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Mickwhitt

Misfire query

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Mickwhitt

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.

 

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953 nut

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

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lynnmor

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

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peter lena

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

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JoeM
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??

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peter lena

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

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Pullstart

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.

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Pullstart

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.

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Lee1977

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

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gwest_ca

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

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richmondred01

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

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Mickwhitt

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. 

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Bill D

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

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Mickwhitt

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 

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Mickwhitt

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?

20201128_135014.jpg.8c4b40a526b4dec9004b0b21672622ef.jpg20201128_135023.jpg.e0030b36a02e115fc744a76e80793704.jpg20201128_135135.jpg.6a11de4bd05ee228d6ba286275ec84e1.jpg

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Mickwhitt

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?

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richmondred01

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

I don’t reuse head gaskets.

69531B85-186E-4E54-B9E5-86D5B9931624.jpeg

Edited by richmondred01
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Mickwhitt

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.

20201129_114300.jpg.5af2d75ad427146e3700fb19fb22f12d.jpgThe fast running jet looks a bit worn at the point. Any views on if it looks serviceable or not? 

20201129_114202.jpg.3e0ce01e822a337eff7703215b7b1bd2.jpg

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 

 

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sqrlgtr

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...

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Mickwhitt

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 

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pfrederi

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???

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Mickwhitt

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.

20201129_183941.jpg.6829366ab2e49fa37c97b827ede1632d.jpgwhen the T mark is next to this cast in rib on the backplate the piston is at BDC.

20201129_183914.jpg.bc42a61cc0924c6941c83c2aaae39f61.jpgthese 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 

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Mickwhitt

20201129_183905.jpg.7980aeb9d8e9c5cb01ff26216fcd4949.jpgThis 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 

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peter lena

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  

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pfrederi
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.

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