore?

[Larr991]

I am going to add some marvel mystery oil to the crankcase and run some through the gas out of a small container. Hopefully it solves the problem, that is my problem, they sit for a long period, then it fights me to start. Hoping this solves it! Not trying to be lazy, but just don’t really want to pull the head off if I don’t have to, worst comes to worse, I will. 

[Plymouthy Adams]

as an added...for those folks that have been using e85 and if it is older stock fuel....you can run into problems with sticking valves easily.  Suggest you use an additive for upper cylinder lube to prevent this if you do not run the fuel through in short order.  Small engines suffer from this even more so.  The ethanol is not your fuel for intermittent use.  While the modern car with zero emissions systems of the modern car seems to do better as there is less air/moisture interaction in the system and thus less issues with longer sitting times between operations.   Sealed containers with no headspace seem to store the fuel a bit longer with less adverse effect as well.  

[Los_Control]

I would not pull the head, chances are you just need to start it and let it idle in the driveway for a 1/2 hour or more and it will clear itself out.

Spitting back through the carburetor is a intake valve that is not closing.  It should be closed and then the intake valve opens to remove the exhaust from the cylinder .... since the intake is open it goes out that way also ..... I do not think any mechanical damage is occurring, it is just not happy.

A good warm up and it should become happy.

 

The MM oil is good and will do no harm .... I have never used it in the fuel tank but many do.

I use seafoam in all my vehicles about once a year, in the fuel tank.

[Larr991]

Will try letting it run for some time, I also have a can of seafoam, so will try that also. I always use non ethanol gas and put some of that lead additive in. I will let it run and warm up to temperature, hate when this stuff happens, but I guess it's my fault as I don't run them enough.

[JBNeal]

for years, I ran into the problem of gasoline and diesel engines big and small struggling to start after extended periods of disuse, and this would drain batteries and cook starters and elevate operators' blood pressures.  Then one day I was reading the MMO label as it had changed packaging a little bit, and I was reminded of MMO as a fuel stabilizer.  Since I started putting it in the tank regularly, engine startups are quick, batteries are lasting longer, and working on starters is not an almost annual chore.  So nowadays, I purchase the 32oz bottle of MMO annually as the container is graduated but the caps wear out, and the gallon jugs as needed to refill that bottle...tell your friends!

[Larr991]

4 hours ago, JBNeal said:

for years, I ran into the problem of gasoline and diesel engines big and small struggling to start after extended periods of disuse, and this would drain batteries and cook starters and elevate operators' blood pressures.  Then one day I was reading the MMO label as it had changed packaging a little bit, and I was reminded of MMO as a fuel stabilizer.  Since I started putting it in the tank regularly, engine startups are quick, batteries are lasting longer, and working on starters is not an almost annual chore.  So nowadays, I purchase the 32oz bottle of MMO annually as the container is graduated but the caps wear out, and the gallon jugs as needed to refill that bottle...tell your friends!

I'm going to give it a try, I really have no one to blame for myself on this, I should be on top of this better, especially being around trucks my whole life! I had a stupid attack,lol

[Los_Control]

I blame it on the engineers  .... A engine with zero compression I removed the head.

I was totally amazed at the amount of pressure it took to move the valves back down .... literally almost nothing ... maybe 2-3 pounds pressure to push the valve back down?

 

If there was just a slightly stiffer spring, they would pull the valve back down and this issue would not happen ..... IMHO

 

I also realize my engine only produced 90 hp stock .... A stiffer spring would probably cost 5 hp and bring it to 85 hp ..... they did what they did.

 

Great little engines, weak valve springs is just a curse they were born with.

[JBNeal]

6 hours ago, Larr991 said:

... I always use non ethanol gas and put some of that lead additive in...

With MMO, you can skip the non-ethanol gasoline...I did a price comparison of non-ethanol vs 87octane +MMO, and it's a dead heat, but ya get the fuel stabilizer benefit of MMO.

 

Chrysler flatheads have hardened valve seats, so they run fine on modern gasoline...skip the lead additive and invest in MMO instead 🏆

[Roofus]

MM oil ? it's what ?

[JBNeal]

54 minutes ago, Roofus said:

MM oil ? it's what ?

👉  Marvel Mystery Oil  👈

[Merle Coggins]

On 9/28/2024 at 12:47 PM, Plymouthy Adams said:

as an added...for those folks that have been using e85 and if it is older stock fuel....you can run into problems with sticking valves easily.  Suggest you use an additive for upper cylinder lube to prevent this if you do not run the fuel through in short order.  Small engines suffer from this even more so.  The ethanol is not your fuel for intermittent use.  While the modern car with zero emissions systems of the modern car seems to do better as there is less air/moisture interaction in the system and thus less issues with longer sitting times between operations.   Sealed containers with no headspace seem to store the fuel a bit longer with less adverse effect as well.  

 

Tim brings up a good point... I have been running Premium, non-ethanol, gas for the past few years as well. Many of the gas stations around here offer non-ethanol in their 93 octane premium fuel. For as much as I drive my truck I don't mind spending a little more for the fuel. Maybe that's also helping? I haven't added MMO in quite a while now. 

[ggdad1951]

22 hours ago, Merle Coggins said:

 

Tim brings up a good point... I have been running Premium, non-ethanol, gas for the past few years as well. Many of the gas stations around here offer non-ethanol in their 93 octane premium fuel. For as much as I drive my truck I don't mind spending a little more for the fuel. Maybe that's also helping? I haven't added MMO in quite a while now. 

 

All I run on my small engines and on FEF is non-oxy...have had little issues (to none) on litteing things sit and fire right up and run right.  My only exception is the weed whip....small 4 stroke that has always been a bit...difficult.