MydT9
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| posted on 26/10/08 at 01:12 PM |
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Intermittent engine stall...driving me nuts
New to the forum but reliably informed that there's always an answer to your problem..within reason 
Here goes, I run a Honda Blackbird engine on carbs in my Darrian rallycar (yes, I know you will wish to stone me now for having a rallycar mentioned
on the BEC forum but....???!!!) which is very reliable on the whole, although the engine has developed a very strange problem for my last 4
rallies.
Off the start line, car drives for around 10 secs then suddenly engine dies and coasts to halt. I try the reserve fuel pump to no avail. Then around
10 secs later it starts up and runs faultlessly for the duration of the rally stage (around 15-20 mins).
The spooky thing is that on my last rally, after the first engine stall, i did one complete lap of around 8 minutes then as I came across the
start/finish line to start my 2nd lap it stalled again in the exact same place....
The electrics have been checked many, many times (Wyn can confirm this) fuel pressure is always right, carbs have been stripped, new fuel filter, new
spark plugs and by now I am running out of ideas.
There is a niggling thought in my head - I do have a braided fuel line which spans across a gap where the exhaust pipe from manifold to silencer
travels underneath (12" away) and could this be causing some fuel vapour lock in the fuel feed to carbs hose when I am sitting in the que ready
to start which means the engine runs for around 5 mins and hence engine bay temp is rising which may be the culprit?
Or does it sound like an electrical item heating, breaking contact, cooling and then re-connecting?
Any suggestions for a solution would be welcome as I really need to solve this once and for all.
Mydrian
http://uk.youtube.com/watch?v=RPWhhbaPG4o
[Edited on 26/10/08 by MydT9]
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Bigheppy
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| posted on 26/10/08 at 01:22 PM |
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Have you checked the vent for the petrol tank. I once had a problem where the vent dipped and fuel occasionally collected causing delivery problems
when I took the cap off a definite hiss could be heard. The fuel pump could not overcome the blockage and caused a vaccum in the tank. Worth checking
? 
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David Jenkins
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| posted on 26/10/08 at 01:23 PM |
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Welcome! (we'll talk to anyone...  )
My first thought was - is your fuel tank vented properly? The classic symptom of a non-vented tank is the engine stopping unexpectedly, then
restartable shortly afterwords.
Otherwise - is any part of the ignition system overheating?
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the_fbi
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| posted on 26/10/08 at 01:30 PM |
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Random idea.
Have you removed the tilt switch or left it in place?
It may be that due to its mounting and the G's it gets off a launch, it may be tripping then resetting?
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MydT9
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| posted on 26/10/08 at 01:38 PM |
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Crikey...the responses are quick !! Fab. glad my post hasn't been deleted by the forum moderator yet ! lol!
Ok, car has two seperate tanks (one either side and both are independantly vented and independantly connected to the fuel pumps (there are 2 red top
pumps...again independant operation of each other for reliability).
G switch? Hmm, not sure if this a wind up? tell me more...
If i told you that its wiring is so simple and consists of the Honda CDI module, rectifier and starter relay, a total of 15 cables and it runs
perfectly...well apart from this minor issue.
Will get some pics of the engine bay up soon which may help.
Engine sits in the engine bay in the same config as the bike, i.e. cylinders 1-4 go from n/s to o/s looking from rear of car.
Myd
[Edited on 26/10/08 by MydT9]
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Bigheppy
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| posted on 26/10/08 at 01:45 PM |
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Could one tank be emptying first and then sucking in air from the empty tank. Then after stopping the tanks level out enabling you to restart.
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britishtrident
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| posted on 26/10/08 at 02:31 PM |
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Just might be a foreign body floating around in a fuel tank --- If Darrian tanks are like the old Davrian ones you might have major problem clearing
it out.
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the_fbi
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| posted on 26/10/08 at 02:39 PM |
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quote:
Originally posted by MydT9
G switch? Hmm, not sure if this a wind up? tell me more...
There's the equivalent of a car rollover switch on some (although normally injected) bikes. Its a tilt swich which stops the engine if you drop
the bike.
In the same way as you'll have the neutral and sidestand switches bypassed, you probably have (if it was fitted) this bypassed too.
Could be carb icing, although I woulnd't expect it to clear and not come back. If its only started since the cold weather its a possibility.
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