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Ninja EX500 carbs on an XS650?
- Thread starter Highside
- Start date
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- cafe carburetors custom engine
Not sure about the pilots, I didnt check, but the mains were 102(!) in this set (The other two sets have 130's stock)
I dropped 140's in because they were at the front of my jet box drawer, Ill see today if they work on the road..
I dropped 140's in because they were at the front of my jet box drawer, Ill see today if they work on the road..
Well, took her on a 5 mile spin..
Shes pretty rideable,very light on the throttle though once warmed I can tell shes generally running a bit weak , mainly mid-range.
As per ippytattoo , Im going to raise the needle using shims to see if I can improve this. Idle is also slow to settle so I'll up the pilots while Im at it .
Out with my box of jets this afternoon.
Ive noticed the needles in this set of carbs(From the Er-5) are different N48Eto those in the GPZ carbs which have N36Nneedles fitted , see the photo below, theyre stepped differently , the ER-5 (the carbs Im using) have needles that have a
longer taper... GPZ500 left. ER-500 RightLooks like my ER500 needles , being narrower (=richer) & having a more gradual taper(=smoother transition) in theory are the ones to stick too
What type are yours ippytattoo?
Shes pretty rideable,very light on the throttle though once warmed I can tell shes generally running a bit weak , mainly mid-range.
As per ippytattoo , Im going to raise the needle using shims to see if I can improve this. Idle is also slow to settle so I'll up the pilots while Im at it .
Out with my box of jets this afternoon.
Ive noticed the needles in this set of carbs(From the Er-5) are different N48Eto those in the GPZ carbs which have N36Nneedles fitted , see the photo below, theyre stepped differently , the ER-5 (the carbs Im using) have needles that have a
longer taper... GPZ500 left. ER-500 RightLooks like my ER500 needles , being narrower (=richer) & having a more gradual taper(=smoother transition) in theory are the ones to stick too
What type are yours ippytattoo?
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The Prospector
XS650 Member
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What did you do with the breathers on the carbs that usually go to the airbox etc.
56nomad
XS650 Enthusiast
Mine's similar: XS650H with shorty reverse cone megas, 1.5 downpipes of unknown origin and pods so your findings willl be interesting. Will be changing the pods for old skool chrome pancakes when I can find some with later K&N-style filter elements inside.
My carbs arrived yesterday and I can't wait to clean 'em up and crack them open to see what I've got. But work comes first so I'll have to be patient!
Im trying to deal with the slide (and/or diaphragm) 'flutter' due to absence of airbox, typical CV carb problem but seems more so with these lightweight components ..Not sure if I can overcome this..Ill try some 'stronger' springs ..
Running out of time due to work commitments too...
Running out of time due to work commitments too...
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jd750ace
Front Toward Enemy
Some people have used sleeves on the outside of he Uni filters to mimic the restriction/normalization of the airbox. When you whack that thing open, there's almost no vaccum left without an intake restriction, and the intake pulses become very pronounced. Heavier springs may help dampen it, but you may have to open the slide lift hole to get a satisfactory bleed off to raise the slide faster and smooth with a heavier spring. It's all theory from me, but I thought I'd chime in, since I'm going to put these carbs on my bike as well. I was already considering an "abbreviated" airbox to join the cylinders' intake pulses again, but with a much less complicated arrangement than stock.
Ah, you understand & explain very well what I was getting at 
I had considered making use of a couple of plastic drink bottles or similar plastic tubing over the Ramairs perhaps joined by a 2" cross tube between the frame & battery box to provide 'still air' ...
With that in mind, if I 'sleeve' the foam pod filters , leaving just the ends to breathe I seem get a slight improvement so....
I had considered making use of a couple of plastic drink bottles or similar plastic tubing over the Ramairs perhaps joined by a 2" cross tube between the frame & battery box to provide 'still air' ...
With that in mind, if I 'sleeve' the foam pod filters , leaving just the ends to breathe I seem get a slight improvement so....
jd750ace
Front Toward Enemy
I have heard of people using a sliding aperature, much like the intake chokes used on many older bikes with Amal and Weber carbs. Something like the draft intake on a cast iron stove. I think the best bet is some form of common chamber for sure, to even it out.
ippytattoo
Just another grumpy old hack.
Well, took her on a 5 mile spin..
Shes pretty rideable,very light on the throttle though once warmed I can tell shes generally running a bit weak , mainly mid-range.
As per ippytattoo , Im going to raise the needle using shims to see if I can improve this. Idle is also slow to settle so I'll up the pilots while Im at it .
Out with my box of jets this afternoon.
Ive noticed the needles in this set of carbs(From the Er-5) are different N48Eto those in the GPZ carbs which have N36Nneedles fitted , see the photo below, theyre stepped differently , the ER-5 (the carbs Im using) have needles that have a
longer taper... GPZ500 left. ER-500 RightLooks like my ER500 needles , being narrower (=richer) & having a more gradual taper(=smoother transition) in theory are the ones to stick too
What type are yours ippytattoo?
I am thinking that the gpz carbs are going to the same as the ex carbs since the needles on the ex carbs are the n36n's and the stock mains are 130's. You will probably find that the pilots in the gpz carbs are 35's like the ex's.
ippytattoo
Just another grumpy old hack.
When I ran mine with the 35's I also experienced a slighly hanging idle and a lot of crackling on decel through the exhaust. Once I changed to 38's and got the mixture screws set to 1 1/2 turns it returns to a normal idle very quickly and the crackling changed to a nice rumble through my wide open 32" exhaust.
56nomad
XS650 Enthusiast
XS1961 & Ippytattoo,
Not sure if this will be any help to you (if you haven't seen it already, of course):
www.dotheton.com/forum/index.php?topic=33247.0 Topic: "CV Carbs and Pod Filters
On the lines of what jd750ace says above, the posters mention fitting a 'tube' inside of a foam UNIfilter pod, baffles and also creating an inlet tract from filter to carb using a length of radiator hose all of which apparently gave good results as far as stable/reliable jetting was concerned. Slide/diaphragm flutter isn't mentioned but maybe the lack of it was an unexpected bonus.
What's your opinion?
Not sure if this will be any help to you (if you haven't seen it already, of course):
www.dotheton.com/forum/index.php?topic=33247.0 Topic: "CV Carbs and Pod Filters
On the lines of what jd750ace says above, the posters mention fitting a 'tube' inside of a foam UNIfilter pod, baffles and also creating an inlet tract from filter to carb using a length of radiator hose all of which apparently gave good results as far as stable/reliable jetting was concerned. Slide/diaphragm flutter isn't mentioned but maybe the lack of it was an unexpected bonus.
What's your opinion?
Excellent Ian, this is more-or-less what I was getting to in post #49, apart from the fact I was going to place the tubing/bottle/can (whatever I decide on )on or over the outside of the filter.
This was roughly my thinking...
This was roughly my thinking...
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56nomad
XS650 Enthusiast
As a car man I keep coming back to the common plenum and velocity stack arrangement I've seen on 4 pot classic rally and race cars. Many used twin stromberg and SU carbs which are cv/cd too. Pity the keihins don't have a flange on to which to bolt a back plate to make it easier to try. Then again, could there be an OEM motorcycle two port airbox out there that could be adapted to fit (outlet ports joined to the carbs by hose?)? I don't know modern bikes so I can't offer any suggestions. Are there any breakers watching this thread who can propose something?
56nomad
XS650 Enthusiast
If I remember rightly we used to top the carb reevoir up with oil , this was the 'dampener' to prevent 'flutter'?
I might even chuck in a stock XS filter-box
Yes, they were oil damped but when they were used in higher performance applications the recommended oil tended to be much thinner than the OEM specified engine oil. ATF was most often used. Dampening, therefore, will have been compromised in preference to getting the slide to rise quicker. And if I remember rightly, once that oil 'disappeared', which it did, the engine developed a bog but not a flutter but I could be wrong. It was this (perceived?) lack of flutter which brought me to think about the airbox arrangement that I typically saw. Unfortunately I cannot recall if the SU/Stromberg carb had an atmospheric port/vent that referenced the airbox. Can you?
This has led me to start dreaming up an airbox that will include a port for the carb vent tube. But before then, like you say, why not try the XS650 airbox but include a reference port/barb epoxied into the plenum between the filters of the standard XS650 airbox? Cobble it up to the CVKs and see what happens.
D*mn! I've run out of time. "Back on my head" as they say over here in Blighty. What do you think, logical or rambling?
56nomad
XS650 Enthusiast
Sounds good to me mate
I'll be incorporating 'logical ramblings' into something somewhere in the next few weeks
Hey up! Have you managed to do anything further? I'm still at the theory stage (my books are out) but my befuddled brain believes the current line to take is to fit a barb to the airbox for the vent and to increase the volume of the airbox by gutting it and fitting after-market panel air filters into the side covers. Had previously thought of fitting pods in the airbox but I'd like to incorporate bellmouths/velocity stacks as mentioned above (but I've not found any yet to fit the CVKs). That said, have you seen any pods with a bellmouth shaped inlet to the carb? If so then I'm thinking: gutted std airbox, barb and these pod filters????
Latest musing over. Bye
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