Topic: CB750 Wet Sump Conversion - Sumpthing

[Bert Jan]

On our demo bike we have a 4 into 1 with k7 stamped into it. Not sure if it's OEM or aftermarket.

[spiffy587]

Will an Automatic oil pan fit a K or F engine?

[Medyo Bastos]

No


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[Sam Green Racing]

Well guys, a year on and the Sumpthing seems to be working well.

[754]

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

[Sam Green Racing]

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

Frank, you can ask Rob who has been testing it under race conditions, he goes by the name voxonda on here.
If you get no answer here, I'll contact him through Facebook for you.

Sam.

[HondaMan]

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...

[Sam Green Racing]

Thanks Mark.

[simon#42]

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...

ah but mark you are missing the point , it does not matter how crap an idea it is ....... people think it looks good

[754]

Mark thanks for the report.  You can pre measure the oil then add.
Custom bike parts , it usually all about looks. Not all must participate..

[Sam Green Racing]

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...

ah but mark you are missing the point , it does not matter how crap an idea it is ....... people think it looks good

Hi Simon, hope you are well my friend but why say it is a crap idea. I think the sight glass is a great idea especially for the novice to these bikes.

Sam.

[scottly]

Sam, I believe what Simon is saying in his usual eloquent way is that converting from a dry sump to a wet sump is a down-grade, not an upgrade, and it's only value is cosmetic. I happen to agree..

[754]

Apparently Bimota did not like the Honda system either.,

[simon#42]

hi sam im fine . sorry i haven't been over to see you have been mad busy but will put that right soon !

scottty understands what i meant and did explain it much better , honda made a very good job of the 750 oiling system . the hipster ring or whatever it is called is worse in all respects than the standard oil system , i have no idea why this thread  is in the performance section .

frank , bimota  did like the honda system they just moved the oil tank .

[scottly]

I wonder if any of the wet sump sohcs had the same longevity of the dry sump 750's, which can exceed 100,000 miles without rebuilding?

[HondaMan]

Back in the [early] 1970s there were 3 wet-sump conversions for this engine. Only one of them held as much oil as the dry-sump OEM arrangements (3.5 or more quarts). I can't remember which one that was, but it was famous for weeping oil around the pan gasket, and you had to use 4-2 pipes to clear it. The other 2 held less than 3 quarts total, so I used to sell oil coolers (Lockhart, mostly) to those guys when I could, to add a little oil and try to cool it down some.

[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.