Kawasaki VN750 Forum banner

1 - 12 of 12 Posts

·
Registered
Joined
·
1 Posts
Discussion Starter #1
Hi, I am a new member to the forum, living in Berkshire united kingdom, I read a thread from a few years ago regarding the possibility of air cooling the vn750, the consensus was that it couldn't be done,
IT CAN, I modified mine to total air a while back with no problems at all, it has a 3inch 12volt duct fan blowing continuous cold air through the waterways of the engine, the hot air exhausting to atmosphere,
have also fitted an air scoop to either side to direct air onto the rear cylinder, and a temp sensor fitted to the rear cylinder top fin, and connected to the original wiring to the temp gauge, and it all works well, have had no overheating problems at all, I did fit the radiator fan to the front of the frame, but have never had reason to switch it on, at the end of the day, cooling is cooling.
 

·
Super Moderator
Joined
·
11,865 Posts
I don’t think it’s really an issue of “it can’t be done” it’s more like .....

Why?


I doubt your mod would work well here on a summer day of 100 degree temperatures stuck in traffic. But what do I know.

some photos would help us understand what the result looks like.
 

·
Super Moderator
Joined
·
2,570 Posts
Yea, it wouldnt work for my area.. right now, on oct 29, the forecast high is 92.. no real relief in sight.


oh, lets not talk about the humidity.. normal dew point for my area in AM is about 75.. note: air temp in AM is about 75 right now too.. makes for some mighty *thick* air
 

·
Retired USAF (IYAAYAS)
Joined
·
674 Posts
Every so often someone will take it upon themselves to try some radical alteration and succeed. People have switched it to single carb operation and you, for example, have changed it to air cooling. As said above, its not really a case of can it be done as much as a "why do it?" type of thing. But I suppose whatever they're changing represents an engineering challenge to them that people want to master.

That's fine. Perhaps not practical but still fun to do for the heck of it.

Let's think about mods that have been done aside from what I just mentioned. Trike? Its been done. Side car? Been done, too. I wonder if anyone has thought about stretching the bike. Hmmmm. Extend the drive shaft, frame or swing arm, put on a better two-up type seat. Next we'll hear of someone trying that. Its an engineering challenge.
 

·
Premium Member
Joined
·
598 Posts
Every so often someone will take it upon themselves to try some radical alteration and succeed. People have switched it to single carb operation and you, for example, have changed it to air cooling. As said above, its not really a case of can it be done as much as a "why do it?" type of thing. But I suppose whatever they're changing represents an engineering challenge to them that people want to master.

That's fine. Perhaps not practical but still fun to do for the heck of it.

Let's think about mods that have been done aside from what I just mentioned. Trike? Its been done. Side car? Been done, too. I wonder if anyone has thought about stretching the bike. Hmmmm. Extend the drive shaft, frame or swing arm, put on a better two-up type seat. Next we'll hear of someone trying that. Its an engineering challenge.
I've seen this pic, this person changed the front end for a longer bike, looks pretty cool
 

·
FREEBIRDS MC CENTRAL NY
Joined
·
16,093 Posts
Yes and I can theoretically run through a burning building...

Sent from my A502DL using Tapatalk
 

·
Registered
Joined
·
7,937 Posts
If the date was anywhere near April 1st, ... well.

The water pump is now a fan. What are the short/long term effects of a dry water pump? What are the long term effects of road grit inside the engine? Is there an air filter?

Pics?

A stock VN will run cool in 40°-50° weather, but it still has the coolant getting chilled to it's molecules. Without a fan in warm weather, below 35mph, it's cooking.
 

·
I'm a rider
Joined
·
964 Posts
That’s not how air cooling works. Engines such as Porsche and VW designed for air cooling have completely different internal designs. Basically “my gauge at the thermostat says my bearings aren’t melting on the opposite end of my engine” isn’t good enough. The reason water cooled passages are where they are is for EVEN COOLING of all the internal components. Putting cold air in those hot passages will crack the engine, not putting coolant in those passages will superheat the areas designed to run cooler thanks to the water flow. All in all, see you soon when your engine either cracks the block, heads, or the engine warps (most likely) and nothing seats properly anymore. As a welder, if I don’t cool aluminum at a specific rate it cracks immediately.

Simple minds engineering doesn’t redesign an engine. They are engineered specifically to meet criteria. One dead engine, coming up........
 

·
Registered
Joined
·
736 Posts
The whole idea sounds interesting, but nothing I could ever try in Florida. Water passages and air cooling fins are distinctly different due to the thermal conductivity of water/coolant being so much greater than that of air. Cooling fins on a radiator are small and thin to provide a ton of surface area to for the cooler air to interface with, since only so much heat can be dissipated to the air for a given surface area. Coolant passages within the engine have a comparatively tiny surface area, making air cooling much less effective than water-to-air cooling. Then again, with enough flow and a cold enough air supply, I suppose it COULD be possible that the flow and temp of the air could make up for the relative lack of thermal conductivity.

I don't have time to scratch out the physics equation (nor do I remember my physics classes very well :wink2:) but in THEORY it sounds somewhat feasible from a thermodynamic perspective.
 

·
Premium Member
Joined
·
3,026 Posts
Average temperature in south central AZ in the summer is 118 degrees. Don't know where you would find any cold air. I seriously doubt this would work anyway, even at the north pole. And it would cause engine temperatures to be very unstable, either too cold or too hot. The engine has no cooling fins, so it doesn't have enough surface area for air cooling. Proper cooling means good heat transfer, and the walls of the water jacket do not have enough surface area to remove enough heat either. Scatterbrained idea that would destroy your engine.

That green bike looks pretty good except for the color. But it has more than an extended fork, it also has a raked frame. I had a bike that was raked out like that once, It handled so badly it was dangerous to ride.

I know this has been brought up a million times, and other bikes have proven it is not only possible but can work very well, and that is a single carburetor. Look at all the people getting rid of most of the intake system to make it simpler. Seems to me a single carb would be the ultimate simplicity modification. It works very well on the 4 cylinder Goldwing. My v twin Sportster runs fine with one carb, and so does my parallel twin Honda Rebel.
 
1 - 12 of 12 Posts
Top