Oil mix question for jonsereds 621

[frankconley]

Hi, I bought another jonsereds 621. The guy I bought it off said if I have any trouble let him know. He is a chainsaw guy. Works on them a lot and uses them every day. Mine wouldn't idle. He said it was because I poured out his 6 month old gas, which it ran fine on, that was 50 to one sthil ultra and put in fresh no ethanol with stihl 40 to 1. We raised the idle and it kept running. We poured out my gas and put his fresh 50 to 1 in. Then it idled too fast. We lowered the idle back almost where we started from and it is fine. My question is could the oil mix do all that? Thanks for any responses. Also is it ok to use 50 to 1? The original spec I saw was 25 to one. That's why I thought 40 to 1 would be better than 50 to 1.

 

[mexicanyella]

I have had to make carb adjustments when switching fuel premix ratios. Pretty common. If you put more oil in the premix, the engine runs leaner. This could manifest as a higher idle speed until you readjust for the new mix.

I’m a 32:1 guy, but lots of people run 50:1 fuel in saws both old and new and seem to get good results. I don’t know your model but I think with correct tuning, almost anything can work with 40:1 or 50:1.

 

[Thommo]

Yes your mixture screws need to be adjusted to suit the fuel and oil that you use. I have even had to adjust my fuel mixture when i tried a different brand of oil mixed at the same ratio.

 

[frankconley]

I have had to make carb adjustments when switching fuel premix ratios. Pretty common. If you put more oil in the premix, the engine runs leaner. This could manifest as a higher idle speed until you readjust for the new mix.

I’m a 32:1 guy, but lots of people run 50:1 fuel in saws both old and new and seem to get good results. I don’t know your model but I think with correct tuning, almost anything can work with 40:1 or 50:1.

Thanks so much. You answered my question so well. Now I have a clear picture of what's going on.

Yes your mixture screws need to be adjusted to suit the fuel and oil that you use. I have even had to adjust my fuel mixture when i tried a different brand of oil mixed at the same ratio.

Wow thanks a lot. Very interesting. I will use 50 to1 like the saw is tuned for hopefully that is enough oil to work right as far as lubrication.

 

[Cantdog]

The key to 50:1 mix is to use high quality full synthetic oil. A good quality modern oil at 50:1 will operate just about any chainsaw fine. All the oil mixtures you hear down to some models even specing 16:1 simply are an indicator of the oil available at the time (in years) of the saw's production date. Oil has made leaps and bounds in the last 40-50 years. The only time I would consider a mix with more oil than 50:1 would be running a saw in a milling operation. But again, you use cheap wally world no name oil and you'll have to use your own judgement. Personally I made the switch to full synth Stihl Ultra maybe 10-12 years ago simply because it is good quality and handy for me to acquire locally. I'm sure there are other oils of as good or better quality but It's always there on the shelf. I run every saw I own on it at 50:1and they run perfectly and have never scoured or seized a piston or stuck a ring. My old Mac 1-52 specs 16:1 I believe.....it runs fine and is just as loud as ever.....

 

[frankconley]

The key to 50:1 mix is to use high quality full synthetic oil. A good quality modern oil at 50:1 will operate just about any chainsaw fine. All the oil mixtures you hear down to some models even specing 16:1 simply are an indicator of the oil available at the time (in years) of the saw's production date. Oil has made leaps and bounds in the last 40-50 years. The only time I would consider a mix with more oil than 50:1 would be running a saw in a milling operation. But again, you use cheap wally world no name oil and you'll have to use your own judgement. Personally I made the switch to full synth Stihl Ultra maybe 10-12 years ago simply because it is good quality and handy for me to acquire locally. I'm sure there are other oils of as good or better quality but It's always there on the shelf. I run every saw I own on it at 50:1and they run perfectly and have never scoured or seized a piston or stuck a ring. My old Mac 1-52 specs 16:1 I believe.....it runs fine and is just as loud as ever.....

Thanks. That's good news. Did you remember about the spikes? Thanks for writing.

 

[Cantdog]

Thanks. That's good news. Did you remember about the spikes? Thanks for writing.

Yep got them out today......NOS in original bag with bolts....they'll hit the mail in the morning.

 

[frankconley]

Yep got them out today......NOS in original bag with bolts....they'll hit the mail in the morning.

Super dooper. Thank you. Also thanks for the oil mix information. I feel much assured.