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Author Topic: Cheap 'Pod' filters - why you shouldn't - Public service posting  (Read 48349 times)

Offline RoadRash

  • Posts: 554
Was thinking about doing some modifications to the Mikunis, but before that I decided to do some testing. I attached the carburettor to a vaccumcleaner. The hoover sucked air through the Mikuni and the flow was enough to lift the slide all the way up to the top. Then I tried both with and without the velocity stack attached, but there was no difference, so I'm leaving the carbs as they are, for the moment. However, I did modify the Dime City velocity stacks, to the rid of them shrouding the slide hole in the carb intake.
:o :o :o

Dude, why are you hooking your carb to a vacuum, and what they HELL did you think that was gonna prove?!


Offline crazypj

  • Posts: 12487
  • Split personality, I fake being smart
Sounds like a pretty reasonable way to test in my opinion.
 Probably had too much vacuum though, need to have some sort of bleed so slide just lifts all the way without filter then try again with filter.
Slides rarely lift all the way on bike, they barely move until 5,000 rpm

'you can take my word for it or argue until you find out I'm right'
I gave my girlfriend an orgasm the other night, but, she spat it back at me
 Some humans would do anything to see if it was possible to do it. If you put a large switch in some cave somewhere, with a sign on it saying 'End-of-the-World Switch. PLEASE DO NOT TOUCH', the paint wouldn't even have time to dry
 Itís not worth doing something unless someone, somewhere, would much rather you werenít doing it  (Terry Pratchett)
CB360's,  http://www.dotheton.com/forum/index.php?topic=11736.0
XS650,  http://www.dotheton.com/forum/index.php?topic=11922.0

Offline manas

  • Posts: 119
No expert but I would think that a vacuum cleaner might not imitate the exact pressure differential but wouldn't exceed the design specs of the carb. I don't think vacuum cleaners are all that powerful, at least household ones. I might be wrong.

Offline crazypj

  • Posts: 12487
  • Split personality, I fake being smart
Topic was covered a few years ago on the XS650 garage board, slides don't lift until around 5,000 rpm, the airflow through motor isn't as high as you would think
'you can take my word for it or argue until you find out I'm right'
I gave my girlfriend an orgasm the other night, but, she spat it back at me
 Some humans would do anything to see if it was possible to do it. If you put a large switch in some cave somewhere, with a sign on it saying 'End-of-the-World Switch. PLEASE DO NOT TOUCH', the paint wouldn't even have time to dry
 Itís not worth doing something unless someone, somewhere, would much rather you werenít doing it  (Terry Pratchett)
CB360's,  http://www.dotheton.com/forum/index.php?topic=11736.0
XS650,  http://www.dotheton.com/forum/index.php?topic=11922.0

Offline manas

  • Posts: 119
That makes sense. I was just pointing out that I don't think a vacuum cleaner would damage the carburetors.

Offline teazer

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  • Posts: 8197
PJ, do you mean that they don't even start to lift until 5500 on an XS? IS that true of the BS34s and 38s?

BS40 on a GT750 lift with a blip of the throttle - probably closer to 3000 but I never stopped to check.  Maybe next time I have it on the dyno I'll pop the pods off and watch the slides.

Offline crazypj

  • Posts: 12487
  • Split personality, I fake being smart
Yep, the slides are a fair way up when fully seated.
If you open throttle gradually you can get a pretty high rpm before they lift
When you blip throttle they flutter
'you can take my word for it or argue until you find out I'm right'
I gave my girlfriend an orgasm the other night, but, she spat it back at me
 Some humans would do anything to see if it was possible to do it. If you put a large switch in some cave somewhere, with a sign on it saying 'End-of-the-World Switch. PLEASE DO NOT TOUCH', the paint wouldn't even have time to dry
 Itís not worth doing something unless someone, somewhere, would much rather you werenít doing it  (Terry Pratchett)
CB360's,  http://www.dotheton.com/forum/index.php?topic=11736.0
XS650,  http://www.dotheton.com/forum/index.php?topic=11922.0

Offline harrydahl

  • Posts: 26
Well, that wasn't my experience. As soon as I opened the throttle the slides started lifting. I was surpriced that the vaccumcleaner managed to draw so much air. Also tried to attach both carburettors to the vc at the same time, but that was too much for it, the slides only went up halfway, but I could confirm that they lifted the same amount, indicating that the carbs seem to be syncronized. Anyway, the purpose of the test was to see if the velocity stack had any harmful effect on the carb, but could not notice any difference with or without the stacks attached. But as I wrote before, I did some modification the the stacks, so now they have the shape similar to the cooling tower of a powerplant (hyperboloid).
Yamaha XS650, 1976

Offline RoadRash

  • Posts: 554
I guess my concern was that it was not going to be an accurate comparison cause an every day vacuum isn't gonna give you the same velocities that they would see on the bike. Way too much velocity to test with, IMO, so of course you're gonna get the same results with or without the stacks.

Offline RoadRash

  • Posts: 554
By the way, sorry if I sounded heavy-handed in my initial reply. Wasn't my intention. Funny how writings don't always read like the writer's emotion.