19 replies to this topic

[Sprocket]

Head gasket maybe?. Do a compression check.

Regarding the carb needle, if the carb was originally tuned for the K&N filter, the needle will either have been replaced, or has been filed thinner.

Refitting the restrictive air box has now altered the entire tune and will likely need a replacement needle of the correct profile, and still may require further tuning (not a simple turn of a screw).

Fast idle and idle speed will need re setting and idle mixture adjusting to give less than 3% CO.

[BaronVonchesto]

Well I got the engine back alive, but the original problem i had before the carb rebuild is still there.

 

To get the engine started I had to set a pretty rich fuel mixture, and set a VERY fast idle (about 3k rpm). Also squired some carb cleaner into the air inlet to give it a kickstart.

 

It seemed to run steady at this high rpm, but as i lowered the idle speed bit by bit, it came to a point where the engine would not hold its rpm and it gradually reduced till it died on its own. Restarted the engine, would run, lose rpm and die within a few seconds. Could reliably start the engine everytime. 

 

Also if i throttled up the engine and released to idle, the rpm would go up and stay there, but as soon as i released it would die in a matter of seconds.

 

Will post videos so its clearer how the engine is behaving.

 

Possible timing issue? or Carb issue?

Edited by BaronVonchesto, 22 February 2018 - 01:16 PM.

[Sprocket]

Compression check! .........?

[hhhh]

 

4 cylinders, 2 inlets. Surely cylinders 1&2 should perform equally, and similarly 3 & 4 then?

Firing order is 1342=> 3421
3 and 2 have more time to refil than 4 and 1, as the previous ignition event was in a cylinder that uses the other inlet tract.

 

Actually 1 and 4 run richer because they get the benefit of inertial ramming from 2 and 3 shutting off just before they open. And the line is more direct to them from the single carb. I don't understand why manifolds aren't routinely made with a bend inwards to counteract this.

[wile e coyote]

Could be timing but if it was fine before and you haven't touched it it's likely fine still , but carb settings will be out due to rebuild - probable new needle required as has already been pointed out (you could mod your airbox to increase flow) ...

 

I'd bet you've an induction air leak...

 

And as a above compression check to investigate why you've an odd burn pattern across cylinders (manifold leak may be a contributory cause here too)

 

At least it runs...