Stroking a Dolmar 7900

[RI Chevy]

Ahhh. I see now said the blind man. Lol. [emoji16]

 

[hseII]

View attachment 150363

He hada pistola.

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[Mastermind]

He hada pistola.

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Oh my God.

We had lunch together.

 

[Fruecrue]

What clearance between crank lobes and case are you shooting for Dave?

Same as factory basically.
I am only taking what the new crank exceeded the old crank by + .003” just in case my grinding is boogered. I never actually measured factory crank clearance.

 

[mettee]

Is it done yet?

 

[thedude74]

Cool thread. Curious to see progress and final. Should gain about 2.4 cc?

 

[Fruecrue]

Cool thread. Curious to see progress and final. Should gain about 2.4 cc?

Little less, about 2.2 if my maffs are right.

 

[Fruecrue]

I got finished with the pto case half, stuck a bearing on the crank and set it in the case .005” off center toward the flywheel thinking any little bit helps mitigate the extra length of the crank stub. That’s .020” and .030” crank to case clearance on the sides.
Mounted oil pump and pushed in worm gear.
Worm gear bottoms out on the crank shoulder .075” before full engagement.
That’s where I left it for now, ran out of time.
will probably find a way to shim the oil pump out to meet the worm gear, Then Mount clutch, drum and mock up a bar & chain.

 

[Dub11]

View attachment 150333

I thought you would of ground down on the crank lobes.

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What will this yield?

 

[hseII]

I thought you would of ground down on the crank lobes.



What will this yield? View attachment 150720

I hear you Gotta Mike It.

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[drf256]

I got finished with the pto case half, stuck a bearing on the crank and set it in the case .005” off center toward the flywheel thinking any little bit helps mitigate the extra length of the crank stub. That’s .020” and .030” crank to case clearance on the sides.
Mounted oil pump and pushed in worm gear.
Worm gear bottoms out on the crank shoulder .075” before full engagement.
That’s where I left it for now, ran out of time.
will probably find a way to shim the oil pump out to meet the worm gear, Then Mount clutch, drum and mock up a bar & chain.

Too bad you don’t know anyone with a lathe that can fix that for you.

 

[Fruecrue]

Too bad you don’t know anyone with a lathe that can fix that for you.

Lol, no longer taking work. You need another task like I need another kid.

Two factors are influencing me to take this path.
1) I’d love to see it done without machine work. 681 cranks could use welding out of the box, that’s an expense if the builder takes that route.
2) it’s not just the shoulder that needs to be set back. If one does that, it separates the worm gear and clutch drum by same amount. This may or may not be a problem. If that’s the case, you may as well run the clutch threads deeper, lop off the end of the crank and machine a groove for the retaining ring.
It’s a whole thing really, at least in my mind, but I’m no machinist.
One could easily be $400 into the crank alone.

 

[smokey7]

I think we all can agree there are several ways to do what needs done to make this work. Im interested to see what the additional stroke does for the timing and performance of the setup on this saw.

 

[Sty57]

If it going to be a dedicated race saw.
Just get rid of the oiler and make drip bottle.

 

[Fruecrue]

It doesn’t appear that chain alignment is going to be an issue.

 

[Deets066]

It doesn’t appear that chain alignment is going to be an issue.

This Love!!!

 

[hseII]

Too bad you don’t know anyone with a lathe that can fix that for you.

Harrumph


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[Mastermind]

Harrumph


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[00wyk]

I was distracted more by the lumps than the haruumphs.

 

[Johnmn]

Great movie!