Hi all, some time this year I will probably bite the bullet and rebuild my late Navigator engine which is getting close to needing a re-bore. Researching piston availability it seems NOS Electra pistons are more readily available than over size Navigator pistons and unless I have misread the available information the Electra crank, stroke and con-rods are the same as the Navigator's with only the bore being different. Are the Navigator and Electra cylinder blocks and cranks the same and if they are is it possible / has anyone re-bored / rebalanced their Navigator to Electra dimensions? The small increase in power would be welcome of course and I would look at putting the frame strengthening plates on. I would welcome any technical advice from anyone who has done this successfully. Regards Nick Clarke
Hi Nick. Andy Sochanik run…
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Previously peter_holland1…
Previously peter_holland1 wrote:
Hi Nick.
Andy Sochanik runs a later Navigator engine fitted with Electra barrels and pistons. I'm pretty sure that the Electra, which runs with significantly lower compression ratio to the Navigator, has different heads to late Navigator.
For completeness I'll answer those points you make.
The late Navigator and Electra cylinder blocks are different. Same height but the spigot diameter into the crankcase is greater on the 66 mm bore Electra.
The drive side of the Electra and Navigator cranks are different. The Electra alternator rotor has a larger hole in it. The crankshaft end is completely different on the Electra because it has to engage with and accommodate the electric start pawl. The stroke and piston spacing of Navigator and Electra are the same.
The Navigator and Electra con rods are the same. Shorter than the early Dominator con rods and longer than the Jubilee con rods. All share the same size big end and small end diameters.
Camshafts, valves, and carbs are the same on Navigator/Electra.
By the time you have increased the capacity by 35cc and decreased the compression ratio, you get the Electra which gives a slightly more torquey ride than the Navigator, but IMHO no more power.
The crankcase of the Electra has larger spigot holes for the larger spigots on the Electra barrel assembly.
If you rebore your bike for the 66mm std Electra bore I'd wager the remaining liner gets perilously thin.
Andy can give you the complete run-down.
Regards
Peter
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Many thanks for such a det…
Many thanks for such a detailed reply Peter, very kind and helpful. From what you say this seems to be a lot of expensive work for little gain even though the extra torque would be welcome! A fascinating insight to the difference between the Navigator and Electra - such a shame they didn't stroke it to make it a proper 400 cc. I wonder if they lowered the compression ratio to give the starter motor a better chance of coping in cold weather! Warm regards. Nick
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Hi Nick.
Andy Sochanik runs a later Navigator engine fitted with Electra barrels and pistons. I'm pretty sure that the Electra, which runs with significantly lower compression ratio to the Navigator, has different heads to late Navigator.
For completeness I'll answer those points you make.
The late Navigator and Electra cylinder blocks are different. Same height but the spigot diameter into the crankcase is greater on the 66 mm bore Electra.
The drive side of the Electra and Navigator cranks are different. The Electra alternator rotor has a larger hole in it. The crankshaft end is completely different on the Electra because it has to engage with and accommodate the electric start pawl. The stroke and piston spacing of Navigator and Electra are the same.
The Navigator and Electra con rods are the same. Shorter than the early Dominator con rods and longer than the Jubilee con rods. All share the same size big end and small end diameters.
Camshafts, valves, and carbs are the same on Navigator/Electra.
By the time you have increased the capacity by 35cc and decreased the compression ratio, you get the Electra which gives a slightly more torquey ride than the Navigator, but IMHO no more power.
The crankcase of the Electra has larger spigot holes for the larger spigots on the Electra barrel assembly.
If you rebore your bike for the 66mm std Electra bore I'd wager the remaining liner gets perilously thin.
Andy can give you the complete run-down.
Regards
Peter