Lean sneeze problem - Page 3

A1an · 14 March 2018, 20:24

Quote:

Originally Posted by Lee1

Did you poke anything metal through the jet holes? Of so the jets may have been corroded and your poking may have changed the jet hole size, I've made this mistake a few times on cleaning old jets so now I just fit new ones if they look blocked.

Never had had a problem with a quick blast of compressed air.

A squirt of brake cleaner for the REALLY stubborn ones.

duggie12 · 14 March 2018, 20:59

Inlet valve closing fully?
Broken inlet valve spring?
Compression test ?

Hi matt I don't know what those things are let alone know how to check them.
And no didn't poke anything through the jets didn't have anything wee enough to hand
I've haven't had a chance to check the accelerator pump thing yet so going to have a look at that this weekend and look at the float thing as well - perhaps I've upset something with it when I stripped it
By the way the outboard is really hard to start. Can take quite a while. But then absolutely fine when running and will idle fine too - it's just when I turn the throttle it does the sneeze.

Thanks

matt h · 15 March 2018, 08:14

If you fancy it, take of the rocker cover and check the valve clearance as this could well be your starting issue.
As its the easiest thing to check i would have a go

Take off valve cover
Pull starter recoil and watch what happens to the rockers. Up down up down.

these are the valves that let in fuel and close and combust and power stroke and lastly exhaust.
Induction compression power exhaust.

You will see that when one shuts the other one opens and so on.

When the valve is shut , the rocker ( the bit that acts like a see saw when you turn it over) which you will see has a slotted screwhead and a lock nut, there has to be a small gap under the rocker.
So turn the engine untill valve comes up and the other starts going down and stop..
You should feel a little gap when you “with your hand” by pushing the adjustable part of the rocker up and down. otherwise :
If there is no gap it means the valves is too tight so not closing fully. There wont be either the induction pressure to draw fuel through or the compression to combust the air fuel mixture.

A tight valve will cause : non starting / popping back etc

Have a go and if you get stuck , put some pics on here

Ps if there is no gap let us know and we can help with correct adjustments with feeler gauges.

duggie12 · 15 March 2018, 08:32

Cheers matt I'll give it a go over weekend and let you know how I get on

duggie12 · 15 March 2018, 16:17

Check fuel pump accelerator and it appears to be fine - it's squirting fuel anyway!

Fenlander · 15 March 2018, 18:16

That's another thing ticked off then.

Good advice from matt h to consider valves now. As I said way back up the thread it's much harder for a 4-stroke to flash back through the carb as the inlet valve should be closed at the point of ignition.

So for me I'd be refining my checks to...

Check valves have the right tappet gaps.
Check there isn't an inlet valve sticking open (would show as an excessive tappet gap).
Check there isn't an inlet valve with a burnt seat (compression test).

Less likely...

Is there an ign fault causing it to fire incorrectly (timing setting).
Could the timing belt have jumped to upset the valve timing.

BTW if you take the valve cover off and it's like mine it will have a metal gasket that should be just a single use. They are stupid money at about £20 so on this occasion I'd advise adding some gasket compound.

Also if you get to properly checking valve clearances with a feeler gauge you have to push them in at an angle such that they feel tight when they really aren't... in this case using a cranked feeler gauge set would help or putting a bend in your own set.

duggie12 · 16 March 2018, 09:16

Thanks fenlander, do you think this is a diy job or is it quite technical? It's all new to me

Fenlander · 16 March 2018, 10:59

I'd wondered that Duggie as you said...

Inlet valve closing fully? Broken inlet valve spring? Compression test ? ... I don't know what those things are

Yes we can talk you through this stuff and it may go fine... but with you lacking experience in this area... and possibly the tools... there is a chance you may miss a cause that we haven't specifically mentioned or make a wrong judgement on something we've asked you to check... where those of use who are very familiar with engines may have spotted it... and in missing something you could spend ages going by our advice and get nowhere.

You're in Scotland aren't you? If we were in the same area I'd get you to bring the OB round and we could get all these checks done in an afternoon.

duggie12 · 16 March 2018, 11:03

Yes Glasgow fenlander

I don't mind fiddling about with the carb's etc but when I'm having to Google what a rocker cover is it's probably a bit beyond me!
I could always be a normal person and put it into a garage but because I've spent so much time on it I'm loathed to ! Plus it might cost a fortune.

Fenlander · 16 March 2018, 11:41

Oh well has to be your choice... you know there's quite a few of us on here that will guide you if you decide to delve further.

duggie12 · 16 March 2018, 11:43

Thanks fenlander - I might give it a go this weekend if I'm feeling brave!

Expect questions from me though :-)

duggie12 · 20 March 2018, 13:07

Guys I put everything back together after checking the fuel accelerator pump and cleaning everything (again)
It's now sneezing less. In fact it only tends to sneeze if I turn the throttle very quickly, which I wouldn't really do with normal use. It also sort of stutters and sometimes conks out when I turn the throttle quickly. If I increase the revs gradually it doesn't seem to sneeze at all, or stutter.

I'm convinced this issue has been related to the carb/fuel and not timing because the engine never sneezed until I stripped the carb to clean a blocked idle jet. This is really just a hunch because I don't know much about engines but it just seems too much of a coincidence that it started sneezing immediately after I put the carb back together

There are a couple of brass rod things in in the carb with very small holes in them (one is the fuel accelerator pump) so perhaps something has been blocked in one of them or somewhere else that I can't get to when I'm cleaning it. I was thinking I'd take the carb to an outboard mechanic and pay them to put it in one of these ultrasonic bath things just so I can be 100% sure it is clean.
Anyway I'll let you know if I ever find out for sure what is causing the problem.
Thanks again

beamishken · 20 March 2018, 13:47

Quote:

Originally Posted by duggie12

Guys I put everything back together after checking the fuel accelerator pump and cleaning everything (again)
It's now sneezing less. In fact it only tends to sneeze if I turn the throttle very quickly, which I wouldn't really do with normal use. It also sort of stutters and sometimes conks out when I turn the throttle quickly. If I increase the revs gradually it doesn't seem to sneeze at all, or stutter.

I'm convinced this issue has been related to the carb/fuel and not timing because the engine never sneezed until I stripped the carb to clean a blocked idle jet. This is really just a hunch because I don't know much about engines but it just seems too much of a coincidence that it started sneezing immediately after I put the carb back together

There are a couple of brass rod things in in the carb with very small holes in them (one is the fuel accelerator pump) so perhaps something has been blocked in one of them or somewhere else that I can't get to when I'm cleaning it. I was thinking I'd take the carb to an outboard mechanic and pay them to put it in one of these ultrasonic bath things just so I can be 100% sure it is clean.
Anyway I'll let you know if I ever find out for sure what is causing the problem.
Thanks again

Id say your probably right about it being fuel related but if i were you instead of paying to get the carb ultrasonic cleaned id buy an ultrasonic bath they are cheap on ebay £40 -50 ish and handy for other things then you have it for next time
Cleaning carbs on 4 strokes is a pretty regular thing

duggie12 · 20 March 2018, 14:03

You're right I'd be better buying one. I though they were more expensive.

Cheers

Xk59D · 20 March 2018, 14:42

How many adjuster screws do you have for mixture? I don't know your carb specifically as never seen one but if it only does it with quick transitions that is normally a lean bottom end. I.e richen it a smidge should cure it. If you have a low, mid and top needle then it could be the bottom 2 need a tweak. If you are doing this then mark where everything is now and you only need small changes!!!!

This is assuming you are certain everything is clean and air tight of course.

I've had this same problem ( technically it isn't a problem actually, just needles need set ) many many times with my 2 and 4 strokes in my other hobbies. I've never had to clean an outboard carb in my life but I always run them dry if I had a carb, maybe that helped or I flat out got lucky. I've had to clean my plane carbs many times though...midgees get everywhere!!!

Another thing is have you put new plugs in since or during this all happening?

If it were my engine I would tweak the low mixture screw and see...put it back worst case.

duggie12 · 20 March 2018, 14:48

Just one I'm sure. I had to access it by drilling a wee plug that covers it out.

Yeah problem first started when I used it for the first time of the year after leaving it stored all winter - I hadn't ran it dry. It wouldn't run at all at idle so when I stripped the carb I cleaned the visibly blocked jet and when I put it back together it would run at idle but it was doing the sneeze thing.

You have a plane? ?!!

jwalker · 20 March 2018, 16:05

Quote:

Originally Posted by duggie12

Yeah problem first started when I used it for the first time of the year after leaving it stored all winter - I hadn't ran it dry. It wouldn't run at all at idle so when I stripped the carb I cleaned the visibly blocked jet and when I put it back together it would run at idle but it was doing the sneeze thing.

You should've said that at the beginning! Sounds like a progression problem. Use it, it may rinse itself out eventually.

duggie12 · 20 March 2018, 16:06

Oops sorry j i thought I had! I maybe did in a previous post.

Fenlander · 20 March 2018, 17:19

Always hard to diagnose at a distance and this thread has meandered over several possibilities.

Initially it looked a carb issue but once this was apparently checked and ruled out plus we heard there was actual firing back through the carb then valve and timing faults came into the equation. But because Duggie hasn't fiddled with these he sees them as less likely.

So yes the "when did it start happening" evidence does point to the carb. But because Duggie's looked at it several times... and even after an ultrasonic carbs can still retain jet problems... well if it were in front of me I'd check compression, timing (ign and valves - could timing belt have jumped a tooth) and valve gaps to 100% eliminate them so the carb can be concentrated on.

A1an · 20 March 2018, 23:37

Quote:

Originally Posted by duggie12

Just one I'm sure. I had to access it by drilling a wee plug that covers it out.

You drilled the carb?