Outdoor Power Equipment (Lawn Mowers, Snow Blowers, Chain Saws and more) Discussions

I bought a used Murray gokart that has a great frame and a OHH65 model Tecumseh 6.5 hp engine.  The engine is hard to start.  The engine has a prime bulb and we can get it started with 5 primes but it will bog down and die when we throttle up.  It is also not idling well and will die after only 30 seconds.  We pulled the carb and thoroughly cleaned it using a rebuild kit.  The carb had white cake and crud under the welsh plugs.  We used wire to clean the 3 small jet holes.  I also pulled the gas tank and cleaned it out with fresh gas. I replaced the fuel line as it looked worn.  However, even with fresh gas and a good cleaned carb, the engine still will not throttle up.  We can get it started but it will die soon and will stall when we throttle up.  When we do get the engine to start, I've spray starter fluid into the air intake (w/o filter) but the engine does not power up.  In fact it seems to die when we inject starter spray into carb.

I checked for compression and found 60 PSI after 3 pulls.  Not sure what compression should be but that seemed OK.

I pulled the air filter and I can see the primer bulb is squirting gas into the carb.  I put my hand on the air intake and while someone else is pulling starter, I don't feel a vacuom on my hand.  When the engine does run, I see some gas spit out of the air intake.  I was thinking the exhaust might be clogged, so I pulled the muffler.  Without the muffler, the engine still does not start nor run well.  Even w/o the muffler, I don't feel any suction on my hand over the air intake while someone pulls starter cord. 

I see good spark on the plug and have replaced the spark plug using .030 inch gap. 

I'm thinking it could be a valve or timing issue.  Does anyone know how to check the timing on a Tecumseh engine?  Any ideas as to what to check next?

Thanks.

-Pete

White crud is about the worse but given the other things you have done the carb passages are not important for now.

 

A compression test is not so reliable in a small 6.5 hp because of compression release but at 60 I would think it would start and run.

 

Your primer is working so it should not be hard to start even if the carb is plugged.  You have good spark so it should fire up easily if everything else is ok.

 

Once started you should be able to run by punching the primer or injecting gas in the throat or timed shots of starter fluid or just about anything else, carb cleaner, WD-40 whatever.  It should be able to run with a plugged carb with those aids.  Unless you are flooding it out by too much.  That’s easy enough to check by pulling the plug.  If you are starting right after a stall then it’s probably not flooding.  I think you would have mentioned it not restarting thought so probably not flooding.

 

Could be timing, broken flywheel key, compression, plug, valves.  Probably the easiest things are plug and check the valve lash. There should be a decent rush of air as you checked at the throat.  Try a leakdown test or dump air into the spark plug hole on the compression stroke TDC and listen at the carb, muffler, oil fill plug and around the head.

Thanks for your reply Trouts.  It will generally start 3 or 4 times but never run for more than 30 seconds.  After that, it will not start so I assume that eventually I would flood it by hitting the prime too many times.  After it runs for 15 seconds and then stalls, it will not start up again unless I prime for 3-5 times.  Once it is running, I have tried to spray starter fluid into the throat but that does not help and seems to have the same affect as giving it some throttle.  It seems to stall the engine out.  I have not tried to hit the prime when it is running. 

I was concerned that when I cover the throat with my hand, there does not appear to be much suction from the throat (i.e. air flow from air filter removed).  If there is not a good air flow, would that explain why the engine is not running?

How do I check the valve lash?  Also, how do I perform the leakdown test?  It sounds like I'd need to know when the piston is in the compression stroke and then forcing air into the spark plug hole.  Would that have to be pressurized air to hear for a leak threw exhaust or carb?

-Pete

>>>It will generally start 3 or 4 times but never run for more than 30 seconds.  After that, it will not start so I assume that eventually I would flood it by hitting the prime too many times.

   If it starts then runs it’s not flooded from 3-4 primes.  Some primers dump in a lot on one push and others only a small amount.   You can check for flooding by pulling the plug.

 

>> > After it runs for 15 seconds and then stalls, it will not start up again unless I prime for 3-5 times.

    This could be just a dirty carb.

 

>>>  Once it is running, I have tried to spray starter fluid into the throat but that does not help and seems to have the same affect as giving it some throttle.  It seems to stall the engine out.  I have not tried to hit the prime when it is running. 

You have to work the primer just right with slow steady primes to get the amount right.  Keeping it running with a spray can is a bit harder.

 

>>>I was concerned that when I cover the throat with my hand, there does not appear to be much suction from the throat (i.e. air flow from air filter removed).  If there is not a good air flow, would that explain why the engine is not running?

    Yes, could be.

 

>>>How do I check the valve lash?

   Take off the head cover and check with a feeler gauge.  There are videos on utube.

 

>>> Also, how do I perform the leakdown test?

A dual pressure gage set reads air in on one and pressure in the engine on the other.  A good engine will read 95% on the engine side compared to the air fed in.  The %5 leak is expected.  The more the leak % the more questionable the engine. Yes, you listen around for where the loss is.

 

 >>>It sounds like I'd need to know when the piston is in the compression stroke and then forcing air into the spark plug hole.  Would that have to be pressurized air to hear for a leak threw exhaust or carb?

   Yes, also head and oil fill.

 

   You description is a bit different than at first.  You could have just a line block, needle seat block, needle seat problem or other area dirt.  Check your carb linkage that the butterfly is opening fully when starting.