Briggs Vanguard V-Twin 16HP - TROUBLE

Hello,

I am looking for some small engine advice.

I have a commercial walk behind mower (Bunton) that has a 16HP Briggs and Stratton Vanguard V-Twin engine on it...

At the end of last year I was going to cut the grass and I started the mower up and was letting it idle for a bit while I was doing a few other things...I heard a LOUD snap or bang and the mower stopped...I immediately went over to the mower and looked at it...I checked the oil level and it was low. I topped it off and tried to start the engine. The pull cord seem to indicate that there is proper compression. The engine does start up, but it seems to have a "hollow" sound to it. I can throttle it up and it seems to run fine for the most part except for a strange "hollow" or "rattle" sound coming from internal...

Also, I know that there is a definite problem because when I engage the blade there is no power to get through the grass, expecially if the grass has any length to it.

I am leaning toward a head gasket problem or piston/rings?

Although I am a Mechanical Engineer, I don't have a ton of experience with small engines. What do you suggest? Bring it to a dealer immediately? Check for compression? How? Could it be such a problem where one of the cylinders now has weak compression and I am not getting power? Is there anyway of telling if it is a seal problem or piston problem without tearing it down? Looking for some advice...I am very willing to get the tools out and pop it apart. But if you suggest this is too trickey for a novice I will bring it in...

Thanks in advance for you advice..

Regards,
Mike
Kalamazoo, MI

 

You probablly, from what it sounds like, it threw one of the connecting rods...., running these low on oil is bad.... they need that oil full, or within range. You can check compression on each side to see which one it is. Is this a over head valve?

 

Thanks V8 Driver...

I just got back in from checking the compression on both cylinders......The right cylinder (standing behind the mower) has about 150PSI or so....The left port has ZERO "0" compression....

So what you are saying is that the piston on the left side is not even stroking if I threw a rod? Or could there be a possiblilty of bad head gasket or cylinder bore?

I did notice when I took the plug out of the bad cylinder (after running it for about 5 minutes) that it had some oil on it...not drenched...But the plug from the other cylinder was dry..

What do you suggest for the next step in trouble shooting...Or is it a matter of digging in from the top down? How tough is it to replace the rod? Or is there standard procedure for doing a total overhaul at this point?

Yes....This is a OHV engine...it has two silver covers on the front of the engine...I have not had those off yet...

Please advise..

Thanks again for you advice..

Regards,
Mike

 

On the one with zero compression, you can try a screwdriver down the spark plug hole, holding it in, and spin the engine over by hand, if the screwdriver goes in and out, that should tell you if the rod is still connected. Otherwise, if no and the rod did go, sometimes it can put cracks in the block, this can cause further and worse problems..., and to "dig into it" requires removing the engine, it can only be gotten in from the sump.

 

Thanks V8...

I just was out in the garage and checked it out...You nailed it on the head! That cylinder is not stroking at all...Therefore the connecting rod must be shot...

As I mentioned before, I am a pretty mechanical guy but just have not messed to much with tearing small engines down...

What would you suggest? I have a work area that I can take the engine off and put it on a shop bench...Is there special tools other than the normal for doing a job like this? Or is it a matter of draining the oil, tearing it down, replacing the rod, replacing gaskets and rebuilding?

Thanks a bunch for the help on this...
Mike

 

Like I said above, sometimes the rod will go, and leave very small, not even noticeable cracks, New gaskets, connecting rod, basic wrenchs and such, and a torque wrench for the connecting rod, as well as a new locking plate for the endcap. You're gonna have to take the head off to pop the piston out. I'd inspect the piston as well.., and clean up any metal shavings you see.

 

Yes...

I think that I will take my time and tear it down...Make close inspections for any other damage...and at the same time clean carbon, etc...Do you know of any good source for the torque specs, etc. that I will need for this engine?

Thanks for the help..
Mike

 

Stop by eBay and acquire the service manual's for your engine. They are worth there weight in gold! They contain most ALL the information you'll need. With an engineer degree, you shouldn't have any trouble getting this thing going again. With a minimum of expense too! Once your diagnosis is complete, eBay is also a good source for the parts you'll need! Dinglberry hones work well as long as the scars aren't very deep in the cylinder walls. Just follow the lead of your service manual and take your time. Curoious to see your progress. Keep the questions coming. Someone here will assist you along the way, I'm sure! Good luck.

 

I agree,

It sounds like you broke a connecting rod. Probably on the upper rod. Check the crankshaft carefully once you get it open. It's likely that aluminum from the rod smeared onto the crank journal. Also, as mentioned, check the block for cracks and broken spots. Check the camshaft bosses in the block, and the part of the cylinder that extends into the crankcase for damage.

 

Wow...this forum is really cool...Pretty neat that others are willing to help out...Thanks!

Right now I have the engine on the work bench..I have all of the covers taken off and am now attempting to get the flywheel off...arrrrrrrrr!! I have the proper 30mm socket, but am having a difficult time holding the flywheel while trying to loosen the nut...This is not by chance a reverse thread is it? Suggestions for flywheel removal would be great...Would a 1/2" drive impact wrench get it? Then I need to get a puller or build one...

Yes...I agree that a good service manual on this engine would be most helpful...I am going to be ordering one tomorrow off from ebay..Hopefully it has good details...

Anyway, that is where I am at right now...up til now it has been smooth sailing...

Once again thanks for the help....I will keep you posted on progress..

Regards,
Mike

 

Well...I finally have this thing popped open like a pumpkin...One of the connecting rods it totally destroyed....Large chunks of metal and many small pieces.....

Upon further inspection it looks like there is some damage to the lower edge of the bore of that cylinder....I am not sure yet how bad it is...It looks like there is a 1/2 moon shape knocked out of the bottom lower edge nearest to the cam shaft...

From my experience, I am not sure if this is critical or not...I am not sure if the piston actually stokes this far and the rings get come past this point...

So, I am now looking at removing the piston...I took the valve cover off and have put it on hold here. (OHV)...Before removing nuts, bolt, springs, etc., I wanted to get some advice. What am I getting myself into by pulling the valve apart on this cylinder? It looks like this is what it takes to get the piston out? Correct?

I obviously have to replace the one connecting rod...The question is if I have to replace the entire upper casting (name)?? The sump looks ok except it needs a good cleaning...

What do you suggest I clean the internals with?

Anyway, any tips from here out would be great...I am also going to buy a repair manual for this thing tomorrow..

Thanks for the advice..

Regards,
Mike

 

i'm not sure if you have to replace the upper entire casting, i've never worked on a vanguardvtwin, someone else should be able to answer that

if you give me the model and type of the engine i can get you an estimate on the connecting rod, and any other parts that may be needed to repair it

 

The engine block, before you go ordering for this one, I'd see how much a short block would be..... doesn't sound all that good. Your gonna have to take the head off, to pop the piston out, when you get your manual it should have most of all you need to know. The damage is at the bottom edge of the bore? the piston shouldn't stroke that far, so you MAY be ok..., can you get any pics?

 

Have a look at these images...

It was hard to get a shot of the damage to the bottom of the cylinder bore...I think that it might be toast...

Pic. 1 is a overall pic...This is the point that I am at right now..Any quick instructions on removing the valve would be helpful...
http://www.pneutekinc.com/images/BS_1.jpg

Pic. 2 shows the remaining part of the connecting rod still connected to the piston...It also shows the chuck knocked out of the bottom of the cylinder bore...OUCH!!
http://www.pneutekinc.com/images/BS_2.jpg

Pic. 3 these are chunks that I have found floating so far...I have a lot of clean up to do if this engine is worth saving...
http://www.pneutekinc.com/images/BS_3.jpg

What do you think??

Also, is there a better way to post pics?
Thank for the help..

Mike

 

You probablly have stress cracks all over the block with that hit, safer and better to get a short block.... others will have they're opinion on it..., as for the head, take the rockers off, making sure to label the pushrods and rockers, which came from the exhaust and intake side, and take all the bolts holding the head on, might take a tap with a hammer to knock it loose.

 

That's the spot I was thinking about when I mentioned damage to the cylinders. Seems like blown vanguards like to knock a chunk out right there.

I can't tell without personal visual inspection for sure (and even then some damage is not readily apparent), but I personally think that block is still buildable if that is the only damage. I would use a dremel tool with a small abrasive stone bit in it and bevel the edge around that small break, then hone the cylinder and build it. That's if it were mine. If it were for a customer, I guess it depends on which customer it was before I suggested doing it that way. There are some I would just quote a new engine to. I bet the piston on the same cylinder has damage to the skirt as well. Check both of them.

 

What are the model and spec #'s on your engine? This would likely be a tremendous help, to some of the folks here, in giving you accurate and correct advice on your problems at hand. I think I have a manual on your engine, I just need the numbers on the engine to look up the correct information for you. I might be able to take a couple screen shots for you to examine while you wait for your manual to come in. You might look on eBay for a parts manual for your engine as well. They will show you exploded views of the parts and in what order they are placed on the engine. Glad to see your making some progress. Looks like your in good hands here!!! Good luck.

 

Here are the engine details...

Briggs and Stratton Vanguard V-Twin
Model # 303772
Type # 1055-E2 (3367)
Code # 97110411

I think that damage on the cylinder bore edge is worse than what the pic shows...By comparing how far the other piston strokes with how big the damage is, I think that I am going to to have problems...

I have found a brand new engine for $565 plus shipping...This seems like a decent price...Does anyone know what the difference is between the 303772 and this one 303777-1165 ? I see that this one has electric start whereas my current one does not... I believe that it will drop right in...Do you agree? Any good news/ bad news about this vendor? www.engine4less.com?

Thanks

 

Thats the only difference, the electric start..... but it doesn't have a recoil starter.... is your mower equipped with the wiring to go to the engine for electric start, battery, solenoid, ignition? if not then your gonna have to find a harness for it, possibly from another mower..
It'll drop in though...

 

It also has a fuel pump, "oil Gard", 1" diameter X 3.19" crankshaft, 7/16-20 threads in the crankshaft end, and 16 amp alternator. The crankshaft size and threads is common to almost all riding mowers. Should fit fine, and you can probably switch the recoil start off your old engine and put it on this one. I guess that's a decent enough price, below retail. Probably about the best price you'll find online anyway.

 

Based on your pics, the oil was cooked (boiled). You need to prevent this from happening again or you'll be buying another engine in about three years or sooner. I'll bet when you removed the blower shroud the cooling fins were packed with grass debris. In the future, these must be kept free and clear...yearly at least. You know the saying. An ounce of prevention...If you do decide to repair this engine, you had better mic all the critical surfaces for wear. I'll guess there is much wear elsewhere.

 

might not want to hear this, but it sounds like it may have thrown a rod, and it threw it just so that it didnt window the block. It probably can be repaired, but it wont be cheap (if that is in fact what it is)

 

Not meaning anything bad by this... but he already found this out and has bought a replacement.