Switched to 100LL, have a few questions

[gmcman]

I have been using pump 93 with Stihl Ultra @ 50:1 for my KM110 and I have decided to try the 100LL. I also have a mildly ported Husky 372XP and a stock 340.

I want to use my Motul 800 now @ 40:1 so I mixed it up and the 110 seems to run ok but throttle response was slow and it seemed to every so often hesitate. From what I have read I need to richen the mix a little with the avgas, but what about changing from 50:1 to 40:1 with the Motul from 50:1 on ethanol 93? Would I need to richen it back up changing from 50:1 to 40:1?

Obviously the saws don't have valves but the KM110 does, I don't want to mess anything up with the 100LL.

I also tried the 100LL in my JX75 walkbehind and it shut down after 1 minute with a residue on the plug. Granted this carb needs a rebuild but it would generally bog after a minute on corn 93 and a slight choke would keep it going after it sat for a few weeks. This time it ran, stumbled and died with no restart. I checked the float and it shuts off the fuel when raised and flows when lowered.I clean the plug and it starts then dies after about 20 seconds. I replaced the fuel line also and it has no kinks, same diameter. Fuel dribbles out of the float through the drain screw when opened.

Could be coincidence going with the 100LL about the JX75 but I want to be sure I'm setting everything up right.

 

[mdavlee]

100LL will be richer than 93. You need to tune accordingly

 

[gmcman]

Leaned out slightly it did settle down and responds well now.

 

[XSKIER]

Is there a good reason to go against Stihl's 50:1 fuel:hp oil recommendation for the 4-MIX engine?

 

[TreeTangler]

Is there a good reason to go against Stihl's 50:1 fuel:hp oil recommendation for the 4-MIX engine?

Same reason as before, more lube. The one thing you have to be concerned about in Stihl's 4-mix is the valves. You want a clean burning oil and I'd keep a close eye on them when running richer than advised.