Stroking a Dolmar 7900

RI Chevy · Nov 14, 2018

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

hseII · Nov 14, 2018

Redfin said:
View attachment 150363

He hada pistola.

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Mastermind · Nov 14, 2018

hseII said:
He hada pistola.

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Oh my God.

We had lunch together.

Fruecrue · Nov 14, 2018

Redfin said:
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 · Nov 15, 2018

Is it done yet?

thedude74 · Nov 15, 2018

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

Fruecrue · Nov 16, 2018

thedude74 said:
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 · Nov 16, 2018

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 · Nov 16, 2018

Fruecrue said:
View attachment 150333

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

hseII said:
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What will this yield?

hseII · Nov 16, 2018

Dub11 said:
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 · Nov 17, 2018

Fruecrue said:
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 · Nov 17, 2018

drf256 said:
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 · Nov 17, 2018

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 · Nov 17, 2018

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

Fruecrue · Nov 17, 2018

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

Deets066 · Nov 17, 2018

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

This Love!!!

hseII · Nov 17, 2018

drf256 said:
Too bad you don’t know anyone with a lathe that can fix that for you.

Harrumph

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Mastermind · Nov 17, 2018

hseII said:
Harrumph

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00wyk · Nov 17, 2018

I was distracted more by the lumps than the haruumphs.

Johnmn · Nov 17, 2018

Mastermind said:

Great movie!

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