Topic: CB750 Wet Sump Conversion - Sumpthing

[Sam Green Racing]

OK guys, it seems that some are in favour of this and others not.
I'll contact Rob (voxonda) who has been testing for the company under racing conditions and ask his thoughts.

Sam.

[754]

 It was never meant as a big jump over the stock system. It was a visual improvement got those inclined that way. For certain styles of build that can be appealing.
 And then , someone said hey do you think it would work on a racer, and then it was, Well let's try it and see..

[HondaMan]

I'd surely suggest using a NON-DETERGENT oil with it, as the gears of the countershaft may be buried in the oil. With the dry sump, this doesn't happen. It could, IMHO, cause significant drag on the countershaft gears, likely degrading high-RPM performance, unless the oil level in a running engine is studied to see how far down the level falls? I distinctly remember the guys who made 3/4" deep extension pans and fittings for the oil pumps to drop the pan oil further away from the countershaft in my old racing days: they also made [complicated] crankshaft baffles (aka windage trays) for the crank area. I don't have any results of their success/failure with the effort, though, as I moved out of Illinois that season and never talked with them afterward.

[simon#42]

this is the reason dry sump engines exist , less drag , less oil going everywhere .

[Sam Green Racing]

It was never meant as a big jump over the stock system. It was a visual improvement got those inclined that way. For certain styles of build that can be appealing.
 And then , someone said hey do you think it would work on a racer, and then it was, Well let's try it and see..

Well said Frank and yes, it was originally designed to be an aesthetic improvement for people that didn't like the looks of the oil tank where it was.

My very good friend Simon#42, and he is a good friend, asked several times, "what's this thread doing here in the High Performance section of the forum"
Well Simon, I was a bit concerned myself at first but I found out that George (gschuld) had been in contact with Jan and asked if a baffle could be fitted to stop the oil from sloshing about under racing conditions. Jan told him it could and that's why I didn't move the thread.
A Sumpthing was made with baffles and as they were local to each other in Holland, it was given to our very own Rob (voxonda) to test under race conditions.
Rob fitted it but with the sump now being lower, he had to re-rout his exhaust system.
I contacted Rob last night via Facebook and this morning got a glowing report on the Sumpthing.
Rob's only criticism was the fact that the oil had to be topped up via the tappet covers so he devised his own system and with that, no problems at all.

There were only a couple of other concerns voiced here by members.

#1, Jan claimed that the motor would run 20% cooler and I'm guessing he must have done some testing to prove this claim and I have my own thoughts on this.
Think about it, if you are going to go racing and fit an oil cooler, where do you fit it ?  Correct, you fit it up front or somewhere where it can get cool air blowing on it, you certainly don't fit it behind the head and cylinders where the oil tank is and is catching more heat. Honda had been making wet sump motors for a few years and only fitted the oil tank to the 750 to make it more aesthetically pleasing to attract owners of old British iron like Norton, BSA and Triumph's.
With that said, Jan's claim for it running 20% cooler could be correct.

#2, would the Sumpthing alter the bikes ability to cover 100,000 miles? I think it was Scott that asked this one. Not many bikes see that sort of mileage unless you do a lot of long distance touring and if you do, I'm sure you would be the sort of person that made sure your bike was looked after and serviced regularly and not thrashed from every set of traffic lights. The last thing that you would want was to break down in the middle of nowhere.
Also, would Honda make a bike that was going to break down every five minuets, they made the CB750A with a wet sump, didn't they ?

Over to you guys.

Sam.

[simon#42]

good points sam  but i dont believe for one second that it runs 20% cooler , 20% hotter more like .  how can taking the oil out of a hot engine circulating it in a tank and then pumping it back into the engine  make it run hotter than leaving it in the engine . the oil tank is just a very inefficient oil cooler , but an oil cooler it is not an oil heater .

[754]

Well it's always good to get real results..
 And if it does work for racing,  or racer feel they can live with it, that will be good for sales..

 I think a lot of 750 Sohc owners  resent the fact that they cant easily run open triangle in the frame..

[gschuld]

I don’t have strong opinions on this either way, but I enjoyed my interactions with Bert Jan as he was finalizing the details of the Sumpthing, and checking in with Rob during fitting and a season of endurance racing with it.

I’ve come to the consensus that though the dry sump system by design is a “superior” system all things being equal, there seems to be no fundamental reason why the Cb750 engine in particular requires such a system for an effective oil system.

Dry sumps were exceedingly rare on motorcycle engines during that period, even for Honda.  The cb500 came about just two years after the cb750 and was by all accounts the result of a great effort by Honda engineers to take the Cb750 and build a mid displacement, lighter, better handling, more refined version of the 750.  Clearly Honda chose to go back to the wet sump.  Kawasaki made an enormous effort over a 3 year period to study and develop their own answer to the hugely market dominating Cb750.  The result was the well loved Z1.  Wet sump like all their other bikes. 

Since nearly all the other bikes of the period (even top level road racing variants) performed just fine with wet sumps(again including Honda), it would be hard to argue there was in the end a significant advantage to the dry sump oil system Honda employed.

The point about oil cooling being better with the Sumpthing wet sump system was most likely a bit of over exuberant wishful thinking on Bert Jan’s part.  Regardless, any road racing or other performance application will have an oil cooler regardless of wet vs. dry oil system.  Easy to install, and they can be sized to suit needs.

So in my view, history would suggest that our cb750 dry sump system was wonderfully designed, and has performed admirably under every racing situation.  But that’s not to say that the dry sump was a functional necessity on the engine, or that the minor benefits of the system outweighed the extra cost and complication(and aesthetics or packaging results) over a tried and true wet sump.  Honda themselves clearly seemed to feel that way anyway(cb500f, cb400f, ch350f, cb350t cb450t, cb750a, cb900f, etc, etc) and the wet sump system was their baby.

Therefore, I can’t see a reason logistically why a properly done wet sump conversion on the Cb750 could not equal the admirable oil system performance delivered by, well, all the other wet sump bikes designed during the period(including all the other Honda bikes)

Rob(Voxonda) offering to endurance road race test the system offered a tough real world trial by fire.  It should take more abuse than about any other situation(other than a big bore sidecar racer or a sit in traffic on a hot day situation perhaps). Endurance bikes will need to stabilize the oil temp(sprint races less so), see many deceleration events pushing oil toward the crank, and deal with all sorts of abuse that may induce air bubbles into the system.

So we have only one racing test subject, but after a full season, all reports so far have been positive.

So I wouldn’t suggest everyone start abandoning their arguably overboard design dry sump oil systems.  They work VERY well.  But if someone felt the desire to convert to a tested wet sump design for whatever reason, I don’t see any fundamental reason why they shouldn’t.  I don’t see it as any type of existential threat to the function or longevity of the engine.  Especially for non racing engines....

Bert Jan has worked really hard on this project.  He will never realistically get his development time back. The profit margin isn’t big enough for that.  He seemed to be doing it because he primarily wanted to offer a “solution” to an aesthetic “problem” for those who liked to build custom road bikes(like he does).  For that I believe he succeeded and I applaud his effort and hope he sells a bunch of them to like minded people.  Potential racing use was an afterthought though it even seems to have promise there too.

George

[Sam Green Racing]

Great response George.

Sam.

[Tracksnblades1]

I'd surely suggest using a NON-DETERGENT oil with it, as the gears of the countershaft may be buried in the oil. With the dry sump, this doesn't happen. It could, IMHO, cause significant drag on the countershaft gears, likely degrading high-RPM performance, unless the oil level in a running engine is studied to see how far down the level falls? I distinctly remember the guys who made 3/4" deep extension pans and fittings for the oil pumps to drop the pan oil further away from the countershaft in my old racing days: they also made [complicated] crankshaft baffles (aka windage trays) for the crank area. I don't have any results of their success/failure with the effort, though, as I moved out of Illinois that season and never talked with them afterward.

What are your plans here Hondaman..?  Are you blending your own conventional formulation of AeroShell or GM Dexos2 oils, a semi synthetic and full synthetic oil. The Shell Aero-offering as a very low or no detergent oil premixed with Lycoming's 16702 load/press/wear additives.  Or the Gm's gen 2 offering of no calcium detergents mixed with their own additives. The calcium detergent,some believe, is responsible for low speed full throttle pre-ignition in the newer direct injected gas engines. Some newer studies suggest the high detergent additives are counterproductive to the friction, load, wear additives. Most commercial diesels still recommend High Detergent Oil.

Since most non-detergent oils  are only API rated SA, what additives do you have planned for the top end.?

good points sam  but i dont believe for one second that it runs 20% cooler , 20% hotter more like .  how can taking the oil out of a hot engine circulating it in a tank and then pumping it back into the engine  make it run hotter than leaving it in the engine . the oil tank is just a very inefficient oil cooler , but an oil cooler it is not an oil heater .

+1  very good explanation.

And as already mention the oil tank may not be ideal in location or aesthetics. But neither locations, the tank ( behind a hot engine) or the wet sump (right above the exhaust header), are ideal at a stoplight. Once moving though I don't think either locations are detrimental. 

I personally like the uniqueness of the dry sump system Honda used on the old 750. Its obvious also to the direction the manufacturers have taken. After witnessing a wet sump crotch rocket continuously wheeling while riding and passing till out of site on the interstate, I don't question the wet sumps capabilities.

My Hat is off to the Bert Jans, Mike Reicks, Mirkos types and others that provide us options for the dinosaurs we all love ❤️.. Thanks....

[Tracksnblades1]

Any other reports on this cool product ? ARE THEY STILL BEING MADE .?

Yes. I just installed one on an uber-custom (every inch polished) CB750K4 engine. It requires you put oil in thru the tappet cover hole(s), so you have to dribble it in (or the shiny engine gets ugly...). Then you have to count the oil, too, as the sight gage (oil window) on the right side goes from full-to-empty when the oil filter gets pumped full, so you have to dribble in some more oil, watch the sight glass, dribble a little more....until it looks full again. It holds less oil overall than the oil tank setup. You must also remove the whole thing to R&R the engine into the frame, so make a protector plate to cover the oil pan's gasket surface enroute, or it might turn into a real bad day after you dent the oil pan surface on the frame.

And, while it has more surface area than the OEM oil pan, the oil does run hotter than with a tank, so use at least 20w50. You could fit one of those oil coolers that use the adapter plate behind the filter, put the cooler up under the triple tree...

Couldn't the manufacturer just add an oil level plug (similar to a Cr trans) higher than the sight glass's level somewhere to compensate for the oil filter full volume.. Making the oil fill a single event.

[simon#42]

is rob racing the honda ? i thought he was doing demonstration runs on it . i have not seen him in any or the endurance races or results .

[Sam Green Racing]

is rob racing the honda ? i thought he was doing demonstration runs on it . i have not seen him in any or the endurance races or results .

I'm not sure Simon. I did ask him to check in but he just had a look and said, still pro and con thinkers.
He's going to put new pistons in the bike and will strip the engine and post pics of how parts are standing up to the Sumpthing.

Sam.

[Tintop]

is rob racing the honda ? i thought he was doing demonstration runs on it . i have not seen him in any or the endurance races or results .

Simon my understanding is that his son(s?) are riding his bikes now.

[simon#42]

i thought his son had been injured racing ,  i know the bike and always keep my eye out for it at the races but have not seen it .
i remember he had an older dutch rider doing a demo run on it . would be interested to know which races the bike has competed in with the sumpthing fitted .
see if you can find out sam !

[gschuld]

Simon,

I believe you are thinking of Tonny Van Schijndel, former Dutch champ.

https://www.sammotorsport.nl/tonny-van-schijndel-over-de-racedemos/

George

[simon#42]

yes the very man !

[scottly]

Honda meant the 750 to blow the minds of the motorcycling world, and it was a spare no expense type of endeavor. They didn't choose to use a more expensive dry sump oiling system for looks, as the tank was hidden behind a plastic side cover. One of the main advantages of a dry sump system is the ability to separate air bubbles from the oil, which requires a certain amount of vertical distance. Continuous high RPM operation can whip the oil into a froth, and with a wet sump there isn't any mechanism to reduce the air, which doesn't lubricate or cool the bearings as well as pure oil. There are documented cases of 750's with over 100,000 miles; notably Ofreen's F with over 160,000 miles now without a rebuild.
Honda was not so worried about the smaller wet sump bikes that followed the flagship 750..
If your use is from one pub to the next, you probably won't notice any reduced engine life with the Sumpthing, but then you won't be putting that many miles on the bike.

PS, for Tracks, the majority of Ofreen's miles were with a K&N filter in the stock airbox.
       

[Tracksnblades1]

Honda meant the 750 to blow the minds of the motorcycling world, and it was a spare no expense type of endeavor. They didn't choose to use a more expensive dry sump oiling system for looks, as the tank was hidden behind a plastic side cover. One of the main advantages of a dry sump system is the ability to separate air bubbles from the oil, which requires a certain amount of vertical distance. Continuous high RPM operation can whip the oil into a froth, and with a wet sump there isn't any mechanism to reduce the air, which doesn't lubricate or cool the bearings as well as pure oil. There are documented cases of 750's with over 100,000 miles; notably Ofreen's F with over 160,000 miles now without a rebuild.
Honda was not so worried about the smaller wet sump bikes that followed the flagship 750..
If your use is from one pub to the next, you probably won't notice any reduced engine life with the Sumpthing, but then you won't be putting that many miles on the bike.

PS, for Tracks, the majority of Ofreen's miles were with a K&N filter in the stock airbox.
     

😀

 Yes, I know change is hard, even when confronted with facts.....I'm guilty too, still change oil by the hours instead of oil analysis...😇

Just think how far it would go with out all that "properly treated" dirt passing through...🤔

https://www.nicoclub.com/archives/kn-vs-oem-filter.html

😂  😂  😂

[scottly]

Yeah, I've seen that "test" before; it's odd that the AC Delco filter came out on top even over filters of similar construction in every test.
BTW, my '82 CR480 came stock with a foam air filter, similar to Uni filters, and was meant for extreme conditions. Did your CR500 have a pleated paper filter?

[Tracksnblades1]

I'm sure Motor Craft, Mopar, Honda, Toyota, and the rest of the OEM filters will test excellent too. They warranty theirs too.

I've noticed there are no oiled cotton gauze type filters available for any commercial vehicles. And mentioning commercial vehicles, here in the bread basket they can really sweep the streets, literally, with all the agricultural and construction. Ask any shorts and sandals clad crotch rocket rider..

Like your Cr480, my CR500 and our other Crs all have oiled open cell foam filters (not a single layer qauze) with 7.5 hours standard service intervals. Some off road construction and agriculture outer primary filters have an optional open cell foam covering to extend service intervals in worse conditions.

It's just a choice we all have. Informed ones are even better...

[754]

I have seen numerous or know of  CB 750,s with over 100K on them . A buddies 71 had an estimated 160 K on an untouched lower end, top end was off a few times.
 However 2 other  bike engines stick out for long life, and one is wet sump.
 Beemer Boxer, have a wet sump...and there are many that have clocked over 200 K miles and some more than that. By design it has exceptional cooling, and I believe quite low amount of oil, like 2 quarts.
 Harley engines, Evo for sure , don't know on Twin Cam . I have seen documented over 400K miles . I have seen one with over 400 K that was near the end of its second motor.

 Curiously the Dyna models have gone over  to a form of wet sump, over a decade ago.

 However I think longevity is not the highest priority for most 750 owners.. no matter how you run or treat them, they usually have a long lifespan. Also a lot of us are getting to the age, where we don't have enough life left in us, to wear out a good running example. Dry sump or wet sump..enjoy the ride.

[bwaller]

Well this reminds me more of political fury on social media than our forum of like minded motorcycle folk discussing topics.



 

[gschuld]

Well this reminds me more of political fury on social media than our forum of like minded motorcycle folk discussing topics.

👍

George

[Tintop]

Well this reminds me more of political fury on social media than our forum of like minded motorcycle folk discussing topics.

👍

George

So true  +1