Topic: Oil tank relocation into swing arm

[HondaMan]

Retro rocket,754 & Hondaman, I like all of your ideas.  So Hondaman do you have instructions and parts to do your suggested idea? Are there any downside to making a "wet sump" out of the 750? Also 754, do you have a photo of the coils mounted under the carb? Retro Rocket, what is the minimum size of an oil tank using your suggestion?

If you go wet-sump (or partially wet-sump), I'd recommend an oil cooler, like a Lockhart (not the silly cooler plate of the F2/3 engines). It holds and extra 0.4 quart, to help keep the oil volume up. You need 0.6 quart for the engine itself (and all the nooks and crannies it will fill) and at least 3 quarts of "moving" oil in the system. The oil filter holds about 0.3 quart, so between a Lockhart-like cooler and the filter housing, there's almost 1 quart? Then, if you can squeeze maybe 2.2 to 2.5 quarts into that cool-loooking rear fender, there could be a great idea!


Keep in mind: it needs to vent somewhere/somehow. The early bikes used a radiator-cap-like pressure relief spring-and-ball-detent gadget in the oil cap on the tank, and a road draft tube (2, actually, one went back into the oil tank from the back of the engine) while the post-1974 models used an oil separator-breather device, located under the battery (yours originally had one of these), with a "dry" draft tube to the pavement. The oil will expand about 10% in volume overall at 200 degrees, what with the 8000 RPM crank and gears whizzing through it, so it can get frothy: expansion needs to be considered for this reason.

[754]

I brought the dry sump thread back up in sohc 4 bikes.. Called Erradicating oil tank.

[HondaMan]

Hondaman suggested that a dry sump be modified to a wet sump by using a CB 750A oil pan and windage plate. Has anyone else out their tried it with success? Hondaman, do you have to manufacture your own windage plate?

Back in the day, a windage plate was available on special order from Action fours, but this vanished in 1975. I think there were pix of it in a magazine (Cycle World? not sure...) and it was made from sheet metal, welded here (not to hold anything together, just bead patterns) and there to reduce sympathetic vibrations by lowering the resonance frequency. The bolts (with collar spacers) that held it down were simply drilled through the bottom of the crankcase, they were 2 per 'section' under the crank weights. It was 2 pieces, one for each half of the crankcase, and they were not symmetric. (Nor cheap!). But, they worked well by the reports from drag racers of the day. The bolts were 8mm size (IIRC), with thin heads to clear the crank weights.

I wonder: does anyone know if R/C ever made one? Certainly Russ's engines would have benefitted from them!

[Cpcracing]

Thanks Hondaman for the low down on the wind age plates and oil capacity of each component.  I would like to know moe about the Lockhart oil cooler.  Do you have photos or links? Are they still available to buy, if so where?

[754]

Look for a Lockhart 700,  I think the biggest,  and threaded ports so you can run real braided lines.
 Earls Supply has some bigger ones too.

[HondaMan]

Look for a Lockhart 700,  I think the biggest,  and threaded ports so you can run real braided lines.
 Earls Supply has some bigger ones too.

That's good advice: the Lockhart on a project bike I have right now has clamp-on lines, and at 60 PSI they weep a bit. Makes a messy engine over time, all across the front of the bike! 

[754]

I think there are two sizes Lockhart that have threaded ports..they would look pretty good with real braided lines
 On Mine, the outlets were by the mounts, so mounted it upside down, bolts at the bottom lines running straight down.

[Old Moe Toe]

I guess you've probably seen this number before. Oil tank in the tail section. At least that'd take care of the gravity feed side of things.

[HondaMan]

I guess you've probably seen this number before. Oil tank in the tail section. At least that'd take care of the gravity feed side of things.

This one works, but IIRC, it needed to use only 10w40 oils or it was too thick to feed the pump when cold? When the tank is this far away, the lines need to be bigger (diameter) if you want to run proper oils. as the pumps provide great flow and pressure, but not a whole lot of suction power.