QuestionQUESTION: I purchased a DR chipper with a 12hp Tecumseh engine about 6 years ago. It has always been hard to turnover. I replaced the original NiCad battery with a standard Lead Acid one and installed larger cables. That helped some. If I try to pull start it, I usually find the rope is ripped out of my hand which is not very pleasant. Jumping the battery with a big battery charger usually gets it running. I suspect the compression release is not working or maybe the valves are not adjusted correctly. I am about the replace the starter battery again as this one is toast and wondered if you had any suggestions for checking the compression release or how to adjust it and the valves. I am assuming it should pull over by hand to start if necessary.
Thanks in advance... Jim
ANSWER: Hello Jim:
If this is an OHV Engine, then the Valve Adjust can Very Well be the Cause of your Problem. A Damaged Flywheel Key will Also Cause this Problem. Usually on the OHV Engines the Valve Clearance is the Cause of this Problem More than the Flywheel Key. I Do Not Use the Setting Called for by the OEMs. I have Found that the Following Works Best. Remove the Valve Cover (on the Dead Cylinder for Twin Cylinder Engines). Set the Cylinder you are Setting the Valves on to Top Dead Center (Both Rocker Arms will have Play in them when the Engine is at TDC) When Setting the Valve Clearance. Now Loosen the Valve Adjuster Locks and Set the Intake Valve Clearance to .004in -.006in and the Exhaust to .008in - .010in. I have had Better Performance Out of the Mowers and Less Burnt Valves Using these Settings. The Valve Clearances are Usually Good for Tecumseh, Briggs, Kohler and Most Small Engines. However, Send me the Model and Type Numbers Off the Engine, Please. With these I can Locate the Proper Manual and Better Assist you. Since this is a Tecumseh Engine, I have a PDF Site Addy that May Assist you Also. http://www.tecumsehpower.com/CustomerService/BSI.pdf. Hope this Helps. I am Here if You Require More Assistance. Let me Know What Happens, Please. Thanks.
Good Luck
Respectfully
John
PS: I am Allowed to Answer 10 Questions a Day. If you See I am Maxxed Out, then Try Submitting your Question at or Just After 9pm EST (US). My New Day Starts then. Thanks.
Respectfully
John
---------- FOLLOW-UP ----------
QUESTION: Hi John,
Thanks for taking the time to help me out. For your information the engine is a Mod: 0HM120 and spec:225704A. I did think that the valve timing might have something to do with this. It is an OHV engine and I checked the gaps on the valves. They were set at maybe .006 for both Int and Exh. I had tightened them down a tad to .002 and .004 respectively based on what I saw in another website somewhere (I can't find it again). This sort of made sense to me because as I envision the compression release, I would think it tends to open one of the valves just a bit more at very low RPMs and if the valves were set too loose, this would not have any effect. It also seems to pull a bit easier now. I just don't want to damage a valve by having it too tight.
I would also be interested in how the compression release actually works as I have never had one of these engines apart but I am tempted to open this one up to see what I find.
Thanks again... Jim
AnswerHello Again Jim:
The Compression Release is Designed Either as Part of the Cam or an Add On Part to the Cam that Opens the Exhaust Valve for a Brief Second During the Compression Stroke. Usually the Closer the Exhaust Valve Clearance is Set, the Valve Stays Open Longer and Sometimes Causes the Valve to Burn. That is Why I Use the Settings I Provided to you. The .008in -.010in Clearance Seems to Work Best. The Actual Setting Suggested by Tecumseh is .004in for Both Valves. You can Look Up the Engine Specifications at this Site Addy; http://www.johnfvining.com/engine_specs/default.asp. Hope this Helps. I am Here if You Require More Assistance. Let me Know What Happens, Please. Thanks.
Good Luck
Respectfully
John
