Topic: CB750 Wet Sump Conversion - Sumpthing

[Bert Jan]

Hey folks,

I would like to try one in my CR. Expecting no temp issue's due to use of large oilcooler. Also feel it can have a positive effect on weight and weight distribution, cause weight is centered more front/down. Only setback is, due to deep sump cant use my 4 into 1 exhaust......

Cheers Rob

Hey Rob,

I see you're my neighbour (in terms of how far the internet reaches) so we could make this happen very quickly. I'd like to hear some thoughts from you, and even better, would love if you could take the kit for a spin. The exhaust clearance is an issue but only to bikes that are done yet. My main focus was on builders still tinkering with the tank, but now i see there could be a demand in other sectors aswell, which is cool!

(Ik volg je al een tijdje omdat ik die droge koppeling een heel toffe vinding vond. Kan er nu niks meer over vinden helaas maar las wel hierboven dat dat een beetje is gestopt. Heb je een email adres zodat we wat sneller kunnen communiceren? Ik zit in Groningen maar moet voor klanten dikwijls naar de randstad. Binnenkort even afspreken? Neem ik een kit mee en kan je er even naar kijken.)

Bert, I brought Rob in on this because he is a top guy in the world of CB750 racing and is right on your door step, about 165km I think it said.

Sam. 

Thanks dude, i know Rob (not personally) because i followed his dry-clutch on dotheton couple years back. Let's see if we can meet up soon. Small world aye

[Sam Green Racing]

The world is only as small as the Internet Bert, hahaha.
I've had Rob's address for quite a few years, it was just a simple step to find yours and put them both into Google maps to see how close you were.

Captain, I wonder why Honda stopped making Bikes with dry sumps, the CB750 must have been one of the last ones they made.

Sam.

[deviant]

Captain, I wonder why Honda stopped making Bikes with dry sumps, the CB750 must have been one of the last ones they made.

Sam.

They didn't.  They continued to make dirt bikes dry sump until the CRF.  They went to wet sump on the CRF to lose weight.

[voxonda]

Hi Bert Jan,

Like mentioned I think it is worth a serious look at it.  As often stated it is one of the only models with dry sump and although it has advantages, it has some negatives too. Furthermore most modern HP engines are wetsump, although Honda offered wet sump kit for some, like the DOHC750/900/1100 series. It will need a close look in how it will work in a mildly tuned engine.

My email : info@voxonda.com



Kind regards, Rob

[Bert Jan]

Hi Bert Jan,

Like mentioned I think it is worth a serious look at it.  As often stated it is one of the only models with dry sump and although it has advantages, it has some negatives too. Furthermore most modern HP engines are wetsump, although Honda offered wet sump kit for some, like the DOHC750/900/1100 series. It will need a close look in how it will work in a mildly tuned engine.

My email : info@voxonda.com

Kind regards, Rob

You've got mail

[NickRafAcosta]

Hey Bert, after all thi I just want to say I think it's a great idea for cosmetic reasons, I'm excited to see how the first conversions perform and I will definitely be ordering my own kit to try with my 750 this spring, I will keep you updated on that build! To help with cooling I am going to be adding an oil cooler to the front as well, and my application will be for a road bike not a race bike, so I'm predicting there wont be any issues technically, seeing as the other CB's of the time we're all wet sump
Nick Acosta

[scottly]

we've also blown several engines to heaven during the early stages.

How did your conversion blow the engines to heaven? Did you not understand the oiling system in the early stages?

I think you are a bit severe here scottly.

I don't think asking about failures during development is out of line or "severe", TG.
I once destroyed a 413 C.I. V-8 after three 1/4 mile runs. The first symptom was the squealing noise from the engine after starting it for the forth run. Autopsy showed evidence of oil starvation, with bits of main bearing welded to the cam lobes. I later determined the starvation was due to the windage tray, which didn't allow the oil to drain back into the sump fast enough.

[Sam Green Racing]

we've also blown several engines to heaven during the early stages.

How did your conversion blow the engines to heaven? Did you not understand the oiling system in the early stages?

I think you are a bit severe here scottly.

I don't think asking about failures during development is out of line or "severe", TG.
I once destroyed a 413 C.I. V-8 after three 1/4 mile runs. The first symptom was the squealing noise from the engine after starting it for the forth run. Autopsy showed evidence of oil starvation, with bits of main bearing welded to the cam lobes. I later determined the starvation was due to the windage tray, which didn't allow the oil to drain back into the sump fast enough.

Scott, I think what TG was saying is like saying, were you not intelligent enough to see that this would happen, haha.
Even Honda dropped their fair share of clangers  with the CR750 Daytona bikes in 70 that all the world knows about but some were kept behind closed doors.

Sam.

[simon#42]

i understand this as a cosmetic modification, it looks well made and it is not expensive
but for a racing bike i see no advantages in using it at all , despite what is claimed the oil will be hotter , its going to cause
much more drag on the crank having the oil sloshing around underneath it . also as you cant take the exhaust underneath
it you are going to have to take them round which is going to cause all kinds of ground clearance problems .
best left to the hipsters .

[voxonda]

Despite it started as a cosmetic modification, there are (possible) advantages to think of. In all my years of working with these 750's never had an issue with temperature, due to mainly measuring both pressure and temp and the use of oilcoolers.
The oil to be hotter is, IMO, as good an assumption as claiming that it is not. Has someone measured it before?
Causing it extra drag on the crank, despite the oil being in a deeper sump, also is an assumption. It is possible, but I will see if it cost any power by putting it on the same bench as I did before.
IMO a big advantage is the loss of weight and the displacement of it up front and lower.
The use of my exhaust is my main concern, although I have an alternative 4 megga system, and will see what happens.
Have never been afraid to try something and see wether it brings something or not.
Am sure there might be some issue's to be solved, but we'll see when it happens........ btw. I have no commercial interest, just from a technical point of view.   

[simon#42]

Despite it started as a cosmetic modification, there are (possible) advantages to think of. In all my years of working with these 750's never had an issue with temperature, due to mainly measuring both pressure and temp and the use of oilcoolers.
The oil to be hotter is, IMO, as good an assumption as claiming that it is not. Has someone measured it before?
Causing it extra drag on the crank, despite the oil being in a deeper sump, also is an assumption. It is possible, but I will see if it cost any power by putting it on the same bench as I did before.
IMO a big advantage is the loss of weight and the displacement of it up front and lower.
The use of my exhaust is my main concern, although I have an alternative 4 megga system, and will see what happens.
Have never been afraid to try something and see wether it brings something or not.
Am sure there might be some issue's to be solved, but we'll see when it happens........ btw. I have no commercial interest, just from a technical point of view.   

taking the oil out of the engine and circulating it around an alloy tank is not going to increase its temperature , in fact the opposite . think of the oil tank as
an inefficient oil cooler but still a cooler
when you are testing on your bench make sure you accelerate the bench up to 140 mph and then brake rapidly back to zero  oh and tip it from one side to the other
as well . otherwise you will not get accurate results 
as for weight loss i dont think there will be any , it looks a substantial lump of alloy . much heavier than a light alloy tank and two rubber hoses .
also putting weight too low is just as bad as putting it too high , at least with a tank you can move it about to get the right balance
i also have no commercial interest  , just from a technical point of view

[bear]

Even Honda dropped their fair share of clangers  with the CR750 Daytona bikes in 70 that all the world knows about but some were kept behind closed doors.

Sam.

Well there you go Uncle Sammy, I was always under the impression that I had the market cornerd when it came to "clangers".
The Lovely Evelyn would tell you that we could have retired into the splendour she would have liked to be accustomed, if I hadn't been
so fixated in offering a constant stream of sacrifices to The Gods Of Speed for 35 years.

Cheers,
Brian

[Sam Green Racing]

I hope these problems that you mention can get resolved by the time I bring my car to be serviced Simon, it'll give us something to talk about, hahaha.

Bert, In respect of weight, can you give us the weight of your conversion compared to the weight of the steel oil tank and oil lines.
And don't forget to include the weight of the standard sump that it replaces. Take the weight of the standard sump away from what you replace it with, then take that away from the oil tank and lines.

Don't forget guys, these sumps were designed for the minimalist Cafe Racer guys to get rid of the clutter and if we want to take them a step further, we need to know more details.

Also Bert, can you tell us how you arrived at the 20% cooler oil claim.

Sam. 

[Sam Green Racing]

Even Honda dropped their fair share of clangers  with the CR750 Daytona bikes in 70 that all the world knows about but some were kept behind closed doors.

Sam.

Well there you go Uncle Sammy, I was always under the impression that I had the market cornerd when it came to "clangers".
The Lovely Evelyn would tell you that we could have retired into the splendour she would have liked to be accustomed, if I hadn't been
so fixated in offering a constant stream of sacrifices to The Gods Of Speed for 35 years.

Cheers,
Brian

I thought the guy that did that was from NZ not Australia Brian. haha.
The lovely Evelyn must be a Saint to put up with your carrying's on mate. haha.
Hope you are both keeping well Brian.

[bear]

At least Bert had the good sense not to marry.
We're keeping well thanks Sammy, hope all is well with you.

[voxonda]

taking the oil out of the engine and circulating it around an alloy tank is not going to increase its temperature , in fact the opposite . think of the oil tank as
an inefficient oil cooler but still a cooler
when you are testing on your bench make sure you accelerate the bench up to 140 mph and then brake rapidly back to zero  oh and tip it from one side to the other
as well . otherwise you will not get accurate results 
as for weight loss i dont think there will be any , it looks a substantial lump of alloy . much heavier than a light alloy tank and two rubber hoses .
also putting weight too low is just as bad as putting it too high , at least with a tank you can move it about to get the right balance
i also have no commercial interest  , just from a technical point of view
[/quote]

For me it is the definitive way to see if, comparing a bike with dry sump, with that same engine equipped with a wet sump has any "measurable" pro's and or cons. Without making any assumptions. Very few have ever done this and I would like to see (and measure). If dry sump would have been the ultimate we would have seen it more, it doesn't and that is not due to cost. Looking at the main competitors of the day, like Kawasaki Z900, Suzuki GS did not have it and every successor at Honda had wet sumps. If it does not work on my bike, no problem and will return to the dry sump. It is like wanting a dry clutch. Looks like everyone is looking after one, but having developed one and using it on track, it is good to know it is not just sunshine. 

[gschuld]

Rob,

I’m glad to see you are taking the risk to run this on your road racer.  I have great confidence that if this conversion can handle the rigors of road racing, you’ll make it happen. 

George

[Bert Jan]

I hope these problems that you mention can get resolved by the time I bring my car to be serviced Simon, it'll give us something to talk about, hahaha.

Bert, In respect of weight, can you give us the weight of your conversion compared to the weight of the steel oil tank and oil lines.
And don't forget to include the weight of the standard sump that it replaces. Take the weight of the standard sump away from what you replace it with, then take that away from the oil tank and lines.

Don't forget guys, these sumps were designed for the minimalist Cafe Racer guys to get rid of the clutter and if we want to take them a step further, we need to know more details.

Also Bert, can you tell us how you arrived at the 20% cooler oil claim.

Sam. 

We've had results with the oil being up to 20% cooler. I never stated it was a constant drop of temperature.  We've attached an oil temp meter and simply checked with and without. No rocket science there 

[Sam Green Racing]

Bert, I don't know what the normal temps are in a dry sump CB750 but my Automatic drag bike had a deep wet sump and no oil tank as standard.
I had a Lockhart oil cooler fitted as oil temperature was critical to running consistent times that are required for ET bracket racing and running in temps ranging from 80 to 100 degrees F, I had to take care when I started the motor before running my race.
If oil is allowed to get to hot, it looses its viscosity and I'm sure Honda would have known this when designing the deep sump Automatic.

Sam. 

[simon#42]

I hope these problems that you mention can get resolved by the time I bring my car to be serviced Simon, it'll give us something to talk about, hahaha.

Bert, In respect of weight, can you give us the weight of your conversion compared to the weight of the steel oil tank and oil lines.
And don't forget to include the weight of the standard sump that it replaces. Take the weight of the standard sump away from what you replace it with, then take that away from the oil tank and lines.

Don't forget guys, these sumps were designed for the minimalist Cafe Racer guys to get rid of the clutter and if we want to take them a step further, we need to know more details.

Also Bert, can you tell us how you arrived at the 20% cooler oil claim.

Sam. 

We've had results with the oil being up to 20% cooler. I never stated it was a constant drop of temperature.  We've attached an oil temp meter and simply checked with and without. No rocket science there 

in fact no science at all

[calj737]

We've had results with the oil being up to 20% cooler. I never stated it was a constant drop of temperature.  We've attached an oil temp meter and simply checked with and without. No rocket science there 

in fact no science at all

Unless you consider a thermometer not to be a tool of science. 

[voxonda]

Rob,

I’m glad to see you are taking the risk to run this on your road racer.  I have great confidence that if this conversion can handle the rigors of road racing, you’ll make it happen. 

George

George, I do not consider it a risk, if fitted and does not work, at least we tried. Have a choice of oilcoolers and a constant temperature gauge on board so will see on the first trail wether it works or not.
And am always willing to help out a landsman.

Rob

[Sam Green Racing]

Well said Rob, I'm glad I pointed you in the direction of Bert.
The only thing that might need looking into is the oil sloshing around under cornering and heavy braking in a road racing bike.
George did mention this to Bert with regards to fitting some sort of baffle and as far as I know he is looking into it.
It would be interesting to know what if any baffle is fitted in the sump of the CB750A.

Sam.

[Captain]

 The very reason behind the CBX running hotter and throwing rods out when racing was all due to oil surge and the crank whipping (aerating) the oil as it all poured into the crankshaft crankcase during heavy braking as the pan is shallow and the oil level is high.  The oil would then rush back again to the pan and some of this aerated oil would make it to the pick-up. Once there it doesn't magically disappear but carries on through the system until in makes it to the main bearings and big ends and when this occurs at full load and RPM then bearing life is going to be compromised, and in very short order (if this is repeated) failure will occur.
   Now I realise that the CBX has nothing to do with the SOHC we are discussing here but it serves to illustrate the events with badly designed wet sumps.  To help reduce the problem a baffled and deeper pan is advisable or anything that "increases" the depth from where the pick-up draws from will help as it allows greater time for the air to float upward/gas out or de-aerate (whichever term you prefer).   Modern motorcycle engine although wet sump have the crank much higher in the cases and the distance to the bottom of the pan is 2-3 x that of what the SOHC or for that matter the DOHC series that followed it, so by design they effect this event and can remove the air better from the oil.   
 Dry Sump arrangement exist to eliminate this problem totally and allow far better control and de-aeration that could otherwise be otherwise be achieved. However they are more costly to engineer and add another level of complexity but without any doubt they are superior in function than a wet sump. Honda realised this and made an economic based decision to drop the feature in the DOHC and the rest is history. It maybe of interest to know that the DOHC engine subsequently has it's oiling problems (although not as bad as the CBX) and I have been involved in correcting these issues where practical. But at the end of the day I still have a RSC Dry Sump fitted as it's the only way to deliver the oil control needed.
 There is certainly room for eliminating the dry sump feature if anyone wishes to do so and for a street bike and cruising around there really isn't a problem, but for the issue I have described above I really question removing it when racing or any heavy duty use.
 
 Captain
         

[voxonda]

Hi Brent,

Clear and you know I understand.........., but..............there are a few reasons why I am willing to try and see if one way or the other brings something. Have had my own idea's about the subject mostly regarding the shape, and size, of the oilpan. Not had the chance to talk to Bert-Jan in person yet but still feel, it is something to take into consideration. But as always love your very constructive criticism. Thanks mate

Rob