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

I have here a piston connecting rod that has just a little too much play in the bearing/bushing that connects it to the shaft.  Is there a bearing/bushing that can be replaced or does the whole connecting rod/shaft assembly need to be replaced? This is off of a Honda 5hp horizontal shaft 4 stroke engine that belongs in a honda single stage snowblower (HS520). 

When I look at the exploded diagram for the part I do not see anything.  But maybe I'm missing something.

Have you put in new bearings?  Or is the slackness happening with the old bearings?  Chances are that if you put in a new set of plain bearings, it should be within tolerance. 

I have not loosened the bolts that hold the rod to the shaft (no new bearings or other parts).  Are there bearings inside of there?  Or does the piston's connecting rod just rotate on the bare metal of the shaft?  If a bearing existed I thought that I would have seen it in the "exploded view" of the part.  How would a new one get installed?  Do they clip on?

The drawing looks similar to Tecumseh snowblower engines - no bushings or bearings.

Aluminum rod, the two pieces bolted together, rides on the crankshaft journal without other parts, aluminum riding on steel. Wear is pretty easy to see. The crankshaft journal will have a thickness spec and the rod diameter will have a spec. Tecumseh provides these online. I think all Honda manuals are pay-for, not online.

I'm not certain if there are plain bearings in that particular engine nor if the small Honda engines use replaceable bearings in the connecting rod big ends.   I know that larger engines have babbitt type flat or plain bearings that can be popped out and replaced. Usually on one end their is small indentation to put a tool in to pry the old bearing out.  Some flat bearings are also removed by tapping the edge of the old bearing to cause it to rotate out of the semi circle of the the bearing seat.  Take the connecting rod bolts out and have a close look to see if there is a very fine cross section line between the outer surface of the bearing and the inner area.  If so, you might be in luck and just need a bearing change. 

Regarding the parts diagram, you're right.  Don't see a bearing there.  I'd look into it nonetheless.

trouts2 wrote:

Yes, honda manuals are "pay for"  so I don't have a thickness spec to go by.  Since the connecting rod is aluminum and the crank shaft is steel, is it fair to say that any wear would occur on the connecting rod (softer metal) and not the steel (hard) crank shaft?.  That being the case, would a new connecting rod solve the problem of too much slop in the fit?  This snowblower is only a few years old and was used on a 15 foot driveway as a "backup" to a larger 8hp 2 stage blower. It's just out of warrantee and the rest of it looks like its been sitting in a showroom (mint). That said, there's no reason to beat a dead horse.  I'll loosen the bolts holding the connecting rod and see what I find .

I found a good write-up on this subject online in a book entiltled "Repairing Your Outdoor Power Equipment" by Jay Webster:

http://books.google.com/books?id=-bEBXd7oUokC&pg=PA35&lpg=PA35&dq=honda+crankshaft+journal&source=web&ots=dj69iuA2Tl&sig=JR3tS3r-CSN5LiKTuzrCN5eMB7A&hl=en&sa=X&oi=book_result&resnum=8&ct=result#PPA36,M1

Don't you hate it when someone only gives you part of the story. So here goes: A small plastic cam pulley in the top of the engine broke.  The engine was serviced by a Honda tech and the plastic cam pulley and small timing belt replaced. When the repaired engine was started you could hear a knocking noise (the motor ran and the knock was most noticable during idle).  The tech made a call to the owner and said "looks like you're also going to need a new piston, connecting rod, and crankshaft."   The cost of all this new extra work (just out of warrantee) was enough for the owner to decide to just throw in the towel.  He decided to cut his losses.  He paid for the work that was done and brought the snowblower home unassembled in 5 boxes.  

Does everything about this story sound right? Tonight while I was looking at the engine I noticed a few things. First, when the engine was re-assembled gaskets were not used. Instead the tech used goopey stuff. And  the piston has indents on top from the valves.  I have sometimes heard that the gaskets act as spacers and dismissing them from the assembly can cause the valves to tap the piston. I don't know enough about honda engines to say that a gasket  should be considered a neccessity on a  small 4 stroke ohv .  But look carefully at the piston in the photo. You can see indentations if you look really hard (sorry for the bad photo).  Are these indentations supposed to be there? Maybe that's the way honda makes pistons on these small engines. Or maybe the broken plastic  timing wheel  caused the valves to slam into the piston.  Either way, now there's just a little too much play between the connecting rod and the crankshaft journal. 

What to do?  Are gaskets the way to go?  Will a new connecting rod be enough to solve the problem?  Does the piston need replaced?  Is this becoming a tangled mess?  no end in sight? Originally I assumed  that the honda tech knew what he was doing  (or at least more than me), so my plan was to follow the tech's  lead and pick up where he left off.  But those valve impressions in the piston have left doubt in my mind. Ussually my advice to others would be to trust your initial instinct.  So I guess I'll go with that for now and  assume that the piston is supposed to have indentations and the tech knew what he was doing. 

Any assistance at this juncture would be appreciated.  Has anyone left out gaskets (and used goopey stuff instead) when assembling honda ohv 4-stroke engines? Will a new connecting rod   (part # 13200-ZL8-000 $39.36) solve the problem with the worn bearing surface?

 

Did this engine knock before the mechanic worked on it ?  I doubt that replacing a timing belt
would result in knocking of any sort.

The depressions in the piston top is normal.  They allow the piston to move further upward without
hitting the valves.  You'd clearly see damage to the piston if the valves were hitting it.

Are you sure there is too much play between rod and crankshaft ?  What about the bearings on the
ends of the crankshaft ? There does seem to be a bit of wear there, how old is this engine ?  Are
the bearings loose internally or is it between the bearing and crankshaft ?

Sometimes knocking is from the piston being too loose (like Subaru's famous piston slap).  This
will show up as scuffing on the piston skirt.

I'd be a bit surprised if you needed a new crankshaft unless the ends are too worn.  It is certainly
the most expensive part in all this.  Replacing the rod, the crank end bearings, and probably the
piston and rings for good  measure, might be all you need and shouldn't be that expensive
(you'd want to rebore but you probably can't on a small engine like this).

Given Honda's prices for parts it may be cheaper to buy an new engine.  What's the condition of the
rest of the machine ?

Paul

pvrp wrote:

Thanks for clarifying the depressions on the piston.  There's no damage to the valves. I looked at the bearings on the end of the crankshaft and they seem perfect in every way. I have not removed the connecting rod from the crankshaft yet.  (is there a replaceable bearing there or does the connecting rod just spin directly on the crankshaft?)

The honda HS520AS was purchased new in 2005.  It was a second "lighter" snowblower for a 10-15 foot driveway in New England.  The owner purchased an extended warrantee and had it serviced every year.  There is almost no wear on the paddle set and the rest of the blower is mint. That's why I didn't want to toss it in the trash.   With electric start  I thought it would make a nice blower for my dad.  

I'm not sure how I would assess a "loose piston." The piston is certainly loose as it flops from side to side but I'm not sure what to guage it on. Same goes for the connecting rod I suppose.  How much is too much?  

As mentioned, the indents on the piston crown are normal.  Whether the piston is good or not is a different story.  If there are no obvious signs of excessive blow-by, it and the rings are probably good. 

What tests did you do to check for play between the crank and the con-rod end?  There should be absolutely no detectable lateral play there whatsoever.  Also, check the crank end play in the bearings.  It also should have no detectable lateral play.   The cases in these engines don't usually have gaskets.  They are metal to metal surfaces and must have a coating of bonding material in between them.  I usually use Yamabond.   All the major Japanese engine manufacturers have their own bonds.  Buy whatever is least expensive. 

Also as suggested, before you start to hemorrhage money on that engine, check the price of a  new replacement.  Check out Small Engine Warehouse.  They have a good selection at very good prices.   Heres a link:

http://www.smallenginewarehouse.com/default.asp  

So the engine is not very old at all.  Why would the timing wheel (whatever that is) break
in so young an engine ?

Personally, I would not go about rebuilding an engine without the service manual from
the manufacturer.  It will tell you (or should anyway) what the various clearances are so
you can tell if there's too much or not.  The manual can also be helpful when you
reassemble things like the timing belt (or chain or whatever) since you want the
valves to open and close at the right moments.  There are usually marks on the parts
to help you align things properly.  Also you'd want to adjust the valves and you need the
clearance values for this.

The piston clearance is measured by inserting a feeler gauge between the piston and
the cylinder wall, without the rings.  There has to be some clearance as the aluminum
expands when heated. Someone around here may be able to say what a normal amount
would be.  My days as a mechanic were decades ago and I can't remember off the top of
my head.  You can probably find the value somewhere on the Internet.

Connecting rod big end bearing clearances can be measured with a sort of putty that
you insert while reassembling things then measuring the thickness of the putty (if
I remember correctly, I've never done it myself).

From the drawing it doesn't look like there are any bearings.  Why don't you remove
the connecting rod so you can see what's going on down there ?  You'll be able
to see some signs of wear if there is any.  Again having the manual would be nice
to know what to torque those bolts to when you reassemble.  They're not something
you want to come undone with the engine running.

It would be nice to know what the condition of the engine was before the mechanic
worked on it.  What happened to break the timing wheel ?

Oh, and using a sealer instead of a gasket is common, but I wouldn't replace a
gasket with it if there was one originally.  The mating surfaces have to be perfect
for the sealer to work properly so you have to be really careful when you're cleaning
the surfaces not to scratch them.

I have trouble accepting that this engine knocked beforehand unless it ran out of
oil at some point.  Or the oil was never changed, and even then it's not really old
enough for that.

Paul

P.S.  Is it my imagination or are there nicks to the little teeth of the bigger gear on
the end crankshaft ?

Looks like I have some homework to do. 
1) remove the bolts holding the connecting rod to the shaft (didn't do it earlier because no manual on retightening). There is definitely some play here.
2) check for nicks in the small teeth of the big gear on the crankshaft.
3) check for wear on the crankshaft.
4) double check the bearings on the end of the crankshaft (should be no lateral play)
5) check on replacement engine costs.
6) check for scuffing on the piston skirt.
7) locate a manual (I did find the parts manual and owner's manual, just not the shop manual)
8) get some prices on gaskets, rings, pistons, yamabond, and a connecting rod
9) take a deep breath.

Here's what's what:

1) remove the bolts holding the connecting rod to the shaft (didn't do it earlier because no manual on retightening). There is definitely some play here. 
Discovery :  See the photo of the bearing surface. The aluminum connecting rod bracket shows wear but the crankshaft looks fine to the untrained eye. (Please disregard the dirt and grit,  the open engine was left outside in an open box and was covered by falling leaves for a few days).
The fit  is not tight.
2) check for nicks in the small teeth of the big gear on the crankshaft.
Discovery: The teeth are fine and show no signs of nicks.
3) check for wear on the crankshaft.
Discovery: This is the first crankshaft I've ever seen in my entire life.  That said, it looks like its been heated by the friction of the spinning connecting rod but it does not appear to be worn down.  The aluminum connecting rod bearing surface does appear to be worn down.
4) double check the bearings on the end of the crankshaft (should be no lateral play)
Discovery:  I slid the cramkshaft back into the bearing.  The shaft fits very snuggly with no noticable play. 
5) check on replacement engine costs.
Discovery: I called a few internet place and got prices.  The best I could do new was $230 .  The engine is a Honda GC160 5hp.  Several vendors told me that honda snowblower engines are constructed differently from other GC160 motors and that they are not interchangeable.  They said something about the cylinders being different but to be honest the explaination was over my head.  Ebay has GC160 engines but Honda mass produces these for so many different applications from compressors  to power washers, to go carts and water pumps that its difficult to know if you are getting an engine with a compatible output shaft .  Honda made 7 different crankshafts for this engine.  Ebay prices run around $120 delivered for  a lightly used motor. Harbor Freight sell a $150 honda knockoff but its 6.5 hp. 
6) check for scuffing on the piston skirt.
Discovery: The piston does have scuff marks on it. I tried to take a picture that would adequitly show the scuff marks.  I would be interested to know if these scuff marks are just normal routine wear or a telltale sign of some other issue.  See photo below.  Note: There is no verticle play in the piston/connecting rod juncture. There is horizontal play. 
7) locate a manual (I did find the parts manual and owner's manual, just not the shop manual)
Discovery:  A vendor in California  will mail me the manual for $30.  .They have to order it from a distributor first. The price seemed  reasonable.
8) get some prices on gaskets, rings, pistons, yamabond, and a connecting rod
Discovery: 
Ring set (13010-ZL8-003) $19.06
Piston (13101-ZL8-000) $34.38
Hondabond (Used as gasket material for cylinder and cylinder head)  08717-0004 $6.50 
Connecting rod (#13200-ZL8-000) $39.36.  
9) take a deep breath.
 I opted for a beer instead.

Here's a 5 h.p. Honda GC engine at Small Engine Warehouse for $170.00.  You're looking at close to $100.00 to fix the old one.  If this engine is suitable, the decisionis a no brainer to me. 

http://www.smallenginewarehouse.com/product.asp?PN=GC160QHAF-TO&desc=Honda%20Engine%20%205hp%20Horizontal%203/4"x2%205/16"%20Keyed%20Shaft,%20OHC,%20Stationary%20Throttle

borat wrote:

I called and spoke with a salesperson at Small Engine Warehouse  ( 800-321-6725) about this  motor ($190 w/ship) and they told me that it was not a suitable replacement for a honda snowblower GC160 engine.
They explained to me why not but to be honest the answer was too complicated for me to really understand.  They said to check back another time because they get engines in all the time.  .  Is there a less expensive online parts dealer?  I understand that Honda keeps a tight lid on parts distribution.  I did find a place (Tulsa Engine Warehouse) that had aftermarket parts for less.

	PISTON RING SET	Piston Rings		$9.00	$9.00
	PISTON ASSEMBLY	Piston		$21.00	$21.00
	Standard Connecting Rod	Connecting Rod		$10.50	$10.50
Estimated Shipping (Best Way)					$8.95
				Total	$49.45

Your connecting rod doesn't seem to be worn much at all which is odd given the
condition of the bearing surfaces on the crankshaft.  I suppose the marks there
are deposited aluminum but there doesn't seem to be much gone from the rod.

What does the inside of the cylinder look like ?  The piston is pretty scuffed up so
it must be pretty loose.  I'm not sure but I doubt your cylinder has much of a sleeve
(probably just some sort of chrome coating ?) so any wear to the cylinder wall could
be costly.

Apart from the 100$ or so for parts, a minimum I'd say, you should also figure
in your time and experience.  Do you have a torque wrench, for instance ?  Have
you reassembled small engines before ?  Not trying to discourage you but an
engine in a basket can be a bunch of trouble.

How much would a proper engine from a Honda dealer cost ?

Paul

pvrp wrote:

I have a torque wrench.  I have never reassembled a small engine before and I'm not an engineer.  I have taken apart dishwashers, washing machines, and small electronics.  I may have bitten off more than I can chew with this project, so don't feel that your words are taken as "trying to discourage."   When I was 15 my dad took a small engine repair class and completely disassembled a tecumseh L head engine off of our ariens snowblower. The next few winters I had to shovel the driveway by hand. 
Here's a photo of the inside of the cylinder. One side is not as smooth as the other. This is the not-as-smooth side:

From the looks of the cylinder, the engine was either run low on oil or run in dusty conditions.   Being that it's on a snow thrower, I'd venture to say it's the former.   I personally wouldn't use that cylinder and being a Honda "GC" series, it doesn't have an iron liner.  Which means that it's pretty much shot.  You can check to see if it can be re-bored but doubt if it can be.  If the engine had been run low on oil, just about all of the other friction surfaces are likely compromised.  Don't want to burst your bubble but I'd say it's a lost cause.  If you decide to get a new engine, the Honda "GX" series are the industrial application models.  They have a cast iron liner and are supposed to be more robust overall. 

borat wrote:

This is good to know. No reason to waste my time.  I appreciate the input. I bid on new replacement engine that sold on ebay today, but lost it  at $140 delivered.  As far as replacement engines go, if I find a Honda GC 160 with a shaft that is the same length and keyed and threaded the same way will it fit?  Are there other parameters to look for?  

 I had thought about parting it out and trying to sell the gas tank, gas cap, flywheel, spark plug, recoil starter, Magneto / Ignition Coil, drain plug, timing belt, plastic cam, and exhaust.  I thought that the sale of these parts might  subsidize the replacement engine. 

 I may try to reassemble this one just for the experience.  If I reassemble this and it starts what will happen?  Will it explode or do anything dangerous? Putting it back together might be interesting.  Maybe not. 

So looking back on the demise of the engine, why would it have run low on oil.  New engines shouldn't ever really run out of oil should they? You are right, it would not have been run in dusty conditions. I'm at a loss to explain what might have happened. Why would the plastic cam wheel and timing belt have broken? (those are brand spankin new)

How bad are the scratches on the bore and crank journal?  As someone on this list once wrote, “can your run your fingernail across the journal and not catch it on bumps and ruts?   If there are no ruts you might get lucky and be able to sand off minor high spots and remain within spec.  You’d have to be very lucky. 

 

   The same for the bore.  Are they scratches or surface marks?   They look bad but again if you were lucky and no ruts then you could re-hone and see how close you are to tolerance limits.  How do you check?  HF sells a bore gauge set for $7. They have a digital vernier for $10 on sale.  The gauge compares well to a much more expensive Starett.

 

   The idea being it might be worth the $50 to get an education.  Rebuild the motor and see how it comes out.  You might get lucky on the first shot.  People on the list helped me out and my first motor actually ran well.  If it runs and sucks as a motor you’ll have made a big accomplishment.  It would be better to hack on this motor as a learning experience then learn on a much more valuable engine. 

 

   Harbor Freight has some decent engines.  I bought three last week at $109 each.  They come with a 90 day warrantee.  For 11 bucks they add 12 months so that will cover these motors over two snow seasons.  The warrantee is also transferable.  The HF motors are made in China by Lifan.  Lifan is one of China’s better makers of small engines.  They are a giant company making all sorts of motorized things.  I know their motorcycles very well and they are excellent.

 

   The HF engine is 6.5hp, OHV, cast iron bore, and low oil shutoff protection, arm throttle control but has holes for a cable, fuel shutoff and choke at the carb.  They are made in partnership with Honda so a legal clone and the parts interchangeable with Honda.  I have mounted a few on great older Ariens bodies. 

 

   One of these engines might be an option.  Lifan is a quality maker but who knows the actually quality of the model HF is selling. ?? We’ll see.  I spent 4 years in China and pretty familiar with their small motors so getting them was not a problem for me.

 

   If you did replace yours I’d still go with the rebuild if the scoring was not prohibitive.  Even just putting it all back together would be worthwhile.  It’s not as complicated as it seems once you wade in.

David

trouts2 wrote:

A finger nail does not snag on any of the scratches. The scatches on the piston and cylinder  are more like surface wear marks. The crank shaft is smooth as glass but darker in color.   My camera does not allow me to get much depth of field with the flash on. That's why the photos are so blurry on the cylinder.
I realize that I'm the only one that can really see/touch the damage. So I'm really the only one in a position to do a fair job of assessing the damage. Infortunately I have no knowledge of what I'm looking at.

I have a 15% coupon to harbor freight and they have a store near me.  I'm not sure how difficult it would be to size another engine to fit (even a honda clone).  I could take the old engine with me to the store and set them side by side.  This being a single stage blower everthing needs to fit inside a plastic housing.  That might also mean the end to the electric start and who knows what else.

As for putting it together.  I found an exploded diagram of the engine so i might be able to get it back together.  The shop manual would probably be a neccessity. Would I at the very least want to replace the old connecting rod ($20 delivered)?  I would need to find some way to clean everything really well. Not sure how I would do that.  There are small piece of grit everywhere from it sitting under the tree. (the owner was leaving it out for the rubbish).

 I would have more confidence/faith in fixing the engine if I had a better idea of why it failed.  Give the benifit of the doubt to the person that set it up before it left the showroom. It was full of oil.  In 3 years on a 14 foot driveway (I saw the driveway and the owner was as honest/respectable/conscientios as they come).  Say 16 storms a year, 30 minutes/storm, 3 years = 24 hours (total).  I cannot figure out what went wrong or why the plastic cam wheel would have broken. 

I think I'll sleep on it.

I would put it back together and see how it ran,  I think someone took it too a shop.   They gave him a high est. and he took i back home apart...there is not much carbon on the piston,  The pictures I  see refer to grit in the engine.  I bet there was not much wrong with this motor as far as running... Shops sometimes will not put something back together after an estimate is preformed without work...   Out of spite they take it apart and HOPE the guy leaves it at the shop for parts in leu of fee...

I must have rebuilt 200 engines over  the years,  I see nothing that would keep a good honda from running, It looks like someone never changed the oil.... It probly had a stuck valve and/  or a gunked up carb...

Put it back together with the parts that are there,  run it on the bench to see if it is usable....  If it runs ok,   then think about how much money to throw into it...

I live and work in the desert... You give a Honda to a illegal  and let and he will do this to the motor in a matter of months,   but it will still run fine for years at 4-6 hours a day...

Friiy

I agree 100%. This isnt an aircraft engine that is used in a critical situation. I dont see any major issues and it will be a great learning experience.  Try your public library for a book on small engine repair a similar Honda engine may be discussed.  Make it a fun project and take your time.  Just make a point of getting as much of the grit out of it as possible especially around the rings and grooves.  I have used Simple Green as a soaking solution on my BMW pistons (81 bike with 152,000 miles and runs great!)
Packo

If Underdog wants to do if for the experience, I agree, go ahead a put it together.  However, I wouldn't put a dime into it.  Doing a fingernail drag around the scored cylinder doesn't let you know if it's out of round.  From the wear pattern on the cylinder and piston, you can pretty much bet that it is.  I'm certain that the engine will run but it will burn oil, be noisy (for a Honda), and will also be low on power.   I'd put it back together nonetheless just to see how long it would last in that condition.  I repeat that I just wouldn't put money into it. 

When I buy Honda products, I make sure I get the "GX"  engine.  It's a bit more expensive but it will outlast a GC many times over if properly maintained.  These B&S snow engines are not much different than the Honda GC series engines.  No iron cylinder sleeve.  I wasn't too concerned with that aspect because the B&S engine I have is on a snow thrower.  Cool operating temps and clean environment will help to extend it's life.  If it does blow, I'd certainly make sure I replace it with an IC series or better yet, a suitable B&S Vanguard which is made in Japan.  

So, go ahead.  Put it together and keep let us know how it runs. 

Being an over head cam engine, you'll have to make sure you have the timing gears properly aligned.   There should be indicators on both gears and the manual should also tell you what position they should be in.    

PACKO wrote:

Thanks for all the input on this decision.  So I slept on it  last night and I think I have a plan:

I'll  start shopping around for a replacement engine.  See what's out there, what it would cost, and how well it would fit.

Meanwhile,  I'll  toss everything in a vat of "simple green" and hose it down. Then I'll  find a shop manual (I might even be able to resell the manual when I'm done with it) and spread all the parts out on the dining room table (a nice warm well lit room) .  After the baby goes to bed I'll spend a few minutes each night and see if  I can figure it out.