LCT 208cc pulsing - Snowblower Forum : Snow Blower Forums
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post #1 of 14 Old 01-31-2017, 09:05 AM Thread Starter
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LCT 208cc pulsing

I'm working on a power (not so ) Smart blower and it is pulsing pretty badly with small backfiring every now and then, It's only a yr old and jets are all clean. Plan to pull and check whole carb for any blockage but what else could be causing this, first Tim working on a LTC and don't know if there are any known issues that can cause this. Might suggest to the owner to have the adjustable needle installed but not so sure it's just a lean condition because only way it doesn't surge is with full choke on, Part way closed and it still surges. Kind of stumped because I've never seen this before, usually a cleaned out jet fixes it right up, not sure if there is even a idle jet but it has no throttle on this thing, either on or off. I like older machines much better.
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post #2 of 14 Old 01-31-2017, 09:21 AM
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if an engine i am working on has a surging issue and a thorough carb cleaning has been done, i use one of these adjustable main jets a forum member sells. they work great. a lot of powermore engines seem to have this issue, but i very rarely see predators with this issue, they are usually set perfectly from the factory. i would also recommend that you install a fuel shutoff valve for your client, and teach him to run the carb dry and drain the carb bowl at the end of each season. make sure to pry off the plastic idle jet below the idle adjustment screw using a flathead screwdriver, they are usually black but i have seen red and yellow ones. i stock these

5PCS 1/4'' Carb Carburettor Fuel Shut-Off Valve Straight Inline Replace 698138 | eBay

and these

5pcs 1/4" Inline 90 Degree Gas Fuel Shut Cut Off Valves For ATV Mower Bike New

in my shop and make sure my customers know how to use them, and tell them no warranty on fuel system repair unless they use the valve

follow this cleaning chart, it will be the same process as cleaning a honda gx series carburetor. the jet i referred to above is below #6


Last edited by 43128; 01-31-2017 at 09:28 AM.
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post #3 of 14 Old 01-31-2017, 10:05 AM
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If you are sure the idle and main jets and circuits are clean then you may have to modify something. I would double check everything and blow it out with compresses air after soaking in carb cleaner for a few minutes. I use a rubber tip on the hand gun to get blow out the jets. I made a small diameter extension tube glued to a rubber tip to get into tight spaces.

The Honda Pics by 43128 above are a great guide in understanding the cirucits and give you guidance on how best to clean them. I assume the carb on this machine is very similar to a honda carb.

If you can wait for a shipment to arrive I would get the adjustable jet on ebay that John makes and sells.
It will work and give you plenty of adjustment for future issues.

You can slightly open the main jet your self with a micro drill or some have used a torch cleaning tip and file it open.

I am not sure what size main jet the Power Smart snow blower engine uses. The Predator comes with an .028, I believe. Many people on here have been happy with the .032 jet for winter use. It solved my surging issues. Good Luck.

Current machines
Ariens 926LE

Yard Machine 22" upgraded with 6.5 HP Predator

Last edited by Toro-8-2-4; 01-31-2017 at 10:08 AM.
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post #4 of 14 Old 01-31-2017, 11:54 AM
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Great answers so far, I've been using .035 drill in a pin vise, from a set that i got from the welding supply store. That seems to get rid of the surging on most of these with fixed jets. Smooths them out without too much fuel. GLuck, Jay
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post #5 of 14 Old 01-31-2017, 12:10 PM
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If i am not mistaken i believe LCT uses old tecumseh carb tech i just did one that was surging.

make sure the idle circuit ports are clear (they control the fuel when not under load and will cause surgineg) the one that was clogged was where the main jet screws into the emulsion tube chamber.

Disassembly, Cleaning and Repair of Tecumseh Carb 640342 on a Sears 143.025071 Engine

Ariens ProPath 21 208cc ...honda HS621 GX160
Toro 621 6hp 4 cycle ....Craftsman SS ???
....Honda HS624 GX160 Toro 828 lxe Tecumseh 8hp
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post #6 of 14 Old 01-31-2017, 01:55 PM
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just took a look at the lct carbs on ebay and most are the same type that honda uses, but some of them look like mikuni clones while most honda clone engines use carburetors extremily similar to the keihin carbs used on the honda gx engines
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post #7 of 14 Old 01-31-2017, 02:05 PM
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It has been my experience that even after a thorough cleaning both mechanically and chemically sometimes the effects of ethanol have corroded the tiniest of carb passages beyond repair and a replacement carb is the only answer. Also be careful when drilling out jets as drill bits leave tiny swirl marks in soft materials like brass and disrupt the flow of liquids. Drill bits also drill progressively larger holes the duller they get. Since most of us will not have access to reamers small enough for this job. I have used an acetylene torch tip cleaner with some success in the past. They look just like the tool in the above drawing.
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post #8 of 14 Old 01-31-2017, 06:00 PM Thread Starter
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I have access to all the tools actually(I work in a machine shop), Had the carb completely apart except what I think is the low speed needle, Had a metal cap over the hole and not sure if it needs to be there for air blockage, Checked the jet with gauge pins and it IS already at .032 so thinking I am going to have to pop that little metal cap off, Will it be a issue if it's not there? and where can I get another if it IS needed? You all have been very helpful and I'm loving the info coming in here on this machine. Well anyway, I do have it back together ATM and in the run position it is still pulsing, But one click of choke and it smooths out. Usable I know but I want this to run in the run position for the owner.

OK re read the upper posts, For the idle jet Yes I did pull the plastic plug, THAT is what they use for a idle jet??? I'm liking the older machines more and more now, But it and the passages are clean. No corrosion on this one, it was purchased last year and stared one summer and the carb looks brand new inside and out, I even have a 10 power scope to inspect the juts for any minute damage and these are all clean. OH and I pulled the mighty "Torch" plug out, I had one on hand that's the wrong heat but it's actually running a little better, What plug would you recommend as a good replacement on this?

Last edited by Dauntae; 01-31-2017 at 06:18 PM.
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post #9 of 14 Old 01-31-2017, 06:40 PM
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The plastic idle circuit jet needs to be opened up about 2 drill sizes bigger
I think I went from a 76 - 74. I just found one that just fit n went up 2 sizes. it should stop the surging on the LCT 208CC
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post #10 of 14 Old 01-31-2017, 06:51 PM
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An engine just running full throttle no load will be drawing Bout 1/2 - 3/4 its feul supply off the idle circuit.
Under load and ON the governor , Butterfly wide open is the domain of the main jet still a little feed from the idle circuit.
If you try to mask the surge from opening up the main too big at wide open butterfly on the governor it will be pig rich
and foul plugs low on power.
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