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). 

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)