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Post by neilvx on Sept 14, 2017 13:02:54 GMT -5
Well I have a Dellorto PHBN 17.5mm which is fitted to my BW's.
i seem to be having an issue setting it up, it has an #82 main jet and the needle clip is one down from the middle.
Now the mixture when turned all the way in stalls the bike, I start to wind it out until the revs start to go mental and then set the revs as required.
it doesn't matter how far I wind out the mixture screw it doesn't seem to get a lean stage. The only thing that seems to happen is I lose about 5mph top speed.
so when I sent it to where it will rev to about 8700rpm at 43mph it's really boggy to get off the line.
am I doing something wrong, any ideas to check or try as it's driving me nuts lol.
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Post by pinkscoot on Sept 14, 2017 13:46:56 GMT -5
neil, The A/F screw only handles the idle to maybe 1/4 throttle. Here is a great thread on Carb tuning that may help you www.49ccscoot.com/faq/carbtune.html. You may find that your main jet is a bit small for a BBK but if you follow Brents tuning instructions you'll get it tuned in. |
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Post by neilvx on Sept 14, 2017 15:50:36 GMT -5
I know it's main job is idle and 1/4 throttle which I what my big head ache is. I believe it also has a small effect at full throttle which is why I lost a couple of mph.
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Post by tsimi on Sept 14, 2017 18:32:47 GMT -5
What is your pilot jet size?
Do you have other main jets or is 82 the only one you got at the moment?
I guess you are running a stock airbox?
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Post by neilvx on Sept 15, 2017 16:59:20 GMT -5
I had an #84 and dropped to the #82. I tried adding a little chock at full throttle an it made the bike bog down.
I am running the stock Airbox.
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Post by neilvx on Sept 18, 2017 4:23:34 GMT -5
Just a quick update, I checked the carb and air / fuel mixture and cant see any issues with my knowledge.
I did take it for a spin and found a big downhill to see what it would rev to, the bike topped out at 45mph @ 9500rpm.
I even tried to apply a little choke to see if it made any difference but no change at all.
think I might have to live with what i got.
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Post by oldgeek on Sept 18, 2017 4:34:45 GMT -5
Well I have a Dellorto PHBN 17.5mm which is fitted to my BW's. i seem to be having an issue setting it up, it has an #82 main jet and the needle clip is one down from the middle. Now the mixture when turned all the way in stalls the bike, I start to wind it out until the revs start to go mental and then set the revs as required. it doesn't matter how far I wind out the mixture screw it doesn't seem to get a lean stage. The only thing that seems to happen is I lose about 5mph top speed....... If the PHBN is operates like the PHBG, turning the mixture screw out is richer, in is leaner. That is why she cuts off with the screw all the way in. Stick with it, it can take some time to find that perfect tune. |
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Post by neilvx on Sept 18, 2017 4:57:41 GMT -5
I thought out was leaner as you are letting more air in the further you wind it out ??
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Post by Raizer on Sept 18, 2017 6:04:52 GMT -5
Depends, could be an air screw or a fuel screw.
Which side of the slide is it on, filter side or engine side?
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Post by Raizer on Sept 18, 2017 6:12:01 GMT -5
Just looked up PHBN, looks much like a PHVA and it has an air screw so yeah in is richer, out leaner.
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Post by neilvx on Sept 18, 2017 14:55:04 GMT -5
Cheers 👍🏻
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