Toro Mower

[lefty]

Thanks guys. I think that's my next step....air testing / valve clearance check.

If that yields no problems, I'm thinking a new carb may be in order? This particular carb's main jet is not removable. That's to say, there's no slot to unscrew it. It's just flat with a small shoulder on one side (unless there's some sort of special tool for it that I'm not aware of) And there are no other adjustments on it...fixed bowl nut (which is super clean at this point) and no mixture / idle screws. (Number on the carb is 799866 per engine manual)

I was thinking of dipping it for a while but there's some foam damper type things on the shafts for the auto choke and throttle links. The linkages are plastic and I'm not sure how they would do in a chem dip.

[KE4AVB]

remove the breather cover (probably the carb first) and check for valve clearance.L heads apparently lose clearance over time. You might have to remove a valve and grind some off the stem.

They do lose clearance from wear and is quite normal.

Here is a couple examples. First is wear of the face and stem; the second is where the retaining tip is completely worn away. In second image the valve would not even operate as the retainer was no longer attached to the valve. If you got stem wear then it time for a new valve guide and valve.

Yes filing the end is how you increase the clearance after which after you lap the valve until good contact all the way around. After lapping the clearance may need readjusting again. Be carefully it can be over done easily. The key here is filing squarely; grinding will take the stem down too quickly. Sometime even the seat is so worn that they need replacing too but most times lapping will do nicely.

[thomd51]

if the air intake comes from inside the blower housing and the cylinder fins are not completely clean pressure (slight) will effect the carb balance and can cause this problem . TOM.

[lefty]

if the air intake comes from inside the blower housing and the cylinder fins are not completely clean pressure (slight) will effect the carb balance and can cause this problem . TOM.

If I understand you correctly, I would say no, the air intake comes through an air filter attachment on the side of the engine not from within the blower housing. The machine is very clean also.

But some of the more experienced members of this discussion may be able to confirm that.

[Fulltilt]

Thanks guys. I think that's my next step....air testing / valve clearance check.

If that yields no problems, I'm thinking a new carb may be in order? This particular carb's main jet is not removable. That's to say, there's no slot to unscrew it. It's just flat with a small shoulder on one side (unless there's some sort of special tool for it that I'm not aware of) And there are no other adjustments on it...fixed bowl nut (which is super clean at this point) and no mixture / idle screws. (Number on the carb is 799866 per engine manual)

I was thinking of dipping it for a while but there's some foam damper type things on the shafts for the auto choke and throttle links. The linkages are plastic and I'm not sure how they would do in a chem dip.

Actually, the fixed bowl nut you refer to is the main jet.

I remove the emulsion tube/nozzle all the time on them little suckers. Here's how: I pry it out from the venturi using a big flat screwdriver and a popsicle stick on top of the brass nozzle. Nothing to it. You want to witness mark it on the bowl side first.
You have to remove one of the shafts though.

[lefty]

I wasn't aware you could push that out. Thanks for the tip. I assumed it was threaded in there like most I've seen. I think I'll give that a try. In the mean time, I've got some more info.

My leak down tester arrived today, which I'm excited about because I have big plans for it. However, on this particular machine, I'm unable to find top dead center because I can't get at the piston from the spark plug hole. I can see a good portion of one of the valves but the spark plug hole is such that you can't get at the piston at all with any type of probe to feel its location.

So I decided to pop the muffler and the valve cover to check the clearances. I have .004 on the intake and .006 on the exhaust. Per the engine specs, acceptable range is .005 to .007 on the intake and .007 to .009 on the exhaust. Should I be concerned with this?

My method was to check each valve while the other was open, which I can clearly see by watching the springs and assume that if one was open the other should be completely closed.

If those clearances are doable I think I would rather pop out the emulsion tube like FullTilt suggested or even get an after market carb. I'm guessing to find top dead center, at this point, may involve buying a new head gasket, which is the same price as an after market carb.

Unless bad rings or cylinder are causing this problem. But from what I've read and experienced those tiny holes in the emulsion tube are usually the culprit.

Learning as I go....

[bgsengine]

My leak down tester arrived today, which I'm excited about because I have big plans for it. However, on this particular machine, I'm unable to find top dead center because I can't get at the piston from the spark plug hole. I can see a good portion of one of the valves but the spark plug hole is such that you can't get at the piston at all with any type of probe to feel its location. .

while the valve cover is off, watch for the springs to "overlap" (the point where both valves are slightly open - intake starting to open and exhaust starting to close) turn engine over slightly until exhaust closes completely and stop, make a mark on the flywheel or note the position of the blade underneath. Turn one full turn (360 Degrees) and you should be just slightly after top center on compression stroke. Lock flywheel in place securely and use leakdown tester.

[lefty]

Excellent advice BG. Worked like a charme. Assuming I did it right. Pressure in on the left gauge was 96. Pressure on the right gauge was 90. Am I doing this right? Seems too good to be true. There was some hiss out the oil tube but assuming that's normal at 96psi. Using an OTC 5609 from Amazon.

https://www.amazon.com/gp/product/B0030 ... UTF8&psc=1

It appears everything is tight. So I dig deeper into this carb?

[bgsengine]

if you had no air coming out the muffler or the intake, then it's probably very likely just the carb. Bear in mind even after a cleaning (including nozzle removal which I never bothered to do) isnt going to deal with corroded aluminum bits plugging up the internally drilled passages - assuming it is a float carburetor, you will also want to make sure the air bleeds (in front of the carb and in front of or to the side of the choke plate) are clear as well - make sure gasket does not squish out and block a bleed hole either. However, carbs are relatively cheap enough that if the first cleaning doesn't do it, may as well put a new carb on it. Only other possibility is a sheared flywheel key or bad spark plug - have seen both cause a governor hunting issue (surge)

[Fulltilt]

Excellent advice BG. Worked like a charme. Assuming I did it right. Pressure in on the left gauge was 96. Pressure on the right gauge was 90. Am I doing this right? Seems too good to be true. There was some hiss out the oil tube but assuming that's normal at 96psi. Using an OTC 5609 from Amazon.

https://www.amazon.com/gp/product/B0030 ... UTF8&psc=1

It appears everything is tight. So I dig deeper into this carb?

That's the same unit I have been using for a few years now. Works/holds up good. Numbers are good.
There's not a lot to them carbs, but as bgs mentioned, the pot metal wants to corrode and get flaky sometimes. ( actually, a lot of the time)
I use a welders SS toothbrush to clean them up, including the nozzle. You can get them at any local welding house, I think home depot and napa carry them too, very handy for a lot of jobs.
https://store.weldersource.com/p-3009-e ... bw190.aspx