Mastermind Meets The J'Red 2188

[Mastermind]

Not really John. But it makes it impossible to tune the engine dead on 13,100, and tough to get it dialed in at 13,000. It's not the extra 100 RPM that I'm concerned with......it's the ease of tuning.

Also, these saws need extra oil when modified and run hard.

This is one that I would not use at less than 32:1

 

[Mastermind]

No burrs with aluminum?

Not really.......no.

 

[JRHAWK9]

Did you keep the Walbro carb? 13,100? My 390 is tuned fat at 13,800. Really likes 14,400ish...lol I've seen 12,500 - 13,xxx in the cut, depending on what I'm cutting and how big.

 

[Mastermind]

These things will eat cranks tuned that lean.......good luck.

 

[Hedgerow]

I eat cranks too....

Poop bearings...

 

[LowVolt]

I am staying away from cranks and just eating popcorn.....

opcorn:

 

[Marshy]

These things will eat cranks tuned that lean.......good luck.

Maybe you missed the part where he said "tuned fat at 13,800"...

Sorry, I shouldnt stir the pot this thread might get derailed.

 

[Mastermind]

No worries about the thread.

Tuned fat at 13,800 is just too fast for this saw. IMHO.

They installed a coil that rev limits it too 13,000 for a reason.

If your 390XP hits 13,100 with a 28" bar buried, then it's a stronger running unit than I'm able to build.

 

[Hedgerow]

No worries about the thread.

Tuned fat at 13,800 is just too fast for this saw. IMHO.

They installed a coil that rev limits it too 13,000 for a reason.

If your 390XP hits 13,100 with a 28" bar buried, then it's a stronger running unit than I'm able to build.

Chain backwards...
Try it... It'll go 13,100 no problem...

 

[Hedgerow]

I do have a legitimate question on the lowers Randy... I noticed they were cleaned up and beveled in both directions...
Not sharp at all... But not round... Is blunt the way to go? What are your findings on this matter vs directing more toward front or back transfers?

 

[redfin]

Not really John. But icaakes it impossible to tune the engine dead on 13,100, and tough to get it dialed in at 13,000. It's not the extra 100 RPM that I'm concerned with......it's the ease of tuning.

Also, these saws need extra oil when modified and run hard.

This is one that I would not use at least than 32@1

I have never run a limited coil. Do they bounce off the limiter like a car engine?

 

[Mastermind]

I like to keep the balance the way the designers intended Matt.

On the way I shape the entrances.....particularly the divider..... I feel that if they are overly sharp, the the flow is directed too much to one side. Just rounded off, and it just flows around the obstruction without changing the path too much.

Does that make sense?

I have never run a limited coil. Do they bounce off the limiter like a car engine?

It sounds a lot like four stroking, and can make the tuner end up with it too lean because it is on the rev limiter, rather than really four stroking. I try to get my customers to buy a tach, and tune to saw to the RPM I recommend.

 

[redfin]

Thanks for answering my questions man.

 

[Olesenofalaska]

Thanks for the descriptions and discussions in addition to the pictures. It makes me realize how little I understand about how these motors function. I look forward to running it.

 

[DexterDay]

Another fine thread!

 

[Mastermind]

Muffler mod anyone?

 

[Mastermind]

 

[Gravedigger]

Thanks for sharing.


Sent from my iPad using Tapatalk

 

[weedkilla]

Porting 101 question....

How do you determine when a saw has too much exhaust duration? Is it all in the timing numbers, do you calculate port areas as well? Or is this something that can be determined from the way a saw behaves? What are the "symptoms" of a saw with excessive exhaust port time area?
My questions are from the point of view of a saw that hasn't been developed over multiple port jobs.
I'm not discounting the role experience plays, just trying to get my head around it. I can see how exhaust port height effects the power band, just unsure what occurs when exhaust port area is excessive.

 

[SawTroll]

Did you keep the Walbro carb? 13,100? My 390 is tuned fat at 13,800. Really likes 14,400ish...lol I've seen 12,500 - 13,xxx in the cut, depending on what I'm cutting and how big.

I am sure a larger carb would help regarding power, if the transfers and the muffler are up to it - but I am far from sure a leaner tune would!