# Pulley swapped mower woes



## Braeden P (Jan 2, 2023)

I got a 1999 lawn general mower (MTD) since it has gears and not a hydro, removed the 9” rear pulley and put in a 2” pulley. Top speed was 36 MPH


----------



## Braeden P (Jan 2, 2023)

Yesterday I borrowed a turbo from my friend from a 1.5L, removed the governor and put it on, went to 40 MPH then at the end of the first run, starting the second there was a loud bang and a puff of smoke, snapped the axle the transmission in half from way too much power, there was no mowing deck and my 110 lb brother was driving it. We had a hose on the turbo going into the intake when it blew up and we were getting a lot of air flowing.


----------



## mmcmdl (Jan 2, 2023)

Why does this come to mind ?


----------



## wayback machine (Jan 2, 2023)

I think maybe you exceeded the original design specs .....


----------



## MrWhoopee (Jan 2, 2023)

Change your name to Tim.


----------



## Braeden P (Jan 2, 2023)

Here are the broken gears


----------



## benmychree (Jan 2, 2023)

Braeden P said:


> Yesterday I borrowed a turbo from my friend from a 1.5L, removed the governor and put it on, went to 40 MPH then at the end of the first run, starting the second there was a loud bang and a puff of smoke, snapped the axle the transmission in half from way too much power, there was no mowing deck and my 110 lb brother was driving it. We had a hose on the turbo going into the intake when it blew up and we were getting a lot of air flowing.


Young dudes doing what young dudes do best!


----------



## Nutfarmer (Jan 2, 2023)

Let me look out at the bone yard at the farm. May have another transmission. It will take a couple of weeks to dry out enough to get to.


----------



## Braeden P (Jan 2, 2023)

Nutfarmer said:


> Let me look out at the bone yard at the farm. May have another transmission. It will take a couple of weeks to dry out enough to get to.


Im looking at get a cub cadet just because they have a cast iron transmission and a real clutch, mine wouldn’t have broke if it had a clutch since you had to grind it till you find it.


----------



## Braeden P (Jan 2, 2023)

Here’s the cut down video of it with the turbo connected, I run it for about 10 minutes until smoke comes from the valve cover, might need to cool it better


----------



## mmcmdl (Jan 2, 2023)

Braeden P said:


> Im looking at get a cub cadet just because they have a cast iron transmission and a real clutch,


Nothing runs like an Old Cub or IH .


----------



## Bone Head (Jan 2, 2023)

Braeden P said:


> Here’s the cut down video of it with the turbo connected, I run it for about 10 minutes until smoke comes from the valve cover, might need to cool it better



Don't know how you're thinking of cooling that turbo, but my bud let's his car set and idle 5-10 minutes.  Oil flow cools it enough to where he runs less chance of cooking the bearings.


----------



## great white (Jan 2, 2023)

Movies won’t play for me but if you had smoke coming out of a valve cover, I think you’ll most likely find that you toasted the rings and piston.

These little engines aren’t built to run on boost. Pumping a couple psi into them without solid ring sealing and adjusted ring gaps will result in a fairly spectacular “boom” most times.

What normally happens is the rings expand in the piston lands and if the ends aren’t clearanced for the extra heat, the ring ends butt together. Once the ends butt together, the ring has no direction it can expand to and it usually just breaks off the weakest part of the piston, the small bit between the top of the ring land and the piston quench area.

After that happens things get really bad, really fast….


----------



## pdentrem (Jan 2, 2023)

Boost and ring gap go hand in hand. About 0.007” per inch of bore works. 2” piston .014”. 4” piston .028” etc.


----------



## Braeden P (Jan 3, 2023)

great white said:


> Movies won’t play for me but if you had smoke coming out of a valve cover, I think you’ll most likely find that you toasted the rings and piston.
> 
> These little engines aren’t built to run on boost. Pumping a couple psi into them without solid ring sealing and adjusted ring gaps will result in a fairly spectacular “boom” most times.
> 
> ...


The engine only runs at full throttle and when I replaced the head gasket there was oil in the cylinder.


----------



## Braeden P (Jan 3, 2023)

Bone Head said:


> Don't know how you're thinking of cooling that turbo, but my bud let's his car set and idle 5-10 minutes.  Oil flow cools it enough to where he runs less chance of cooking the bearings.


There a small chunk milled out where I can hold 1/2 a cup of oil and I fill it up each time and hope it oils it properly


----------



## fixit (Jan 3, 2023)

I did 60 in a go-kart one time and nearly craped my pants. can't imagine 36 or 40 on a lawn tractor


----------



## great white (Jan 3, 2023)

Braeden P said:


> There a small chunk milled out where I can hold 1/2 a cup of oil and I fill it up each time and hope it oils it properly


Not to be critical, but that isn't going to do squat for cooling a turbo. You need oil flow (and lots of it) to carry away the exhaust heat that's imparted to the unit by just the way it operates.

You can't just bolt a turbo on to an engine and expect it to live, no matter what foolishness you see on "roadkill".....that's even more true for a cheap little engine like those used on lawn and garden equipment.

They're just not built for it. Heck, they're barely built to handle the loads they are going to be used for on a day to day basis. They're built to a cost point and the result is something that just barely meets spec for it's use. Anything more than that is just wasted R&D money on the manufacturers part.

Now, you start getting into older designs like the Kohlers and Briggs where they had cast iron blocks and such and they can be built up, but there's a HP ceiling there also. Manily becuase they're all flathead/side valve engines and that design just doesn't flow well enough to make big HP when talking 500-600 cc's....


----------



## Braeden P (Jan 3, 2023)

great white said:


> Not to be critical, but that isn't going to do squat for cooling a turbo. You need oil flow (and lots of it) to carry away the exhaust heat.
> 
> You can't just bolt a turbo on to an engine and expect it to live, no matter what foolishness you see on "roadkill".....that's even more true for a cheap little engine like those used on lawn and garden equipment.
> 
> They're just not built for it. Heck, they're barely built to handle the loads they are going to be used for on a day to day basis.....


The bushings are shot and my friend got if for free from tec school, it’s toasted already but I’m going to try to get an oil pump


----------



## great white (Jan 3, 2023)

Braeden P said:


> The bushings are shot and my friend got if for free from tec school, it’s toasted already but I’m going to try to get an oil pump


I don't think you're quite understanding what I'm trying to get across.

The sump in that little banger is a splash lube case. The engine internals are splash lubricated, meaning there is no oil pressure and no pump. If you add a pump to feed the turbo, you're just going to draw down the level in the sump and you'll be looking at seized con rods and a window in the side of the block in short order. You'll also be adding heat to a sump that already can't really cool itself as it is.

You'll probably suggest a second or separate reservoir next, but that is just going to create it's own set of problems to overcome.

Dump the turbo and go back to messing with pulley diameters if you want speed (you're only going to get so much out of a lawn mower anyways). All the turbo is going to do is turn that little one lunger into aluminum scrap.

Find yourself an 820 transaxle. They're about the strongest lawn tractor transaxle you can get (I've got one on the shelves in the garage) and will bolt right in like your orginal (blown up) one. They're strong because they are rated for ground engaging attachments (IE: plow, harrows, etc), no other aluminum bodied transaxle is rated for that. The cast iron transaxles in the older tractors are stronger (IH, cub cadet, etc) but they usually have a different input that your vertical belt drive engine won't interface with, As a minimum, most use a horizontal shaft engine. If you want to go that way, you're better off just buying a complete tractor to build up. If you go that way, look at the websites that build the Kohlers for lawn tractor pulling. But you're still not going to get a lot of speed out of them. It's gearing as much as anything else. Garden equipment is built for low speed torque, not top speed.

Now, if you don't care if you destroy that little single cylinder modern engine, turbo away.....heck, at this point, might as well spray it with NAAAAWWWZZZZZ too.

But I'm guessing you've already mortally wounded it so anything you do to it now is just going to be wasted effort.

Sorry to sound negative and not trying to bring you down, I'm just being realistic about the design you're trying to overpower. Just keep in mind that speed is primarily a function of gearing, not HP. With enough HP you can overcome gearing, but we're talking ridiculous amounts of hp that you won't get from a lawn mower engine. Even then, you need to be able to rpm an engine to overcome gearing limitations and that little lawn mower engine redlines somewhere around 3600 rpm. You can sometimes press them to 4000 rpm, but much more than that and you're be firing con rods and pistons across the yard.....they're just not designed to make a lot of power.

A drivetrain is a system. you have to build all of it for the task you have in mind. From the water pump right back to the tires and everything in between. That's engine power characteristics, power transmission methods and final gearing (that's both axle gears and tire size). You can't just "improve" one part of that system and not expect it to negatively affect the rest of it....


----------



## tq60 (Jan 3, 2023)

You could create a separate oil system just for the turbo, a cooler pump and reserve tank..

But the engine needs much work to at least have a chance.

Sent from my SM-G781V using Tapatalk


----------



## Braeden P (Jan 3, 2023)

great white said:


> I don't think you're quite understanding what I'm trying to get across.
> 
> The sump in that little banger is a splash lube case. The engine internals are splash lubricated, meaning there is no oil pressure and no pump. If you add a pump to feed the turbo, you're just going to draw down the level in the sump and you'll be looking at seized con rods and a window in the side of the block in short order. You'll also be adding heat to a sump that already can't really cool itself as it is.
> 
> ...


That engine is toast and only runs at full throttle, has lots of blow by, im going to try to get a new tractor and just have as much fun as I can on the engine.


----------



## WobblyHand (Jan 3, 2023)

Turbos are fun.  They can increase the power - if you correspondingly increase the fuel and air.  They greatly increase the demand on cooling, and generally require enough oil pressure and flow to cool their bearings.  Some turbos are both water and oil cooled.  If you run a little turbo like that hard (of course that's what you are doing!) you need some oil flow through the turbo bearings.  The turbo is turning well over 80K RPM.  Static oil is not enough and will probably coke the bearings due to overheating if dino oil.  Synthetic oil will live longer, but even it requires oil flow and cooling if on a long run.  A well set up turbo is a heck of a lot of fun, but it takes a bit of effort if you want the engine to last.


----------



## mcostello (Jan 3, 2023)

Used to modify parts for a Guy that had the record for a 10hp garden tractor. Some one pulled in front of Him and He ended dismounting at 60 mph, SuperMan flight. Had leathers on, no problems.


----------



## Braeden P (Jan 5, 2023)

I need some help here, there is 3 holes and the green one you can see the shaft and bearings, I think that one just needs oil, then there is two next to each other but don’t connect in between them, I think this is for the oil to cool, correct me if I’m wrong.


----------



## WobblyHand (Jan 5, 2023)

Which turbo is this?  Can't read the nameplate.  Some turbos have both water and oil ports.  Usually you can look them up by the part number on the plate and get an idea what is needed.


----------



## matthewsx (Jan 5, 2023)

Um, you got just about what I'd expect from the mods you made.....

I used to own a racing kart and engine building business we would make 40 honest HP from a Briggs 8hp ohv motor. This required a highly modified cylinder head, billet rod, piston, crank, cam and flywheel to name just a little of what we did.

Here's a sample from the wayback machine if you're interested.



			Heartbeat Racing Products
		


If you're going to do this to an engine with a stock flywheel please get some plate steel and fab up a guard for the engine shroud. Cast iron flywheels can and do come apart when you test the limits of rpm on these little motors and people have been killed....

John


----------

