Generator

[longbedder]

I've got a Coleman Powermate Maxa 5000 ER generator. It has a 10HP Tecumseh engine (Model HM100 engine, L-head design). It was last run in October in the demo derby pits.

I went to fire it up last night just for maintenance purposes, and had just changed the oil. I spun it over a few times (recoil start only) and it wouldn't quite catch, so I pulled the spark plug to check for fouling. While the plug was out I yanked the starter just to free-spin it, and the engine made a "clunk" and stopped turning.

I pulled the recoil assembly off the end of the crankshaft, and the crank will turn backwards about 3/4-turn, and then back to where it was but not a bit further in either direction. It was late and I was tired, so I said, "Fock it" and grabbed a beer.

Soooo, what are your guesses for what I'm up against?

 

[wasted wages]

Loosen the bolts and pull off the generator first...it could be the coupler broke apart or the rotor in the generator is striking some thing....

Have to determin which won't rotate 360 degrees first...

 

[longbedder]

Yeah, I figure it's gonna take more beer and disassembly until I find some broken part somewhere.

I did use a flshlight and look through the cooling louvers in the generator end and couldn't see anything.

 

[Fordum]

Well, my first thought was that something fell in the spark plug hole, but I would expect it to turn farther backwards than that.

Well, I went back and reread your post, and 3/4 turn might be about right. Is your sparkplug in one piece?

Thinking part of the insulator on the bottom may have fallen off.
Shine a light in the hole and see if it stops just as the piston approaches TDC. If so, then there is probably something on top of the piston.

 

[longbedder]

It's not the sparkplug (or pieces thereof). I checked that first.

I also looked into the bore with a light already - couldn't see anything useful, as the plug hole is out of line with the bore. If it was an OHV engine, I'd say I was smacking a valve with the piston, but it's an L-head.

It is stopping near TDC.

Oh well - I'm not skeered of troubleshooting. I just wondered if someone has had a similar experience with this setup.

 

[Fordum]

Sure sounds like something in the cylinder. Saw a piece of carbon break off and do the same thing on an engine that was badly carboned up.

Only other suggestion I got, is to rock it back and forth and listen closely to see if you can tell where the clunk is coming from.

Unless its obviously coming from the generator end, I would pull the head.

 

[longbedder]

Sure sounds like something in the cylinder

I would agree. I ran the shop vac over the plug hole to no avail. I may bend a piece of wire and see if I can sweep all the way across the piston top next.

 

[Fordum]

Problem with the vac, is that if its something hard with any kind of sharp part, its probably embedded in the top of the aluminum piston.
You might knock it loose with the wire and then get it with the vac.

 

[diesel4me]

I've seen quite a few Tecumsehs inhale one of the throttle butterfly screws,and imbed it into the piston,or it gets caught under a valve head.......evidently many didn't get locktite or staked in place at the factory...............................................................................................If its something worse like a connecting rod cap bolt that came out,or the cam ,lifters,etc,you can buy a generator version of that HM100 brand new,from www.surpluscenter.com for 135 bucks,they have about 120 of them left in stock last time I looked..they have a crank PTO thats 1-3/8" stepped down to 7/8" then it tapers down,and has a tapped hole in its end for the rotor bolt...

 

[longbedder]

I've seen quite a few Tecumsehs inhale one of the throttle butterfly screws,and imbed it into the piston,or it gets caught under a valve head.......evidently many didn't get locktite or staked in place at the factory...............................................................................................If its something worse like a connecting rod cap bolt that came out,or the cam ,lifters,etc,you can buy a generator version of that HM100 brand new,from www.surpluscenter.com for 135 bucks,they have about 120 of them left in stock last time I looked..they have a crank PTO thats 1-3/8" stepped down to 7/8" then it tapers down,and has a tapped hole in its end for the rotor bolt...

Cool - thanks!

 

[diesel4me]

Better hurry if you want one of those new engines,as of last night when I looked ,they had only 90 of them left!.......guess they are selling fast!...Getting Tecumseh parts can be a challenge lately,as they went belly up about 5 years ago,but some companies are now making reproduction parts to a limited degree..

 

[longbedder]

Better hurry if you want one of those new engines,as of last night when I looked ,they had only 90 of them left!.......guess they are selling fast!...Getting Tecumseh parts can be a challenge lately,as they went belly up about 5 years ago,but some companies are now making reproduction parts to a limited degree..

I'll probably try the wire trick and tear the head off tomorrow morning, as debris seems to be the #1 possibility. The last thing I did before it stopped turning was pull the plug, so I'm betting there was a bit of something in the plug well or I chunked off some carbon like Fordum suggested.

If it's debris, then it's a new head gasket and I'm back in business (as long as the piston is OK). If it's something that's going to cost a significant amount, I may just save up for an 1800RPM diesel generator - it's a little ironic: I was actually thinking about the diesels before this problem cropped up. I was grumbling about having to keep gasoline fresh, plugs unfouled, etc. Oh, and the noise - the Tecumsehs at 3600RPM are straight-up banshees!

 

[diesel4me]

Cheapest way to get a good 1800 RPM generator is to look for one from an older Winnebago type RV,they had twin cylinder Onan engines about 16 HP that are quiet and can be hooked up to a car muffler pretty easily....most put out 5000+ watts too..only bummer about Onans is parts are real high in price now that Cummins owns then,and are sometimes hard to find............................................................................................................................................................................................................I bought a Lincoln gas powered welder/generator off CL for 125 bucks a few years back-- with a CCKA Onan 16 HP ,the same engine those RV generators use,that have a tapered crankshaft..I had another Onan off a street sweeper thats 24 HP ,I wanted to swap onto the welder when I learned it smoked badly on one cylinder and had a rap after getting a stuck exhaust valve freed up on it..unfortunately my 24 HP Onan has a 1-7/16" "straight" crankshaft,it wont work...........................................................................................................................................................................................................sucks,because I've always wanted a gas powered DC welder,I never have been able to use my AC buzz box one well here due to lack of proper wiring and amperage..and I could take the welder anywhere too,and not have to listen to whining about the increase in the eletcric bill every time I go to weld something up too...so far I've left it together,in case I have to sell it--at least as it sits it can be used and I could show a potential buyer it does weld,run and generate...in a basket case scenerio,I'd be lucky to get scrap value out of it...I learned the generator part of it is 50 cylcle AC too,so its not good to run anything frequency sensitive off it too,and its 110V AC only..no 220V tap,so I couldn't run our well pump with it..