Export thread

Hey all, have a 10hp Tecumseh HM100 engine off a John Deere Snowblower that's giving me some trouble. As winter is coming and Lake Erie is giving me that leery look, I did my usual maintenance on the snowblower. Checked belts, changed spark plug, replaced oil, added fresh gas, and even removed and cleaned the carb. Didn't find any junk in the carb, which was promising. Got her all back together, and did the carb adjustment procedure in the manual. Dialed needle valve till finger tight, backed off 1 1/2 turn, choked, primed, fired right up. Turned needle in till she got rough, out till she got rough, split the difference. She sits fine at full throttle. Slowed her down, did the idle speed adjustment needle on the carb (same procedure).

Throttle back up to full and now that she's nice and warm drop the drive lever, engage the belt and the engine starts slowing and returning to full throttle. I can see the throttle linkage going in/out. Problem gets more pronounced when I hit the auger as well putting more load on the engine.

What would you guys do? Tweak the carb a little first? Or might this be a governor problem? Or perhaps some nefarious fuel or exhaust trouble?

Tecumseh Service Manuals Locate your manual & see troubleshooting section, let us know what you find, thanks.

Posted this earlier today,but it also applies to your problem.


Take the carb off and remove the float bowl. Tip the carb upside down and look to see if the float is level. I'll bet that the side opposite the hinge pin is higher. If it is I would follow this procedure and replace the float needle and seat with kit number 631021B. We're getting snowblowers ready around here and I do at least one of these carb rebuilds a day.

Needle and seat replacement

Remove the carb, and then remove the float bowl. Check the float bowl jet (which is the bowl screw) and make sure the jets both horizontal and vertical are clean and open. Tip the carb upside down and remove the float pin and float with needle attached. Look in the float needle passage and you should see the red float seat at the bottom of the passage. This is where a #5 crotchet hook would come in handy as you need to remove this seat. If you have no hook, but compressed air, you can blow through the fuel inlet and try to pop the seat out. Put your thumb over the passage to prevent the seat from flying who knows where. No air or hook try bending a stiff paper clip to dig the seat out.

I would either give the carb a good 24 hour soaking or have it ultrasonically cleaned at this time.

With the seat out clean the passage way with carb cleaner. Now you must find a drill bit slightly smaller than the passage way, to be used to press in the new seat. Apply a very, very small amount of a very light lube to the new seat. 3-1 oil or lighter, to help seat it better. Carefully insert the new seat in the passage way with the rings on the seat down toward the carb body. Slowly and carefully force the seat down with the back end of the drill bit. Once it is seated, check to see that it did not flip and the rings are up. *Next check to make sure that the float does not have any liquid in it. *If it does, replace. *If everything looks correct, attach the new needle to the float and install with the float pin centered. It everything is correct, the float should seat level to the carb body, when looking at it upside down. If everything looks good reattach the float bowl, making sure that both the bowl gasket and the nut gasket seal properly. Reinstall on the engine and test unit. Remember to have patience and take your time. Good luck, but I don't think you'll need it.

PS: *On the side of some Tecumseh carbs you will find a plastic cover. *Under this cover will be an idle jet. *Remove it and check to see that the jet is open both horizontally and vertically. *You should be able to push the old float needle wire through the vertical opening.

Thanks guys. Will start with a carb rebuild and then move to governor adjustment I guess? Parts in on saturday so wish me luck.

Why rebuild and adjust the carb when you can get a new one for $25?

I would love to know where you will find a good carb for this engine for $25????

http://www.google.com/aclk?sa=L&ai=...%2Flike%2F281215553476%3Flpid%3D82&adtype=pla
http://www.google.com/aclk?sa=L&ai=...%2Flike%2F231109590577%3Flpid%3D82&adtype=pla

Don't know how they got those prices, as they are well below dealer costs. Are they Tecumseh carbs or knockoffs?

I doubt they are genuine Tecumseh carbs, but they could be. I don't think it matters whether the carb is OEM or not. So many things are made in China these days that the aftermarket and OEM could be the same quality.

If they work fine, but for $5 they can clean the carb and rebuild and get back to work. The posters on this forum are looking for help and have more time than money. I know cleaning carbs with my procedure works, because I average one plus carb cleaning every day and can do it cheaper than what it costs me to replace it. I will admit that it is cheaper to replace Honda carbs, but all others I clean first.

How do you get $5? I have never seen a carb kit that cheap. I have had so many failed carb rebuilds that I prefer to replace the carbs.

Tecumseh #631021 and Briggs #398188 are the two kits I use most often and can be purchased for less than $5. Most of the time you don't need new needles and welch plugs if you know how to clean them, using my procedure. Just spraying with carb cleaner and running a wiring through holes won't do the job.

I clean my carbs with an ultrasonic cleaner which I got for $60 at Harbor Freight, and then blow them out with compressed air. I stopped using carb cleaner after it ate a hole through the side of a metal carburetor.

If you have read any of my posts, you will see I also use an ultrasonic cleaner with SimpleGreen as my cleaner. Only time I use the gallon bucket of cleaner to soak a carb, is if they are extremely dirty. Ultrasonic gets turned on every morning when I punchin and is always kept hot. Only have to replace less than 10% of the carbs, 90% come clean after one 8 minute cycle.

These are made in China, there is no high speed adj. They work but are not the same as the original Tecumseh carb. I do not think that they will perform as well or last. I would rebuild. Just my 2 cents worth.

These days even the OEM carb could be made in China.

Well, I live in Buffalo, and those of you not living in a hole know what it's been like here the last week... Mercifully I was able to tweak the full throttle adjustment on the bottom and get it to run well at full throttle and full load. And full load wasn't a problem with all this Fing snow. Anyways, the snow is finally removed and we're warming up here with a good week break from it, so I just took the carb off. Lo and behold there is no seat for the needle in it. It's just straight up not there. Can't imagine how I was able to get it to work without one, but whatever. Will be replacing it within the hour. One question though if anyone's still reading this. The rebuild kit came with 4 parts. The main bowl ring, needle, needle seat, and another Oring/washer about 3/8" in outside diameter. Is this for the full throttle jet to seal to the bottom of the bowl?

OK well something's fishy here. This snowblower is used to me, so I'm not even sure if it has an original carb on it. I'm guessing it doesnt because there is no seat and the needle itself has a rubber tip. If I insert the seat into the carb, there isn't enough clearance for the needle to sit in it along with the float. It pushes the float too far "down" in normal operation. There are no real markings on the carb itself, just the numbers 516 on the side near the idle speed adjustment screw. I'm gonna go ahead and re-assemble here cause any way you slice it I don't have the parts to fix it and see if you guys have other advice. I can suffer with it working the way it does, but I'd of course rather fix it the right way.

Sorry i didnt get back to you sooner, its deer hunting season in Wisconsin and didn't have Internet access. You are correct, that carb is no original to that engine. If it has a rubber tip, my suggestion at this time is to put the carb back together, with the original carb pieces you have. Set the float height slightly rich, meaning the side of the float away from the float pin, is a little lower than the pin side. Reassemble and install on unit. Adjust the carb as you did before. Once things slow down for you, would you post a picture of the carb and we'll try to identify it and start this process over to help you.

Well, if anyone's still reading this, somehow I remain alive. Buried under more snow than I've ever seen in my life here in Buffalo and that's saying something. Remember that whole, "once things slow down for you" comment? Yeah, well, Mount SkiFletch here pictured at the end will offer some perspective :frown:. Long story short I've managed to limp the snowblower along. I've had to run it for long periods at half choke. Eventually, it warms up enough so it starts actually choking out, I pull the choke off and quickly dial back the carb rich and I'm able to keep it from faltering and run. It's definitely rich. Can smell the unburnt fuel, muffler gets REALLY hot, and the spark plug has gone full carbon by now (roughly 100 hours). Can barely get it to run with the plug like this, though that shouldn't be surprising.

So first off, enough of this cheap Chinese junk carb, where can I find a quality carb that will work with my engine? Don't care what it costs.

Second, When I pulled the plug, I put a compression tester I borrowed from a friend on the engine just to make sure. Having never used one, and not knowing what I should be seeing, here's what I got. One pull, pressure up to 30 lbs, held there. Two pulls up to 60lbs, stayed put. Three pulls up to 90lbs, stayed there too. Couldn't pull it after that. Is that what I should be seeing for this engine?

Thanks again for the info guys

Your symptoms definitely indicate a lean running engine on startup. When you close the, choke you are increasing the richness of the fuel/air ratio. As the engine warms up, it does not need as rich a mixture, so you open the choke. As I posted earlier, you need to rebuild this carb and after reinstalling it you will have Togo through the adjustment procedure unlined in the manual. As for your cmpression reading, they are a bit low, but if the engine is cold that could be a factor in the low readings. I doubt that the carb on you HM100 is a Chinese knockoff. It was produce long before we had the influx of knockoffs. Post the spec numbers of your engine and I'll find you a new carb.

Thanks for your help Rivets. The reason I'm pretty sure I don't have an original carb is cause I ordered Tecumseh #631021 rebuild kit. When I dis-assemble my carb, it does not have a rubber seat in the needle hole. Instead where the seat should sit is just solid metal and the needle itself has a rubber tip. Every Tecumseh carb rebuild video I've watched all over youtube shows a full metal needle with a rubber seat. Furthermore, the washer that is supposed to fit between the bottom of the bowl and the lower adjustment from the carb kit does not fit the carburetor that I have.

Here's a picture of the code atop the engine. It's off a John Deere TRS 32 whose manual indicates the engine is a Tecumseh Snow King HMSK100. I'll take a pic of the carb I have when I get home tonight, but for now, here's the engine info which I happen to have on my phone .

As to your thoughts regarding the compression, yes, this was done with the engine at atmospheric temp (not warmed at all); which since I've been transported from Buffalo to the planet Hoth this winter (you guys in Wisconsin feel the temperature pain) was around 0 degrees F at time of testing.

Thanks again for your help, it's MUCH appreciated. Off to buy a spark plug to get through another snowstorm this weekend :thumbdown:.

Checked your numbers and have found that carbs are still available. The carb you need is #632370A. You should be able to get it through your local repair shop, if you want to go that route or order it online. Depending on which route you go prices range from $50-$100. Good luck and if you need more help, post back. PS: Temp this morning -16, wind 21 MPH, nice day to work outside.

Thanks for tracking down the part number. So I went out after work and got a replacement spark plug. Tossed it in there, primed it up and gave it a pull. It started running a bit at full choke but then died out on me. Not unexpected since I had it dialed very rich. So I backed the carb needle out a little, re primed and tried pulling. It felt a little stuck. So I gave a harder pull, and it turned over and ripped the starter chord out the engine. It sputtered a bit then spat exhaust gas out the carb for maybe 3 cycles before stopping. Thoughts while I fix the starter chord?

Sounds like the float needle has given it's last gasp, not shutting off properly. Cylinder filled with gas. Check the oil level and make sure the crankcase has not filled with gas. If no gas in the oil, you can run the unit.

Understood. What would I see on the dipstick if it's got gas in it? A strange runny appearance?

Edit. Looks like the kick back broke the spring in the starter cable. It won't wind anymore. Guess I'll be purchasing that too

OK, checked the dipstick, looks like good oil only in there, proper level. Of course my pull cable is still not working. Here's where things get fun. My father tells me that he just threw away a snowblower with a Tecumseh engine that had compression problems (things that could have been brought to my attention yesterday!). So what did I do? Go dumpster diving for parts in -30 wind chills. Hah. Cut the belts, removed the 4 mounting bolts and just took out the whole engine. It was mercifully not windy inside the dumpster. Anyways, get it home and find DOH, it's not an HMSK100. It's an HMSK90 . The recoil does not fit in the fitting on the flywheel of my engine. And I don't have a pipe wrench big enough to grab the fitting to loosen them and swap. So I'm back to square one leaving me with two questions:

First, any chance anybody knows the part number for the recoil on my engine? I'll call around locally and see what I can find tomorrow and pray someone has one. Cause it's gonna snow again sat night and I REALLY don't want to try and shovel and pick snow up 7' over Mt Skifletch.

Second, would any of the parts from this HMSK90 fit on my 100? Or, in a crazy option, could I just swap engines on the snowblower assuming I can get this other one to run? Go full on franken snowblower

Thanks for all your help

Part number for starter is 590689B. Sorry to say, but there are parts that will interchange between the two engines, although not any of the ones you need. Local shop may have a used starter around, I would check with them before ordering.

Thanks Rivets. I was unable to find one locally but did manage to repair it myself by removing the pin, taking it apart, re attaching the spring, re winding and re assembling. Blower ran much better with a new spark plug but is still back firing out the carb especially on startup. Looks like the weather is breaking here soon and I can try a new carb on it. Praying there isn't an exhaust valve or cam problem that's contributing

So I just had an epiphany. What if the reason it's ripping the handle out of my grasp when starting is because the flywheel key is messed up? Would that cause the problem? Furthermore, anybody know the part number for the flywheel key?

Flywheel key number is 32589. Yes, a sheared key will definitely cause a kickback.

This may help to easy your mind about the key

Thanks guys. This is cheap, easy, and the guy down the street has them in stock. Gonna pick one up in a couple of days and give it a try.

So after slight struggle I managed to get the flywheel off this afternoon. They key didn't look perfect, but it also didn't look all that damaged either... I replaced it anyway and still have the ripping the handle out of my hand thing when starting. There's not a whole lot to this it looks like right? The magnet on the flywheel crosses the transformer, jacks the voltage, and creates the spark right? In theory this happens at top dead center so the piston drives back down and continues the clockwise motion of the crank shaft when looking at the flywheel end. If the spark fires too soon, OR the piston does not reach top dead center when it should, the spark happens, fires and knocks the crankshaft counter clockwise ripping the chord out of my hand. Interestingly enough, once I get it started, it runs fine. Still not perfect at no choke with the junk carb with the surging, but it runs and sounds smooth.

So given that the flywheel does not look damaged and they key is new, what else can I chase? Is there something I can adjust with the position of the flywheel magnet, or the magneto/transformer itself? Or should I be chasing a mechanical problem with the crankshaft/arm/piston? Am I right when I think if the crankshaft to piston arm joint was loose, it would be really rough/knocking and sound terrible? (cause it doesnt). What about if the joint between the arm and the head of the piston had play? Would that make noise? Cause if either of these joints are loose, the piston wouldn't reach TDC in time and have this trouble, but once there was some inertia, it would work fine right?

Sorry for all the thoughts/questions. Hope I'm making sense.

Just reread the entire thread and a few things popped out. First you are over thinking many things in your last post. I never seen any of those possibilities. I'm going to sound like a smart a-/(&, but please bear with me. Remember I am not there to see, hear or feel your problem. First, are you sure that you torqued the flywheel nut correctly. If it was a bit loose the key may have sheared again. If you feel you did it properly, do not got back and check. Second, I still think it may be a carb problem, so I would like you to try this procedure in adjusting the carb. If the carb is allowing too much fuel in at startup, a kick back could result.

Adjusting a carb
Ok, the first thing I would suggest is to reset the armature air gap with the single thickness of a business card, unless you are sure you have a gap of .010 inches. *I don't normally recommend doing it this way, but in your case it may be best. *Second, this is the procedure I always taught my students to adjust a carb with two fuel controlling needles.
1. *Start the engine and move the throttle control to top speed.
2. *Adjust the high speed needle (this is the one under the float bowl) clockwise very slowly until the engine starts * * *
** * to bog down.
3. *Back the needle out 1/8 turn, the engine should now run smoothly.
4. *Now move the throttle control down to idle. *If the engine stalls out turn the idle speed screw in one full turn,
** * restart the engine and bring the throttle control down to idle. *If the engine is running to fast, turn the speed*
** * screw slowly out until the engine seem to want to die and then in 1/8 turn.
5. *Now with the engine running, adjust the idle needle out until the either gains in RPM's or starts to bog down. *If
** * the engine gains in RPM's, continue to adjust out until the engine starts to bog down. *At this time turn the*
** * screw in 1/4 turn. *Now the engine may be running to fast, so turn the idle speed screw out until you get an*
** * RPM you like.
6. *Now you must repeat step 5. *If the engine bogs down right away turn idle needle back in to your starting point*
** * and go to step 7. *If it speeds up, repeat step 5 again.
7. *Turn idle needle in until the engine bogs down and then out 1/8 turn.
8. *Now the engine should run smoothly at all speeds.
9. *To check, set the engine to idle, then quickly push the throttle control tohigh speed. *If it dogs and does not*
** * come to speed, open the idle needle 1/8 turn and repeat.
10. Set to go.

There are 2 *reasons I have it done this way is, first the high speed needle controls the fuel going to the low speed circuit and second is that the idle needle controls how much fuel is used when going from idle to high speed. *You should also review the section in the manual I posted before starting this procedure.

Now if this does not solve the problem we will have to look at the valves. If the exhaust valve is sticking or not seating properly, hot gases may be igniting fresh fuel entering the cylinder causing kickback. This will mean that the head will need to be removed, so pickup a new head gasket before disaasembly. I don't know how far into this you want to go, just giving my thoughts. Will trade snow for our cold in payment for this advise. Let us know if you need more help.

Guilty as charged for over thinking things. As for the flywheel, I torqued the piss out of it with my impact wrench, so I'm pretty sure it's seated hard. I've got a new real OEM carb on the way on tuesday instead of this junky cheap POS with the rubber tipped needle. Will try your carb procedure with the new one.

As for the possible valve problem, I get how a sticking valve would cause hot gasses to auto ignite, but it does the ripping the handle out of my hand thing usually on the first pull when the engine is cold and hasn't turned over more than once. That's why I was more thinking timing issues as opposed to sticking exhaust valve.

And for the armature gap, I have gap measuring tools to check it. Not going to mess with it till later in the week cause it's going to snow, AGAIN tonight/tomorrow and it's running atm.

If it is kicking back only under cold starting, my guess is too rich a mixture and/or a sticking valve. Try starting with no choke.

primerbulb120 said:

These days even the OEM carb could be made in China.

Click to expand...

A lot of OEM is made in China but most of it is made to OEM specs.
The stuff that fails QC gets sold to evilbay discounters through middle men.
Then there are the copiers who get one, make something that looks similar and sell them into the distribution networks.
Big difference in quality.

Now as for the air gap pn the ignition coil.
The closer it is to the flywheel the earlier it will spark,
The further away it is from the flywheel, the latter it will spark.
Now we are not talking massive differences but it has been a tuning trick to tweak the beast out of these engines for a long time.
The other thing to "over think " about is the electronic ignition trigger.
A lot of these will revert to full advance when they are on the way out.
They are not replaceable in most engines being an inergral part of the coil.
You might like to try swapping the one from the 90 with yours.

The magnets should start to cross over the first leg of the coil before TDC and should be past the last leg as the piston starts to drop.
Contry to popular belief & terminology the advance unit does not advance at all. The coil is set in the full advance position & the "advance unit" retards the spark so they fail either completely or fail to the fully advancd position.
When in your position , just before I run the Gillette across my wrists I put a dollop of white paint on the flywheel where I can see it at the TDC position.
I then start & run the engine with a timing light on the plug lead ( you will need an external battery to power the lamp because of interference ).
At idle the spark should be on or slightly past your mark.
At full speed the spark should be before your mark.

Worth while doing if for no other reason than eliminating timing problems.
Also if it is inconsistant or flickering then you do have a coil problem

Thanks for the extra thoughts Berts. Still haven't had a chance to even look at the gap cause I'm not ripping it apart while it's still snowing. And since I continue to reside on the surface of Hoth, it may not be till late this week that I get a chance to dig into this. "They" were thinking rain on tuesday... Now 6" of snow

YATZHEE!

Tried checked gap, was fine. Maybe a SMIDGE loose with the checker but not worth messing with. Tried your procedure for tuning with old carb Rivets. No dice so I threw new real OEM carb in there. No problem with pull beckon startup, so was instantly excited. Ran through he tuning procedure, and voila! It idles smooth, runs FFB no problem. Gorgeous.

Lesson for anyone else that reads this far: you get what you pay for with those cheap Chinese knockoff carbs.

Thanks again to everyone that helped. Fired up!

We appreciate that you are letting us know about you success, most posters aren't that nice. Please make sure that you drain all the fuel from the float bowl at the end of the season, so you won't start next season with the same problem.

Oh you know it. Got at least a month before I'm willing to risk putting it away though. This is still Hoth, I mean Buffalo

mrmechanic said:

buy a new carb. that is what is going to fix your problem. We see 100's of these a year, 10% can be cleaned but 90% have to be replaced.

Click to expand...

I hope the web page you keep spruking works better than your eyes.
This post is closed the OP fixed his problem back LAST YEAR