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Brent_Baumer

Two problems with my "new" 712H - help

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Brent_Baumer
Well, I finally got around to messing with the $80 712H w/ a kohler K301.

After installing a new plug, having the carb rebuilt and new throttle shaft installed (it was very loose, seen this problem before), bypassing the plugged? fuel pump, turning the throttle arm around the "right" way, checking the governor cross shaft adjustment and putting the governor spring where it is supposed to go per the manual she starts and runs. It idles fine and runs OK at full throttle. Problem #1. Between 1/4 and 3/4 throttle this engine surges (varies RPM at constant throttle) bad. Don't know how else to describe other than it goes rrrrrmmm rrrrmmmm rrrrrmmmmm, instead of a constant rrrrrrrrrrrrrrrrrrrrrmmmmmmmmmmmmmmmm....... Reducing the tension on the governor spring does not help at all. Changing idle and high speed fuel mixtures also do not help at all. Like I said, the fuel pump is bypassed. I put enough gas in the tank to gravity feed the carb. Problem #2. Hydro was very slow to respond. Checked fluid. Poured in about a quart and a half of Simplicity multi-purpose hydro oil per the manual. Can now barely see fluid in the fill tube. Let run for a minute and bled the air off throught the poppit? valve on the left side. Now the sucker is the most responsive hydrostat I've seen. Barely move the lever foward or reverse and you'll go flying. It is very hard to find "neutral" now too. Top speed in forward AND reverse is faster than any gear or hydro 7000 or 7100 series I've had, and that is about 10 of these. This thing is so sensitive and fast it is dangerous to operate. What is going on here? Thanks, Brent

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rjgoth
Here is an idea for something to look into regarding your engine question. I think that it is surging at 1/4 to 3/4 throttle because of an air leak. Since there is more vacuum at 1/4 to 3/4 throttle it is sucking air in somewhere it is not supposed to, then at full throttle there is less vacuum and it runs fine since there are no air leaks. Another idea is clogged or blocked jets internally in the carb, in which case a good carb cleaning with new gaskets might be the ticket. Good luck, Ryan

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Brent_Baumer
Bowl, carb to block and carb to air cleaner gaskets are new. Carb is freshly cleaned and rebuilt. I'll get out the gummout and check for air leaks by spraying around the carb and see what happens. Thanks for the tips. Brent

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Dutch
The mid range surging sounds like the governor. Sometimes those can be tricky to set and lock on the K Kohler. The hydro sounds like a linkage problem (sticking, binding, loose, etc.). Those can be tricky to adjust too. Are all linkage springs in place? Is the nylon roller free?

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cranemech
Brent, I am not familiar with these tractors, so I'm just talking out of my hat, but does this hydro unit have acceleration valves that could be stuck or had the positions switched? Just a thought. Later, Chad

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rjgoth
One quick thing Brent. I would use starting fluid instead of Gumout. I remember gumout being non-flammable. I would think that starting fluid being more flammable would be better for checking for air leaks since it is more flammable. I have seen posts contrary to this so can anybody shed any more light on the carb cleaner vs starting fluid for checking for air leaks? Ryan

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maxtorman1234
I agree with dutch, several times I have had to adjust my 10 and 16 to get them to stay where they belong. Had the same problems, idled good, but much higher it would do what you described. I'd Reset the governor, and It should solve the problem.

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Brent_Baumer
I'll fiddle more with the governor tomorrow, although I have already changed the spring positions in an attempt to correct the problem without luck. I'll go to the extremes I guess. As far as gumout being flammable - it is. I prefer using it to starting fluid. Starting fluid will blow your head gasket. You can run these small engines on gumout without even having a carb by spraying small bursts into the intake. Not recommended for long periods of time but it works good if you are trying to find out if you have a spark or a fuel problem. The hydro linkages are free. The nylon roller is at the center marker as it should be. The hydro is so touchy it is unbelievable. Thanks for the help thus far. Brent

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10HorseMan
Air leaks could be coming from the throttle shaft or (Bushings) bieng worn, Carb out of line(bowl and top part have more space than usual between them) which causes hard starting and not the best running. Hope this helps. :D

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Brent_Baumer
As stated earlier, the throttle shaft WAS worn. I do not know how to repair this myself, and have had that problem before (fairly common on these K series) so I took the carb to the dealer. He got the right kit and replaced the shaft. The shaft does not "wobble" any more. Nice and tight. Bowl looks installed properly to me. Brent

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Brent_Baumer
Oh - also guessed at the setting for the max speed stop. Checked it with my trusty Sear 8 cyl. Tach. Works out to about 3400 RPM max right now, although the accuracy of the tach is not great when you have to multiply 420 RPM (reading) x 8. At least I know I'm not over-revving (over 3600).

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Brent_Baumer
Changed the filter in the hydro. Jacked the ass end up to get rid of the "creeps" that developed after the filter change. While adjusting the hydro so the wheels quit spinning in the neutral position, the surging mysteriously stopped. Took her for a spin. The severe jerks and high speeds are gone, although still not as smooth as I'd like, and so too is the engine surging. Just hope it stays that way. Brent

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roma3112
Brent If that jerky/hydro problem keeps up check the linkages like sombody said and the nylon guide, i know you said you checked that the guide was centerd but if it dosent spin free it can cause it to jerk creep and act weird. If you need it i will post a link to a post i made on my hydro when it had a problem. It has a nice illustration supplied by maynard that is helpful should you tryto look more into it. good luck john http://www.simpletractors.com/club2/topic.asp?TOPIC_ID=24902

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Roy
Brent, If I remember correctly a jerky hydro can be caused by loose BGB bolts. There were several previous posts on the subject. Do a search on hydro probs and you can probably find them. Might be part of the problem. Just a suggestion.

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MPH
Those bolts that hold the tranny side plates on are worth checking now and then. Have found mine loose before and tonight I'm in process of replacing the right side on my B-112 with one I got from Kirk some time back. The clutch linage on my old one was in some sort of sorry shape, all holes outta round, rods worn half though. Anyway, didn't take much of a grunt to break the bolts loose and I know I checked them less then a year ago.

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