Misfire query

[Mickwhitt 5,131]

Hi all.

Fred has developed a starting problem since I moved the silencer to vertical.

Could be a coincidence, but it only popped up recently.

Sounds like diesel knock and a misfire.

Any thoughts please, im not running him till I know what to look at.

 

[953 nut 59,958]

            Could it be running a bit rich and the unburned fuel igniting in the exhaust pipe developing backpressure?

[lynnmor 7,815]

It almost sounds mechanical, check for a loose flywheel or pulley.  Try to isolate the noise source by directing the exhaust into a box.

[peter lena 9,271]

agree with others on possible causes, try going back to past exhaust system , to verify possible cure , pete

[JoeM 8,337]

14 minutes ago, peter lena said:

try going back to past exhaust system

that would be one of the first things to try. It does look like exhaust is blowing around under the tins and hood when it does chug??? Muffler plugged or plugging?

is the exhaust rich? lots of Q's. could be as simple as a bad spark plug??

[peter lena 9,271]

JOE , that's what  I  was thinking , if it ran good before , and a muffler swap is making it bad . easy to go back , and find the problem . the exhaust , blowing under the tins , is showing you the way .have a good turkey day , pete

[Pullstart 66,716]

My tractor “Leroy” used to chug pretty bad like that and it was running rich for sure.  Often times if I shut it down on high rpms then restarted, the exhaust would shoot a massive flame, being all full of fuel.

[Pullstart 66,716]

It might not be a terrible idea to double check timing as well.  If the spark is happening too far past top dead center it could still run with low power, but not have complete combustion when the exhaust opens.

[Lee1977 7,206]

Have you checked the valve clearance, they are adjustable on the Kohler. My 312 was bad to misfire until I adjusted the valves.

[gwest_ca-(File Mod) 11,475]

Looks like you have a timing light connected.

Have another condenser you can try? Or remove the condenser wire from the coil (-) and see if that eliminates it. Possibly the condenser body is not grounded.

 

Garry

[richmondred01 2,307]

The “shaker plate” models at times have grounding issues. 
I run a separate ground Wire from the block to the frame.

[Mickwhitt 5,131]

The plug is sooty so probably running rich.

It began with a bit of a kick back on starting which shattered the clutch plate it was so violent.

I will go through the checks recommended and see if I can find the problem. I don't have a timing light but the cam timing is fixed by gears so that can't have changed.

Will have to bone up on checking the timing as I'm not at all sure.

I can't see the exhaust making a difference as it ran perfectly well with it on until the big kick back.

Hoping its nothing terminal. 

[Bill D 2,248]

Do as others have said.  Run an extra ground wire from the battery to the engine block.  New points and condenser.  Set timing with a timing light.  If it's kicking back that hard,  your ACR could be failing.  Bill

[Mickwhitt 5,131]

Spent today servicing a husqvarna  T130 ride on for someone, paying job so it was a priority.

I have read up on the trouble shooting tips for the engine on my C125 and I will work through them over the weekend.

Im pretty sure it will sort, just go through things methodically. 

Mick 

[Mickwhitt 5,131]

So, a few things to report...

Exhaust off not much difference. 

Air filter clean and clear.

Fuel up to carb.

Plug cleaned and sooty again in no time. 

Played with idle jet and it at least started up but ran rough.

Took off the head as there was oil on the top face of one side of the cylinder barrel fins. Looks like the gasket could be blowing. 

ACR looks to be working fine. 

The drive/PTO pulley had shaken loose, looked like the key is worn so that is what caused the clutch plate to shatter. 

So need to rebuild. Sort out the carb settings and try again.

Coukd the idle jet screw have vibrated out richening the mixture?

[Mickwhitt 5,131]

While I'm typing, do I need to replace the head gasket every time it take the head off? 

This one has only been on a few months, not sure if its goosed. 

The sealing area looks a bit flat. 

Could I have under, over tightened it?

[richmondred01 2,307]

After about two hours after being replaced, let the engine cool down and retorque.

I don’t reuse head gaskets.

Edited November 28, 2020 by richmondred01

[Mickwhitt 5,131]

Hi Richmond red, thanks for the head gasket information.  I have ordered a new one but they are £25 a pop so not something I want to tear down every day.

While Fred is stood i decided to check the carb as I kind of did a rush job to get the engine running.

The throttle butterfly shaft is badly worn, the bottom end is ovalised and so it rattles about quite a bit. I will Mill a new one from 1/4 inch silver steel and that will correct that.

The fast running jet looks a bit worn at the point. Any views on if it looks serviceable or not? 

Finally the static timing needs checking so now its torn down i will hit the manuals to check everything and reset anything that looks wrong.

The exhaust system looks OK so I'm ruling that out as a problem for now.

Mick 

 

[sqrlgtr 705]

I seen it already mentioned,but Bad condenser will sometimes cause your problem.A bad condensor will make you pull your hair out,sometimes seems like it run lean next time rich....I would replace it first and try it.If I read it right it was running fine than just started acting up.Was working on one and couldnt get it to run a worth crap and an old timer mechanic told me to swap condensor for a known good one problem went away but had to go back and retune, carb, points,etc lol...

[Mickwhitt 5,131]

I've been looking at the static timing.

When the piston is at TDC the T mark on the flywheel is in the area of the starter pinion. 

Thats way away from the window on the front of the engine blower cover. 

What is wrong? 

Obviously the timing of the points is well out. So what have I done during the rebuild? 

Bear in mind it ran before so could I be that far out and still get it running, albeit not properly?

Im genuinely confused.

Mick 

[pfrederi 18,669]

Is the blower shroud original to the engine??  Some older K series the timing hole was on the back of the shroud, newer ones had the hole up front (Carb side).  Guess the timing mark on the older ones had to be in a different spot on the flywheel)

You said it ran before but had you checked the timing back then???

[Mickwhitt 5,131]

I thought i had timed it up correctly but that's what is confusing me.

If I did it right how could it be so far out. 

As far as I know its all original.

when the T mark is next to this cast in rib on the backplate the piston is at BDC.

these are the marks on the flywheel. There is also a mark on the other side of the starter ring which would be at the 12 o'clock position when the piston is at BDC. 

Im going to pull the flywheel off tomorrow and check the key has not sheared off. 

Mick 

[Mickwhitt 5,131]

This is the mark on the opposite side of the starter ring gear.

You can see the piston is at the bottom of the bore.

The S and T marks are over by the starter pinion where it woukd be hard to view them and there is no window.

Mick 

[peter lena 9,271]

BILL D , agree with you on the added grounding point , since adding a number of points on my horses , any and all starting , charging and general running is very solid. especially engine block corner / frame to grounding rail behind dash on side of battery ,also added SERATED WASHERS AND DIELECTRIC GREASE ,  to every bolt down point , MICK the internal condition of the engine looks terrific , your methodical detailing will find it , hope its a simple fix , pete  

[pfrederi 18,669]

32 minutes ago, Mickwhitt said:

This is the mark on the opposite side of the starter ring gear.

You can see the piston is at the bottom of the bore.

The S and T marks are over by the starter pinion where it woukd be hard to view them and there is no window.

Mick 

 

 

That was my point.  On the older engines the timng hole in the shroud was back by the starter pinion.  I wonder if either the air shroud or the flywheel as replaced.