Agree'ed check the alignment of the starter and starter drive action.
Idle speed and starting: Blower motors like a lot of initial and not much total advance.
As a base line lock out the advance curve and set the locked frozen timing at 28deg BTDC. It will range from 28deg to 34deg depending on wether you employ boost retard or methanol injection or high octane fuel. Start at 28deg.
The vacuum sec carbs will need to be dialed in to work with the blower correctly.
Start by removing both carbs and presetting the pri and sec throttle opening/idle transfer slot exposure at idle Aprox .020" on all.
As said above the starting proceedure is critical.
Pump it one /twice then close the throttle and kick it over. It will fire instantly. When it does, catch the throttle to 2500rpm and warm it up.
Do not wing the throttle when its cold. Let it warm up.
Once there is some heat in the blower case, manifold and carbs you can set up the idle. Set the idle mixture, then fine tune the idle speed. You must keep all 8 barrels throttles even at idle. It should idle at 900-1000 once fully warmed up.
Do not open the throttle when cranking/starting.
Once it catrches, raise the rpm to 2500-3000 but do not wing the throttle.
The carbs accelerator pump shooters and cams/linkage will need tuning.
If the moto4r is hard to crank when hot wiht the locked timing, install a ignition power interupt switch. Crank it over,throttles closed 1-2-3 and hit the spark switch.
The carbs will need blower motor calibrating , Jetting, idle and high speed air bleed tuning and possible idle feed restriction tuning. The power valves need to be boost referenced. The poer valve channel restriction may need tweeking.
I would consider upgrading the 600 vac sec carbs main bodies to the Proform HP style main bodies and billet base/throttle plate to gain some tuning flexability/capability. Essentually you'll be resusing the fuel bowls,metering blocks,metering plates and vac diaphram housing. The sec metering plates and be swapped,drilled or modded to accept screw in holley main jets.
At minimum you will need rejetting and boost referenced power valves and connected vac sec housings.