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Discussion Starter #1 (Edited)
I read a lot of the posts on ear shaves and considered doing it but didn't really want to mess with it and down the bike for awhile. The ears didn't bother me as much as that lousy plenum chamber did. I didn't want to increase my carb noise and I didn't like the idea of jacking up the tank to fit the pod filters. I really didn't like the price of the pod filters at $60 x 2. Well the bikes been down for electrical problems so I decided to try something a little different.

I got to looking at the different K & N filters available and found the RC-2720, which is an oval with 2 holes in it. The holes are 2" and the centers are 5" apart. Our bikes are about 5.5 inches apart on the centers where the rubber boots go into the plenum. I found the filter for $42 shipped at Leading Edge Air Foils when everyone else wanted $42 + shipping. Here's the link, http://store.leadingedgeairfoils.com/product_info.php?products_id=5364

I was concerned about airflow and did some research, found the filter is used on Rotex 503 Ultralite 2 stroke engine. The engine develops 49.6 HP and runs at 6800 RPM, that's roughly twice the flow requirements for our bikes. Assured that it would provide enough air flow I ordered one and waited for it to get here. Here is what the Rotex looks like with the filter on it.



My biggest concern was space, the filter should fit by the measurements but reality is sometimes a different story. When it got here I did some fitting and found I needed to make sure the harness on the Lt was fastened tightly to the frame and down low near the 5 o'clock position. I had to modify the water inlet for the cylinder head water ports. The water port connection at the thermostat housing going to the rear head is just to long to let the hose flex around the filter, so I cut it and repositioned the end opposite the one for the front head like so. To modify it, I cut the tail port off and drilled a hole opposite but slightly off the connection for the front head hose. I made the hole a little tight and used the piece from the back I had cut off. I just used solder to seal it up. To close up the back I used a freeze plug I had ground down to fit in snugly and soldered that in also.



and



With that done, I had all the room I needed to put the filter in place. I used the original rear hose and put a schedule 40 plastic 90 degree elbow to turn it and used a Kelly Springfield S-4355 heater hose from Autozone that is moulded in a U to connect to the new port. I cut the hose and only used the U part of it.



I had to modify the rubber boots and take the flange off where it goes into the plenum, the rear one I had to take down a little further. I used a chop saw blade to slowly grind away the rubber until I had removed what I needed to get the depth I wanted. I used 2" muffler pipe to connect the filter to the rubber tube, keeping the distance as short as possible. The pipe in the front is slightly longer than the one in the back.





The filter fit in there perfectly. The tank does push down on it slightly but there is plenty of flex in the rear tube and all it does is make it all snug in there. There was very little increase in carb noise, it's protected from water and well hidden. I bought the $11 dollar stainless steel breather filter from Autozone, made a bracket for it and mounted on the front using the original hose that went to the plenum. Here is the finished product.



At this point, I'm still using the stock jets and I haven't noticed anything different. It seems to have plenty of power for the way I drive. I may rejet at some point but for now it seems to be fine like it is.
 

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and the Adventure Cycle
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A single filter ear shave, Nice! Certainly does look clean!
Have ya had the bike to the upper end of the RPM's to see how it runs then?

Great job :smiley_th :smiley_th
 

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Did you ever read my thread about my air filter catching fire?

No, really nice job. I've thought the same thing but using the air box. I've done the research and have been told a number of times that CVC carbs should use a common air box for the smoothest ride.

DT
 

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Discussion Starter #6 (Edited)
I haven't had it past about 5000 RPM, but it does just fine there and seems to be willing to go more. I've got R/R problems with it so it's been down until I get money for a Rick's replacement.

I considered using the rear portion of the air box, (cutting it at the bend), and putting a filter on the front and top side. I think it would work and there is certainly enough room for it but ended up discarding that idea as to research and labor intensive. Building the mount for the filters where they are easily changeable. The filters that would work are common to small engines, but will they flow enough air. I suppose you could use foam filters at that point since they are hidden. Like I said, it seemed like a lot more work than just adapting the bike to an existing filter.

If the filter catches on fire I'm running.
 

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Nice Job!!! Nice and Clean! Would be interested in the power range. 5,000 is about the speed limit. Let me know if you have to rejet?
 

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Growling at the World...
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Damn fine looking modification. Unique and professional looking. You did good...
 

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HAWK
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That is great thinking, looks excelent
 

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Simple Solutions
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its been a few days since u done it what are your settings with the air mix jets and how is it runnin if i can find my old jets i may goto this eventually....
 

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Discussion Starter #13
I've been posting a lot of questions for the past few months but this is my first real contributing post and it's very nice to have it so well recieved, thank you all for the kind words.

The bike has been down getting the stator rewound, I have that back and in the bike and only took it out for one test drive so far. I'm waiting for a Rick's regulator since the one I got from TPE does not seem to work or it got overloaded and died. I expect that by the end of this week and hopefully that will cure my charging system and get me up and riding again. Having said that, I was very pleased with it during the ride. I don't hear very much carb noise at all since the sound is deflected down, and it seems to have more than enough power.

Right now my mixture screws are out 3 turns. That's not my final setting yet I'm still playing with them. The hose I got from Autozone is a Kelly Springfield S-4355 heater hose, cost $12. The U is moulded so you don't have to worry about hose collapse bending it that tight and I cut the hose and used only the U portion. There may be better hoses to use but this was the first one I came across that fit the need. Like I said the 90 degree elbow is just a schedule 40 elbow I got from the local hardware store, I did trim the length of the ends down to where it only had two ridges on it.

Here are a couple more pictures showing what you see when you take the filter off:





 

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The Professor
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Awesome job on the shave! :smiley_th

I would like to hear of the improved performance results, fuel mileage and what jets are needed to compliment your shave. I would like to compare to the standard K&N pod filter and re-jet.

After building several of these engines and doing and helping with a bunch of earshaves and re-jets I know what these bikes can do. I recently completed a rebuild/restoration on an 89' with mojor engine problems for a member here vulcan89.

Aside from rebuilding the bike top to bottom front to rear and complete engine rebiuld. I did some performance mods. I.E rebuild and re-jet the carbs, remove all emmission and install my custom polished coasters, install K&N pod filters on the carbs, relocate the R/R with my custom bracket, de-goat and install my custom bypass kit, change th pickup coils from 1.0mm to 0.5mm, adjust the pilot screws to 3.0 turns out, install Iridium plugs with my custom wires and NGK caps, sync and tune the carbs.

Even though I have tested the engine @ 90000 rpm in my garage I never put it on the road. I knew this bike was ready to kick ASS and take names, so I set one of our members up to test ride. Mainly because he said he will never do an earshave! LOL

I knew Jason "VN750_Dawgsfan" was stopping by to have my custom made voltmeter cup installed. I asked him if he would be a Ginnie Pig and test the bike. When he got back the first words out of his mouth were "I want you to do that to my bike" Still laughing I said "I thought you didn't want to do an earshave" With the short ride he took he was impressed with the throttle response and performance.

I also had TPE rebild the stator for his bike and Tim did an awesome job. It works better than factory and it has higher output @ lower RPM. I know Tim tests each stator before it leaves so I think your problem is something else. I would go through your wiring and check the JB and R/R connections.

I was not trying to HIJACK your thread, just wanted to give some inside onfo and maybe get some returned.

I commend you on your diligence and fabrication skills. :carryflag
 

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Discussion Starter #15 (Edited)
K & N has another filter with the same dimensions as the RC-2720, but is shorter. The RC-3240, is 1.75 in height, the 2720 is 2.375. The shorter filter would fit the space better. I didn't use it becasue I was concerned about not getting enough air flow out of it. It may very well flow enough air for our bikes, I didn't research it that well since I was pretty confident the 2720 would fit.

Lance, I hope I don't disappoint you but the only reason I did this was because it seems to be a simple win-win way to get rid of the air plenum. I had grown to hate that thing having had the engine or carbs out and in several times and having to fight that thing. I wasn't really looking at increasing my performance just making sure I didn't decrease it.

I'm a 50 year old single dad with three kids, you won't find me roaring down the freeway at 110 MPH, I do good just to get it to 70 MPH on an open freeway, I'm a whole lot more comfortable at 65 MPH. The bike is way more capable than the way I drive it. I can get you mileage information once I get it running but I can tell you at this point is that I weigh in at 230 lbs and that bike has no trouble hauling my weight through the gears to get on the freeway. I don't notice any hesitation on any shifts with stock jets, when I open the throttle I get all the power I need.

Having said that I have limited experience on these bikes. I've only had experience with 2 different engines on the same bike. My first engine had 32k on it and had been run pretty hard and not taken care of, it was worn out. This engine is still pretty young at 6k and it's got way more giddy up than the first one.

My stator is fine, I'm very happy with the work Tim did on it, you saw my test in an earlier post. 60 VAC at 3000 is higher than stock from what I gather. The problem was, I got a 5 wire regulator from Tim at the same time. He told me the wire from the key excites the regulator, this one doesn't use it as it is self exciting. He assured me it would work and it did for about 15 minutes. I think the regulator wasn't matched up to the stator and it flat burned out. Trouble is, I can't get in touch with Tim and I don't know the values to ohm it out to tell for sure. So I just took a loss and ordered a Ricks from CheapCycle. I did call Ricks and asked if their regulator could take a 100 VAC input and he said that it would handle it just fine. It's built in Taiwan, as you know, and built to a higher standard than mainland China parts. I'll keep you posted, I expect it by the end of the week.

BTW - If you're ever in the Fort Worth TX area, stop by, I'll let you take it for a run and then you can tell for yourself if it makes much of a difference in performance.
 

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CFM Update

K & N has another filter with the same dimensions as the RC-2720, but is shorter. The RC-3240, is 1.75 in height, the 2720 is 2.375. The shorter filter would fit the space better. I didn't use it becasue I was concerned about not getting enough air flow out of it. It may very well flow enough air for our bikes, I didn't research it that well since I was pretty confident the 2720 would fit.
I called K&N and had someone in tech run some numbers for me.
Our 750's draw 125.9 cfm @ 9500 rpm.
The RC-3240 is rated @ 223.0 cfm.
The RC-2720 is rated @ 302.44 cfm
He told me that the RC-3240 would work fine even when it's dirty.
I ordered a RC-3240 from Summit Racing $40.62 plus $9 something for shipping. One week delivery.
If someone knows if the 125.9 cfm is incorrect please let me know.
 

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well.. using just the math.. 750cc on a 4stroke at 9500rpm means the cylinders are drawing in exactly 125.809 cfm.

so your cfm number is correct mathematically.

750cc * 9500 / 2 / (2.54cubed) / (12cubed)

divide by 2 because a 4stroke only sucks in air every 2nd stroke.
divide by 2.54cubed to convert from cc to cubic-inches.
divide by 12cubed to convert from cubic-inches to cubic-feet.
 

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Old thread, but has anyone tried this with the 3240 filter that can verify whether the coolant pipe still needs modified?

Filter arrives next week & trying to get parts prepped in the mean time...

Thanks!
 

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The 3240 is shorter, so it will allow for clearance under the tank, but I just jacked the back of my tank up with a half inch spacer at the rear bolt and that works fine if you need more height. IMHO, you have to modify the coolant pipe if you intend to go the single filter route. It's the width that makes it necessary, and it is dictated by the carb intakes.
 
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