Jump to content

stream of bubbles appear after 3 sec


Recommended Posts

Trying to get to the bottom of No Idle on ...PA125 fitted with the WG8 carb, after priming engine the top fuel filter is full apart from a regulation small bubble after 3 sec a stream of bubbles is seen to come from the carb side .

Im assuming this is something to do with the 'no idle' situation and running slightly lean!. I have changed fuel lines , primer bulb and all that seemes airtight . I have stripped and cleaned carb twice , Have ordered new membranes and will check meter level but seemes ok , but while waiting for them to arrive does any other causes spring to mind?.

missing this nice weather is painful!! :cry:

Link to comment
Share on other sites

Sounds like either your fuel pump (membrane) is stuffed, or you have an air leak at the point where the hose joins to the carb. If you are using a cable tie here, make sure it is wrapped around twice.

You can try inspecting the fuel pump membrane, and if one of the parts used as a valve is bent, try and make it flat again.

You could also have clogged jets etc - that ended up being my issue.

Link to comment
Share on other sites

Sounds like either your fuel pump (membrane) is stuffed, or you have an air leak at the point where the hose joins to the carb. If you are using a cable tie here, make sure it is wrapped around twice.

You can try inspecting the fuel pump membrane, and if one of the parts used as a valve is bent, try and make it flat again.

You could also have clogged jets etc - that ended up being my issue.

Thanks Notch. yes suspected that join, and I replaced that bit of pipe and double wrapped cable tie all to no effect , more and more suspecting the needle valve , but should get the membranes and kit tommorow so will see !

When cleaning Jets in the carb there seemes to be 5 holes in the chamber , near the butterfly anyone know which are responsible for the idle or are all of them ?

Link to comment
Share on other sites

First thing is to fit the carb service kit, the bubbles are probably a result of a defective flap valve or dirty / worn needle valve.

Secondly if your carb has a choke why Do you need a primer bulb? A healthy carb will not allow fuel / air to flow back to the tank.

Primer bulbs will also restrict fuel flow at low revs, another cause of rough erratic idling .

If you do need to prime the carb after a service or long time without use try blowing into the breather pipe while depressing the diaphragm button / hole on the carb :-)

Sent from my iPhone using PMC Forum mobile app

Link to comment
Share on other sites

When cleaning the jets system in a wg8, make sure you:

- Clean all the low speed holes around the butterfly valve. Some of these are tiny, and there is like 5 of them!

- Clean the main nozzle valve. Yes the walbro carbs have a very strange (compared to other carbs) "valve" after the main jet :shock: . If crap gets in here (which, if it got in the low speed holes it will have got in here as well), you have to be really thorough in cleaning it out. I had to make an miniature hose adaptor which blew carb cleaner BOTH ways through the nozzle valve. Only then did the crap come out, and I could get my CHT's down.

Link to comment
Share on other sites

Thanks for the ideas! will try the priming with blowing technique!

hopefully new membranes and new needle valve will sort but will give another clean , Id used a tube with angle cut in end to blow carb cleaner in small holes , but really fiddly !

beginning to regret advice from PAP to remove internal filter!! believe that started with the Ross 125 and they recommended for PA125 as well

Link to comment
Share on other sites

here is your problem described and how to solved http://wind-drifter.com/technical/wg8walbro.php ,its really works just you need plastic reducer http://www.ebay.co.uk/itm/6mm-4mm-BARBE ... 5893015a62 and http://www.ebay.co.uk/itm/FUEL-PETROL-P ... 485752cd32

and 15 min job

its works for me ,one think more take off primer bulb -inside its 2 valves ,this valves restrict fuel flow that impact engine power ,fuel need get as short way as possible from tank to carburettor without resistance.

if you want i can paste my photo how I solve that .

Link to comment
Share on other sites

To reduce restriction in primer bulb.....

Remove from fuel line

Carefully disassemble, labelling all relevant parts. a sharp blade may be required to remove the valves. Clean thoroughly, wrap the various bits in a plastic bag. And then lob the lot in the bin [sMILING FACE WITH SMILING EYES]

Sent from my iPhone using PMC Forum mobile app

Link to comment
Share on other sites

Fuel vaporisation occurs in the fuel line when you have things like fuel filters in line. I have a single Walbro fuel filter/clunk at bottom of tank. The pipe that exits tank goes directly to the carb, no filters inline or pumps. If you add weight to the fuel pipe by adding a fuel filter its an agitator when vibrating (caused by engine vibration) this then assists fuel vaporisation in the pipe and appears as tiny bubbles. You then pull out lots of hair trying to work out where leak is and there is no leak. I have attached a picture but not sure if that is clear enough.

Link to comment
Share on other sites

here is your problem described and how to solved http://wind-drifter.com/technical/wg8walbro.php ,its really works just you need plastic reducer http://www.ebay.co.uk/itm/6mm-4mm-BARBE ... 5893015a62 and http://www.ebay.co.uk/itm/FUEL-PETROL-P ... 485752cd32

and 15 min job

its works for me ,one think more take off primer bulb -inside its 2 valves ,this valves restrict fuel flow that impact engine power ,fuel need get as short way as possible from tank to carburettor without resistance.

if you want i can paste my photo how I solve that .

thanks for all the ideas

and links ! really useful

My carb has a 3.2 mm inlet . I have fitted the carb kit and now great! no air bubbles , leak solved !

However the bloody thing still wont idle ... :cry:

so leaning back towards dirty idle Jets...

anyone tried sonic cleaning ...as my attempts with carb cleaner havent worked me thinks

Link to comment
Share on other sites

The trick is to get carb cleaner / and or compressed air going both ways through them there holes.

I did the nozzle valve this way: Remove the main jet & idle jet. Take some thin plastic flexible tubing, heat up the end with a torch, melt it into a cone shape so that it fits the diameter of the nozzle valve inside the throttle body.

Heat the tube again and bend a 90 degree curve in it so it can fit in the throttle body. Take a bit of stiff steel, wrap some tape around the tube and steel (to stiffen the tubing) so you can hold the tube inside the throttle body, directly on top of the nozzle valve.

Take the thin hard plastic extender tubing from the carb cleaner aerosol can, wrap some tape around it so that a bigger diameter hose can fit and seal over it.

Put on safety glasses. The first time it did this I got carb cleaner in the eye, was not fun!

Then insert the assembly onto the nozzle valve and squirt away. Then use another section of the plastic tubing to squirt cleaner through the hole where the main jet was.

Repeat several times.

Link to comment
Share on other sites

To reduce restriction in primer bulb.....

Remove from fuel line

Carefully disassemble, labelling all relevant parts. a sharp blade may be required to remove the valves. Clean thoroughly, wrap the various bits in a plastic bag. And then lob the lot in the bin [sMILING FACE WITH SMILING EYES]

Sent from my iPhone using PMC Forum mobile app

ROFL :D

So you use the blowhard method? Tried that... was blowing for bloomen ages, still couldnt get it up :shock:

Link to comment
Share on other sites

The trick is to get carb cleaner / and or compressed air going both ways through them there holes.

I did the nozzle valve this way: Remove the main jet & idle jet. Take some thin plastic flexible tubing, heat up the end with a torch, melt it into a cone shape so that it fits the diameter of the nozzle valve inside the throttle body.

Heat the tube again and bend a 90 degree curve in it so it can fit in the throttle body. Take a bit of stiff steel, wrap some tape around the tube and steel (to stiffen the tubing) so you can hold the tube inside the throttle body, directly on top of the nozzle valve.

Take the thin hard plastic extender tubing from the carb cleaner aerosol can, wrap some tape around it so that a bigger diameter hose can fit and seal over it.

Put on safety glasses. The first time it did this I got carb cleaner in the eye, was not fun!

Then insert the assembly onto the nozzle valve and squirt away. Then use another section of the plastic tubing to squirt cleaner through the hole where the main jet was.

Repeat several times.

Thanks notch

...thats this evenings activity then ! cheers

Link to comment
Share on other sites

  • 2 weeks later...

an update ! after repeated attempts to clean the carb, I still couldnt get a reliable idle., followed a suggestion from Rowena carbs I bought a Maplin ultrasonic cleaner..I was a bit skeptical I thought it was last thing to try before ditching, but what a difference http://www.maplin.co.uk/ultra-7000-ultr ... ner-223108 I cleaned twice both sides (tray not quite deep enough to imerse all of carb)on 8 min using the cleaning fluid and got the idle back!

I got rid of the primer pump but found couldnt start the motor well ! probably needed more practice or puff! so re -installed that

still running a bit lean, so that was sorted by bending metering lever up to 0.75 below carb body as it had been set using the walbro guage at 1.7mm

first time in a long time the motor sounds right and plug nice colour :D

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

 Share



  • Upcoming Events

    No upcoming events found
×
×
  • Create New...