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XS650B : Air filters and air box question
- Thread starter oyajicool
- Start date
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- carburetors
Yes, they suck but will fit. All the BS38's are the same size where the filter fits.
On the sucks part, the pleated element filters Like the K&N and their knock offs cause excessive air flow turbulence through the carbs. This leads to a poor vacuum signal for the slides. This gives you an off idle flat spot that is very hard to tune out.
The shorter, more tapered the filter the stronger the effect. The long straight ones have the least effect.
A lot of us have found that running a straight round foam filter works much better. very little air flow turbulence. I spent way to much time, weeks trying to tune out my flat spot. I tried the round straight foam filters and the flat spot was gone.
Maybe not as pretty but they work.
Leo
On the sucks part, the pleated element filters Like the K&N and their knock offs cause excessive air flow turbulence through the carbs. This leads to a poor vacuum signal for the slides. This gives you an off idle flat spot that is very hard to tune out.
The shorter, more tapered the filter the stronger the effect. The long straight ones have the least effect.
A lot of us have found that running a straight round foam filter works much better. very little air flow turbulence. I spent way to much time, weeks trying to tune out my flat spot. I tried the round straight foam filters and the flat spot was gone.
Maybe not as pretty but they work.
Leo
I think the K&Ns may fit your boxes. I think the only difference between your filter and the later ones is that yours is open on the back where it fits against that crossover tube between the boxes. I think the only difference between your boxes and the later ones is that you don't have the pipes for the engine breather hoses to attach to. I guess the only way to know for sure would be to compare your boxes to a later set.
rbjenterprises
650B in SW Virginia
So the crossover tube is a bit of over engineering?
Due to the extra openings on stock filters on 650B, two filters work as one unit as I see it.
A small metal tab that is on the lower side of left box of mine is worn out. One end of the lid is supposed be hooked onto that tab while upper part of the lid is screwed down with 10mm hex bolt. I think it can be repaired easily but I am reluctant to do so since K&N filter is not available for this model year. K&N filter shall be economical choice in the long run since they can be washed. This is the main reason for me wanting to use them.
Anyways, I have found a set of boxes off of 78 on eBay. Less than $40 with shipping for a set is something I can give a shot. But as far as filters are concerned, the filters for 78 may fit just fine on 75 as 5twins says.
A small metal tab that is on the lower side of left box of mine is worn out. One end of the lid is supposed be hooked onto that tab while upper part of the lid is screwed down with 10mm hex bolt. I think it can be repaired easily but I am reluctant to do so since K&N filter is not available for this model year. K&N filter shall be economical choice in the long run since they can be washed. This is the main reason for me wanting to use them.
Anyways, I have found a set of boxes off of 78 on eBay. Less than $40 with shipping for a set is something I can give a shot. But as far as filters are concerned, the filters for 78 may fit just fine on 75 as 5twins says.
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rbjenterprises
650B in SW Virginia
I guess I am trying to figure out I block off the crossover the K&N will work in my 650B.
As others have said the K&N pods are what I was talking about. I have not used the in the air box style K&N filters. Can't really comment on them.
The crossover is to allow filtered air from both filters to flow through each carb. As the piston moves down to draw in air, only one piston is going down on the intake stoke. So one piston can draw from both filters.
Do you still have the stock filters? If so you can clean off the old filter element off the housing and wrap new filter elements on the stock cages.
I did this on my 81. Works very well.
Try searching for "air filter fixes" there are fixes for most years on here somewhere.
Leo
The crossover is to allow filtered air from both filters to flow through each carb. As the piston moves down to draw in air, only one piston is going down on the intake stoke. So one piston can draw from both filters.
Do you still have the stock filters? If so you can clean off the old filter element off the housing and wrap new filter elements on the stock cages.
I did this on my 81. Works very well.
Try searching for "air filter fixes" there are fixes for most years on here somewhere.
Leo
Yesterday, I got an air box assembly off of 78 delivered. The seller had included air filters along with the box, to which I didn't know if they were included in the deal.
The 78 box has different way of having the inlet air enter into the compartments for the filters than 75. There is that cross over tube/duct between left and right boxes. The air filters that came with the assembly are old and elements are crumbling as I touched.
I installed the 78 filter onto my 75 and it seems to fit well enough. The 78 box had leaf spring retainers, even. I think these can be used on 75 as well since my 75 had them missing.
Now, since I have these air filter cores that cut-to-fit foam can be used, I think.
The 78 box has different way of having the inlet air enter into the compartments for the filters than 75. There is that cross over tube/duct between left and right boxes. The air filters that came with the assembly are old and elements are crumbling as I touched.
I installed the 78 filter onto my 75 and it seems to fit well enough. The 78 box had leaf spring retainers, even. I think these can be used on 75 as well since my 75 had them missing.
Now, since I have these air filter cores that cut-to-fit foam can be used, I think.
Attachments
Yes, that later style cage is easily re-wrapped. Bulk UNI filter foam can be had for about $15 a sheet .....
http://www.amazon.com/Uni-Filter-65...im_auto_1?ie=UTF8&refRID=178TJPD43NNFVP3YKRAH
They make special oil for it but I really don't think you need it. We just use plain motor oil on the UNI pods. But do use something, don't run them dry.
There's no need for the filter to be open on the back and fit up snug to the cross over. The cross over will do its job just the same (equalize pressure between the two boxes) whether the filters press against it or not. Yamaha probably realized this after a couple years and re-designed the element. No doubt the new style was easier and cheaper to make too. You could probably just run those later filters in your '75 boxes.
http://www.amazon.com/Uni-Filter-65...im_auto_1?ie=UTF8&refRID=178TJPD43NNFVP3YKRAH
They make special oil for it but I really don't think you need it. We just use plain motor oil on the UNI pods. But do use something, don't run them dry.
There's no need for the filter to be open on the back and fit up snug to the cross over. The cross over will do its job just the same (equalize pressure between the two boxes) whether the filters press against it or not. Yamaha probably realized this after a couple years and re-designed the element. No doubt the new style was easier and cheaper to make too. You could probably just run those later filters in your '75 boxes.
Thank you for the link, 5twins.
Going with foam filter around 78 filter cores will be more economical than going with K&N, it seems.
I am still undecided whether to use 78 box on my 75 or continue to use 75 box after fixing the tab for the lid to hook onto. If I was to use 78 box and wanted to use lines for breathers, do I need to get the breather box off of 78? Or can I just hook up lines to it? I think I read it some place to use PCV(s) in between the air box tubes and breather box.
Do you have any input on this?
Another question......
Can I use K&N oil on foam filters?
Going with foam filter around 78 filter cores will be more economical than going with K&N, it seems.
I am still undecided whether to use 78 box on my 75 or continue to use 75 box after fixing the tab for the lid to hook onto. If I was to use 78 box and wanted to use lines for breathers, do I need to get the breather box off of 78? Or can I just hook up lines to it? I think I read it some place to use PCV(s) in between the air box tubes and breather box.
Do you have any input on this?
Another question......
Can I use K&N oil on foam filters?
Last question first - no, K&N oil is made special for the surgical gauge that K&N filters are made from. It's not designed for nor recommended for foam filters. Use a dedicated foam filter oil if you like, or just motor oil as I mentioned earlier. For our pods, we use a 50-50 mix of motor oil and gas. I use an old 1" paint brush and just lightly brush the outside of the filter all the way around. Then I let it sit 10 or 15 minutes, rotating it end for end a couple times, to let the oil soak in. You don't need or want to super soak them, just a light coating is fine. It will spread throughout the foam as the filter sits. You really can't over-oil them. The extra will just work its way to the bottom of the filter eventually and drip out, or will get sucked in through the motor. They sort of properly oil themselves once put into service. The excess comes out, leaving the right amount to aid in filtering.
Your breather housing should be the same as the '78 model, but may be plumbed differently. You may have one of the outlets blocked off and only one breather hose. The '78 had two hoses, one on each outlet. It also had rubber reducer plugs in each outlet, reducing the I.D. to about 1/8".
PCV valves don't work on the breather hoses. What we use are power brake check valves, but you won't need them if you're hooking the hoses to the airbox.
Your breather housing should be the same as the '78 model, but may be plumbed differently. You may have one of the outlets blocked off and only one breather hose. The '78 had two hoses, one on each outlet. It also had rubber reducer plugs in each outlet, reducing the I.D. to about 1/8".
PCV valves don't work on the breather hoses. What we use are power brake check valves, but you won't need them if you're hooking the hoses to the airbox.
