Abby's Guide to Outdoor Power Equipment (Lawn Mowers, Snow Blowers, Chain Saws and more)
Username Password
Discussions Reviews More Guides
Abby’s Guide > Outdoor Power Equipment (Lawn Mowers, Snow Blowers, Chain Saws and more) > Discussions > Tecumseh HM80 flywheel magnets and coil question.

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

Search For:
jrtrebor


Location: Michigan - 3 hours north of Chicago on the lake
Joined: Feb 10, 2010
Points: 526

Tecumseh HM80 flywheel magnets and coil question.
Original Message   Mar 5, 2010 11:07 pm
I've got a 8hp model #155634s tecumseh. Having some major running rich problems. Was wondering if anyone knows where the flywheel magnet should be in relation to the solid state coil. When the piston is at TDC. I had checked the keyway once before and it was fine. But the engine runs very, very rich. It will start up. It will idle just fine. But when you run it up you'll get a short burst of dense gas vapor out of the muffler. It will then run at higher rpm and fairly well (but your eyes almost burn because it's running so rich). If you then idle it back down shut it off, plug the plug. The plug and in the cyl. are wet with fuel. Had different carbs on it, EPA carbs with different jets. So I don't think it's a carb problem. Replaced the head gasket. Checked valve clearance twice. Put a different coil on it. Then today when I pulled the plug after running it. I noticed it was also wet around the plug hole underneath the plug washer and the bottom of the plug washer was also wet. So now I'm wondering if I have a problem with the plug threads in the head. That is keeping the plug from seating tight against the head (even though the plug feels tight when you tighten it down). It idles so well and there isn't any real signs of compression leakage at the plug. But maybe it's just loose enough to drop the compression ratio and keeping the fuel from fully burning. I don't know. I'm really kind of stumped right now. This could be one of those times when there are multiple problems and you don't know it. Back to my original question. Right now when the piston is right at TDC the magnet has completely cleared the coil. Don't know if that is correct. I also pulled the piston out today and found the oil ring and second compression ring end gap were aligned. With the compression ring end gap only 1/2" to one side of the other two. Though fixing that was going to take care of things, WRONG. Tomorrow I guess I will try a different head. If that doesn't work the whole thing is coming apart (again) and I'm going to, I guess check clearance on the rings, piston everything don't know what else to do. Any help would appreciated. I feel like I'm missing something but I don't know what it is.
Replies: 1 - 4 of 4View as Outline
friiy


Location: Las Vegas, The Desert
Joined: Apr 12, 2008
Points: 600

Re: Tecumseh HM80 flywheel magnets and coil question.
Reply #1   Mar 6, 2010 7:58 am
     The magnets should be clear or past the center point of the magneto..   A Magneto only fires (all systems) at  the highest densisty of magnetic flux, called "e-gap" on the dischage of the coil as the magnets are passed/ passing the arm. 

      I don't think you have compound problems, you may have created a few ..   You seem to be in this engine pretty deep,  Are you sure you timing marks on the cam and crank are correct?

      Changing carbs? epa Carbs?....    These carbs may all fit the same engines, but the carbs are made for the same engines doing diffrent things.... Put the original carb back on..  You may have a Vent on the carb that is blocked because it is mismatched with the wrong intake manifold / gasket or the carb is trying to run position (throttle setting) that the carb is not manufactured to pull a load at.. 

     The spark plug gasket on the plug is a crush gasket,  even though they seal fairly well more than once,  they are made to only to seal once..   I bet you have had this plug off alot right?   I supect it will leak now...    Not to worry it will not effect running of the engine..  Don't change the head.. 

      Have you checked the valve seats in your travels through this engine,  how is the valve surface? or the valve guides... These issues may cause a rich running motor...

    What was the first problem you had that made you want to break into this engine so deep?  

   We need a little more info to work this out..

Good Luck,

Friiy

jrtrebor


Location: Michigan - 3 hours north of Chicago on the lake
Joined: Feb 10, 2010
Points: 526

Re: Tecumseh HM80 flywheel magnets and coil question.
Reply #2   Mar 6, 2010 10:06 am
Thanks for your reply. A little history on the engine. I bought it at a weekly auction. It was said to be new. Didn't have any oil in it just a small amount of red fluid that I assumed was some type of assembly lube. I removed the muffler to install a different type. Will be using it on a snow blower so I put on the correct one when using a carb heat box. The exhaust port was perfectly clean no soot / carbon of any kind same inside muffler. So I assumed that it was indeed a new engine. It also had an Impluse fuel pump on it, mounted behind and just below the carb. I removed the pump and placed a rubber cap over the block fitting for the fuel pump. Put the tank on it and connected the fuel line as it would normally be set up. I'm familiar with the reason for using an Impulse fuel pump (remote tank). And the "pulse fitting" that the block has for operating the pump. But not sure if you can just remove the pump and cap the block fitting the way I have ?? The breather vent tube was connected to the air cleaner backing plate. I removed that vent tube (won't be using an air cleaner) and installed a typical one that just points downward. Make sure that the drain holes of the breather assembly were down and put the breather back on the block. I do have the original (epa) carb back on it. The bowl nut is stamped 163. Which I guess is the jet size. In answer to your question about the valves and seats. I haven't yet checked them because I was assuming they were okay judging by the condition of the engine. But maybe there not. Have checked the valve timing (crank and cam gear marks) an the punch and chisel marks are aligned. I have had the plug out quite a few times. So I'm sure the crush gasket has been flattened. I may go ahead and put another plug in it. ( J19LM) I will take some pictures and maybe shoot some video of what the engine is doing. I also had to install a throttle plate on the engine shroud for controlling the throttle. Believe I've gotten the gov. rod and butterfly rod in the right holes. But I don't believe that those things would affect the rich running problem?? Thanks for your suggestions and help. And you could be right I may created a few of the problems myself. Taking into consideration the condition of the engine. Nothing was making logical sense, so I started looking for problems in illogical places.
friiy


Location: Las Vegas, The Desert
Joined: Apr 12, 2008
Points: 600

Re: Tecumseh HM80 flywheel magnets and coil question.
Reply #3   Mar 6, 2010 10:49 pm
Disregard looking at the valves,  That all should be good... I was assuming this was a Used engine..Take a little video of how it runs,  Idling,  mid speed and full throttle..

kinda point out what it is doing..   It is very rare that a new engine  fails,  Does this happen with both carbs? (same Symptoms).. I would try a good ND or NGK plug,  The Champ plug that is in it is a resistor plug (and the cheapest thing they make).   I have had those bad from the box at the shop.

Also, take a look at and post a few pictures of your govenor links and set up of the throttle plate,,,

Does this unit have a oil alert on it ? (low oil shut off)...

Ok..

Good Luck,

Friiy

jrtrebor


Location: Michigan - 3 hours north of Chicago on the lake
Joined: Feb 10, 2010
Points: 526

Re: Tecumseh HM80 flywheel magnets and coil question.
Reply #4   Mar 6, 2010 11:39 pm
Well this has been a very interesting saga. The engine as I said was purchased from an auction. I've actually purchased 4 of them in different conditions. This one was described as being new, never used. And judging by the way it looked as I described in my last post I assumed the description was correct. It was clean as a whistle. But, when I had the head off today I took a good look and the cyl. walls. They are in great condition, but you can't see any cross hatching. So how does a supposedly new engine not show any cross hatching (accept at the very top of the bore) ? And if it's not new if it had been used / run how in the world did someone get the ports perfectly clean. And I do mean perfectly clean??? Who knows. Anyway, when I went to get a new head gasket I was explaining and talking to the guy about all of this and what things I've been running across with this engine. He said he believed that it was probably the one of both of the o rings on the throttle tube that were bad. And that gas was being sucked by them causing the over rich condition. Made sense seeing as how the engine idles perfectly and starts up pretty well. I hadn't even considered looking at the o rings assuming that they were new. I'm also not that familiar with the EPA carbs and any problems that they may sometimes have. So I pulled the tube out of the carb. the top o ring looked okay. But the bottom one was pretty out of shape it almost looked like it had a small flange on it one the bottom ( I guess from the pressure of the bowl not) . And one side looked a little flat. The top of the throttle tube also looked rough. Almost jagged and saw tooth like. The guy at the shop of course was out of the kit. And the other shop had already closed for the day. So I'll have to wait until next week to get the carb back together and on the engine. Hope that takes care of things. Sounds like it might. Would at least explain why the engine runs fairly well but extremely rich. Also to answer your question. It does not have an oil alert on it. I would love to post some pictures of the throttle / gov linkage for you to take a look at. But I'm having the same problem I read that your having. I don't have a toolbar that is supposed to show up above the message box. Don't know how to fix that problem. Hoping someone will post a fix. I have a Mac running Safari and was thinking maybe that is the problem. Just don't know. Will let you know what happen when I get the carb back on. Would be interested in what you think about that being the cause of my problem. Thanks again for your input I really appreciate it.
This message was modified Mar 6, 2010 by jrtrebor
Replies: 1 - 4 of 4View as Outline
Outdoor Power Equipment (Lawn Mowers, Snow Blowers, Chain Saws and more) Guide   •   Discussions  Reviews  
AbbysGuide.com   About Us   Terms of Use   Privacy Policy   Contact Us
Copyright 1998-2014 AbbysGuide.com. All rights reserved.
Site by Take 42