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

    The results of Borats Craftman seem pretty good even in comparison to the newer Toro's with 141cc engines and curved paddles runing stock rpm.  I gave up on MTD straight paddles a few years ago so stopped buying them. BUT given the good showing of Borats machine decided to give an HSK850 a fling for which a cheap MTD or Murray is a good candidate.

   This morning I picked up an MTD 5.5 in excellent shape, (mostly) for $100.   The body is excellent, no rust no scratches but the inside of the bucked has the paint scrapped.  The guys 3 car lot was sand and gravel with mounds and holes.  It's electric start, 4-5 years old but only used for two seasons due the owners heart condition. 

    It came with a line cord and for some reason three brand new belts, a bottle of Sta-Bil and a gallon and a half can of gas half full.  His son gave it to him with a bottle of Sta-Bil which he thought was the mix required.   He only ran it with Sta-Bil, no oil and from what he tells me only ran about slightly less than a gallon of gas through it since he got it.  He claimed that one can of gas half full he gave me was the only fuel he ever bought for it.  

   It fired up on the first pull and seemed to run strong so I ignored the no oil part and bought it.  It gets 95psi compression on three rope pulls and 115 on electric start so seems ok. 

Borat,

    I'd like to compare the flat paddle section of this one to yours.  If you can please measure your mid-paddle section flats.  What's the L and W of one section and what's the distance front to back?  The MTD is (2) 1 3/4 x 4 1/4 sections and the front to back span is 8 1/4.  If they match then the MTD should compare your Murray with booted RPM.  I've got an excellent condition Toro 3650 I'm using this year so have a good machine to compare with.

I've been looking at the spark plug heat ranges for HSK850 engine.  The Champion RCJ8Y is the equivalent to the NGK BPMR4A.  Number 4 on the NGK scale sounds kind of hot to me.  Most machines I operate run in th 6 to 8 range.  They're generally air cooled two stroke motorcycle engines with no fan cooling.  I'd say that if the engine is going to be run hard and long, I'd probably lean toward a NGK plug in the 6 range.   If it weren't for all the effort it takes to get at the spark plug, I'd pull the one on  the Craftsman to see how it looks.  

It's safer to run a cooler plug than a hotter plug.  One thing we have to remember is that with the added RPMs, there's also added fan speed which produces more air across the cylinder head and around the cylinder.  With relatively cold air keeping things cooler, the engine might be fine with the stock plug.   Maybe tomorrow I'll cut a flap/hole over the engine head to access the spark plug.  Might as well cut a hole big enough to get my whole hand down in there.  I can see dropping the plug sooner or later and having to fish it out of the belly pan.   Going to be a pain in the butt to get the location right unless I pull the lid off of it and I really don't want to do that.  Especially in the cold.  

Damn you and your foresight Trouts!!  I never thought of the spark plug heat range issue on the hopped up machine.  Now I have to know!

Edited this morning....

I found this chart published by Champion that cross references heat ranges between different brands of spark plugs.  According to the chart, the "8" series Champions are equivalent to the "7" series NGKs.  if that's the case, the RCJ8Y should be alright.  It's not all that hot of a plug.  The BPMR4A is a fairly hot plug as rated by NGK.  Which leads me to another quandary,  if there is that much of a difference in heat range between the two brands, how does an NGK BPMR4A qualify as a replacement plug for the RCJ8Y?   Something doesn't sound right.   Comment?

I edited the above post to include more information concerning spark plug heat ranges in the HSK850 engine.

Looking for additional input and comments concerning the differences between the Champion and NGK brand heat range comparisons.

Did a bit more research.  It seems that the RCJ8Y is a common plug used in grass trimmers, chainsaws and other small, high revving two cycle engines that will be run in hot ambient temperatures.   With this recent acknowledgement, I'm not as concerned about the stock spark plug being used in a higher revving HSK850.  After all, the Tecumseh will not likely be spinning past 6500 rpm and usually working in cool conditions.  Many of the chainsaws using the same plug do twice that and much hotter conditions.   

I was looking around a month or so ago, trying to figure out NGK equivalents for the Champion plugs in my "new" machines. I'd been seeing comments that people prefer NGK to Champion, so figured I'd give NGK a shot. I was looking around to replace an RCY8Y, I think it was, and I was finding suggestions for either the BMPR4A or the BMPR6A. But I couldn't find a consistent answer (and I did not have your multi-brand cross reference, borat), so I was worried I might end up making things worse if I picked the wrong heat range. Finally just gave up and bought the suggested Champion plugs. I've never really had a problem with them, so I figured why potentially foul the plug or whatever because I picked the wrong substitute?

Your chart would fairly clearly make it sound like the 6A plug would have been a better match. But I wasn't sure. They don't go out of their way to make it easy to figure out a replacement.

Edit: These are two cross-reference documents I found while reading up on this previously. Maybe they'll help someone. As a point of reference, for NGK replacements for an RCJ8Y, the first link shows BPMR6A. The second link shows BPMR6A, BPMR4A, and BP6ES.

http://www.sparkplugs.co.uk/pages/technical/Champion-to-NGK-cross-ref.htm

http://www.jsesc.com/mfg_docs/ste/Spark_Plug_Interchange.pdf

For some reason, the information that I've been gathering leave me a bit unsettled regarding the comparative heat ranges.  The information on chart, although published by Champion is quite a bit different than proposed cross-equivalent plugs between NGK and Champion.  Three heat ranges difference "7" on the chart and "4" on the recommended NGK plug doesn't appeal very well to my logic.  Regardless, as per my edited message above, I've come to the conclusion the the RCJ8Y is likely cool/hot enough to work well in the HSK850. 

I've got several hours of hard work on my Craftsman with no signs of problems.  It just keeps on keeping on.  The only time it slows down or stops is when it runs out of fuel.


edit...

An NGK 6 makes much more sense.  Why some vendors recommend the NGK 4 is beyond me unless the actual heat  variance between a 4 and a 6 is not that great operationally. 

Regardless, I'm satisfied enough not to bother pulling the Craftsman apart.   When the temperatures warm up, I still think I'll make an access door in the cover to make spark plug maintenance easier. 

RedOctobyr: a mystery hole in the back, facing the operator

   Often there’s an empty opening for models sold without optional electric start.

 

RedOctobyr: I can't just pop it on to quickly check the RPM'

   Last year 4 machines were setup with wires on the plugs running to the handlebars.  That end had a quick connect and the mate on a short wire on the RPM meter.  It worked out OK for static readings but underway snowblowing the machines are changing speeds rapidly.  The small variations in load cause the RP M meter to re-compute which takes a few seconds and it presents fuzzy readings until the machine gets more stable.  I was looking monitor engine sagging and that usually happened too fast and unsteady for the meter’s response time.  That was on two stages which are much more stable than single stage machines.  On the riding mower things are more stable and the meters readout well but for those a few readings with a vibratech and you know what’s going on so a fixed meter there is not so worth the effort.

 

boratify- (v) to enhance the performance and value of an engine for very little money, by increasing RPM's, esp. by means of a string on the governor. Usage- "My snowthrower was OK, but kind of underpowered. But then I boratified it, and now it's awesome!"

 

Great definition.  Can that expand?  To borat…..When borating…..When finally borated…..

 

Borat and RedOctobyr:

  

    I had poked around last week because the dealer sold me a Honda BR4HS and my machines call for 6 and 8’s.  ??  Not sure why but I’m going to get the spec’d plugs.

 

   For all the reading I did what I’ve come up with on plugs is use what’s spec’d unless there’s a consistent plug condition that indicates going up or down would help.

 

   My asking about plug temp was for overall chamber temp.  It looks like the dissipation on a plug is so local that it won’t have any effect on the chamber.  So that’s out.

 

    For raised temps getting lowered by running a cooler plug.  ??  All I got from looking into that was confused.  Getting to know for sure requires equipment and test procedures I can’t do.  The only view into this is probably noting when the engine explodes, melts or throws a rod.  Better than that would be as you suggest, monitor the plug occasionally.  That’s easy, telling enough and probably all that’s required.

 

   An interesting point Borat made was that some OPE that scream and use 6 and 8’s at least by Champion charts.  Using an 8 in a pushed HSK850 will probably be fine.

 

   In some of the heat range stuff they talk about fitting a plug into a 500 to 800 degree range.  The heat ranges are big and broad so picking a plug you don’t really know about other than by 4, 6 or 8 indicating a temp range you don’t know for internal temps you don’t know is too much to deal with.  I give up.  The result of all that whatever is knowable by pulling the plug and having a look.  If something is suspected and another range might help then the charts are somewhat helpful for a ball-parking another range. 

 

  After mucking with the boratified machines 4000 seems like slow motion. 

 

"After mucking with the boratified machines 4000 seems like slow motion."

No kidding. 

I can't get my head around why single stage snow blowers were never manufactured with a throttle similar to a chainsaw?   What could possibly be the reason not to do it?  Just don't make sense to me.   Since modifying the Craftsman and seeing how soooo much better it is, I'm even more bewildered.

Maybe too much of a good thing.  With SS machine performance like that, they might not sell as many dual stage machines.  Who knows? 

trouts2, excellent points:
- You're probably right on the mystery hole on my machine. Mine does not have electric start, but it was an option. That must be what the hole's for, thanks.

- Tachs: I'll admit I'm not quite sure what the connector that you're talking about is for. But my Tiny Tach type device has 2 wires, one that you ground to the engine, and a wire that you wrap around the spark plug wire. You reminded me of something I'd been thinking about before, along the lines of what you described. Perhaps I could wrap another wire around the plug wire, and run that out to somewhere accessible. Then, to check the RPM's, I might be able to wrap the tach wire around *that* one. I don't know if that would work, however, since the tach would not actually be wrapped around the plug wire.

- Definitions: The dangerous verb would be to over-boratify. Something along the lines of "I boratified my machine to 6000 and I loved it. So I decided to try for 9000, and over-boratified it. Now I have a hole in the block" Kids, boratifying is done by trained professionals in a controlled environment, and should not be attempted without adult supervision. boratifying involves risk, past performance is not necessarily indicative of future results; may cause dry mouth, sweaty palms, envious neighbors, and childlike glee as the snow flies further than it ever has before. Consult a medical professional if symptoms persist more than 4 hours.

borat, that's a good question. Realistically, the higher RPM's will increase the wear on the engine (higher inertial loads), add to vibration, possibly start to take their toll on motor mounts, cause more wear on the belt as it engages, use more gas, more noise, etc. My manual makes note that the brake must be adjusted to stop the paddles within 5 seconds or something. The higher speeds would increase the time it takes for everything to stop. These are at least some of the "theoretical" drawbacks, I couldn't say whether any of them are actually significant (eg- maybe the lifespan of the engine goes from 800 hours to 700 hours, and no one will ever care). And I'm willing to replace a belt more often if it means much better performance, gas usage is very small anyhow, etc, so many of us might be OK with those tradeoffs. But then again the people here tend to be more of  "enthusiasts" vs the general public.

It's certainly an interesting question as to whether they avoided adding a throttle to try and stay away from cannibalizing 2-stage sales. One argument could be that an appeal of a SS is its simplicity and lack of controls. So it's friendly to use. Do these 2 things to start it, then just squeeze this handle. Less intimidating than the multiple levers and handles on my 2-stage, I suppose. Add a throttle, and you start to get away from that slightly. You'd have to set the throttle such that the default was a normal snow-blowing speed, and you could also squeeze it to rev even faster. You couldn't do it like a chainsaw, where no throttle input means very little happens.

Actually, as I type this, I think I saw someone make mention of an old (60's-70's?) machine their family owned which had kind of an "extra power" button or lever. You used that, and you'd get a little more out of the engine. It might have been on a SS, I don't recall. So perhaps some company did try something along those lines?

>>>Perhaps I could wrap another wire around the plug wire, and run that out to somewhere accessible.

   That's it.  I got lengths of hookup wire 6 feet long.   One end of that wire wrapped around the plug.  The other end ran up the handlebars.    A simllar wire was run from ground to the handlebars.   The tack wires got the mating connectors.  The tach could be detached and moved from machine to machine.  The tach did not get mounted perminantly.  Each time it was just put on the machine dash, plugged in and taped down.   Four machines were setup that way so one tach could be moved around.  I had a few tachs and some machines got "perminant" mounts and others connect wires only. I did not like leaving the tach out all winter. 

     Vanilla hookup wire is not shielded and engines can generate electrical noise of many frequencies that could interfere with the plug signals.   I also tried some Belden shielded signal wire which was very small like 20 but it did not improve response time. 

     What you need is a nice warm afternoon, open up the SS and install the wire.  Give the wire around the plug 4-5 tight wraps and electrical tape over that.  Then run it up the handlebars.   The harder part is planting the gauge where it will stay, not vibrate off and be easily removable.  One possibility is to get some thin aluminum plate about the size of the gauge and form it to an L  with foot of the L part just larger than the thickness of the gauge.  Drill a hole in the L foot and another through the handlebars at the side.  Bolt on the L and epoxy velcro on the tall section of the L and the back of the gauge. 

I put a Tach lead on my Toro  machine as well while I had the cover off.  Way too much work removing the cover to not do it.  I didn't leave a wire on the Craftsman or MTD because it's not all that important once the lower rpm is set.  It's not much more than an idle on those two.  On the Toro however, being set at a fixed rpm is where the machine works.  Hence the necessity to ensure it's set right.   I made  a couple wraps around the spark plug lead then used a small tie wrap to keep it there.   See pic below.  No sure why the picture is so big.  I resized it to 400 x400????

 Took the picture out.  It was screwing up Trout's post.

One thing that I wanted to re-iterate is the point of ensuring the oil ratio is changed to deal with the added load on the engine.  I've always been a believer in using a bit more oil than less.   Two cycles are hard working engines and have scant amounts of lubrication running through them.  Despite the fact that lower oil to fuel ratios will work, you can rest assured that a bit more oil will enhance performance and durability.  Particularly when the engine is being run beyond the normal parameters of the engine's operation.  Not that I'm all that worried about the engine's durability.    Four thousand rpm, in my opinion is not much more than a lively idle for any decent two cycle engine. I believe the HSK850 is designed and built well enough to handle far more than the 4000 rpm lope of a snow blower.    

RedOctobyr wrote:

I think you hit the nail on the head there.  Mfrs. are always looking for ways to dumb down their products - saves them many phone calls/rma's from idiots trying to figure out how/when to operate throttles, etc.

The other issue is, I would guess, emissions regulations.  I think even OPE is regulated somewhat, and probably even more in the near future, and that is why throttles are locked on most new OPE.  The mfr. can reduce emissions significantly if they allow the engine to run at only one speed.  They can also maximize fuel efficiency for that one engine speed, and that helps out their emissions issues, too.