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

  A newly acquired 5hp 70’s Ariens snowblower started fairly well over several days with test starts and running the engine for a minute.  Then it started a bit harder and just barely putted along having very week combustion after 10-to 16 cycles and died.  It’s been about the same every since then.  It won’t start easily now with gas through the carb.  I can get it going with gas through the plug but it only sputs along for about 10 cycles, very faintly and dies.

   It has 60psi compression after 5 pulls cold.  There was no to  very faint spark so I replaced the points which were pitted.  The spark is good but the same thing of running faintly for a short time and dies.

   My test of the coil was a little fuzzy so I replace the coil but the same thing happens.  It only starts by dumping gas through the plug and it does so in an unusual but consistent way.  I have to pull about 10 times and I hear a faint put or two with a slight breath of smoke.  The next pull or two a few more puts, the next pull about 6 to 10 puts, the next a couple then nothing.  I can do that over and over.  What’s unusual is that it never fires quickly but takes many pulls. 

   If I change the plug often it does not change things.  I check the spark and it seems very fine. I have a plug with the arm cutoff so the spark jumps to the rim.  I test the tester on other machines and their spark is about the same as on the 5hp. 

   Gas is not an issue, spark is not an issue, air is there.  I pulled the head and the gasket is fine.  The valves look ok.  The intake lightly covered with black carbon, the output a light brown ash.

   The timing is set as best I can set it.  The points gap is correct.  I don’t have a dial indicator so guessing BTDC, take off the point wire and use an ohmmeter so just get the points to open at BTDC.  I’m sure I’m at the right cycle as I’ve checked it over and over with a flashlight through the plug watching the valves and watching the key turn on the crank. I’m probably not on the money for BTDC but think I’m close enough.

   The only thing I can think of is if there was a compression leak from a wall crack or rings.  With 60 psi I think I should be running with no load fine.  It should at least run and sound like a good motor even it did not have any power. 

    I’ve obviously missed something so the reason I’m posting.  This business of running fine then within a few days very hard to start or no starting with running only for a short period and with very week combustions has happened before with a lawnmower and a chainsaw.  All very quickly deteriorated to non-starters unless gas was dumped into the plug.  When they did catch and only after many pulls they ran only for a short time and very weakly.  Since it’s happened three times it must have happened to someone else and be a fairly common thing but I’ve never seen a write-up on the web similar.

trouts

you check valve clearances between the valve stem (end of valve) and the lifter. and for checking piston gap you can use a feeler between the piston and cylinder wall.   hope that helps

Hey Touts'

I think you are going the wrong way on the valve job, A  snow machine works in a controlled work enviroment.. (lot- a -snow ,  not much dust and grit).  a lot of the engines we preform valve jobs on were mowers in dirty areas (grit eroding the valves, mostly intake),  or mowers that had plugged cooling fins that overheated the block and tipped the seats or pounded them into the case, (mostly exaust side)... or  floor buffer propane motors that would build large deposits in the chamber that break and lodge on the valve seat (ex side),   cheap generators that only run at full speed ALL the time do have valve and guide wear issues.  Other than the odd situations of throttle shaft screw ingestion, most valves on a aluminum bore engines outlast the most of the motor, sometimes they need to be adjusted  and lapped.  But  97% of the time they are just fine.

I would think before you had a worn valve, you might have a gummy intake stem..old gas varnish slowing down the intake valve when you crank it over. this can be unnoticeable when the engine is apart and you are turning it over by hand slowly.   So spray some type penetrating oil on the stems if you still have it apart and turn the valves to wash any sticky gas goo away.

Please, please, please,  pretty please set the points only at TDC.

Always best of luck,

Friiy

P.S.  If you are going to lap the Valves, in the field I have hot glued a wooden dowl to the valve face instead of valve lapping tool, and used a sharpie pen instead of Prussian Blue.. At very least it will show you the shape your valves are in.

niper99,

  

    OK, on the clearance check being between the valve stem end and its lifter.  I’m still fuzzy on what gets worked to change that distance.  I suppose when I get in there it will be obvious.

 

    The cylinder wall piston check is the part that confuses me.  I have a wide and thin set for plug gap checking.  They are flat and the wall curved so the I can’t see how jamming in a flat feeler would give an accurate measurement.  It seems a round gauge would have to be used.  I’ll have to google around for that.

 

 

friiy

 

>>I think you are going the wrong way on the valve job,

  That’s a high possibility.

 

>>a lot of the engines we perform valve jobs on were mowers in dirty areas (grit eroding

  OK, a lot of interesting info.  The high likelihood is not valves but if valves then not burnt but other issues.  The gummy stem is a new one for me.

 

>>Please, please, please,  pretty please set the points only at TDC.

 

   This is really my next step before messing with the valves.  I have just not gotten to it yet.  It seems that if it’s set to TDC and the valves or rings are marginal I should still get healthy combustions.  My readings were 60 dry and 80 wet.  I think that’s enough to get a proper sounding fire even if there is no power. 

 

  In a post above I mentioned not knowing just how much leeway there was in setting BTDC before poor performance becomes noticeable.  For example if I’m 5 thousands off or 20 thousands off where is the breakpoint for noticeably degraded performance?  I figured by setting to TDC I could eliminate any BTDC error so it’s on the top of the list.

 

   Bare with me I’m still learning a bunch.  This past year I’ve picked up a number of older snowblowers with mostly carb and gas related problems and learned a bunch.  Getting a non-starter or stumbling dog going by stripping the carb, flushing the tank and line and have a machine starting and running reliably in about 20 to 30 minutes.  This forum has a lot of good current and prior posts which I search all the time for info.  It’s been a big help.

 

   Some of these engines, like the current 5hp, have issues that possibly could be cleared up without too much work or expense.  I’m still learning how to deal with those things.

 

   The 5hp has an issue with valves or rings given the compression tests.  It should be able to fire though and before I go further with valves or rings clearing up the firing problem seems the first thing to do. 

trouts

Hey Touts,

You grind the stem of the valve  to adjust clearance of the valves ( a little goes a long way,  start slow - finish slow. Try to grind flat /square.)

Good Luck,

Friiy

    No luck on the timing adjustment.  The engine is a HS50 67008 and the BTDC setting .035.   I finally found a dial indicator with a long enough leg to take a reading. I found the timing set at .1 BTDC so .065 before BTDC.  The timing was reset  to.010 BTDC. 

 

   The flywheel was spun many times with a multimeter attached to the points arm to check over and over that it was on the compression stroke and the points were opening at .010 BTDC.

 

  The result was the same.  It would only start to fire after 8-10 pulls, very weakly, with one or two fires.  Then on the next few pulls a string of 2-4 weak fires.  No strong combustions so the same behavior as it has been before the new points, condenser and coil change.  It had the same behavior after the incorrect timing setting of .1 BTDC.  And the same behavior after setting .010 BTDC.

 

    My guess is it’s the valves or valves and rings.  The engine was hanging around for a long time.  I wonder if it was possible to have a wall or ring buildup that would seal the chamber for a while but get burnt off causing the apparent quick demise over a week.  Possibly some carbon got burnt off the valves which opened things up more all of a sudden. ??

    Valves are next then rings.

trouts2

trouts2 wrote:

trouts2,

just wondering if you set the timing to TDC yet ?. anyway l think your making this diagnose way to complicated stick to to the basics, SPARK/FUEL/COMPRESSION u need those three things before the engine will run, you have compression so l dont understand why u think its valves or rings?, and as far as timing goes l have never if my life set points with a multi meter or dail indicator ever, did you put another carb on this engine or repair the orignal one?, if the engine is pulling back while cranking then u have a timing problem period not maybe for sure,  any how elimanate one problem at a time make sure u have fuel then check compression then spark and as far as the valves go there non adjustable other than maching as fitty menthioned.

Niper99

 

>just wondering if you set the timing to TDC yet ?.

  No,  .010 BTDC is fine, close enough. 

 

>>l have never if my life set points with a multi meter or dail indicator ever

 

   Neither have I.  The points were set with a feeler gauge.  The timing was set with the multimeter and dial indicator.  You use the mulitmeter set to ohms to check continuity of just when the points open.  That place is located with the dial indicator. 

 

The process of setting the timing is:

 

1.      The points are gapped at .020 with a feeler gauge at the peak of the cam dwell.

2.      The points are isolated by removing the coil and condenser wires.

3.      An ohm meter (multimeter set to ohms) is connected to the point arm and ground.

4.      The piston is then rotated to .010 BTDC.  The dial indicator is used to tell where that spot is while rotating the crank.

5.      The points are located in a holder which can be rotated.  The length of rotation is just enough to allow the points to move on the cam dwell a small amount, about .40. That allows the timing to be adjusted from TDC to way before TDC. 

6.      You set the timing by rotating the holder to the place where the points just open as indicated by the multimeter. 

7.      That sets the timing.

  

   So the process is set the points(feeler gauge), get the piston at whatever BTDC you want(dial indicator), then make sure the points open at that spot(multimeter). The timing is then adjusted. 

 

   That is the process described by the Tecumseh Technicians Handbook, “3 to 11 hp 4-Cycle L-Head Engines”.

 

>>you have compression so l dont understand why u think its valves or rings?,

 

   Your right.  I would think that 60 dry and 80 wet would be enough to get healthy combustions so I’m not sure what’s going on. 

 

   There is air, a healthy spark, and gas.  It does run but weakly.  I’m guessing that it’s weak because of valves or rings. 

Hey Touts,

Niper is right,  all you have to do is put the engine at TDC and set the points at .020  .

I have NEVER used ohm meter for that.

I think you're reading more into this than is needed.

I know this flywhell is a pain tin the A$$ to take off, but please do this for us.

All the engine requires to fire is fuel, spark and compression.

You have compression,  you have been bottle feeding it,  all you need is set your spark.

Good Luck,

Friiy

hey trouts2,

i didnt mean to affend you in any way if did,  just trying to help u get your engine running l know the tecumseh manual say that about setting the timing that way, but lve never set the timing that way before and l never  had a problem, l'm just concerned about pull back while cranking and what could possiably cause that and the only things that l could think are (timing to far advanced/ flywheel key sheered/ camshaft timing marks not aligned) but l was thinking and l'm not sure about this but when you replaced the points u probally replaced the condensor and l just thought maybe u got a bad one and its causing the pull back or inconstant spark if u still got the old one maybe u could try it and see what happens.

I have read every post to double check the most important thing. You may have several pieces of OPE equipment that may run fine on the gas you are using because the compression is better and/or spark is better BUT....your problem engine engine may DEMAND the freshest gas beause of weaker spark or weaker compression.

Is your gas fresh?

I have had problems with starting if the gas I use goes just slightly stale.