Max IV - B&G Vanguard 18hp V twin - engine work to do

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Thread: Max IV - B&G Vanguard 18hp V twin - engine work to do

  1. #1

    Max IV - B&G Vanguard 18hp V twin - engine work to do


    I haven't posted much...but have read through a fair bit to get my Max IV running (gear train/drive line stuff).

    If you keep'll be able to tell that I don't know a whole lot about engines....LOL

    Now the engine won't start...worked ok one weekend, started and died the next. The ancient in-line fuel filter fell apart, which I'm sure didn't help keep junk out of the carb. I cleaned out the carb as best as I could from above, took out the ?main? jet (the one on the side behind a bolt that you reach in to unscrew) and the other long jet that you unscrew from the once you have the carb cap off. Not sure that there's no other jets. I took the floats out and cleaned out the reservoirs. Put it all back together and it's still a no-go.

    Spark plugs look really black and carbonized (I had replaced this spring, with oil/filter change). I cleaned them off and tried joy (it might just barely sputter if I keep the starter motor going).

    So...I think I'm going to have to take the engine out of it and go through it. Been watching lots and lots of youtube videos of tear downs and reassemblies of similar motors. Aside from being a bit handy, cleaning the odd carb on chainsaws, weed wackers, generators, etc...I've never torn down and rebuilt an a bit nervous.

    Workbench is all cleared off and ready...

    Before I do that though, I'll check the valve rocker tolerances/gaps while it's still in the Max IV. I've never checked those.

    I does/did often backfire when I turned the motor off.

    The muffler is a while I have it all apart/off I'd like to swap that out. It bugs me (not sure that it muffles anything anymore) and it melted part of the cover.

    1. Will the engine plate/tag give me whatever identifying number I need to order the right gasket kits, parts, etc?
    - i.e. can I just look that up and find a muffler that will have the right flanges/spacing/etc to bolt right onto the engine? Is there anything else to watch out for to ensure that I get the right thing?

    2. Are there full rebuild kits for these engines (sorry if I'm not naming the parts right...e.g. seals for the crank shaft and fly wheel, piston rings, etc) to get all the bits at once...or do you order a-la-cart for what you need when you need it?

    3. Is there a consolidated (newbie friendly) list of the torque specs for the various bolts? Head bolts, rocker arms, case, etc?

    4. Specific to the Clutch (the thing that the drive belt runs around and squeezes as the engine revs up) for the Max do I get that off the horizontal spindle? I see the bolt on the end...I'm assuming that it's a morse-like taper and probably really stuck on there. Do I need a specific tool...or is it a pry-while giving the shaft a tap sort of thing?

    5. This thing is probably about as old as I am (I'm now closer to 100 than 0). I bought it relatively cheap on a lark and the kids/friends kids love it. It was probably much abused before I got it, and it's been abused on weekends since I've had it.
    - What else should I do to the rest of it while I have the engine off and have better access to the rest of whats down there? Brakes seem fine, shifts fine, no weird noises/etc. I replaced the chains, a couple of sprockets and idlers last year and the drive line seems ok. Doesn't leak in the pond so the axel seals seem ok.
    - What else should I do or what else to pay particular attention to with the engine while I have it apart?

    Please and thank you,


  2. #2
    Tyson, I will try to help. An engine only needs 3 things to run, fuel-spark-compression. I always check in the order. Confirm you're getting gas and spark. Then do a compression check. If you have all three it'll run. May run poorly but run enough to tune from there.

    If you have the motor serial/model number you should be able to download the manual directly for Briggs website. I would also look on eBay for a hard copy of the manuals. Once you have a factory parts manual with the factory part numbers you won't have any problems sourcing parts/kits.

    The shop manual will have all your torque specs listed. The driver pulley should just be on a straight motor shaft. Retained with the end bolt and driven with a key.
    Last edited by Nortonscustoms; 11-15-2023 at 02:20 AM.

  3. #3
    Thank you!

    I'll be draining the tank/lines of the fuel that's in there...more just in case it's bad (but same fuel in ATV...generator...50:1 mix for other things). I don't have a compression tester thing that you screw into the spark plug holes...but will likely get one (it'll be handy for many things).

    I'll recheck the spark...kind of tricky since the key is up front and engine is at the back. I might get one of those spark testers that flashes/lights up when it cranks. Or I might use jumper cables and provide power directly to the starter so I'm close enough to hold the spark plug to a ground point.

    I think that I'll pull it anyways and bring it home to the basement. Too cold to work in the utility shed for long.


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