Tagged: Briggs World Formula Rebuild
August 8, 2013 at 8:25 pm #6505
At long last our super-trusty WF (block version 2.5?) was taken apart tonight. Early years, it was SCCA autocross as well as track lapping, with up to 4 kids spending a day running it. That was just the beginning. When the kids got big enough, and a seat was installed that adults could wedge into, the track days became a free-for-all, and the WF was only shut off long enough to refill the fuel tank. Everyone who has driven it has loved it. I long ago lost track of how many hours it has run, and how many full-tilt laps it has been the motive power for speed thrills. BTW, it got the PVL flywheel/ignition conversion about 5 years ago.
Yes, I was strong on maintenance, with frequent oil changes (at the track after the morning, prior to afternoon flogging again) ran good fuel, and put a fresh plug often.
So, what does it look like inside?
It is going to need some parts for sure. The rod had managed to gain a significant amount of side-clearance on the crank journal. Spank me for running it so long and hard that the coating on the piston skirts had pretty much worn through. The bore does show some slight scratching, but a good honing might clean that up. Is there such a thing as a .001 piston? One of the lifters does not look right, and to me that indicates a cam too. One bright spot appears to be the head, which looks great. I’ll know more when I pull the valves and check the guides.
So I am new to the inside of this great motor, and looking for advice on the rebuild. The goal is to have it last as long and give as great a service as it has done since unpacking the orange crate and putting it on the GoldKart, some 9 years ago.
Note that I am not looking to make it nationally competitive with a blueprint and high-tech re-machining. I want a solid-performing reliable track-day power plant, one that will again happily run 100 laps with no issues, then do it again another time. And another, etc.
So, I can read manuals, get specifications, and follow standard engine reassembly guidelines, but those are the basics. I know there are many on EKN who have a trick or two, suggestions that might be of help, or tips which can be shared about this motor. No need to fear that I’ll be bringing it to compete against you, I run a shifter in autocross to satisfy my competition hunger. Top secret stuff you can send by PM if you want, I won’t pass it on to anyone.
Note: I will not be blueprinting. No machining unless the valve guides need it. No decking, no head shaving, no hot cam or stroker billet crank. The plan is to keep the engine stock, and legal for SCCA autocross, in case some big kid needs a ride some day. And, I figure it will last longer with no mods anyway.
Where to source parts? Tricks to reassemble? Whatcha got for me?
August 9, 2013 at 8:33 am #6533
August 9, 2013 at 11:08 am #6551
The biggest thing about any rebuild is going to be measuring, the most critical being cylinder and crank journal. If your cylinder is worn you’ll need to have the new piston fitted, if I remember correctly Briggs starts oversize at .020 over so you’ll need to find a machine shop capable of honing small cylinders (try your local motorcycle shop). If the crank journal is worn it’s best to replace it since the WF rod doesn’t have replaceable bearing shells. On the other forum Jamie Webb has a very nice article about building a stock Animal that will give you details on rebuilding including the admonition to “clean everything like it’s going on the Space Shuttle”.
But, given your usage and desire for a trouble free experience I’m gonna suggest you consider the option of just buying a new engine. Over the years I’ve seen plenty of engines like yours where just about everything is worn beyond spec. All those parts add up and having one piece with a hairline crack you didn’t find can compromise the engine in a very serious way. Not to be discouraging but the chance of your first rebuild being
” a solid-performing reliable track-day power plant, one that will again happily run 100 laps with no issues, then do it again another time. And another, etc.”
are fairly small. A much more likely result will be either an under-performing engine or a bucket of parts when something lets go. With the amount of effort it will take to rebuild an engine of this age and usage back to stock specs you’ll be much better off replacing it and having all new stuff IMHO.
Honestly, it sounds like your goal is to have fun with the kart and the best way to have your reliable powerplant back will be to open another box from Briggs and bolt it on. As somebody once said, it’s not so much a matter of CAN you do it but SHOULD you do it when it comes to rebuilding something with a ton of hours on it.
Either way feel free to drop me a PM or give me call at 231-264-8707 if you have questions.
August 13, 2013 at 9:08 pm #6956
Thanks for the advice guys, I’m going to start by measuring everything, to see what parts are out of spec, and what needs to be done about it.
For sure I’ll need a piston/rings and a rod. Beyond that… maybe not much.
I’ll keep you posted, but this is a back-burner project now, as it is unlikely for me to get that kart to the track before October. Too many things going on!
August 15, 2013 at 10:42 am #7118
I believe Burris has these new pistons in .005″ increments now. You don’t have to go very far to get a new +.005″ piston to fit.
Might be a better idea for the wear factor to use a billet rod with a bearing insert. ARC has these in stock.
If you can at least change the oil at every fuel tank fill up, that engine should have another 5 years left in it.
August 16, 2013 at 5:13 am #7203
Alan If I were you I would keep reading John’s reply over and over untill your convinced it’s good advice. You really need to think twice about putting maybe $400 -$600 worth of parts into a $1000 engine that’s completly worn out.
August 16, 2013 at 7:38 pm #7311
Not trying to stir the pot – this is just my experience.
I priced it out and IIRC you can replace almost every wear item with new for about $650. Head, block, everything. Just keep the intake, exhaust, ignition and exterior bits and the rest is basically new. A motor that’s not in that bad of shape might not need much more than Alan describes. For a play motor, it’s hard to understand why it matters if it’s new or not.
Spent $750 to have my block align-bored to first over and put a new head on mine. Ran great afterwards and that’s a lot cheaper than a grand but I didn’t get a box of good spares from the deal. <shrug> Dono.
August 20, 2013 at 6:55 am #7533
I currently run an outdoor power equipment shop where I constantly have to tell people their equipment isn’t worth repairing. They rarely want to hear it but spending 2/3 of the price of a new piece of equipment on repairs is a bad investment since a new one will be new and under warranty.
Of course racing motors are different but a stock World Formula is pretty close to a riding mower in this respect. Now, if the OP wanted to build a modified motor and already had a bunch of parts it would be a different story but since the stated goal is to have a reliable (RELIABLE) recreational motor I’m pretty confident saying his best bet is replacement, not repair.
The process of doing the rebuild is definitely worthwhile from a learning perspective but doing it right could easily require several tries. I learned a whole lot working with Mike Clements, and it’s possible that this particular engine just needs a new piston, rings, rod, crank, and the valves lapped but without experience it’s gonna be tough to know what can be reused and what should be trashed.
The best solution of course would be to get another kart with a WF already on it and rebuild this one so he has two packages….
Would be interested in knowing what he decides, it helps everyone on here when the OP reports back on what they learned in the real world.
November 9, 2013 at 4:10 am #15128
Any updates on the course decided, Alan?
November 9, 2013 at 8:33 am #15140
Any updates on the course decided, Alan?
Eh, not yet. I was out earning the money to do one of the above, and have not gotten back to the guy who would supply the parts. Waiting for my paycheck, and a good conversation with a small engine expert on the best path to follow.
February 28, 2014 at 1:38 pm #22918
A stock Animal or LO206 is about $550, and you’d have enough parts off of the WF to get it on the kart and running without spending more than that. An LO206 short block is about $280, so you could even consider putting your WF head on that block and running it . Seems pretty pointless to rebuild the WF if it’s not being raced
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