OutdoorKing Repair Forum Forums Repairs and Maintenance Questions on Engines Questions On Tecumseh / Kirby Engines Tecumseh Ultima 5hp - running rough

If it runs well except at idle, there are two most-likely causes. The first is that the idle mixture is adjusted incorrectly, and the second is that the needle and seat is leaking very slightly. If the latter cause applies, though, it would idle properly when first allowed to idle, then would gradually become rich after a delay of probably more than half a minute, during which the float level would be slowly rising.

If it is neither of those, the key question is whether it is rich or lean when it misbehaves. You can probably find out which by letting it idle for a couple of minutes then looking at the spark plug.

I�ll try to address each of your points individually;

1) I am pretty sure the idle mixture is not able to be adjusted on this type of carby. This type doesn�t have a form of adjustment that I am aware of. I might be wrong though
2) When re-installing the new seat I inspected the needle and it was in good condition with a nice point and no buring. I was using a standard tecumseh kit so I could not replace the needle as the ultima needles are different to the standard tecumseh needles. The seat was replaced like I mentioned earlier
3) It definitely did not idle correctly and then gradually become richer. It would simply not idle at all. Full speed was too fast � but it was smooth. Installing the seat has improved the situation.
4) The spark plug confirmed the engine was running rich as it was blacker than expected.

My main issue was to do with the flooding however I am reasonably confident this issue has now been resolved. I am assuming the float must have got stuck. I didn�t get a chance to try it this morning before work but I did confirm if was not flooding and Hydrolocking the engine like before.

I have wound the idle and full speed screws right out on the linkages after adjusting the carb last night. I also made sure the linkages are functioning correctly, which they were.

The possibility that seems to stand out, since you've just replaced the seat, is that the float level is now higher than it was. I gather you now have a seat from one model carburetor and a needle from another. Let's see if there is a way to adjust the float height. It is usually done with a metal tab at the pivot, which can be bent. Don't adjust it though until you get a picture of the tab, and a measurement of the current float height.

The float on this type of carburettor is not adjustable unlike some Tecumseh�s models which have the metal tang to adjust. This model is not adjustable to the best of my knowledge. It just has the plastic insert which is fixed where you place the needle prior to re-installing the float.

Last night I re-checked the carb and float operation and it looked all ok. The float was opening and closing as it should. To the best of my knowledge the seats on all Tecumseh�s are pretty much the same. To date I have not found a seat which is different however I haven�t worked on all Tecumseh�s by any means. I compared the seat originally taken out of the ultima to my spares and it was exactly the same. Well as best as I could distinguish.

I put the unit back together and fired it right up. It coughed a chugged a little at the start however it evened right out and allowed me to get a very smooth low idle and a nice full speed (no over-revving). I re-checked the unit again this morning and no flooding was evident.

At this stage I am going to assume the needle & float got stuck upon re-installation.

I ran the mower for 10-15 minutes and it ran quite well. No chugging, knocks or clunks were heard.

I will reserve my judgement until I give it another couple of test runs over the next few days.

Please let me know if you think there is anything else I should check.

If it delivered correct mixture in the last two tests, Peter, it is very unlikely that the float level setting was wrong. The problem has therefore been an intermittent one. Dirt in jets and passages causes intermittent or permanent lean mixture, not rich. So does an intake leak. Intermittent rich mixture at idle only, only has one cause on my list of likely faults, and that is an intermittent float, needle or seat problem. It could be dirt between the needle and seat, or the needle happening to sit slightly askew in the seat due to its position in the float lever clip, or temporary binding of the float lever on its pivot. Most of those possibilities (all except the dirt) can usually be avoided by smoothly raising and lowering the float through its full movement half a dozen times before you put the float bowl on, then keeping the carburetor the right way up thereafter.

At the moment I don't suggest you do anything except run it a number of times before you consider it ready to deliver to a customer. Note that all of the possible causes I listed are likely to be self-curing anyway: the pronounced vibration of a single cylinder engine cures a multitude of ills.

I think your comment on moving the float up and down before re-installation has merit and I am pretty sure because of the design of this carby I failed to complete this step, meaning the float is in the bowl prior to re-installation unlike most carby�s which you attach the float to the carby and complete the instalation off with the bowl and jet nut.

I agree with you the mower needs to be thoroughly tested before it goes to a new home. I very rarely get complaints about the equipment I fix as a hobby and I don�t plan on getting a complaint from this mower that�s for sure.

Late night the mower started first pull from cold (no coughing or chugging) and ran very nicely. The idle was smooth and at full speed the mower sounded pretty sweet. As discussed with Theo before these are great units when they are set right,

I will give the mower another couple of tests from cold over the weekend before it goes off to a new home. Not one of the ultima�s have caused me any problems in the past and I suspect this one wont either. Most people just wont take the time to get them right. Personally I think they have more power and run smoother than most quantums of the same era.

Things are still looking up despite the list of repairs:

New Blades
New Air Filter
Refurb carb including new o rings and seat
New Pull rope
Second hand ignition coil � the old one was dead!

It will still be done for under $50 including the cost of the mower so as far as Im concerned it was worth the time.

Thanks for the update, Peter. I'm aware that you are careful to test mowers several times before you sell them on, and you are quite critical of their performance, so there is a good chance your excellent record of customer satisfaction will continue.

I haven't had much hands-on experience with Tecumseh engines, but from what I've seen the side valve ones seem to be very durable in a mechanical sense - probably substantially more so than aluminium bore Briggs engines - but the carburetors are fiddly to operate and even more fiddly to repair. They don't seem to be notably smooth-running either. At the moment I'm not about to change my opinion that side valve Briggs engines are a better bet as a simple, reliable, and easily repaired power plant for mowers. I'm not ready to say the same of the large Intek engines though (the small ones seem OK so far).

As I keep saying, my idea of the best deluxe walk-behind mower engine is a pushrod Honda, and the most practical cheap and cheerful engine - as long as you don't mind fixing a few trivial faults when you first get it - is a chonda. I prefer to avoid OHC Hondas, and for the moment am withholding judgement on the small pushrod Briggs engines. For your hobby repair jobs, I think you'll find yourself tidying up chonda engines before long, but heaven help you if you keep them on their original mower bases.

I'll leave this thread open for now - please let us know when you've finished testing the Ultima and are satisfied with it.

Thanks Grumpy.

I have a few Chonda�s at the moment ready for spring which are all 1-2 pull start smooth running units. I personally find the Chonda�s some of the smoothest running engines.

I regularly get Pope�s with Chonda�s � These are a good unit as pope make a great base and wheels
Gardenders Choice Chonda�s � Engine is pretty good � I always make sure these are not used for mowing large yards
Sanli � Reasonably good Chonda�s and easy to start � Same rule applies � these are only sold for small to medium yards. When set up correctly they run really well.
909 Chonda (Good GMC base but questionable catcher) � fine for mowing large yards if you don�t use the catcher or are prepared to empty it carefully.

1 in 4/5 units on average that I pick up now for repair are Chonda�s and they are all quite easy to repair. The majority of time they have been put together incorrectly in the linkage area and with some minor adjustments and correct operating instructions to purchasers, they get a sound unit.

Back on the subject now.

I gave the Ultima another run and it seems pretty much done � nice easy one pull starts from cold. I will reserve my judgement until I give it one more test during the week but I suspect this time it will be all good.

Lastly its funny you mentioned small pushrod briggs engines as I just picked one up on the weekend on a very rickity base that will be used as a transplant. I�ll start a separate thread over the next day or so as its something I�d like to work through. Files on outdoorking are limited in this area.

Thanks

Peter

I agree that we haven't seen much of the small pushrod Briggs engines yet, Peter. People seem to like them when they are new, but we have yet to see what a few years do to them.

At least one type of chonda engine uses a flexible rubber-like plastic flap valve for a PCV valve instead of a rigid plastic disk like the other chondas. There have also been quite a few chondas that have been used for years without an oil change, and they ended up with blockages in the PCV compartment. I'll be interested to hear more about PCV issues, and in particular about the reliability of the flap valves in older chondas. I've seen some very worn and sad genuine Hondas, always with disk PCV valves, and I haven't yet seen a stuck or blocked one. (I have seen them with the disk valve pretty much worn through, though.)

The Engine is still running nicely after multiple tests but I would like to get it to slow down a little at full revs. I have a very smooth idle but full speed is just a little quick for my liking.

No matter how I adjust the full speed screw it is not making a notable adjustment in speed.

Any suggestions would be appreciated.

Can you post pictures of the governor spring, and linkage please Peter? There may be a choice of holes to attach the spring or link to. If the governor is a mechanical one (inside the crankcase) there is also usually a process for ensuring the shaft is fully clockwise on full throttle, the same as for a Honda engine.

Sorry Grumpy I forgot to take photo�s of the governor linkage and spring. It is pretty much the same as your standard TVS tecumseh�s where the governor spring is connected to the throttle linkage from the govenor shaft and the linkage is connected to the carb butterfly from the govenor shaft.

There is no choice of holes to attach the spring. One hole only is present. On the weekend, I had another crack and try to lower speed via the full speed adjustment screw. No matter how I adjusted the screw it just wouldn�t make any noticable difference. It was still too fast for a 5hp engine. I also completed the governor shaft adjustment as you indicated.

I spoke with Theo (Bigted) last night and we went through a number of potential causes and eliminated them accordingly. The last shot was to remove one link from the spriral of the govenor spring and stretch it out ever so slightly to reduce the rev�s. Simple in principle but a time consuming process as you have to strip the engine down to the block in order to remove the govenor spring and stretch it out. The first link probably added 3-4mm to the springs total length.

I gave the engine a quick run this morning and it had slowed considerably down to a level I am comfortable with, very much similar to how a nicely tuned Briggs Quantum revs.

This morning I still got nice easy one pull starts from cold, a smooth idle and nicely reving full speed sound that I am accustomed too.

I will warm the engine right up tonight and make sure everything is running properly. I will also give the engine a final idle and full speed tune prior to finalising this somewhat difficult refurbishment.

A longer governor spring would reduce the speed, Peter - it sounds as if a previous tenant had shortened it, or it was the wrong spring.

I think "difficult refurbishment" is something many people experience with side valve Tecumseh engines, mostly because of the carburetors. On the other hand they are mechanically robust and very durable. Back in the 1950s, when people expected such things to last a couple of generations and didn't really mind having nasty experiences with the carburetor, it was probably the right engine for its time.