Valve timing :(

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  #1  
Old 02-14-11, 02:37 PM
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Valve timing :(

I have been working on this engine for a while to get it running again but a problem has occurred. When i was working on it i took the case off to see the valves and all (I Know, that was stupid, please don't patronize me for it) but when i put it all back together the valves were mistimed. I have been trying to get the timing right again by trying to turn the engine over and making small adjustments to the timing on each starting attempt. The problem is that i don't know if the rest of the engine works. It is a tecmuseh ohh50. Is there a way to get the timing right (guaranteed)?
 
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Old 02-14-11, 07:50 PM
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Here's a link to the service manual http://www.cpdonline.com/695244a.pdf Hope this helps,,, Roger
 
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Old 02-14-11, 08:56 PM
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I assume you mean the valve clearance? When you say you took the case off, do you mean the rocker box cover? Not familiar with your engine specifically, but here's my general valve clearance adjustment procedure for OHV lawnmower type motors.

Find top dead center on the compression stroke. The way I do it probably isn't the most scientific, but seems to work. I remove the spark plug so you can easily spin the engine slowly. I stick a long screwdriver in the spark plug hole so the tip is sitting on the top of the piston, and the handle is outside. I slowly pull the pull starter to spin the motor. When the screwdriver is at it's highest point, you are at TDC. At TDC on the compression stroke, both rocker arms should have free play. If only one has play, your on the exhaust stroke, and you need to spin the motor one revolution to TDC again which should be the compression stroke.

Once you have TDC on the compression stroke, you can set the valve clearances to the appropriate specs using feeler gauges. There are usually threaded adjusters. There should be a lock nut or screw, and a hex nut for the adjuster. Sometimes the lock nut requires a torx bit. Basically, you loosen the lockk nut/screw, then you can loosen or tighten the adjuster nut. When you have the clearance right, you hold the adjuster in place and tighten the locknut up.

Here's a vid that shows the basic procedures on a different engine but same basic procedure.

YouTube - ( HOW TO ADJUST VALVES) FIX HARD TO START Lawn Tractor with OHV Briggs Engine- MUST SEE- Part 2/2

Here's a site with valve clearances. According to this site it looks like .004"

Tecumseh Engine Intake and Exhaust Valve Clearances
 
  #4  
Old 02-14-11, 09:14 PM
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Here's another vid. he doesn't do the adjustment at TDC, but instead adjust one valve when the other is open, then revierses. Otherwise the adjustement is the same

Lawn Mower Repair Valve Adjustment | Mulch Werx

Here's a description that's probably clearer than mine
lawnmower overhead valve adjustment
 
  #5  
Old 02-15-11, 06:09 AM
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no, its not the rocker cover but the large plate on the side of the enginge were the crankshaft is located. I have looked at the service manual (Thanks!) and i am wondering if the engine will preform better if i took the Govenor off?
 
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Old 02-15-11, 08:47 AM
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Is this on or for a go-kart?
There are some Tecumseh engines that have an ignition timing adjustment...I don't believe the ohh50 does though.

If this is for a kart or similar application, you can get better performance by removing the govenor but also risk damage to the engine....lawn mower racers do it all the time.

Any other application I would not suggest it...
 
  #7  
Old 02-15-11, 12:52 PM
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well, the valves are as they should be. I cant get it starting. Is there a troubleshoot list to this engine and engines in general?
 
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Old 02-15-11, 10:03 PM
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I'd leave the governor alone and get the thing put together right. While reading this thread and the others you have started about this same engine, there is no telling what all is wrong with this engine, but it sounds like you've put the cam in incorrectly. It will only run right if the cam is in the exact position it should be in. One tooth off and it will not work.
 
  #9  
Old 02-16-11, 04:14 AM
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Well, I have the cam set up so the two little dots n the crankshaft and driveshaft line up perfectly. Even in the brief time that the engine was running, it took a while for the engine to get up to speed and had weak power so it muat be the carb. Even now the engine is close to starting with the throttle wide open. Im planning on soaking the carb right now and going from there.
 
  #10  
Old 02-16-11, 07:20 AM
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Originally Posted by thedancingman43 View Post
Well, I have the cam set up so the two little dots n the crankshaft and driveshaft line up perfectly. Even in the brief time that the engine was running, it took a while for the engine to get up to speed and had weak power so it muat be the carb. Even now the engine is close to starting with the throttle wide open. Im planning on soaking the carb right now and going from there.
I assume you mean dot on camshaft gear lines up with dot on crankshaft gear.
 
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