OutdoorKing Repair Forum Forums Repairs and Maintenance Questions on Engines Questions On Briggs & Stratton Engines Briggs 12 HP Year 87.

Woohoo look at moieeeeeeeeee.My first ever help me out post .So Please HELP ME!!!
Ok Got given a cox XL 28,dont want it,dont like it,have no room for it.Anyways did a top end inspection,didnt look to bad inside no major play in the piston,no excessive build up valves looked good,so i threw on a head,exhaust and carby gasket,tidied her up and kicked her over.Fired fine spluttered for a sec and calmed down.rev range is fine,the main problem is knocking at low speeds.dissapears at rev increase.Ok so im gonna list this as a tired runner,better for parts,just wanted to see how and if she ran before i got rid of it.3 questiions.the plug in it is a cj 8 im sure incorrect,what are the needle settings main jet and air the bowl or main is 3 3/4 turns the top one is at 4 3/4 is this correct? and shall i change the oil,see if i can gauge whether the knock is timing or wear related?,Anyways really only doing this for my own experience as Im more a 2 stroke restorer....And btw,If this was a car and came into my shop,id quote a new engine...lols...So maybee i answered my own question...Na just want to learn a little on something i dont usually get into before i sell it...besides...its FUN...:)

CJ8/rj19lm are the only plugs I have ever used in them

I start the jets at 1.5 turns for a base tune then adjust as neccecery to get a smooth running mixture. The 12hp I have here of similar era has synchro balancers, etc there are a lot of moving parts compared to a normal briggs, I would expect a little clattery noise but no loud knocking

You haven't given us the model, type and code, which makes it difficult. I'm guessing it will be old, and have a large one-piece Flo-Jet carburetor like this:



Initial adjustment (just to get the engine running) for all types of Flo-Jet, both main and idle jets, is 1.5 turns from fully screwed in. If the jets have been opened as far as you say it sounds as if the fuel system or jets have become quite clogged - if so it probably won't run with the correct initial settings Joe has quoted. The gravity fuel system and the FloJet should be easy to clean out and are pretty well bomb-proof, though the needle and seat may leak after all those years. If they do, please say so and we can talk about how to fix that problem, which is the only relatively difficult operation on a large Flo-Jet.

If it has the reciprocating weight type of balancer (Synchrobalance) it is quite common for the link pivot mechanism, and the crankshaft bearings that move the weights, to wear if the oil has not been changed regularly, causing a rattling/thudding noise. Usually if the wear is bad the crankshaft is worn as well as the link, and fixing it requires major work so the engine is often scrapped when the noise gets serious. If it goes away off-idle, yours doesn't sound as if it is bad.




As you can see, it is not a very lovable mechanism.

Thanks Joe And Grumpy,great info.
Ok model is 281707 type 0163-01 code 87062311 and as I said an 87 model. ok backed the screw in and changed the oil.Big difference.I guess when I said knock it was more a half knock half bang,as in a forced misfire,I was surprised it ran so well after so long when i adjusted nothing on start up.As for the carby yes Grumpy this is the one,although I dismantled this when i did the rest.the whole unit was stripped and cleaned and blown out.the bowl was trashed so i gave it a sandblast to get all the rust off,like new now,and no leaks that are visible.The knock is definately less and the missfire is gone,It blows absolutely no smoke which is surprising for its age.acceleration is quick and almost presise with virtually no lag,which again i found odd since the smaller briggs ive played with seem to hesitate on acceleration.And this system while youve stated it may be noisy,definatley works well as at idle and hi end it is very stable and smooth.
Thanks heaps guys,Your info has been awesome and well directed for quite a good outcome for something so old....Keep up the good work Guys!!!!

Thanks for bringing us up to date on the project. In case it is useful, here is the Illustrated Parts List:
http://bsintek.basco.com/BriggsDocumentDisplay/Z6ntzHVJ1DajI.pdf
and here is the Operator's Manual:
http://bsintek.basco.com/BriggsDocumentDisplay/mssAIQ-K_ny7tH217FzoPu.pdf

I believe the Flo-Jet carburetors used on the gravity feed fuel systems are better suited to easy starting and rapid throttle response than the suction carburetors used on the small engines, but you have the hassle of turning off the fuel or suffering the consequences, which sometimes include a sump full of petrol.

I'll close this thread - if anyone needs to post to it, please PM a moderator.

Good stuff.

The added value of it now being a good runner will definately be worth the effort.