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
Has it been rejetted?
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?
Sounds like the carbs need cleaning
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?
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]
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]
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
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.
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
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.
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
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.
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