Indybird88
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| posted on 27/6/17 at 05:38 PM |
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Blackbird help
His guys and girls.
Having a bit of issue with my bird indy.
First off, has anyone with a blackbird carb model running it without an air box? If so how ?
Basically I have an issue when driving it will not rev over 4k, it bogs and fouls a lot.
I've read a lot about airbox differential pressure with the carbs and needing an airbox I'm getting stumped I'm running bike fuel
pump with regulator and I've got a facet too no different I've tried a lot of things but I'm running out of optons. I just want to
know if it will work if I need an airbox.
Any help would be great even if someone is close by with one.
Liam
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CosKev3
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| posted on 27/6/17 at 06:13 PM |
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Has it been rejetted?
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Indybird88
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| posted on 27/6/17 at 06:24 PM |
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Not yet no but it won't even rev properly standstill. It bogs droppe's the revs then picks up again. I know it will need re jetting but
surely not to just run?
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ian locostzx9rc2
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| posted on 27/6/17 at 06:39 PM |
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Sounds like the carbs need cleaning
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CosKev3
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| posted on 27/6/17 at 06:40 PM |
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No airbox could well be the issue as you think,as it's just like running a open foam filter.
Have you got a manifold on it?
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Indybird88
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 posted on 27/6/17 at 08:03 PM |
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Yeh I've got two set of carbs both spotless.
Do you mean in or ex manifold? Its a blackbird engine so bolt on.
May I ask what happens with an open foam filter?
[Edited on 27/6/17 by Indybird88]
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CosKev3
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| posted on 27/6/17 at 08:15 PM |
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Just causes running issues until the carbs are rejetted correctly.
Exhaust manifold also alters the way the engines run,the ones used in a car set up
[Edited on 27/6/17 by CosKev3]
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Indybird88
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| posted on 27/6/17 at 08:33 PM |
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Yeh I have a Scottish kit car manifold. So do you think if I reject it it would rev properly without the filter?
Thanks for your help so far
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feckn7
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| posted on 27/6/17 at 09:26 PM |
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I have a carb'd blackbird and have found that they are very fussy when it comes to jetting.
Changed the muffler - re-jet the carbs and adjust needle height.
Changed filter from socks to large UniFilter unit - re-jet the carbs and adjust needle height
When I had the sock filters I had to go quite big jets. The UniFilter - smaller jets (but still bigger than standard)
As my filter(s) are protruding through the bonnet and in the airflow, I found the UniFilter to work better as its effectively a large foam airbox
which seems to give the carbs less disturbed air.
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CosKev3
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| posted on 27/6/17 at 09:27 PM |
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It's hard to say for sure,but bike carbs/engines do behave strangely in a lot of cases once fitted in a car until the fueling is sorted
correctly
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CosKev3
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| posted on 27/6/17 at 09:29 PM |
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quote:
Originally posted by feckn7
I have a carb'd blackbird and have found that they are very fussy when it comes to jetting.
Changed the muffler - re-jet the carbs and adjust needle height.
Changed filter from socks to large UniFilter unit - re-jet the carbs and adjust needle height
When I had the sock filters I had to go quite big jets. The UniFilter - smaller jets (but still bigger than standard)
As my filter(s) are protruding through the bonnet and in the airflow, I found the UniFilter to work better as its effectively a large foam airbox
which seems to give the carbs less disturbed air.
There you go someone with some Blackbird specific info/experience! 
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Angel Acevedo
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| posted on 27/6/17 at 10:26 PM |
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Line of action.
- Clean
- Adjust float height.
- Ensure equal jets all carbs.
- Verify accel enrichment pump dumping fuel.
- Ensure equal butterfly opening.
- balance carbs.
- adjust Idle.
- Adjust mixture (is it possible on those carbs?)
Then you may go about working on jet size...
There are a couple of ways...
Old school reading plugs
or Rolling Road..
HTH
Beware of what you wish.. for it may come true....
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Indybird88
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| posted on 28/6/17 at 08:33 PM |
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Thanks guys for the help. I need to get in touch with dynojet then.
So is it a bit like mapping out an air box with the jets?
Sorry to be dumb.
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feckn7
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| posted on 28/6/17 at 09:52 PM |
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There's a fair bit of trial and error involved.
The standard jets on my Blackbird are 142 for 1 & 4 and 145 for 2 & 3
When I had the sock filters and my first exhaust system I ended up with 162 on all 4 with the needles raised (washers as my jets don't have a
series of slots)
Changing the muffler required re-jetting to 156 (I think) and the needles lowered slightly. Changing the filter then required re-jetting again (152
from memory) and the needles back at standard.
Also had to adjust the idle jet screws each time.
It's still not perfect - running a little rich, but I'm happy with how it goes. Running a little rich is a lot safer than running lean
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