Tecumseh 6.5 hp Power Sport running rich

[Espeefan]

Here are some photos I took this afternoon, of the governor linkage, springs, and arm. I also took a photo of the manual I have, which is kind of a generic manual for a variety of Tehcumseh engines. What I think I have on my engine is what the manual refers to as the OHH RV control. At least that's what it looks like to me. I took a guess and moved the spring on the governor arm from where it was to the bottom most hole (#5) on the arm. It was in the #4 hole; in my photos I had already switched it to #5. I took a ride and used a gps app on my phone to check top speed. Before making any changes my kart hit 30mph. After switching the spring to the #5 hole in the arm, it hit 31. I put the spring into the #3 hole, expecting to see it slow the kart down, and it hit 29mph. Maybe just a coincidence, maybe not. Hard to say. I would have expected to see a larger change. I also tried bending the governor arm just a bit, to see if I could limit it closing the carb butterfly, even just a little bit, but that didn't really change anything. It might have been my imagination, but the throttle response felt a little more snappy with the spring in the #5 hole and with the arm gently tweaked a bit. I basically bent it only enough to counter the slop in the wire linkage and still allow the carb butterfly to hit the idle stop screw. So all in all, I really didn't gain much of anything. I guess maybe I need to experiment with spring lengths and tension next. Any thoughts from the pros?

 

[Espeefan]

Apologies for the sideways photos. I uploaded them from my phone the right side up. For some reason they got turned again. Maybe you can just tip your lap tops!

 

[Clifton]

You shouldn't need to bend the governor arm itself in order to get more rpm, if the carburetor butterfly is opening all the way then that's the best you can do. You can accomplish this with the governor linkage by design, it has two metal tangs that you can bend back/forth for high rpm and idle rpm adjustment.

Your linkage isn't hooked up exactly right. The one long hook isn't suppose to be attached to anything after it goes through the hole in the tang.

This is how it should look (notice the one hook isn't attached to anything):

As for the holes on the governor arm, the #1 hole should be for the most rpm because it has the least distance between the tang and the hook (see attached picture), it is also the closest to the pivot point of the arm, so it requires the least amount of motion to move the arm.

On my linkage, I shortened the length of the hook that goes through the tang even further, which also has a similar effect to changing the hole number on the governor arm.

You have two idle adjustments, one is a screw adjustment on the carburetor that adjusts the idle rpm after the engine is warm. There is also an idle tang that can be bent back and forth to adjust the governed idle rpm and is mostly for idle speed when the engine is cold.

 

[Espeefan]

Clifton, thanks for the information and the photos! I see what you mean about the spring position and the hook end kind of floating after passing through the high rpm tang. I will have to make the changes necessary to match your photos. I guess somewhere along the line my engine's governor linkage was messed with and not assembled correctly. So am I right in assuming I can adjust the max rpm with that high speed tang? My spring looks way more stretched than yours, but maybe that will work in my favor? Thanks again for the photos. Can't wait to give this a try.

 

[Clifton]

So am I right in assuming I can adjust the max rpm with that high speed tang?.

That's right, bending the tang forward towards the end of the hook will allow it to pull it further. You could also shorten the hook as I did on mine (not shown in pics) if you wanted to, I haven't had any problems with it.

Just a few things to be mindful of with the engine (though it really applies to most engines):

They are notorious for carburetor problems, I installed an inline fuel shut off and I run the gas out of it after I'm done to keep clogged jets from old fuel to a minimum. I still occasionally have to clear some junk out of the small holes in the bowl nut (there are 3 holes, one in the end and two on the sides.. one is pretty small near the threads), but lately its been starting first pull.

They are also prone to connecting rod failure, I'm not sure exactly what causes the failures and I haven't personally had that problem, but make sure to keep the oil clean. I have had the float in the carburetor get stuck before and got gas all mixed in with the oil. With that in mind you wouldn't want to run high RPMs without a load on the engine or for a long period of time either.

 

[Espeefan]

Thanks for the information and advice. I have a new carburetor ordered for my engine. It's an adjustable carb for OHH80 engines. Both idle and main jet mixtures are adjustable. I'll probably go through and check my governor linkages once I get around to installing the new carb. I'm not really looking for a lot more speed. Just a couple hundred more engine rpm, I think. If I can get the kart to hit 35mph, I'll be happy. It runs so rich right now that I think a proper tube should give me a little more power. I might add a fuel shut off valve too. I've seen needle valves that leaked also. I have a feeling I'll be getting an open element filter and if I do that, I might as well get a less restrictive exhaust as well, as long as it's not louder than stock. I already wear hearing protection when riding anyway, so why not.

Any thoughts on the engine surviving 3,800 or 4,000 rpm long term?

 

[Hellion]

You would do well to give it the best possible fuel and avoid alcohol at all costs. I imagine 90% of the problems with small engine carburetors lies with ethanol in gasoline.

I switched to 100%-E0. They sell it at quite a few places locally. It actually smells like it used to.

 

[WeddingRing]

You would do well to avoid alcohol at all costs.

I switched to 100%.

Hypocrite!!!!

 

[Clifton]

Any thoughts on the engine surviving 3,800 or 4,000 rpm long term?

Mine has been over 4000 a number of times and survived it but I'm mostly off road with lots of turns and things so I never hold it there for more than a few seconds.

I believe arc sells a billet rod for ohh50 that also fits the ohh60, but I'm probably just going to run mine until it dies and then throw on a predator engine from harbor freight which can probably be bought for the same price as a billet rod for the Tecumseh.

 

[Hellion]

Hypocrite!!!!

You funny guy!

Whoops. GASOLINE, 100% GASOLINE.

...I'm probably just going to...throw on a predator engine from harbor freight which can probably be bought for the same price as a billet rod for the Tecumseh.

If you haven't already worshiped at the golden altar of the Predator 212, then there's something wrong.

That's some willpower....

 

[Espeefan]

Update! I successfully installed a new carb, purchased from eBay. It is a carb designed for a Tecumseh OHH80. It fits perfect and bolts right up. I started tuning it today and got it somewhat dialed in. I didn't have enough time to really finish, but it's close. The engine feels much more lively under acceleration now. It also seems to rev a bit quicker and higher, so my tune is better than the non adjustable carb. While I was messing around with the throttle linkage, I noticed that the carb butterfly never really reaches wide open position. It's more like 3/4 open at most. The problem is that the governor arm which pulls on the carb butterfly, actually hits the intake manifold before the butterfly ever reaches full open. In other words, the governor arm has limited travel because it is hitting the intake manifold. Is this normal? Truth be told, I never noticed this because I never checked it with the original carb, but it's not a matter of the carb being different. The travel of the governor arm is limited with either carb. The intake manifold is effectively being a hard stop. Thoughts? The governor arm is not loose. It looks to be properly adjusted. Anyone else able to confirm this is normal operation?

 

[bob58o]

I had an issue with my Tec carb not opening all the way...
Here's a post from that thread...

There is a metal tang on the carb.

It seems to be used as a throttle stop and idle setting.

If I bend it in one direction, the butterfly seems to be able to open a bit wider. (not sure if it completely parallel with the bore of the carb, but it is better)

However bending this tang this way doesn't allow the throttle plate to close all the way.

With out removing it, it is tricky to bend.

Lets see if I can get a picture after I try to get it bent how I like.
______

Not my carb but a tang like this.

Lets say the tang hits the flange and stops.
If I bend it to open wider....
The tang hits the body of the carb instead of the screw when closed

 

[Espeefan]

Bob, thanks. I have no problem with my carb opening 100%. The problem is that my governor arm hits the intake manifold that the carb is mounted to, before it can pull the butterfly 100% open. I am familiar with the tang limiting the amount of travel on the stock carb though. That's not my issue. What I am wondering is if this is normal, or if I need to adjust the governor arm, although the linkage from the arm to the carb butterfly is so short, and the two are in such close proximity to one another, I really can't move the governor arm closer to the butterfly bellcrank on the carb. Then I would probably be creating other issues with the governor arm forcing the butterfly too far closed. It's kind of strange that the governor arm is hitting the intake. I don't know if it ever hits it in normal operation. If I pull the cable for the gas pedal, it really doesn't hit, but it doesn't come anywhere close to wide open throttle either.

 

[Espeefan]

Got it figured out! I had to adjust the governor arm on the governor shaft. Now the arm pulls the carb link plate to the wide open position and I get full throttle! I wasn't able to take the go kart for a rip, but I suspect it will pull harder now that it's properly adjusted, and maybe I will even pick up a few rpm to boot. My next project is to bend the high speed tab on the governor a little to see if I can rev the little Tehcumseh to 3800 rpm or so.