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Discussion Starter #1
What is the best and easiest way to diagnose a leaking exhaust valve on a tecumseh 8hp? I do believe that might be the problem with my engine since i can see glowing red inside of the muffler with occasional spitting out of bluish flames out of the muffler while using machine at night.
 

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I'd say you've already diagnosed it. The valve hanging open is allowing still combusting hot gases to leak into your muffler and to burn there.You need to check your valve clearance soon. MH
 

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I just did 2 of my engines (HM80)...much easier than I anticipated. If your head bolts come out, then this job should be pretty straightforward. Order a new head gasket, breather gaskets and hit the auto store for a lapping tool, lapping compound and a feeler gauge. Seafoam + a nylon brush makes short work of the piles of carbon that you'll likely find! :cool:
 

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Discussion Starter #7
Only problem with waiting for spring, is this is my only machine. I might just soak up the head bolts over x-mas time and tackle that after the holidays.
 

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Only problem with waiting for spring, is this is my only machine. I might just soak up the head bolts over x-mas time and tackle that after the holidays.
I'm with ya! What I'm saying is that you may be able to correct the gross problem by doing a simple seafoam decarb (you don't have to pull the head).

One warning, it smokes like CRAZY from all of that crud burning off! :eek:
 

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Discussion Starter #9
Yeah, read the link you posted... can just see the curious bitter neighbors bitchin' hahaha. Thanks for the info, will mull on it and see what I do. My other neighbor offered me his honda in case of emergency. I huess it's Christmas after all hahaha.
 

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Yeah, read the link you posted... can just see the curious bitter neighbors bitchin' hahaha. Thanks for the info, will mull on it and see what I do. My other neighbor offered me his honda in case of emergency. I huess it's Christmas after all hahaha.
Oh yes...'Tis the season of giving...and receiving! :p
 

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Discussion Starter #12
Thanks Tim, I was thinking the same thing... after all, no use to do all that work when springs are the culprits...
 

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in many cases the cause of the problem is the valve reseeding into the valve seat causing a lose of clearance or lash between the lifter and the valve stem. The lash on that engine should be between .008 and .012 if i remember correctly. Check the clearance on the exhaust valve with the intake valve slightly open to insure the exhaust should be closed. If you have too little clearance you will need to remove the valve file or grind the stem down to get the correct clearance.

here is a youtube link

 

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Discussion Starter #14
Got everything apart... now time to get the feeler gauge going. Up to now, springs are intact and no visible looseness noticed. Some carbon build up on top of valves and piston but everything looks good, even cylinder wall is smooth. What would be next step if everything is specs?
 

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Does this engine have points/condenser? If so I would check ignition timing. Late timing would cause the exhaust to be hotter than normal. Or possibly a lean condition.
 

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Discussion Starter #18
Valves are lapped and gaped, de-carbed with seafoam, only waiting on my valve spring compressor to put it all together. Anxious to see the end results.
 

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In a pinch, I've used a 7/16 open ended wrench, with holding the valve down with my thumb. I just slide the wrench, retainer and spring, into the breather opening. Coaxed it into position, slide the valve down, and carefully compress the spring by prying up. Call me cheap , and follow the safety suggestions above.
 

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I have compressed the valve springs in a vise and used two small nylon ty-raps 180 degrees apart to hold the spring compressed. After inserting on the valve stem, cut the ty-raps and pull them out with pliers. As Stated, use eye protection, just in case. :eek:
 
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