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Stroking a Dolmar 7900

Fruecrue

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Lobes swing about .027” further than the dolmar crank.
When time allows, the cases will get clearanced .030” and I will assemble the bottom end with new Nachi bearings and leave the seals out temporarily.
Goal being to find a way to run this crank without machining.

No balls, no babies!
 

hseII

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Lobes swing about .027” further than the dolmar crank.
When time allows, the cases will get clearanced .030” and I will assemble the bottom end with new Nachi bearings and leave the seals out temporarily.
Goal being to find a way to run this crank without machining.

No balls, no babies!

Well you have proven that to not be your problem.


Sent from my iPhone using Jon1212 Pro
 

Fruecrue

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When this crank swap is completed, is the saw going to be ported? I'll be interested to see if the transfers are raised - (think about it).
It will be.
An interesting saw for sure. I’m thinking she’ll run a high exhaust with 28 degrees BD.
Interested in your thoughts.
 

Terry Syd

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The 'induction stroke' for a two-stroke is from transfer closing to TDC. When you raise the transfer height, you reduce the induction stroke. (you can get the same time/area by widening the transfers without reducing the induction stroke)

It would be interesting to see what a stock 7900 performs like when the crankcase is machined out to give an extra .30" of clearance. The added crankcase volume will reduce the crankcase compression and broadened the powerband.
 
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