Problem Solved

[ZeroKnowledge]

posting this as it may help someone else.

 

2L DOHC 8v with bike carbs & megajolt

 

I had a problem when running at redline revs, after a 1/2 mile or so the engine would cough & splutter as if it was running on 2 cylinders, when I slowed down it would be ok

 

thought it was the coil so changed it, but still the same.

Someone suggested it could be fuel starvation

I have a facet cube pump with the little bullet filter attached which was 5 years old so thought it may be blocked.

I took it off & cut open the filter expecting it to be well clogged but it was still v clean.

I decided to fit a bigger filter to get more fuel through and hey presto problem solved

no more embarrassing cutting out when overtaking etc

 

photos of old & new filters

 

 

 

 

 

[fry61]

Yor new filter looks like an injection filter --- if so is it O.K for use on low pressure? I guess so if your motor is now running well.

[ZeroKnowledge]

Yor new filter looks like an injection filter --- if so is it O.K for use on low pressure? I guess so if your motor is now running well.

yes its running great

what would be the difference between a FI & a carb filter ?

[Guest Ian & Carole]

Nigel !!!!!!!!!!!!!!!!!!

 

Were are you

 

Fill your boots.

[Longboarder]

Devil spawn!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

 

 

 

 

But seriously. Been there. Done that. Took me 2 years to work out the facet filters are only suitable for the bin. Mine got to the stage where I would conk out on the motorway. Restart after 2 minutes and run problem free for 300 miles or more before mysteriously grinding to a halt again. Did it one time driving to cheltenham for a rolling road session at about 8 in the morning just after Exeter. Slight missfire, 3 cylinders, two, few pops and coasting. Got down to about 2mph on the hard shoulder. Engine restarted, got to cheltenham, whole day on the rolling road and home with no further problem. Didn't have a clue why.

 

Don't use the facet pre-pump bullet filter. Use a £1 ebay plastic one. Seriously.

There is another issue with suck through filters. Most fuel pumps don't suck well although they blow a treat. Fitting a fuel injection microfilter and sucking through it will have the problem recur in short time.

 

This is one situation where I would advise 'go cheap'!

 

Nigel

Edited July 22, 2015 by Longboarder

[Snapperpaul]

And you can see the fuel flow and the state of the filter

I have a bag of them in my spares

[nelmo]

Would a swirl pot prevent the problem anyway?

[Longboarder]

 

Would a swirl pot prevent the problem anyway?

Different problem. Pumps don't like swarf, sand, gloopy sealant residue, etc. So a low resistance, easy to suck through basic pre-filter is essential. Buy a pack of 5 for a quid each off ebay and change them every 6 months.

 

A swirl pot is to ensure a constant supply of fuel is available for an injection pump to draw from and is plumbed to be full or nearly full of fuel all the time, even when the fuel tank is down to its last half gallon. Most fuel tanks don't do this. On cornering/braking the fuel sloshes under G forces and the pump could suck air. Causes loss of or no power and injection pumps will die if they suck air for any length of time. On track it's worse. Most carbs have a float chamber (built in mini swirl-pot) which keeps some power going on corners and a simpler pump tolerant of sucking air for longer.

 

Nigel