19 replies to this topic

[BaronVonchesto]

Sooo... if anyone followed my last thread, you would know that I've been having carb troubles. It all started one day when I decided that my K&N  pod filter was too noisy and decided that I'd go back to the airbox with a standard paper filter.

 

It took a lot of work and some forcing but I eventually got the airbox on properly with both bolts screwed in. Unfortunately from that point my engine troubles started. After changing the air filter the engine sputtered to life but couldn't hold its idle rpm for more than a few seconds before dying. Flooring the pedal produced a very lagged response, almost as if the engine simply was not getting the fuel it needed. Messing with the air fuel mixture ratio only made things worse.

 

Noticed that fuel was leaking from the carb (which previously never happened) so I decided to go for a full carb rebuild. Fast forward a few weeks, carb was rebuilt following haynes manual instructions to a T, but engine still couldn't start and fuel was still leaking from an inlet pipe (see my last thread for details).

 

Now i need to wait 24 hours for the threadlocker blue to fully cure and then I will reinstall it and try to start my engine. Here's what I plan to try

Replace spark plugs (even though they are good)

Spray some carb cleaner into all 4 cylinders to act as a engine starter fluid.

 

Here's what I've checked so far
- good sparks from all 4 spark plugs

- fuel is flowing from the fuel pump

- Valve tappet clearances have been set as per the haynes manual to 12 thou.

 

What else should I be checking for? Earlier when i tried starting it just felt like the engine was not getting the fuel as the fuel would leak from the inlet hose, though the float bowl still had fuel in it. I tested blowing with my mouth for both the float needle fully open and fully closed, and it seemed like the float needle (new carbon tipped one) was sticking closed. Could that be a problem, or does it only free itself with higher pressure?

[BaronVonchesto]

don't know if its worth pointing out, but prior to the engine problems, cylinders 1 and 2 would always be black and cylinders 3 and 4 always white, meaning the fuel mixture was never balanced between the two sides of the engine. This with the fuel mixture set correctly.

 

also im using a hs4 waxstat carb and a stock 998 A series engine.

[DomCr250]

Stupid question from me ...you do have the fuel pipe going to the float valve ans not the vent tube ... If it's the wrong way round it will leak a lot?

Apologies if you have already checked this.

[ukcooper]

wrong needle more than likely as you need a another needle  for every set up or if you change ,air filters ,  exhaust ect 

pipes connected wrong

fuel pump packed in 

knocked the coil wires

earth wire come off the engine

 

why did ua have to force the old air box on ????could be it not on propa / check the manifold gasket aint leaking .

 

or the exhaust leaking if it not fitted propa like the air box ....guessing a 98 steady bar fitted instead of a 1275 bar or the other way round yes they are different ,,ones longer 

[viz139]

Stupid question from me ...you do have the fuel pipe going to the float valve ans not the vent tube ... If it's the wrong way round it will leak a lot?

Apologies if you have already checked this.

My thoughts to.

The air box not fitting easy I would think the spacer is missing between the carb and manifold.

The differance between cylinders 1,2 and 3,4 I would do a compression test to check head gasket.

[wile e coyote]

I think you have a combination of problems -  It's usual when running a single carb for cylinders 1 & 4 to run weaker that 2 & 3 but as you describe is not normal so follow above advice. 

[MiniMoe2008]

 

Cut Them and use a socket.

+1

 

+2. i agree. 

[BaronVonchesto]

 

Stupid question from me ...you do have the fuel pipe going to the float valve ans not the vent tube ... If it's the wrong way round it will leak a lot?

Apologies if you have already checked this.

My thoughts to.

The air box not fitting easy I would think the spacer is missing between the carb and manifold.

The differance between cylinders 1,2 and 3,4 I would do a compression test to check head gasket.

 

The spacer between the carb and manifold is there. Unless theres supposed to be more than one?

Its possible that this were just bent out of place a little or something. If a spacer was missing no amount of forcing would line up both bolts of the airbox i reckon.
 

Question. Why is it common for 2 cylinders to run leaner in a single carb setup? The intake manifold splits equally into two halves.

[BaronVonchesto]

Stupid question from me ...you do have the fuel pipe going to the float valve ans not the vent tube ... If it's the wrong way round it will leak a lot?

Apologies if you have already checked this.

Having rebuilt the carb im 100% certain that my fuel hose is connecting to the inlet (the one with the needle) and not the overflow pipe :)

[BaronVonchesto]

 

 

Cut Them and use a socket.

+1

 

+2. i agree. 

 

Cut them and use a socket?

For what>?

[Dusky]

 

 

Cut Them and use a socket.

+1
 

+2. i agree. 
 

Cut them and use a socket?

For what>?

Think you were copying of the wrong post. I havent connected on this one :)

[dyshipfakta]

The mini is Siamese port so shares inlets so fuel is never perfectly even for all cylinders. Atleast not on standard heads. Maybe some pics will help people point you in the right direction. It has to be a problem with the carb or you have used so much force you have caused a manifold air leak.

Edited by dyshipfakta, 21 February 2018 - 09:32 AM.

[BaronVonchesto]

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

[Dusky]

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.

[viz139]

The spacer between the carb and manifold is there. Unless theres supposed to be more than one?

Its possible that this were just bent out of place a little or something. If a spacer was missing no amount of forcing would line up both bolts of the airbox i reckon.

 

Do you have the spacer AND the cable bracket. not possible to bend the spacer..

The principle of two cylinders running leaner on a mini is standard and refairs to cyl 1and 4 running leaner than 2 and 3 not what you have described.