Carb question

[factory 487]

31 minutes ago, Fishnuts2 said:

I think the best fuel mix for these little engines is the alkylate premix fuel you buy in home improvement stores or small engine shops. It stays fresh for a considerable time longer than regular pump gas. I was skeptical at first but now use it in all engines smaller than 40cc.

 

I'm not sure about that Alkylate premix stuff, there isn't enough oil in it for my liking, also it uses synthetic oil.

But they do have ethanol free fuel on it's own, which I could mix with the Stihl mineral oil at 32:1.

 

David

[CNew 404]

3 hours ago, Fishnuts2 said:

I think the best fuel mix for these little engines is the alkylate premix fuel you buy in home improvement stores or small engine shops. It stays fresh for a considerable time longer than regular pump gas. I was skeptical at first but now use it in all engines smaller than 40cc.

Definitely use high quality gas without ethanol, avoid pump gas. I get a high quality small engine gas from a good mower store for my mixes- no ethanol in my units!

[Mebob2 8]

Thanks Cnew for filter tip. Got one ordered. 
Wallfish, governor vein is connected.tks
   I have stated it a few more times. A couple primes, half choke and second pull it will start right up, it seems to open up to a good rpm but for only 3-4 seconds then quits. Even monkeying with choke as it starts to quit changes nothing. It seems like it just runs out of fuel. 2-3 pumps of primer and it starts up but pumping the primer will not keep it running or even get an extra bit of run time, Plug doesn’t look wet, still running the 30w 24-1mixed fuel, piston and cylinder wall look well lubed. Does seem to get quiet hot for 3-4 , 4 second runs. It runs smooth, with a bit of blue smoke. No air filter on it and no exhaust on it. Can the primer have enough suction to open brass check valve but carb not enough pull to keep it open?

  I did hook volt meter up to DC terminal and it’s giving 12+ volts, didn’t check ac yet. 

[Mebob2 8]

Also the advice about taking out the air filter before starting an old O&R was huge. I gingerly took mine apart, laid filter on bench it looked almost perfect, a little push on the top of it and the hole thing literally disintegrated, turned to powder. 

[Mebob2 8]

I have this stuff, comes premixed from STIHL , expensive but I wouldn’t mind buying it for the amount I would use them but i comes premixed at 50-1, no ethanol. 
this is likely what David is talking about.

[Fishnuts2 22]

I use a similar product called Trufuel at the 40-1 level. If you want more oil in it, just add a little quality 2 cycle oil. 

[Mebob2 8]

I’m going to try the STIHL 50-1. Mix it to 32-1 like mentioned and see how it runs. 

[Wallfish 698]

10 hours ago, Mebob2 said:

Can the primer have enough suction to open brass check valve but carb not enough pull to keep it open?

Yes, especially if the case seals are leaking since the diaphragm works by the pulse pressure of the air inside the case.

Try adjusting the needle setting too. Some can be difficult to dial in and again, leaking seals also effect this setting. You can try to keep it running by continually pressing the primer and use the other hand to adjust the needle valve or prime adjust, prime adjust, prime adjust. Trust me, this can be a common frustration. 

 

[factory 487]

12 hours ago, Mebob2 said:

Also the advice about taking out the air filter before starting an old O&R was huge. I gingerly took mine apart, laid filter on bench it looked almost perfect, a little push on the top of it and the hole thing literally disintegrated, turned to powder. 

 

They can really ruin your day if they get sucked in, here are pictures I took a while ago to show how bad they are even if they look in one piece. They usually don't survive long enough for my to get the camera out.

Before

After

 

There are two pieces of foam to clean out of the double air cleaner, I find one piece of new pre-filter is usually enough in both types (this may vary depending on type of foam you use).

 

David

 

P.S. I find similar disintegrating old foam in the vintage electronics I repair, I had to replace some yesterday in a HP voltmeter from the 1970's (used to either keep circuit boards in place, or prevent vibration being transferred to certain parts, such as some vacuum tubes).

[factory 487]

12 hours ago, Mebob2 said:

I have this stuff, comes premixed from STIHL , expensive but I wouldn’t mind buying it for the amount I would use them but i comes premixed at 50-1, no ethanol. 
this is likely what David is talking about.

 

Yes that is similar to what I found when I searched for Alkylate pre-mix, the Stihl one also uses synthetic oil (the Ultra one), we had one member complain that their O&R overheated with the synthetic version, it would be interesting to hear if anyone else has had problems using it or not.

 

I've been using the red Stihl HP (mineral version) in my vintage 2-stroke engines, which was recommended to me by someone who uses chainsaws for a living and has a collection of vintage ones too.

 

I'm definitely going to look for a can of the non-mixed Alkylate fuel (advertised for 4-stroke engines) and mix it using the Stihl HP mineral oil at 32:1 for my O&R engines.

Most petrol stations in the UK have the pumps marked as having up to 5% ethanol (E5), but this will be increasing to 10% (E10).

 

David

[Wallfish 698]

4 minutes ago, factory said:

but this will be increasing to 10% (E10).

Horrible stuff as 10% is what's sold here. And, the corn lobbyists are continually pushing for more and E15 but all of that crap really needs to go by way of the Dodo altogether. In my state there are no pumps without ethanol except for small airports and some marinas for boat engines. Some states still have non ethanol available at the pumps.

[Fishnuts2 22]

I've used synthetic oil in all my 2 stroke engines since 1977.  (Saber) I wouldn't be afraid of overheating an engine.  I currently have close to 90 2 cycle engines, mainly chain saws 35 to 118 cc,  that all get the same mix.  The only small 4 stroke motor I have is a generator, and he gets mixed fuel too!  It's at the cabin and I don't want 2 types of fuel around.  Gas is E - Free though,  I have done many carb overhauls because of ethanol gas left in the tank for too long.

[factory 487]

Thanks @Fishnuts2 that's why I mentioned it, as no one else had complained or mentioned problems with synthetic oil, the only other oil I tried (many years ago) was some crap sold by petrol stations & was intended for mopeds, it was horribly smoky compared with the Stihl oil (it never got near any O&R's).

 

I've just been reading the comments on a Norton motorbike forum, they also have problems with fuel lines getting dissolved by modern fuels, which can be a fire risk if it leaks all over a hot engine.

 

David

[CNew 404]

1 hour ago, factory said:

 

 

Silly question, but what sort of tool do you use to get such precise cuts on your foam filters?

[factory 487]

8 minutes ago, CNew said:

Silly question, but what sort of tool do you use to get such precise cuts on your foam filters?

 

Not a silly question at all, many years ago I bought a NOS industrial punch kit (as shown below at the current price) for about a third of the normal price on ePay from a seller that clears stock from closed down companies;

 

Things to note about the above kit, the punches are all metric, it also includes the arm with cutter for other sizes.

The filters can be cut in one go, as some of the punches can be used together, this depends how close the two sizes are.

 

David

[CNew 404]

Nice set!  I’ve thought about just buying a single punch that is the filter size, might still look for one. Osborne makes some large punches and I can probably find a used one.

[Wallfish 698]

20 minutes ago, CNew said:

 

Silly question, but what sort of tool do you use to get such precise cuts on your foam filters?

 

If you have an old rusted air cleaner cover to use, Insert a long bolt through the center hole and heat the cover with a torch. Press them out perfectly every time. It's not so critical to have them perfect as they should get squished inside the air cleaner anyway.

[JUST O&R 237]

I Have a piece of pipe sharpened the out side that work great. Air filters, Gas cap inserts and so on just need to find the rite size works great.

[Fishnuts2 22]

On 4/18/2020 at 8:07 AM, factory said:

Thanks @Fishnuts2 that's why I mentioned it, as no one else had complained or mentioned problems with synthetic oil, the only other oil I tried (many years ago) was some crap sold by petrol stations & was intended for mopeds, it was horribly smoky compared with the Stihl oil (it never got near any O&R's).

 

I've just been reading the comments on a Norton motorbike forum, they also have problems with fuel lines getting dissolved by modern fuels, which can be a fire risk if it leaks all over a hot engine.

 

David

Regarding the Norton comments, I remember quite well the time I was riding my BMW cycle and mistakenly put ethanol mix gas in it.  As I was riding my left boot became cold, and I looked down to see gas pouring out the gas line to the Left side carburetor.  The ethanol gas had dissolved the gas line as I rode!

I hate the stuff.

[Mebob2 8]

So, to eliminate issues that causes it to start but not stay running I really should replace the case seals? Or could it just be the stiff check valve ? Could valve be stiff enough that it won’t open properly good case seals or not?   I didn’t try it with different fuel but primer has little to no effect to keep it running and choke position has no effect. 
 

thanks