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Discussion Starter #1
Hey guys, I have an older (1999-2000 I believe) MTD Gold 2-cycle with a HSK845/850 engine in it. It really stinks when running and tends to make a "popping" or "bouncing" sound to it. There is some white smoke on startup, and I notice a little while running.

Now this is a "backup" snowblower, it starts right up on the first pull and runs with good power. I am just wondering if anything can be done about the smell and what the heck is that popping sound?

Is the popping the equivalent of a miss? I know it is a new plug, gapped properly. Do the coils get weak on these?

I run some sort of synthetic 2-stroke oil in it mixed 50:1 per the instructions. The oil I use is red in color.
 

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Sounds like it's just running a little lean Dennis..... typically the popping is an ndicator of that anyway. BUT - the smell can also mean it's rich and there is some unspent fuel being discharged and "lit" in the muffler. Do you get a bunch of smoke when you first start it? If yes then it's rich and you can adjust the carb to a more lean condition. Some carbs are not adjustable however..... see some of Donnyboys vid's on youtube about tuning a carb
 

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Discussion Starter #4
Well, I decided to replace the coil, since the Champion plug I pulled was a little wet when I was checking it out...

So, got the coil in, pulled the top-cover of the snowblower off, pulled the muffler to check it out and I was surprised to see basically no carbon on the exhaust port. Only a oily stained port. In looking in the cylinder with the piston down you can see there is minimal scuffing to the wall, minimal scuffing on the piston, rings are clean, basically there is no carbon anywhere but the top of the piston itself, and there is no blue heat marks or anything else.

The muffler has an almost clean exit pipe.

I just mix the gas with a 50:1 ratio, no stronger. I also use seafoam in the gas in the recommended 1oz per gallon strength. I know the oil I use has stabilizer built in, but I figure the seafoam has other benefits as well.

I also did a compression test. With the gauge hooked up and one single complete full pull on the starter cord I get 90psi. I do know when I turn it over slowly I only get like 30psi per cycle. I don't know the proper way to get a good reading on a 2-cycle, but I figure a complete pull of the starter cord would pretty much give me a good idea what it has.

So, I got the new coil on, got it back together. I must say I got a hold of a pretty decent machine as in no rust at all on the outside, nothing inside the chassis, only very minimal by the scrapper bar/paddles. All the bolts came out smoothly.

I started it up and it runs strong, but it pops like crazy. I pulled the plug to see it was dry and the color looked good, maybe a little blackish on the insulator, but I considering it was darker black and wet before I did the coil I can only imagine the coil helped.

I looked up some videos on 2-cycle HSK845/HSK850 engines and even tho I saw some that smoked way more than mine, it seemed like the ones I watched had almost no popping to them while running.

I guess I am equating the popping to a misfire condition. I guess it could be a rich or lean condition as well. The **** carbs for these are still cost-prohibitive (like $90+), otherwise I would just replace it. Could the carb just need to be taken off and rebuilt?

Like I said it does start on the first pull. I would just like it to run smoothly without popping.

Is the clean but oily look in the exhaust port concerning? I did notice a whole bunch of gunk in the muffler and it looks like a bunch of it was liquified and oozing out of the seams. But who knows if this is the original muffler??? Even if it is does that mean the someone de-carboned it in the past before I got it?

I will say with the new coil it only seems to smoke a bit on startup and cleans up quickly. It was night-time when I ran it so I can't say for sure that it is cleaner while running after warming up.

The OCD side of me wants to splurge on a new electric starter (the guy that sold me the snowblower must have taken the electric starter off to sell for extra cash, boy do I despise scummy profiteers like that), since I already bought a new coil, new gas cap (old one has the seal in the top breaking apart), new scrapper bar, spark plug cap (mine was missing), and I will probably end up ordering new paddles and a new belt. But, it does start on a single pull without fail, so an electric starter would probably be overkill. Then again, I would rather the wife and kids use this one instead of my Cub Cadet 221 LHP, so who knows I may just splurge for the electric starter when all is said and done.

Any feedback on the engine would be appreciated. I really would like to know why this one pops and a bunch I have seen online don't. I already tried to see if there was an adjustable carb available for the HSK850 and I still can't find one. The complete engien number is: HSK850-8327C

I will say I get vibrations from the popping that is noticeable, thus my major concern. If it is just that I need to pull and rebuild the carb completely, so be it. I just don't want to go through all that work to find it is something else entirely. Especially if my carb is in perfect running condition as it is.
 

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Discussion Starter #5
well, went out and did some work on it, turns out I have to cut down an allen-wrench to get the carb off, so I did as much as I could while it is still installed.

I found out the vent on the side of the carb was plugged, got some wire through that to clear it up..

Then I pulled the bowl and cleaned out the carb nut/jet... seemed clear already...

I also pulled the float and needle valve... Here is where it gets interesting... Turns out the needle valve does not have a seat installed. The float also does not have a damper spring on it.

I figure I will order a rebuild kit to get the seat, but is the damper spring needed?

Could the needle valve missing a seat and a damper spring cause my popping?
 

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Does the carb parts list/diagram show a needle seat?

This is only speculation on my part, nothing more. But if it was supposed to have a needle seat, and it didn't, I'd expect the needle wouldn't actually seal the valve closed. And in that case, I'd expect the gas from the tank to keep filling the bowl until the carb starts to drip, or maybe allows liquid gas to overflow into the intake. The engine would likely run poorly in either case, I expect acting as if it were too rich (which it would be).

Again, this is just me thinking out loud. I'm curious to learn from those with more experience, about what might actually happen.

Oh, for compression tests, I'm used to just pulling fast until the reading stops climbing. In my opinion, using just a single pull doesn't tell you much.

Every compression tester has some volume of air inside it, a cavity that must be filled with compressed air from the engine. This is the hose, the sparkplug adapter (if used), etc. Most testers have a 1-way valve at the tip of the hose, so air can be pushed into the hose, but not come back out again.

If you have a small engine (chainsaw, etc), maybe it compresses 1 cubic inch of air with the piston at TDC. Let's say this air is at 100 psi. But if your compression tester's air volume is also 1 cubic inch, then if you turn the engine over once, you will only measure 50 psi. 100 psi of 1 in^3 air, but now filling 2 in^3 of volume, including the compression tester, so it will show 50 psi.

But remember that there's a 1-way valve at the beginning of the hose. So keep pulling, and with every compression stroke, a little more air gets pushed into the tester's air volume. Pull until the reading stabilizes, and you still may not get a reading of exactly 100 psi, but you'll get a lot closer to reality.

Use fast pulls on the cord, to minimize the air being allowed out of the cylinder by the automatic compression release, if it has one.
 

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If there was no seat in there the gas would just run out of the carb and never shut off essentially? I think you would notice that..? Some of them do have a spring in there to keep the float from bouncing. It wouldn't hurt to add one in there. Kinda tricky to get it back together.
 

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Discussion Starter #8
Thanks for the reply.

As far as the seat, both parts listings (one for the original 640093 and the newer 640309) both list a seat. They also both list a float damper spring. As far as I can tell only the 2-cycles have damper springs.

I ordered up a Tecumseh seat/float tool along with a mini-rebuild kit (new needle valve, seat, retaining spring, bowl gasket, nut gasket), along with the float damper spring.

Once everything comes in I will get it all setup properly. I figure the way it is the needle valve just seals enough into the upper seat orifice. But, that means the bowl is over-filled as well. That might just be my overly rich condition, which I can assume can cause popping?

Or at the very least the rocking of the engine would cause the float to bobble, and without a seat it would inconsistently dump extra fuel here and there, thus causing the popping as well? (basically it is flooding the engine off and on?)
 

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I figure I will order a rebuild kit to get the seat, but is the damper spring needed?

Could the needle valve missing a seat and a damper spring cause my popping?
If the needle seat is actually missing, the carb would be leaking gas like crazy and I doubt the engine would run at all. The seat maybe discolored and appear to be missing so look closely in the bore.

The float spring is typically used on machines that are subject to a lot of bouncing around, such as roto tillers. The spring is not needed on a snow blower but could be added if you wanted.

There is an over lap of the intake and exhaust ports which will cause some popping and may be more noticeable if the muffler isn't up to par.
 

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Discussion Starter #10
Thanks guys, I did double check and the needle valve seat is there.

I already have the parts I mentioned ordered, so I will be replacing the seat, the needle valve, adding the float spring and double-checking the float height.

So, a bad muffler can make it sound like it is missing left and right?

I mean, while running I can tell the popping actually affects the power output as I notice it as vibration in-time with the popping.

Hmm, I wonder if the flywheel isn't out of time? Is it common for these things with electric starters to shear flywheel keys?

I already replaced the CDI module and used a business card to set the gap, so I should be good there.

The max PSI on a single pull for a compression check is about 95psi. From what I gather it is in good shape. Again, I noticed no carbon on the sides of the piston, not carbon in the rings, no major scoring in the cylinder (only counted like 3 or 4 marks on the intake side), no major scoring on the side of the piston either (this time 2 or 3 small scratches, again nothing to be worried about). And when I mention marks it is a single 1 fine line mar.

I just can't see someone buying one of these and having popping like this from the factory. So, if that is the case and they are supposed to run smooth without popping, I want to fix this one so it doesn't do it either.
 

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I wouldn't be surprised to feel it, if the pop is a misfire. You'd suddenly miss a power stroke, so you'd probably feel that.

If the flywheel key had sheared, I'd expect it would run consistently weird. The idea that the flywheel could be in-time, shift out of time for a instant causing a pop, and then back in-time, seems unlikely to me. The flywheel key could perhaps be sheared by a starter, or something else, I suppose, if the flywheel nut was too-loose, reducing the friction on the crankshaft's taper.

Is it possible that something is grounding out the ignition for an instant? Do you have an inline ignition tester, so you could see if the igition-flashing suddenly stopped at the same time that you heard a pop? That could help understand if it's related to the presence of a spark (it wouldn't tell you about timing/flywheel key, of course).
 

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Discussion Starter #12
I actually tore everything down, except for the shortblock. The carb is off, cleaned up awaiting parts.

I also pulled the new ignition, pulled the nut and pull starter cup and the flywheel is on the key and the key appears to be in the slot. So it doesn't look like it is out of time.

I really don't get it either in regards to the ignition. I will put a manual ground wire on it and take the ignition key out of the equation (just in case that is the problem) when I redo it.

The magnet on the flywheel seems to be plenty strong.

The kicker is these things are so simple it is amazing they can have any issues outside of spark and compression.

I wonder if carbon on top of the piston could be causing issues?

That is the only place I could see any carbon buildup, on the very top of the piston itself. Even that didn't look too bad though, but it did appear to be an even layer. But without even a hint of carbon on the exhaust port I am hesitant to blame the top of the piston.

So, what is the best way to clean carbon off the top of the piston? I know the service manual only talks about removing carbon out of the exhaust port.
 

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So, what is the best way to clean carbon off the top of the piston? I know the service manual only talks about removing carbon out of the exhaust port.
seafoam & a nylon brush is a gentle/effective way for doing a decarb.
 

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I've used a wooden scraper to remove carbon. I'd think that carbon would increase the compression ratio, and could cause hot spots that can light off the fuel charge before the spark plug fires.

I could see it causing preignition (pinging), in a severe case, but it doesn't seem like it would cause misfiring, to me.
 

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Discussion Starter #15
Well, I will give it a go with some seafoam and a nylon brush though the exhust ports...

One thing I noticed is the plug I have in there is a CJ8Y. Now, I know the newer packages of these plugs show it it as a CJ8Y/RCJ8Y, but I can only assume it shouldn't matter if it is resistor or not on this setup? I tried a E3.12 (listed for this application) just to be sure, but it didn't make a difference in how it ran at all.

I can pickup another plug, but I figure it even if I order a RCJ8Y, the plug I end up getting will be labeled exactly the same as a CJ8Y.
 

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Well, I will give it a go with some seafoam and a nylon brush though the exhust ports...

One thing I noticed is the plug I have in there is a CJ8Y. Now, I know the newer packages of these plugs show it it as a CJ8Y/RCJ8Y, but I can only assume it shouldn't matter if it is resistor or not on this setup? I tried a E3.12 (listed for this application) just to be sure, but it didn't make a difference in how it ran at all.

I can pickup another plug, but I figure it even if I order a RCJ8Y, the plug I end up getting will be labeled exactly the same as a CJ8Y.
I've mic'd business cards and the're not all the same thickness. And check to see if there any possible striking points.
 

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Discussion Starter #17
I've mic'd business cards and the're not all the same thickness.
Yeah, this one is exactly .0120" thick... Definitely close enough considering spec is .0125".

I have already totally stripped the machine... I ordered a new auger and idler pulley along with new bearings. There was a little excess play in the left side wheel because that is the side with the engine on it, so I just pulled a bolt and swapped the axle and wheels around to balance it back out.

I also have bent up a L-strap to use as a flywheel cover to support frame mounting bracket for the back to help stiffen things...

Next I will be wire brushing the minimal surface rust (noticed a couple of powdercoat bubbles, even the the outside is rust free) and then I will use POR-15 to paint the inside of the auger housing, then I can hit it with some Valspar gloss black tractor paint.

Once I get the parts in next week I will have it totally finished. All new parts, spent about $110 on everything (not including the paddles for the old auger), but I figure it will be good as new when finished. Oh, totally forgot I need to also put together a list of stainless hardware I need to buy.

I figure the best way to combat rust on all the bolt holes that thread into the sheet metal is to use some Super-Lube while assembling and making sure the sheetmetal itself doesn't have any exposed raw steel. The stainless fasteners and grease should keep things from rusting in the future.

I am also going to see about fabbing up a stainless steel "strip" to go over the area the scrapper bar bolts to in the auger housing to stiffen it up. That is the only thing I will say about this design blower is that area tends to "bend up" when people hit expansion joints and stuff.

I am conflicted on how high I should go with the RPMs... I know "spec" is 4000rpm +- 300, so 4300 rpm is "max". But since I have heard they set these up initially to run at 3600-3800 rpm I am thinking 4000rpm is a good mid-point without going crazy.

Is there any way to get these things to stink less and smoke less?

I get the smoking on startup, just for 2-4 seconds, then it mostly goes away once the choke is turned off, and you can tell just a hint of smoke while it is running. Again, I don't know how much of that is because of possible missing and such (even though I must say, I listened to about every video online of 2-cycle 4/5HP tecumseh snowblowers and they all, except for one or two, which might just be recording issues, have the sputtering/popping I am referring to).

Once things are back-together I will take a video of it running and then I can hopefully get some feedback on how it sounds.
 

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Discussion Starter #18
Well, I was cleaning stuff up and noticed a little seepage on the underside of the motor from the where the bottom of the case mates up to the upper portion.

So, since I am considering disassembling the bottom, should I go as far as to pull the crank/piston out and cleanout the inside of the chamber and piston?

Since I am that far, should I look to replace the rings and do a quick cleanup hone on the cylinder?

I assume if I go that far I am going to have to replace the needle bearings on the rod to crank interface.

It looks to be about a cost of $31 for the Loctite 515 to seal the bottom to the upper halves, the needle bearings for the rod and the new rings.

Or, is there an alternative to using Loctite 515 on the bottom and should I just say screw it and pull the bottom, reseal it and leave it all alone?
 

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In my minds eye - it's not that old of a motor so I wouldn't go any further. Snowblowers just don't get the hours on them like mowers do. If you lived in Nova Scotia it migh tbe another story....
 

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I'm probably being too-simplistic. But I doubt I would split the engine in the first place :)

If your needle valve may be leaking a bit, it's conceivable that it is slowly letting gas leak from the tank into the bowl. Which may eventually overflow and make its way through the carb body, to the intake.

On a 4-stroke, this gas would contaminate the crankcase oil, which can be a serious problem. But on a 2-stroke, it might just collect in the bottom of the crankcase, then get burned/blown out when you start the engine. This could contribute to extra smoke at startup. And it could also contribute to fuel/oil slowly leaking past the crankcase seal, giving seepage.

So perhaps your seepage is a symptom of the possible carb issue? I'd probably clean up the outside of the engine, and rebuild the carb. Then once it's running again, see if the seepage continues. Honestly, if it wasn't causing a crankcase vacuum leak or something similarly "meaningful", I'd personally be inclined to just leave it :icon_whistling:
 
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