X-flow missfire

[Molecular--Bob]

I had to take my carbs off to get at the dipstick tube to replace it as the original had perished and was blowing oil all over the engine bay. But on putting it all back together it has a bad missfire, not fixed by re-balancing the carbs at the linkage, or by changing the plugs. I therefore think that i have a full on induction side air leak to deal with.

 

Just want to check a few ideas here before i go spending money on stuff i dont need.

 

1. I have hooked the timing light up and am getting a stable signal from each of the leads, giving a stable picture of the timing marks, so can i assume that i still have a working electrical side?

 

2. The misabs are quite old, so i may have fractured one of the O rings moving the carbs, so should i just replace them?

 

3. The rubber bobins and cup washers are equally old, so should these join the misabs in the bin?

 

Is there anything else that i should look at that might be causing this?

[Roger King]

Ancient, but very useful trick - while it's running, spray WD40 or similar over the manifold to head and manifold to carb joints.

 

If at any point, the engine note changes, you've found a leak.

[LesG]

to Roger; it usually does the trick! I've just sold a customer a more advanced machine for this very job; basically a box that you connect into your air intake, block up the exhaust tailpipe, and then watch in amazement as the machine pumps your engine full of smoke! Well, watch at least where the leaks are! Just a little more expensive than a can of WD40.

 

I suspect you're right with the misabs though, so start there.

 

On the subject of your dipstick tube, what did you rplace it with? All I have is a length of rubber hose, and if I push too hard on the dipstick, it bends at the 'max' mark on the end (it appears to have been ground out with a grinder!) I have the flat-bottomed alloy Caterham sump, but do not have anything to stop the dipstick from being forced downwards (and therefore not bending it).

 

Any ideas?

Les.

[Molecular--Bob]

Hello Les, I replaced mine with oil hose of the same internal diameter (5/8ths i think). I cut out the top metal fitting and re inserted it into the new tube. I think i have the same sump as you, it's the James Whitting alloy trough style one. My stick doesn't bottom out as you describe (at least i don't think it does) as there is a metal collar on the dipstick that stops it going any further than the metal part of the dipstick tube that is inserted into the block. If you want i can take a picture that shows the collar i am talking about.