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2 stroke enthusiast
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Helping out an erderly gent on his originally owned 7265. He said he thought the engine was worn out due to it loosing power in taller grass. I could tell this guy managed a golf course in his day as the mower was set at #3. Too short for me, anyhow, I told him I would give it a good check over and repair/replace what I found was worn out. First off I'll tell you hes' been using Opti-II for the last few years, which made me feel better after learning he did run it in the past on single grade motor oil! Ouch! I told him how detrimental that actually can be.
First thing I did when I got it home was to check compression. 105??!! What? Didn't think any D series would pull a number like that, but it did! Very little carbon on the dome, but normal carbon on the skirt, but the rings were very clear. Ports needed some opening as he said he did just a few years ago, but still were partially blocked. Also needed a fresh set of seals as they were weeping from the signs of dirt, greasy buildup both under the flywheel and around the base. Problem I have now seems to be the modular carb. The t-shaft is quite worn to the point of the govenor not being able to hold position on startup. If you reach under and 'help' it open, it comes up to speed properly and maintains it.
I'm quite green(no pun intended) with D series govenor setups/repairs etc, though it must be operating as I followed the manual in reinstalling the parts including cleaning everything well and regreasing the steel washer. I really feel it must be just a worn t-shaft. I have one spare carb to use for back up as I promised other modular parts to another member here. Worse case scenario is that I replace the reed cage and use the other standard, aluminum bodied carb of which I have one or 2 laying around.(I think).? Another question. Can the govenors be adjusted without using the specific tool to hold the govenor weights down? Can a deep well socket provide the leverage needed? Reason I ask is that though the engine sounded about right in NORMAL mode, it tested on my tach at only about 2850 and around 2500 in light. Should this be running about 3100 or so in NORMAL mode as most?
What's with the different colored springs that some of the older manuals talk about in regards to rpm? This spring looks bare, it may have had color, but I'm not sure what, as it's gone after 34 years of use. Want to return this mower dialed in just right as the owner is 82, but quite spry for his age and fond of the mower I can tell, even though he flat out offered it up free to me if he ever replaces it with another(2 cycle LB preferred). Just gotta love this guy! Sorry for all the ?'s fellas. Trying to get more familiar with these D's as I have a few in storage myself.
 

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Some tips on D governors:

The governor part called the collar (602634) will sometimes get a groove worn in the top where the weight arms ride, this will tend to lower the RPM.

A quick governor check on any D engine is to look at the throttle arm angle when the engine is not running. It should be around 45 degrees or 10:00. Several parts if worn will cause this angle to increase up to the 12:00 position including wear of the throttle shaft, link rod, governor lever and the above mentioned collar.There are always ways around buying new parts to take up this wear.

The D-400 link rod is 3 1/16 in. long overall. The D-600 link rod is 2 3/4 in. long overall.

The D-600 modular carburetor with the round plastic float with needle attached should always be replaced with the standard float model or the metal version.

Finally this may be helpful:

Lawn Boy C & D Governor Notes

The Lawn Boy C and D engines use a flyweight type governor that spins at engine (crankshaft) speed. This governor uses a spring of calibrated tension working against the centrifugal force generated by two spinning flyweights to set the maximum engine RPM. Lawn Boy used 4 different governor springs over the years:

Green – 2500 RPM
Red – 2800 RPM
Yellow – 3200 RPM
Blue – 4000 RPM
The spring with the lowest tension (Green) produces the lowest RPM and the spring with the highest tension (Blue) produces the highest RPM. Note: A variable speed spring is also used on some Lawn Boy models and allows for two RPM settings. The spring is positioned to add its tension to the main governor spring thereby raising the engine speed. The speeds are usually 2500 RPM on the light setting (green spring alone) and 3200 RPM on the heavy setting (green spring plus additional tension of variable speed spring).
Governor Operation: With a properly adjusted governor and when the engine is not running, the throttle disk is held in the wide open position by the throttle link rod in contact with the governor lever. When the engine is started the flyweights begin to spin and the resulting centrifugal force causes them to fly open and through mechanical linkage compress the governor spring which in turn lowers the governor lever pushing the throttle link rod down, partly closing the throttle until a balanced condition is reached. This balanced condition is the RPM at which the engine will continue to run steadily and is determined by the governor spring(s) used. Now if a load is placed on the engine (heavy grass) slowing it and the flyweights down, (and creating an unbalanced condition) the governor lever will be allowed to rise thereby opening the throttle, raising the RPM and rebalancing the system. Governor operation is automatic and quickly adjusts to varying load conditions continuously while the engine is running. This closed loop system depends on a steady flow of fuel to operate properly. Which brings us to one of the problems that can arise with flyweight governor control: Surging. A lawn Boy engine can surge at startup when cold or at any time when hot. In both cases the surging is almost always fuel related. We have all experienced a Lawn Boy that surges from low RPM to high RPM, over and over, never holding a steady speed. Basically the governor system is seeking its balanced state but cannot attain it. The usual culprit is not the governor itself but the fuel flow entering and vaporizing in the crankcase. On a cold engine at startup this fuel may not vaporize fast enough to allow the engine/ governor to reach and hold its balanced RPM state. Pressing the primer to inject extra fuel or using the choke if equipped with one usually will overcome this temporary condition and when the engine is warm it disappears. Also on warm summer days you may not have any problems at startup. A properly adjusted carburetor main needle can minimize this condition.
On a fully warm running engine surging may occur for no apparent reason. Again we must suspect interrupted fuel flow, which can be anything from dirt plugging the tank screen, fuel line or carburetor main jet or a sticking or plugged float valve. Even leaking crankshaft seals that allow air to enter the crankcase and lean out the fuel mixture can cause surging. Explanation: Whenever fuel starvation occurs and the maximum governed RPM cannot be held for the system to balance itself, the governor does what it is mechanically designed to do: it opens the throttle wider. However there is not enough fuel flow and the RPM continues to drop. A point is reached where all of a sudden some fuel becomes available and the engine starts to pick up speed again. As the engine/governor comes back up to set point speed fuel starvation occurs again and surging has begun. One other point: A binding throttle link rod or very worn throttle shaft can also contribute to surging.
 

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Echoman: If you need to use the carb you promised me go ahead. I just found one on ebay, the "improved" style p/n 681843. Says it's NOS, but is the only 1 of 3 that dosn't have a picture, however for $36.95 versus $100+ the others want, and $111.77 from partstree, I guess I will hedge my bets.

Hopefully you will have the parts you need to get that guys mower back in top shape! Sounds like its in pretty good condition already with that crazy compression.
 

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2 stroke enthusiast
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Discussion Starter #4
Thanks for all the input Mike72! Yes, I noticed a slight groove forming in the top of the spring collar as there was alot of dirt/grease buildup from the seal aging. Don't think it will require a full out govenor replacement though I have 2 complete kits should I need them. I will check into the t-position as you stated, but I think it's about where it needs to be. I did notice the wrong(vented) p-bulb is installed so I will be changing that out first this since I have a few spares(new) sitting around. I'm going to work with what I have right now LawnboyKS in terms of parts, and what I offered you still stands should you still need them. Worse case I'll replace the reed cage/carb with the aluminum bodied version. Thanks for your help guys!
 

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2 stroke enthusiast
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Discussion Starter #5
Well, after replacing with another modular with a better(tighter t-shaft), I pulled the flywheel off to re-inspect the assembly. It all appears okay with slight wear grooving in the top of the spring collar. Not sure if this will throw off the govening action of the weights, but it only stammers on start up. Once up to speed it runs and holds well. Also wondering if the 'starting side' on the coil circuit is on the fritz? Don't think I'll spend much more time or parts swapping($) to get it figured out, though I may just toss on a spare coil to see if infact it clears up. What seems simple or obvious can be the most frustrating when it fails to prove your troubleshooting theories!
 

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Glad you got this sorted. Wish I coulda helped you but I get an "F" in "D" engines-only worked on one and it ran fine so I didn't mess too much with it....:banghead3
 

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2 stroke enthusiast
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Discussion Starter #7
Never did change out the gov parts. Still think that's the issue. I cleaned and relubed only. The owner was happy and knows I'm around for anything else he needs or wants including another Lawn Boy. Not too many shops in my area(several towns) around wanting to work on Lawn Boys of the 2 cycle nature these days. Usually tell the owners "they're not worth the trouble or money to fix". Phooey! They'll out run and live anything out there or currently being made!
 

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Never did change out the gov parts. Still think that's the issue. I cleaned and relubed only. The owner was happy and knows I'm around for anything else he needs or wants including another Lawn Boy. Not too many shops in my area(several towns) around wanting to work on Lawn Boys of the 2 cycle nature these days. Usually tell the owners "they're not worth the trouble or money to fix". Phooey! They'll out run and live anything out there or currently being made!
Phooey is a GREAT word.! Can be used in alot of contexts. Nice revival.!
 

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Can the govenors be adjusted without using the specific tool to hold the govenor weights down? Can a deep well socket provide the leverage needed?
I son't think anyone else discussed this tool. I don't think it has anything to do with leverage or anything like that. I think it's a calibration tool...it only allows you to push down on the governer a predetermined amount, such that you can measure the gap between the governer lever and the rod as the manual discusses.

I haven't been able to find any details on how deep the inside of the tool is though.
 

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Discussion Starter #10
Yep, you're right Coopster! It's set at a predetermined depth as you push down on the weights and hold the t-shaft down(closed) to measure the gap between the rod and plate. I need to check into gettin' one of them there things. My 7263 only was pushing out around 2900 today also, as was that 7265 I just returned to the owner. Seems as these parts wear and the spring gets weak, they loose some rpm. I'd like to keep them closer to 3100.
 

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Yep, you're right Coopster! It's set at a predetermined depth as you push down on the weights and hold the t-shaft down(closed) to measure the gap between the rod and plate. I need to check into gettin' one of them there things. My 7263 only was pushing out around 2900 today also, as was that 7265 I just returned to the owner. Seems as these parts wear and the spring gets weak, they loose some rpm. I'd like to keep them closer to 3100.
I have never had to replace a spring, and I only replace the collar and the weights, never do buy the whole assembly, those are the only parts that wear out.
Going to ask my son , the machinest, if he can make some D series governor tools, I saw how many dollars they want for new ones,,, gawd.
Ron
 

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It would of been nice if OMC had designed that T-shaft to be adjustable, the aircraft that I have worked on over the years that use the same design to move a butterfly valve usually have a fine toothed geared shaft and the lever that moves the shaft has a real small slotted screw with fine teeth that mesh with the shaft. You just loosen the small lock screw on the opposite side and use a jeweler's common screw driver and adjust the butterfly position without having to disassemble anything.

Something even simpler and much cheaper, they could have designed the T-shaft in 2 pieces, where the lever fits over the shaft with real small splines and if you want to adjust the lever one way or the other you just put a small reference mark on the end of the shaft then pull the lever off the end of the shaft and move it CW or CCW one tooth or so depending on what you need.
 

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Very informational project going on here. A lot of folks stand to learn some in depth tips on working on this model of engine. Good thread and input everyone!
 

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I'm going to have to take the time to re-read this whole thread more carefully later. I thought I understood how these things work, but I guess I only understand part. Is that manual that tells you how to adjust these things on the Lawn Boy website?
 

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Discussion Starter #16
I have never had to replace a spring, and I only replace the collar and the weights, never do buy the whole assembly, those are the only parts that wear out.
Going to ask my son , the machinest, if he can make some D series governor tools, I saw how many dollars they want for new ones,,, gawd.
Ron
You have the actual tool used for govenor adjustments Ron? I would surely like to have one if infact he can/does reproduce them. :thanku:

One other ? for this 400-600 series nooby. It appears that all the gov parts are the same for both models, other that the nylon collar? I had bought 2 complete kits on Ebay awhile ago, but then discovered they had D-400 collars and not 600's, so i ordered 2 new 600 collars along with new springs which the kit leaves out. Must be for the reason you mentioned you never replace them bald-guy. I guess they don't have enough tension on them to ever really get 'weak' over time.
 

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You have the actual tool used for govenor adjustments Ron? I would surely like to have one if infact he can/does reproduce them.
:ditto:
 

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You have the actual tool used for govenor adjustments Ron? I would surely like to have one if infact he can/does reproduce them. :thanku:

One other ? for this 400-600 series nooby. It appears that all the gov parts are the same for both models, other that the nylon collar? I had bought 2 complete kits on Ebay awhile ago, but then discovered they had D-400 collars and not 600's, so i ordered 2 new 600 collars along with new springs which the kit leaves out. Must be for the reason you mentioned you never replace them bald-guy. I guess they don't have enough tension on them to ever really get 'weak' over time.
Yes, I have the actual tool, I use it every time I have one opened up for any reason, just to make sure.
If I replace the governor, I set it with the tool, takes all the guess work out of it.
The nylon collars will wear over time, but is not necessary to replace it EVERY time.
The D 600 nylon has to be rotated clock wise when using the tool.
I have to see my oldest this afternoon to deliver him a belt for his rider and am taking the gauge with me to see how hard it will be for him to make one or six more.
The factory one is heavy steel but I see no reason it can't be make from aluminum. Not like it gets beat around, just drops over the crank shaft end and pushes the lever down.
I looked the part number up the other day and they were like 60 bucks and some change,, geeze.
 

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Is that manual that tells you how to adjust these things on the Lawn Boy website?
Do your typical model search (any valid model number) and hit enter. Select a model from the list, than on the row of bottons near the bottom, select [MANUALS]. On the next page, it's the link on the bottom left.

or https://lookup3.toro.com/ttcGateway/acrobat/manuals/lball.html

and here http://www.scribd.com/doc/26622228/Lawn-Boy-Service-Manual-1950-88-Complete


I have to see my oldest this afternoon to deliver him a belt for his rider and am taking the gauge with me to see how hard it will be for him to make one or six more.
The factory one is heavy steel but I see no reason it can't be make from aluminum.
I'd be happy just to know how deep it is, how far it pushes down on the governer.

I don't see any reason it couldn't be turned from aluminum either, or a piece of threaded pipe for that matter, with a cap turned onto the end, and cut to length...or even copper pipe with a cap soldered onto the end and cut to length.
 
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