Briggs engine failure...paging Lubemaster
 

My son has a Briggs World Formula Racing Kart. It run a variation of a Briggs Animal engine with a racing cam and more compression from what I understand.

We were at the track last night and his engine let go. It blew out the crank case. I am unsure what happened.

Lubemaster, what kind of oil should I be running in this application. I was running full synthetic in it and I am wondering if this lead to the failure.

Some pics of the carnage for your enjoyment:

http://i6.photobucket.com/albums/y21...3/DSC_0709.jpg
http://i6.photobucket.com/albums/y21...3/DSC_0710.jpg
http://i6.photobucket.com/albums/y21...3/DSC_0711.jpg
http://i6.photobucket.com/albums/y21...3/DSC_0712.jpg
http://i6.photobucket.com/albums/y21...3/DSC_0713.jpg
http://i6.photobucket.com/albums/y21...3/DSC_0714.jpg

Are those 'pieces' piston parts? Where are the piston rings? What does the piston top look like?

What's the top of the piston look like? Did you drop a valve? I've seen several of these motors do this. Weak design of the crankcase. Valve drops, imbeds in piston, and pops off the jug. What rpm were you turning?
As a side note the clutch looks awfully blue. How bad was it slipping? What rpm was it coming in at?

I am not too sure about those newer styled Briggs engines, but I used to race go carts with the older 5hp Briggs engines and they had a "dipper" tang attached to the bottom of the connecting rod cap that dipped and splashed the oil around on every down stroke. In the class that I ran in, we ran with the governor removed (approximately 6000 rpm vs 3600) and we were running alcohol instead of gasoline. The "dipper" when subjected to the higher rpm, sometimes would fatigue and snap off which would mean no more lubrication so the rod would eventually come unglued and blast a hole in the case. If these newer engines have an oil pump in stead of the oil dipper/slinger, then disregard my comments.

It has a rev limiter on it and my son does not hit the rev limiter on this track when I take it out I can hit the limiter but I have only driven it for maybe 4 laps a few weeks ago. I think the limiter is set to 7,200 RPM's and this is set by Briggs.

It looks to me like the cylinder portion of the engine tried to launch off the top of the crankcase.

Here are pics of the Piston top and the head:

http://i6.photobucket.com/albums/y21...543/piston.jpg
http://i6.photobucket.com/albums/y21...543/valves.jpg

My guess is that Tim nailed it...The flathead Briggs uses a "splash" lube system...too many revs, not enough lube, regardless of type of oil. Higher compression is also harder on the rod bolts.

Oh...question? How can a flathead "drop a valve"???

Its not a flathead its an OHV setup. Look in the 3rd picture and you see the camshaft gear meshing with the cranshaft gear. You can see the

There does not seem to be a valve issue either no marks on the piston and it looks like everything was fine in the valvetrain.

Its a pushrod setup if you look close you can see it.

It has a splasher and I was not running it any different than the factory setup.

I did buy this kart used (1 year old kart) and I cannot be certain about the history of the engine.

Another full engine costs $1K. :(

I am looking for a short block since the externals are all still good.

BTW - I am buying anew engine, I just want to know what kind of oil to run in it to reduce the chance of revisiting this ordeal.

Jim, I don't know much about those type of modded briggs engines, but small industrial based engines typically are governed to 3600 rpm and the fact that the race modded Briggs can hit 7200, to me, means that it is taking a beating compared to what it sees in the normal use it was designed for. With higher compression along with increased fuel/air and the high rpm, you have to figure that the stress on that relatively thin aluminum case is sometimes just too much for it. It probably fatiqued and gave up the ghost at a stress riser emanating from one of those tapped holes in the crankcase. In the cart class I used to race in, blown motors on occasion were part of the price of admission. Maybe a new motor each season is to be expected?

I felt sorry for the guys on track last night. We left a LOT of the engine on the track. :D


Tim your probably right. I will poke around the 4 stroke forums and see what they say.

I just think Lubby is pretty god at what he does and might shed some light on what kind of oil to use in this engine.

I need to fly out to Texas and drink beers with him and discuss my Rotary too some day.

Hey Jim, just out of curiosity, were the side case bolts loose? The clutch side of that crankshaft is supported by a bearing in that removable case and if it was "breathing" due to loose bolts, that would allow a hammering effect that would severely fatigue the case. Evidence of this might possibly be visible in the case sealing surface as fretting (kind of a gouging type thing).

I have an airplane engine that "threw" off a cylinder due to a mechanic applying silicone type sealant on the cylinder base where none is supposed to be. It allowed the cylinder to hammer enough that the attachment steel studs broke and allowed it to depart from the engine. I could see evidence of the fretted aluminum case that I could feel with a fingernail.

Ultimately I guess it doesn't matter as that engine is done.

Funny you should mention that.

I have been having issues with the engine since I bought the kart with it backing out the crankcase bolts on that side. I have just bought a tube of loctite and had applied it to all the crankcase bolts and retightened them over the weekend. Then this happened.

I think this engine was done since the day I bought the Kart 3 months ago.

Funny thing is, I walked into this shop to buy a set of calipers for a 10 year old Cali Kart I have with a KT100 engine on it and I was "upsold" this kart. The reason being that a new Kart would prove to be more problem free for me in the long run. This kart has broken down on us ever time we have been out.

My KT100 has some carb issues and I gave up and have it in the track pro shop right now. It will be ready next week.

I am going to get a new engine for my sons kart, I am in no hurry right now because we cannot go out for 3-4 weeks now. I am traveling a lot over the next 3 weeks.

I hope to find a short block instead of a whole engine setup.

Mike is up North in the frozen tundra this week.

Maybe I should buy a lottery ticket that was a wild guess:D

Was the oil you used rated CJ4/SM?

Richard Hearn, Father to Ritchy...runs a 6 hour enduro race with up to 20 teams at a time running these.

google RCH motorsports or Richard Hearn Karting. I'm sure that he can tell you far more about that engine than you care to know.

nascar voice on// "dat darn motar , she just done blown up"// nascar voice off

this really messed up spell check

The WF engine is very reliable if built correctly. I think it was not assembled correctly or perhaps the cylinder was loose. If the crancase and cylinder are not mated properly, then they can cause alot of stress on the crankcase. It doesn't look like any lubrication failure since the crank, rods, and piston look good.

Jim,
I had this thread forwarded to me and I wanted to give you some feedback. Looking at this engine I would date it to be about 6 or 7 years old. The starter brace is missing and that was added in 2005. The ignition is not the PVL system that was implimented in 2006 and so on. Not knowing the history of the engine we have no idea how many hours are on it. I'm guessing more than you think. :)
The clutch also is a likely factor for why your sidecover bolt torque was an issue. Right down to the gasket material these engines are engineered to dampen the majority of the harmful harmonics that come with racing. Even with that the repeatative engaging of the clutch or slipping of the clutch over time all loads up through the side cover. I would recommend rebuilding your clutch and even look at lower engagement springs. This will allow the clutch to function properly and limit the in and out pounding. Ultimately I would recommend checking your sidecover and head bolts on a regular basis just as part of your normal engine routine. These are engineered for racing but the harmonics, a lean condition, or just the pounding over time that comes from racing mean we need to have a general engine routine. Everything from the track surface to an out of balance tire feeds right back through your hard mounted engine.

I would not recommend using any oil. As fast as you pour it in it will run out of all those frikkin' holes you blew in it.

This is not a lubrication failure. I'm guessing a assembly failure or a casting flaw.

WWW.4cycle.com

there is no site better than this.....post the pix and I'm sure you will get all the answers you need. The best builder are all there and will answer your question regarding 4 cycle kart engines.