I'm having a difficult time getting the 14hp Te***seh OH140 single-cylinder engine on my 1977 Sears Craftsman garden tractor to fire since yesterday when I replaced the head and valves with a newer set I had from another same-model engine. This type of engine has the OHV design with the rockers located in a box or housing right above the head, as seen in the pictures below. Pushrods run up the side of the motor through a couple tubes that work the rockers which work the valves, obviously. Here is the full story: Previously, the engine ran alright and made good power but smoked quite a bit from the head and valves' housing (presumably from a crack(s) somewhere). I had another same engine sitting in my shed that had a cleaner head and valves, so I figured I would pull the old top end off the engine and replace it with the better parts. I carefully dis***embled the parts from the running engine (valves and head), and s****ed off all the carbon and crud that had ac***ulated on the piston. Then I generally cleaned up the newer head, valves, and valve housing, and installed it on the engine, with a new head gasket. I tightened it all up evenly, and re***embled everything I had taken off to do the job. I made sure there was some good gas in the tank, and sprayed some starter fluid in the carb. When I turned the key, the engine cranked over just fine, but it wouldn't fire. I sprayed some more starter fluid in there and it still wouldn't fire. I kept messing with the throttle and choke but with no luck. Here's the facts: - Replaced the old head, valves, and valve housing with a cleaner set that weren't cracked from another engine. - S****ed off all the carbon and crud build up on the top of the piston. - New head gasket installed and bolted down tight with the newer head. I tightened the six bolts in a criss-cross pattern to draw the head evenly against the block. - Has good spark - Cylinder has approx. 22 psi pressure. However, it had less than that when it ran before with the old head and valves. - Cylinder and piston looked to be in really good shape. No pits, grooves, or any other visible faults. - Has the same carburetor with the same old adjustments. - The only thing that was done to the engine was the installation of a new head with a clean set of valves, cleaning the top of the piston, replacing the cracked valves' housing with one that was good. Here are a few pics: Replacement head Piston cleaned up with new head gasket Any ideas? Valve adjustment tips? Advice? Any help would be greatly appreciated... Thanks --Matt
did you lap the valves in? 22 psi sure does sound low even for a old motor are your valve clearences to tight? i would think you would want about .004 to .008 clearance.
loosen the rockerarms a little. they are too tight. When the valve is closed you should be able to wiggle the rocker arm a little. Edited to say 22 is way too little compression.
While replacing the head did you readjust the valves , switching the parts may have changed the valve settings. Try setting them at .014 and see what it does,usually on air cooled eng. the valve setting is a little more than with a water cooled eng. The aircooled eng runs a little hotter .
Hey thanks guys, good tips about the valves. When I reinstalled the rockers I DID tighten them so there was zero clearance. I don't know why; I wasn't thinking, duh. So I'll loosen them up a little bit maybe around .008? The owner's manual doesn't tell me anything about valve clearance specifications. Yeah good thing you said that. I remember specifically when I began to take the engine apart that I noticed the rocker arms had some clearance and could move a bit and up and down above the pushrod and the valve. And that's when it ran, so this obviously indicates that I have them adjusted way too tight now. _____ I know 22 psi is ridiculously low; I laughed when I read it too. But it did run before that with even less pressure.
not to steal your thread---but where can I get a wiring diagram for a Huskee rider with a Briggs 14.5 engine?
I just adjusted the valves, and gave it another try. It didn't start, but this time it did pop out of the carb a couple times. It wasn't backfiring, it was more just popping/spewing gas out the front. I wonder what could be the problem now... Could it have something to do with the head from the other engine? Maybe the valves aren't fully sealing/closing around the valve seats? That's what I am suspecting now, but I wouldn't mind any of your advice. The combustion chamber has to be totally sealed off (valves completely closed with no gaps) at the point of ignition to run, correct? Thanks a lot --Matt
first thing is did you drop the sparkplug by any chance? because once you do it is no good. it will pop and skip or not even fire at all.second thing did you lap in the valves ? i allways lap in the valves and ckeck by using a flash light shining ontop of the valves and then look thru the intake or exhaustport in a dark room to see if i can see any light between the valve and seat if you see light keep laping until you see none. maybe that will help you some what are your valves set at?
That's what I hate about this JUNK they build these days.......drive the piece-of-**** thirty years, and the ****in' thing flies all to pieces!
I just checked my Te***seh OHV book. Valves Intake-.005, Exh-.010. It doesn't list compression specs. Doing a compression check is difficult because of the compression release built into the cam. You won't get an accurate reading. I normally install the tester and see what it is during the cranking phase. Just so I can have an idea of what it is. Not accurate by any means, but it sometimes helps to diagnose. 40standard, you have to get that from huskee themselves. Every mfg. seems to do something different from the other.
Hey thanks for the quick responses. I didn't drop the spark plug, and it has a really strong spark. I have the valves set correctly for the intake and exhaust at .005 and .010, respectively, however I did not 'lap' them. In fact, I don't know what that means or how to do it. I suspect that this is my problem, because of a few other things which would lead to this conclusion, for example: When I cleaned up the head, the valve seat was actually out a little bit (the exhaust side), and I just tapped it back in with a hammer, and didn't really know what I was doing. I figure I got it misaligned, and therefore the valve obviously won't close properly and fully on the seat. If someone can tell me how to lap in the valves, I'd be appreciative.
I just read this article on valve lapping; I think I get the idea. http://www.v6z24.com/howto/valvelapping Pretty informative how-to. Where can I pick up some of this stuff? The local auto parts store, hardware store, or?
yes! matt their is a forum i stumbled accross on the internet about lawnmower engines. it's been some time but it helped me fix a old craftsman mower. if i find it i will send it to you good luck.
I know about these active forums... http://www.perr.com/forum/viewforum.php?f=2&sid=9ec610ad86546958413e6de9307a0ada http://www.mytractorforum.com/ http://www.tractorforum.com/ http://www.ytmag.com/cgi-bin/boards.cgi
In my sordid past with lawn mowing machinery I remember if the thing blows fuel out of the carb inlet quite often the muffler is plugged. When the valve wouldn't go in all the way and you tapped it with a hammer it was stuck in the guide. It will proably continue to do that .
You pretty much got all of the good ones, yesterdays tractors is my fav. I would lap the valves, and if there's problems after that, maybe find a small engine shop in town.
Alright guys, I bought some of the valve grinding compound at the local Advance Auto, and tomorrow I plan to tear the engine down again to lap the valves. But while I have it apart for the second time, is there anything else I should check/do while I'm in there? Thanks --Matt
hmm..i do a lot of messing around with tractor/lawnmower engines...never worked on one quite like this though...maybe sand/adjust the points, spark plug, sounds like little compression.
anybody have a easy straight wiring diagram. my rider has so many safety switches , now it won't start. I just want wire it with a push ****on and byp*** the safety **** thanks
Yeah well I read on another forum that it is difficult to get an accurate compression reading on these small engines because they have some sort of built in "compression release." Good idea on checking/adjusting the points; I didn't touch anything that had to do with them when I did this job, but I might as well still take a look at them...
Okay, I lapped the valves, and the engine started up and ran really smoothly. Thanks for all the help!
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