Cafe Racer Build with Stock Air Filters

[nofun]

Hey Everyone,

After enough research, I have concluded, thanks to the fine folks on here, that converting these CV Carbs to AirPods is a job I don't want to take on. I love the hunt/tuning process, but am unwilling to have my bike run like garbage for a mild aesthetic shift. Converting to a Slide Carb is an option, but for a budget conversion of carbs around $600-800 just ain't it for me. So I digress, I want to do some simple (simple is laughable) modification to the frame for a custom seat, new electrical system with the m.unit, battery upgrade, etc., etc., etc., the classic cafe/brat mods, if you will.

The decision to keep the stock airbox changes the expected modifications of deleting the battery/filter housing and welding in a new electrical pan below the seat. So my question: Does anyone have experience, or examples, of how people have modded the 80-83' generation to house the stock air system with the deletion of the stock electrical system and battery? With the standard modification usually dropping the battery to the center stand mount and hiding the wiring in a new seat pan, I can't seem to wrap my head around how to clean up the bike visually and still run a new system.

I attached the inspiration bike I am eyeing from the incredible rebuild by Marfil Moto. It looks to me like they kept the stock air/carb build, but the post mentions a full electrical re-work. So, any help, guidance, threads, or sources y'all can push me to is so greatly appreciated.

 

[akirasan]

why does everyone butcher/modify the xs.
a generic frame cut with generic seat and generic bobber look????

ffs ride it.

 

[Peter B]

Hi Jacob,
Looks as though your inspiration bike still has the original airbox and battery box fitted - very sensible. My cafe racer style XS is now running ok with RAM air foam filters (look similar to Airpods) and an extended air intake tube but I know the jetting of the carb was toyed with back in the day but no specific details. I think i'm fortunate it is running as well now with foam filters as it is, it still runs a touch rich albeit no flat spots. The Airpods were really junk / unfit for purpose / very frustrating to try and get the bike running sweetly - I tried two different sets of the very cheap Airpods. I spoke with a number of folk including Stuart Weyer, who built the bike back in 2014, and it transpired it never really ran that well with Airpods but someone purchased the bike from him (before he had it dialled in) as they wanted only to mount it on a wall not use it. I suspect the bike has largely remained in collections and unused since it was built. Almost everyone I have spoken to has said CV carbs and Airpods bad combination and I would agree. An XS650 tuner suggested Ram Air foam filters as the go to for XS 650 Airpod style look but I suspect the original airbox still better solution. It will be interesting to see how the foam filters work out over extended period of time thankfully my bike is for high days and holidays pleasure / posing use not a daily commuter. If it was daily commuter it would have an airbox or the Mikuni flat sides solution...

 

[akirasan]

I have foam filters on my 78 xs400 electronic ignition and it runs great.
apparently the filters with solid chrome ends disrupt air flow

 

[nofun]

Hi Jacob,
Looks as though your inspiration bike still has the original airbox and battery box fitted - very sensible. My cafe racer style XS is now running ok with RAM air foam filters (look similar to Airpods) and an extended air intake tube but I know the jetting of the carb was toyed with back in the day but no specific details. I think i'm fortunate it is running as well now with foam filters as it is, it still runs a touch rich albeit no flat spots. The Airpods were really junk / unfit for purpose / very frustrating to try and get the bike running sweetly - I tried two different sets of the very cheap Airpods. I spoke with a number of folk including Stuart Weyer, who built the bike back in 2014, and it transpired it never really ran that well with Airpods but someone purchased the bike from him (before he had it dialled in) as they wanted only to mount it on a wall not use it. I suspect the bike has largely remained in collections and unused since it was built. Almost everyone I have spoken to has said CV carbs and Airpods bad combination and I would agree. An XS650 tuner suggested Ram Air foam filters as the go to for XS 650 Airpod style look but I suspect the original airbox still better solution. It will be interesting to see how the foam filters work out over extended period of time thankfully my bike is for high days and holidays pleasure / posing use not a daily commuter. If it was daily commuter it would have an airbox or the Mikuni flat sides solution...

Holy smokes, your bike is gorgeous. I am into quite a few inspirational builds for our bikes, and this is now in the running for the beauty I hope to achieve.

Since I posted this, a few things have changed in my plans. I got the bike back up and running and took it for a longer test ride, but it was bumping into gnarly hesitations and lurching in my acceleration. Did some more research, tuned, dialed, rebuilt the CVs three times, checked richness, everything above. I have struggled with the CVs since I got this bike 5 years ago, and finally had it with them, especially considering my original wish for this bike was to go full pod, and to some, butcher this bike. So I took the plunge and ordered some VM carbs (from MikuniOZ), and I am so excited about them.

I spent the past month waiting for the VMs by rebuilding the clutch and clutch release (I had this horrible issue with an incredibly sticky and heavy clutch that was unridable, and now it's butter), installing a new XS650 petcock for a more reliable gravity feed, swapping to the 78' exhaust pipes with new mufflers, and swapping my original instrument cluster with a mini speedo from Emgo.

If you had beaten me to the punch with your message before I pulled the trigger for the new VMs, I would have definitely tried this out. But the Mikunioz order was international for me, so I can't go back now, haha. Thank you for sharing your bike and thoughts!

Edit: My VMs arrived today, so if you are curious, I can report back on how that goes.

 

[Peter B]

I have foam filters on my 78 xs400 electronic ignition and it runs great.
apparently the filters with solid chrome ends disrupt air flow

That's interesting maybe I should try a set of them too before I fully commit to the cost of Mikuni flatsides. Do you have them fitted directly onto the air inlet of original BS34 Mikuni CV carbs or on the back of the original air inlet manifold (with a balancer tube) that joined the carb inlets to an airbox with filters?

 

[Peter B]

Holy smokes, your bike is gorgeous. I am into quite a few inspirational builds for our bikes, and this is now in the running for the beauty I hope to achieve.

Since I posted this, a few things have changed in my plans. I got the bike back up and running and took it for a longer test ride, but it was bumping into gnarly hesitations and lurching in my acceleration. Did some more research, tuned, dialed, rebuilt the CVs three times, checked richness, everything above. I have struggled with the CVs since I got this bike 5 years ago, and finally had it with them, especially considering my original wish for this bike was to go full pod, and to some, butcher this bike. So I took the plunge and ordered some VM carbs (from MikuniOZ), and I am so excited about them.

I spent the past month waiting for the VMs by rebuilding the clutch and clutch release (I had this horrible issue with an incredibly sticky and heavy clutch that was unridable, and now it's butter), installing a new XS650 petcock for a more reliable gravity feed, swapping to the 78' exhaust pipes with new mufflers, and swapping my original instrument cluster with a mini speedo from Emgo.

If you had beaten me to the punch with your message before I pulled the trigger for the new VMs, I would have definitely tried this out. But the Mikunioz order was international for me, so I can't go back now, haha. Thank you for sharing your bike and thoughts!

Edit: My VMs arrived today, so if you are curious, I can report back on how that goes.

I will be interested to see how that works out for you please let me know. I'm still not convinced by foam air filters with the original CV carbs. I want to use the bike when I want to use it, even if only occasionally. I do not want to have to worry about temperamental CV carbs and I had trouble with them today hopefully the airflow issue mentioned by Akirasan above... it was cooler today....worrying about air density is not something for which I hanker.

 

[Peter B]

I have foam filters on my 78 xs400 electronic ignition and it runs great.
apparently the filters with solid chrome ends disrupt air flow

Well akirisan having recently invested £50 on the non-chrome ended foam filters I am an in a position to confidently let you know that what you have been led to understand is "apparently" complete bulldust ... not a jot of difference. Please elucidate, with a picture preferably, how your foam filters are set up with CV carburettors?

 

[akirasan]

No pic needed the filters just fit the back of the standard carbs without airbox.