My 1977 1250 QL

[Mike1450]

The new ISO mounts are worth the money. I changed mine on my 1450 about 2 years ago and they are holding up and doing a great job. On my 1450 at WOT there is very little vibration in fact if you put a cup of water on the hood you will see very small ripples in the water if any.

I found many things contribute to vibration and all need to be looked at to get it running smooth. A well timed engine (use a timing light), correctly adjusted carb and new rag joints (if they are old they maybe out of shape and stiff ). Also I found on mine that the engine had a slight tilt to the back (fly wheel side) most likely due to the weight. To counter it I tighten the front ISO mount down a little more than the rear, not much maybe 2-3 treads more. Now the engine and drive shaft are at a perfect 90 degrees.

Time also helps as the new ISO mounts break in they get a little more flexible

[Matt G.]

Originally Posted by bkw3614

I don't think the mounts were deformed by tightening to recommended specification. When I loosened them from my original install, they relaxed well and yet, still had vibration.

Yes, they were, you said so yourself in this post:

Why, then, do I experience more vibration with the mounts loose in their mountings, such as with the nuts at two threads showing?

If they were loose with two threads showing, the mounts are permanently deformed, or you're using too long of bolts, but I'm fairly certain you said you obtained new bolts in the correct length. The engine was not loose in the mounts for the many other people that have done this, myself included.

I continue to be amazed at the diverse opinion on this subject. From what has been discussed previously, there seems to me no correct or incorrect answer; but rather, many different experiences.

Really? I have been following this subject since I got into this in 2003, and aside from people trying to use solid mounts and chassis mounts in place of the OEM mounts, so for the OEM mounts, there's two routes you can go, and two sets of experiences: follow the directions that come with the mounts (incorrect, proven to not work by you and countless other people that have tried it) and tighten them with 2 threads showing through the nut on the original length bolts, which many people have done since the idea was first posted on another forum 10 years ago by someone who had several QL tractors and experimented with various things and found this method to actually work.

[justanengineer]

I managed to get the 1250 completely reassembled yesterday and spent a bit of time wirebrushing the adjustable links in the deck.

The good news is that it now holds oil and runs a bit better/smoother than it did previously. On the subject of vibration, its pretty similar to my brother's 147 that I spent quite a bit of time working on everything BUT the engine previously in addition to using. Both tractors vibrate a good bit while at low RPMs, but smooth out nicely at high RPMs, so I believe the new ISO mounts are working pretty nicely. Previously this tractor shook like crazy regardless of engine speed due to flattened rear mounts. For the record, I used the 2-3 threads above the nut method for ISO mount installation.

My question now is how to tune the engine. Despite today's rain, I took it for a test ride to see how it behaved and it still is acting similar to when I bought it. It doesnt idle and seems to have very little power. Climbing a very slight hill (more of a slight rise) in the lawn at low (crawl) tractor speed and high ~3600 engine speed with the mower going requires stopping several times as the engine is "lugging" down close to stalling. It also will occasionally backfire through the carb upon shutdown and/or while cranking.

I have cleaned the carb thoroughly and installed the standard Kohler carb kit for gaskets/needles etc, but something still isnt right. The engine starts right up on 6-8 revolutions, but requires full choke everytime to begin firing, then once firing requires choke off and mid-full throttle to actually run - idle needle too lean maybe? Once running, it doesnt really want to idle. It will run somewhat consistently in the mid RPM range, but doesnt really run smoothly until up around 3600. Ive tried adjusting the needle/jet from the factory settings (2.5 turns out) both directions per the service manual, using the sound of the engine speed increasing/decreasing with a final setting halfway between, and that seems to work for the main jet for the high RPM range, but the idle needle doesnt seem to affect the engine in the least regardless of the direction turned even at full in, which makes me suspect an issue there. Any ideas?

One other thing Ive tried is adjusting the points gap. When the engine was out I found the original points in a glob of greasy crap in the frame so I pulled the cover and found the gap at something over .020. I reset them to .017 and it ran a bit better, but I suspect this also may be a bit off. I tried Matt's static timing method, but unfortunately I cannot see a timing mark close to the opening point. I see a vague one ~1/2 revolution out, but could be seeing things. Is there supposed to be a stamped T and S, or are there simply two dash - marks on the smooth portion of flywheel to the left of the gear teeth? I suspect I need to get in there with Q tips or brake cleaner to clean some rust/crap off the marks.

As always, thanks for all of the assistance. I am hopeful that with your assistance I can get this similar to my brother's 147 - a good solid tractor with plenty of power that runs smoothly, quietly, and is an absolute joy to mow with.

Carl

[Matt G.]

Your timing is still off. It may be easiest to remove the flywheel shroud and then find and clean the timing marks and then put some paint in them. They are stamped in the flywheel, sometimes a bit too lightly. If they are rusty at all they will be nearly invisible.

[samiam44]

Matt,


Just a comment on the iso mount instructions- could it be that they are correct IF you use a new IH metal locknut? Metal deformed locknuts take more torque than a used one or nylon-locknut.
I used the 2-3 thread rule and locktite on the old nuts.


Michael

[justanengineer]

Originally Posted by samiam44

Just a comment on the iso mount instructions- could it be that they are correct IF you use a new IH metal locknut? Metal deformed locknuts take more torque than a used one or nylon-locknut.

Not to get too off topic but I could believe it Michael. When I replaced the bushings I used metal deformed nuts from TSC, and I could be wrong but believe I close to if not over 8 lbs-ft at 2-3 threads.

On the off chance that someone here is a big box store shopper for common hardware I thought I should give a price comparison between the local Lowe's which is a few hundred feet from my home and TSC which is a few miles. Four (4) 3/8-16 grade 8 black oxide finish metal deformed "nylock" nuts - Lowe's = ~$5.50 TSC = $0.18. Hopefully not many here are silly enough to buy by the piece when you can buy by the pound.

[Matt G.]

Originally Posted by samiam44

Matt,


Just a comment on the iso mount instructions- could it be that they are correct IF you use a new IH metal locknut? Metal deformed locknuts take more torque than a used one or nylon-locknut.
I used the 2-3 thread rule and locktite on the old nuts.


Michael

Who knows? Unless we know the running torque of the locknuts they used when the wrote the instructions, and use the exact same locknut, the resulting amount of compression probably won't be what they intended, and what they intended may not be right anyway. As I recall, the instructions don't specify, and there may still be variation between brands. And as you probably know, the metal ones are one-time use, and some people don't know that and will try to re-use them, so then the amount of compression would be different then too.

This is why using nut torque to compress the mounts is ridiculous; the results will be very inconsistent. 2 threads above the nuts on the original length bolts is pretty consistent, with only slight variation due to nut height.

[justanengineer]

Thanks for sticking with me on this fellas. Ive spent the last several evenings tinkering with this tractor to fix/adjust as many of the lil issues as I can to improve its operation. Luckily for me there arent too many, but a few did leave me scratching my head and looking for a monkey with a wrench.

At this point in time I believe I have the timing adjusted pretty close to what it should be. I tried Matt's static timing method several times, but unfortunately this resulted in rather late ignition as evidenced by frequent backfires and poor running overall. On the positive side, it was easy to perform. I then tried a timing light, but found it rather difficult to adjust timing with any consistency, so I settled for "decently close" being ~.017 as I originally thought.

While experimenting with timing, I noticed that the throttle and choke linkages didnt quite look right. Sure enough, according to the book the governor linkage was set for the LEAST sensitivity, and this engine never seemed to have much power due to a lack of governing. A few trials later, I came to the conclusion that the 4 least sensitive positions (closest to end of governor arm) resulted in no/almost no governing. Coincidentally, at all four of these positions the engine will reach full RPMs without issue, but under load it lugs down until it stalls or load is removed. With the spring hooked into the fifth position, the tractor will happily chug up and down hills while mowing without issue and appears well governed, but unfortunately will not reach full RPM with the mower deck engaged. Despite the throttle being wide open, the governor keeps the engine at relatively low speed (~1400) under load, which means the mower barely spins fast enough to cut and not enough to cut at any normal tractor speed. Without the mower engaged and simply driving, or if I push on the governor arm/carb throttle arm it gets up to ~1800. Ive tried adjusting the link between the governor and carb, but had no success. Its possible via this link to lower the top speed by lmiting max carb open, but doesnt appear to increase it. Ive considered putting more tension in the throttle spring adjustment, but hesitate to do so as I think it will just hurt the governing.

Any ideas?

[Matt G.]

Reset the governor arm as per the manual and put the spring in the original holes (probably the ones with the most wear, it may be obvious). There is no need to put the spring in any of the other holes. If the governor isn't working properly with the spring in those holes, something else is wrong. I will also add that a lack of power can be caused by the timing being off. I'm not sure why you're having so much trouble with that...what kind of meter are you using?

[samiam44]

thanks for the comments back.. absolutely the instructions don't state anything.. the should include a new proper nut, if that is what is required for the 100 in-lbs to work.
Did ppl use a small enough torque wrench? If your in the bottom 20 % of the range, the tw's can be off by quite a bit.

In the airplane world, we specify running torque. The mechanic must determine the initial torque for the lock nut, then add that to get the total torque. There is a mil-spec for new and min-reuse for locking nuts. Nylon ones are limited to exposure <225 F.

I didn't realize you could buy them reasonably for a box. I did splurge and get the bevel locking washers and heim ball joints for the cub.

A big public THANKS to Matt for answering my questions.