Kohler Magnum 16 popping spluttering.

[Robins 55]

Hi All, 

Been trying to get my Kohler Magnum 16 engine running. It starts really easy hot or cold, tick over is fine and very smooth hot or cold, but, when increasing the revs it pops and splutters and does increase but still popping a bit, when trying to drive it just goes flat and gutless, a small bit of choke does help but still wont rev nice, will drive but not well.

The pump is mechanical and came off my K301 12hp.

Carb is rebuilt and been tested on a rebuilt engine so came set, I have re-adjusted it slightly but doesn't make much of a difference.

I've not had the engine running before so can't say i've done anything to it that would have made a difference, all i've been told is it did run years ago.

Don't know if it's normal or not but when throttle is full, with engine off, it opens all the way round on the carb. When engine running and throttle on full it only goes half way and splutters.

Any ideas chaps?

[Stormin 4,458]

I'd check ignition timing. What's the air filter like? Another possibility, as it's not been run for some time, is a sticking valve. Condenser? Coil?

[Robins 55]

It's a Magnum so all electronic, not sure i can adjust timing can i? I've set the gap between module and flywheel. It does sound like ignition but not sure.

Tried it with and without an air filter.

Thanks

[Stormin 4,458]

Had a re-think and it sounds as if it's possible fuel starvation. Rebuilt carb so that should be ok. Any fuel filters? Kinked/block pipes?

[slf-uk 914]

I was thinking stuck value too. A quick compression test should rule that in/out. I had that problem with the exhaust valve on a Tecumseh that had sat for a while.

 

In your last paragraph you mentioned a difference in throttle opening with the engine running, this could point to a governor issue or adjustment. I can't remember what the governor arrangement is on a Magnum, but it might be worth disconnecting the governor and see what difference it makes. 

 

I am sure more knowledgeable people than me will be along soon.

[Triumph66 1,256]

Hello Daniel, a very simple thought but how old is the fuel ? because as you know modern fuel goes off very quickly. Popping and banging is one of the signs of old fuel. Just a thought.

Also change the HT lead to see if that makes a difference too.

[Chris 642]

My money is on the valves & ignition

 

The coil is electronic, you cant do anything with it apart from replace at great cost. Have you changed the plugs, correct gaps etc??

 

If you say the carb is refurbed & tested it cant be that

Edited November 8, 2014 by Chris

[meadowfield 1,900]

sounds like some of the issues I've had...

 

my M16 worked as soon as I brought it home - well 6 months after I collected it

 

It started on the fuel that was already in the bowl after standing for almost a year, and it seemed ok. However on about the 5th - 6th start it just wouldn't fire and run. Spark was ok, and if I pour fuel in the bore it fires (not good, now I know the state of my oil rings).

 

I stripped the carb and gave it an uber clean and set both jets to 2.5 turns (it's a walbro btw). Put it back in and it started pretty well straight away, note I've put a new fuel tap and filter, new fuel line and new filter on.

...it worked fine for a week and then did the same, new plug, stripped fuel pump, still didn't run. Rebuilt carb again, started first time!!!!

 

My lesson is clean everything and don't trust that it is clean. I think my fuel pump (donated by Ian) was the issue, possibly full of crud.

 

If you are certain fuel is ok as well as timing and valves, then check the plug. We've changed a brand new plug before now on my brothers raider because it didn't run properly and it was a crummy plug.

 

Whats it run like if you rev it ungoverned?  does it miss and pop at full revs and backfire?  that's what mine did when it was intermittent.

 

My money is still on fuel starvation as if it runs better with choke then it must need more fuel...

[ranger 373]

Shouldn't the throttle butterfly be partialy closed when running at full throttle with no load,? That would show the governor is working if revs maintain when load increases.

If it,s an NGK spark plug I would change it,they don't seem to be very good nowadays. I had problems with my C121 which turned out to be the exhaust valve too tight on clearance.

The problems I have now are with Honda engines if they are left for over a month without starting I have to strip & clean the carbs to get them to run properly on the c**p they sell as petrol Wth the Briggs V twins it's air filter off & flat out then hand over the carb which usually clears it.Try a temporary fuel supply ie a can above the level of the carb & see if it improves things.Iv'e lost count of the number of lawn mowers that iv'e stripped/cleaned carbs on for neighbours with starting/running problems, ( thats the mowers,not the neighbours ) :)

Doug.

[Robins 55]

Thanks guys I'll have another try today. 

The pipework, filter and pump are the same i had running my 12hp, but been empty of fuel for a couple months.

My suggestion to people experiencing engine trouble is usually first how old is the fuel However i do now wonder if i picked up the wrong can? doubt has been placed in my mind as i do have some stuff that 18 months old and some thats 3 months. But also fuel starvation? wonder if the fuel tap has broken up inside, or the pump may have been on last legs.

I have had one of those spark testers fitted and the spark looks constant and good so 

 

I will change to the electric pump, different pipe with new fuel. Also try it ungoverned.

I did set the valve gaps accurately but will see if a stuck valve, will it tick over smoothly with a stuck valve though? ticks over very smooth at the moment.

Will change the plug as well just in case. 

 

Thank you all

[Robins 55]

I've had a tinker today and made some progress   Tried a few things with no change, but fitted an electric Facet pump and things have improved hugely! I guess my want for a mechanical pump were the issue, also old fuel, it seems my cans have been moved in the shed (shared shed) so not sure how old the fuel is i have put in! This being the case i'm getting new fuel, pipes and replacement filter Monday and will see if i can get this running perfect  Not sure what electric pumps are ment to be used but if the Facet one works i'll have to make a bracket up. 

Thanks all for your help, i'll let you know how the new fuel and lines go in the week.

Thanks, Daniel

[Triumph66 1,256]

Daniel,

How did you get on with the new lines being put in etc?

Cheers

Andrew

[Wristpin 399]

Sounds as though you may have cracked it but with any unknown engine I believe that time spent making sure that the valve condition and clearance, is time well sent. Short of a worn bore and piston valve condition is fundamental to a sweet running engine ; if the valves are not right no amount of tinkering with ignition and carburettor will achieve a permanent cure.

Also don't rely on a compression test as an indication of valve condition on an engine with automatic decompression to aid starting. The only reliable non-invasive test is with a leak down tester - not usually found outside a professional workshop.

For the time spent doing a valve job and probably a head gasket you will have sound foundations on which to fine tune carburettor and ignition.

[Robins 55]

Funnily enough i finished work with a bit of spare time today and fitted the new pipes, filter, filled up with fresh fuel, wired in the electric pump and had a test. Much better  Still not perfect though, feels flat on full throttle but hoping this is now down to tuning which i will tinker with, but the popping and spluttering is gone

 

Heres a pic I took tonight of the engine and stack fitted.

 

Think i may check valve clearance again now ive had it running just to re-check things are perfect in their.

[Triumph66 1,256]

Good news Daniel and a great photo too.

[Chris 642]

 The only reliable non-invasive test is with a leak down tester - not usually found outside a professional workshop.

 

 

I have a leak down tester

[Wristpin 399]

Then you'll know how useful they are, but you don't mention having used it in this instance?

[Robins 55]

A leak down tester sounds good, how do they work different in comparison to a compression tester though?

 

I have a compression tester somewhere in my other garage but haven't thought to use it as i have nothing to compare the result to like on a 4 cylinder car. 

[Wristpin 399]

With the leak down test you position the piston just past top dead centre on the firing stroke so that both valves are shut, lock the crank and then pressurise the cylinder via the spark plug hole. The gauge on the tester then indicates the rate of leakage via the rings, valves and may be a blowing head gasket . Leakage is often easy to pin down by listening to escaping air from the carb , exhaust or oil filler/dip stick tube.

The problem with a compression test on a small single cylinder engine with Automatic Compression Release is not being able to spin the engine fast enough overcome the release and obtain any sort of meaningful reading. On some engines the ACR may be "by passed" by spinning the engine the opposite way to normal rotation but this has issues of its own!

[the showman 4,074]

 The only reliable non-invasive test is with a leak down tester - not usually found outside a professional workshop.

 

 

I have a leak down tester

Ive got one two, does that mean were professional's Chris

[Robins 55]

Well I think   things are sorted    Engine is running so much nicer today. After a bit of messing around, much thinking, and a light bulb moment, i realised the governor was fully open at half throttle, this explains the flatness. There is no way on earth this engine ran nicely, if at all, before it was removed by the last owner. With this set right i could then tweak the fine tuning and all seems good. There was a slight odd misfire, one when increasing the revs from idle and then intermittent on full revs, but this seems to have cleared up with some driving round the garden. I will test again tomorrow from cold and make sure So then got on and put my cement mixer back together. The real test will be fitting the cutting deck or pulling a trailer load of mud around can't wait!

Thanks all

[Hillsider 16]

Re the leak down tester it certainly means you have gathered your tools wisely.

I must have lead a sheltered life as I have yet to see one in the flesh either in or out of a "professional" workshop.

 

Just out of interest what sort of pressure needs to be applied? I have a Mity Vac tester kit that I use to test two strokes for vacuum leakage that is also able to provide positive pressure and it would seem fairly simple to make an adaptor for the plug hole.

Ray.

[Triumph66 1,256]

Excellent news! Another vintage garden tractor in action.

I will expect the same thoroughness on my 1254!

[Robins 55]

Will do Andrew

I haven't had an engine give me quite so many trials in a very long time! When an engine is sold to you and said only to be removed due to a broken starter motor and thats been replaced now, you wouldn't expect so many settings to be completely out of adjustment, i was daft really to disguard things thinking it can't be that as it apparently ran before. Lesson learned, always check anyway. I only checked most of them because im a bit of a perfectionist when it comes to the running of an engine

[Robins 55]

Rummaging around in my shed at my parents place I found what i was looking for A K&N air filter from my boy racer days on my Morris 1000's Even better, i found a new one i bought for my pickup but never used, thought i'd sold it on to be honest, but fits nicely on the Magnum 16

 

Still to test properly under load, but running nicely just racing round the garden