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n8in8or

7016H starts really rough, runs fine warm

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n8in8or

Hi guys, I have one that has me scratching my head. I did a search and didn't find anything so I'm hoping maybe someone has an idea of what may be going on while I continue to figure it out. Here's the story:

I have 2 7016H's - for the winter I use one with a blade and one with a snowblower. For about a month and a half now I've been having a problem with the blade tractor. It runs rough....really rough when it first starts. It acts like you've started it and not pushed the choke back in yet, but if I push the choke knob in it doesn't make it run better really. However if I leave the choke pulled all the way out it will choke out and die eventually. After a little while of chugging it will finally idle smoothly with the choke pushed in, but if you give it more throttle it starts chugging again. As it warms up it will accept more and more throttle until it will finally run smooth all the way up the RPM range. Once it's warm it will run completely normal. I can shut it off and start it back up and it's just like nothing is wrong. I've never had an engine run like this so I'm baffled. Also, this is something that happened all of a sudden. At the beginning of winter it was fine. Then I went out to use it one day and it was like this. I don't recall how long it had been sitting since its last use, but it wouldn't have been more than a week.

Recently I tried to start it and it would never light. It eventually looked like it was blowing puffs of smoke from under the head so I figured that I had a blown head gasket....which I could kind of reason in my head as being the problem - low compression when it was cold but as everything warmed up it would seal. Last night I changed the gasket and spark plug and it runs exactly the same. So I took the carb apart and cleaned it with carb cleaner - still runs the same. I ran a file over the points - it still runs the same.

Usually if a condenser goes bad, it's fine cold then starts breaking up hot, but that's the next easy thing I'm suspicious of. Also the throttle shaft is loose in the body of the carb, so I'm also suspicious of that - I'm going to try swapping the carbs between the two tractors so I can at least find out if it's carburetion related or not.

I don't know that I'll get to work on it tonight since my daughter has a band concert, but if anyone has any ideas or has experience with this very problem I would love the input. Thanks!

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fishnwiz

I would go with the condenser first and do a new plug right of way.

I would doubt that excessive air through the throttle shaft would give you the symptoms you described. I like the idea of the carb swap out as a way to narrow down your issue. Is the governor working freely and adjusted properly? When you pulled the carb did you clean the imulsion tube and pull the low speed adjustment to be sure it was clean?

Best of luck and keep us posted on the issue.

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n8in8or

I did a new plug last night with the head gasket and that didn't make a difference. The governor is working fine and I've also tried manipulating the throttle lever directly just to try to analyze what the engine is doing without the governor contributing and that hasn't helped. When I cleaned the carb I did pull the emulsion tube and low speed jet and give them and the passages a good cleaning as well.

In addition to the carb swap, I think I'll also try the condensor from the other tractor first and see if that might be the problem because that will be easier than the carb swap.

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powerking_one

I assume this is a Briggs 16hp C.I. singe engine? If so, consider the "early" stages of a partially sheared aluminum flywheel key that is wreaking havoc with the coil/ignition timing. The only way to tell is to pull the flywheel off and inspect. The coil itself could also be a suspect. The flywheel nut MUST be torqued to a spec of 145 FT-LBS.

My 2-cents worthsm00 of opinion....

Tom (PK)

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fishnwiz

Tom makes an excellent argument for the flywheel key. If I remember right I had the same symptoms years ago on a 16 and it was the flywheel key. Have you had any engine backfires before your issue developed? At times the key might not shear but the key itself has a slight dent from flywheel slippage causing a slight out of time issue.

I myself have seen coil issues that cause poor running conditions but it has always been the opposite with the engine running good at start up and then continue to run worse as the engine warmed up but coils can be a finicky thing.

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n8in8or

Thanks guys. Yeah I was kind of suspicious of ignition timing, which the key would cause. If external fixes don't take care of it then I guess the engine is coming out so I can work on the flywheel and ignition parts. No I don't remember it backfiring.

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powerking_one

Nate,

I have not owned/seen any 10-16 C.I. single engines with a partially sheared flywheel key, but many others (on this site) have. If the torque on the flywheel nut is not to spec then that's when things can go wrong; like slight rocking of the flywheel against the key; clockwise when starting; then counterclock-wise w/engine running. If it is a sheared key issue, then it makes sense that the engine falls flat trying to rev up (severe timing retard condition). It blows that one has to remove the engine to check this 10 cent item.

If this is a points/condenser ignition system, then consider a quick 12V Delco/Kohler type battery ignition coil plumbed in to eliminate the flywheel key and magneto coil. There are many of them out there on eBay and cheap. It is also a great tool to have in one's "satchel" to help in troubleshooting on any magneto points/condenser ignition engine.

Tom (PK)

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GrincheyOne

Tom, Does make a good point considering the bypass of the internal coil. BTW Auto-Zone also carries the Dura-Last line of auto replacements for about $30. It's a quick swap which I used on my B&S 10HP Landlord, using a 12V ignition coil from my sons junk box.The points are used to control the frame (or ground) side of the power source the + can be taken from the ignition switch, or an external toggle switch. An auto salvage yard is another source for the coil, just make sure it is a 12 volt, else you will need a ballast resistor on the + side of the circuit.

Wayne

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n8in8or

Thanks for the coil tip, I will keep that in mind as I keep diagnosing this problem. I didn't get a chance to work on it last night but hopefully by this weekend I can start doing some parts swapping to hopefully figure out which system is the culprit.

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n8in8or

Ok, I finally had a chance to seriously work on it last night and found the problem. I had checked the condenser with my multi meter the other day and the capicitance checked out ok so I felt pretty sure it wasn't that...so I decided it was the coil and/or a partially sheared key.

I got a car ignition coil and rigged up a new ignition and......it ran the same. Grrr!

So I grabbed the condensor off the other 7016 and.......it ran the same! So now I'm suspecting a stuck valve maybe.

But first I try the carb from the other 7016 and.......it ran the same!!

At this point it's starting to kind of run, but it's still chugging pretty good. I had the cover off the points box and was watching the points....it looked kind of funny to me, so I pressed on the points arm while it's running with a screwdriver (basically tightening the gap) and it cleared right up!! I let off and it goes back to running like crap. So I screwed the adjuster screw and again it clears up. It turns out that all along the point gap was too big. So once it's running well I turn it off and check the gap with a feeler gauge and it's right at .020" - the factory spec.

I still don't quite get how it ran SO bad cold (again it wouldn't start at all the other day) but once it warmed it ran fine. I'm guessing it was an ignition timing issue? Anyhow, I felt pretty dumb, but I hope my experience helps someone else.

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