Camshaft & Valve Train: Small Engine Performance Mods

Camshaft & Valve Train: Small Engine Performance Mods

Hey everybody, its the founder of KartFab
here and today we are looking at another performance mods video. It will show you specifically how to install
a performance camshaft, billet lifters, lap the valves, install the valves and valve springs
on a performance engine built to race. I put this on a chinese baja heat mini bike
and it goes really really fast, so lets check out how I did it. The first thing we are looking at here are
the lifters. The one on the right is a billet lifter, the
one on the left is the stock lifter. These things are pushed up and down by the
lobes on the camshaft, which indirectly or directly move the valves themselves. If you are going to get a performance camshaft,
make sure you look into getting lifters. I decided to go with billet lifters because
they are able to handle the extra spring pressure. I am using assembly lube, that’s what you
are going to need to install these before you break your engine in. Assembly lube has special ingredients in it
that keep the parts from wearing too fast before they mate together. If you look closely, the lobes on the camshaft
are touching the lifters there. Next is the performance camshaft. If you look here on the right vs the left
(right is the performance cam, left is the standard). You look at the lobe, and the lobe is shaped
differently, which affects how high the valves go, and how long they stay open. I have a list of all the performance cams
that I think are good as a mild performance cam for your engine, whether that be a briggs
and stratton, honda, predator 212cc. You line up the dots on the camshaft and the
crank, and you put a (I would actually recommend putting in a new seal here for the side cover
and bolting everything down). Again, links are in the description for all
that. Torque your bolts down on your side cover
and you are good to go. Next is valves those are very very important
for your engine build. Once you have your crank, your cam, and everything
in there, you gotta work on valves, retainers, and choosing the right springs for your valves. I looked at the cam card on the specific cam
that I had, so you might need to get the cam, or look at the cam card first before you choose
the right springs. What I am doing here is I actually ground
the ends of the valves. If you look on this engine, since it is a
flat head engine, not an overhead valve engine; the lifters touch directly to the valves themselves. So, you actually need to physically grind
them to set your lash. Unlucky for me, but lucky for you if you have
an overhead valve engine, you actually don’t need to grind them (the valves), but you do
need to lap the valves if you are doing a rebuild, or if you have a new engine and you
want to have the best compression possible. Lapping the valves basically uses liquid sandpaper,
valve grinding compound, link is in the description for that; and, a little suction cup on the
end of a stick, which is called a valve lapping tool. You basically stick it to the end of your
valve and you rotate it back and forth, pushing down, and adding a little pressure. You sand down the seats and the valve and
you wipe it clean. You want to make sure that you wipe it with
a wet rag until there is nothing left on the rag. You just wipe it and it stays white. Notice how even if I do wipe it a little bit,
there is still stuff coming off right into the rag there? You can actually just wipe it as best as you
can, spray it down with some carb cleaner, and you are set. Then, you put your valve into some assembly
lube, and then you put it back into your engine, just like that. Next, we are going to check our valve lash,
which is basically checking the clearance between the end of the valve and whatever
it is connected to. In this case it is .006 inches for mine, which
is perfect, (that is what my cam card specified). I have a description of all the different
lashes that you would need for your specific engine in the description as well, so check
that out, it is really important; so you don’t have to ask me later and me say, ‘oh its right
in the description’. Anyway, this is a valve spring compressor
tool. You dont really need that for a flat-head
engine, you can do it by hand if you have an OHV engine. Basically, you put the retainer and spring
together, compress it, lift it up a little bit, pops right out just like that. It is that simple. Alright, to wrap everything up, we have seen
performance camshafts, you should probably get a mild one for a boost overall, and how
to put in valve springs, lap your valves, set valve lash. All of this is part of the performance build
that I have got going on. If you need any advice, feel free to comment
below. Thanks for watching the video, if you like
it please give it a thumbs up. If you have any questions about how to do
something on your engine, let me know in the comments below. Also, the last video was how to install a
billet flywheel. The next video is how to install or modify
your compression ratio with your head gasket, as well as indexing your spark plug. So stay tuned for that. All the links are below for the playlist and
all the parts, so if you have any questions about which one to get, they are all down
there. Thanks.

About the Author: Michael Flood


  1. you never did answer my wheel hub question… also, can you do a live axle go kart build video? I wanna make my one wheel drive 80s model one seater go kart into a two wheel drive but i dont know how

  2. My motor I messed up how do I fix it
    I hit a bump in the road and now it doesn't run properly
    I give it full throttle and it dies
    Now it doesn't go as fast
    It back fires to much
    And it sounds like it dies for a split second then comes right back on
    It badly sound like it's running well idling

  3. Love these videos I learn a lot about engines from them. I sort of want to see how good the karts go after these upgrades are done, that would be cool. Or even just a before and after of the engine running.

  4. if you don't know how mutch these videos help, I have 2 kart frames, 3 wrecked 4 wheelers,and 8 dirt bikes in the family to work on I am only 12 but my dad can't do it all for us. thank you

  5. I have the same engine with no carb. I wanna put a honda carb on it, but I dont have a tig welder(only arc). Any advice?

  6. I had a question i need help making a break system like a rod for my manco kart just wondering can u give me a few ideas I'm running disc break and caliber as well

  7. man is there any reason i cant get my head off??? the bolts seem to be torqued so hard im just ripping them up trying to pull them out

  8. I'm planning on doing this to a 8 horse Briggs flathead, any suggestions for a carb? I don't want to use the updraft carb

  9. I just ordered a predator 212cc I'm just going to ride it for fun. Does the valve springs come installed already in the motor or do I half to put them in.? And is there any other parts that don't come with it that I need to order? Please tell me

  10. I watched all your videos on this engine build and i am planning on doing a predator 212 performance build. Here are my questions.
    (1). are all of the torque specs the same for the predator as the briggs
    (2). i am a kid and dont have money, so what i wanna do is like add parts on to the engine as i go on and get money and once i have everything remove the gov…. due to this, is there a certain list of what i should do first and last(like should i do the piston first and cam last etc.)
    (3.) if i add all of these parts, do you think it will be safer, if not totally safe to rev my engine to full throttle w/out governor for like 20 seconds?

  11. It's a flat head with stock internals carb been modified for methanol don't think the motor is ever been a part it sat in my garage for 10 years

  12. I looked on and couldn't find the springs. what does "19lb stock appearing" mean? Love the videos. Thanks.


  14. Lapping valves only works at startup. Correctly done valves and seats have a 1° difference on the angles at ambient temp. At operating temperature the heat difference between the valve and seat causes them to expand differently, taking up the 1° difference.

  15. I've been looking into racing karts. Do they have rules about driver weights? I only weigh about 90lbs so I thought I might have quite the advantage in terms of top speed and acceleration.

  16. if you put a camp in one of these engines I have seen on the dynocams website that it is recommended you to weld the lifter bore. Is this necessary if you don't plan running the engine at high rpms?

  17. I have a cmxx ohv 136cc engine (very similar to a 212) I have removed multiple different govenors on multiple different engines and sizes but on this during the removal the camshaft fell out and does not have the dots to line the cam up with the crank. What should I do? Any help would be greatly appreciated!

  18. First of all thanku very much sir! It was very useful! Please let me know
    how can i change the stroke length of my engine without changing the connecting rods?
    or what are the ways by which we can increase our compression ratio?

  19. I have a sigma 212 and put on a stage 1kit on IT and I fell air coming out some whare near the carburetor I do not now why and the kit only gave me 2 more miles per hour is this right or do I need to do something

  20. I was wondering why does my pull start rip out my hands I set the valves right and the flywheel key is not split ? Do you what it would be

  21. Looks like itll be a good runner im building a flat head now its a tiller block but has a new raptpr 3 piston arc rod arc 3hp flywheel has the brows shaved and ported and polished intake and exaust well i didnt polish the intake left it rough got a raptor carb for it just have to pic my cam and valve springs

  22. Are there any retainers that go on the top of the valve springs or do the springs just sit against the block? Thx.

  23. Any idea on if there are performances mods similar to what you used but for a 6.5hp Briggs and Stratton flat head and to convert the motor from horizontal engine to vertical?

  24. Доброго дня! Ви купляли вже готовий розподільчий вал з розширеними фазами чи виготовили самостійно? Дякую!

  25. I have a 127cc briggs 550 series and I'm trying to find performance parts as well but don't know where to start. Briggs don't seem to have much aftermarket.

  26. Maybe you know where can I get a performance cam and springs for my old 8hp flat head [email protected]? I can't find anything for it. Has a really wierd rod on it too that I have never seen before and both of the valves are same size too.

  27. I have royal enfield continental gt 535 and I'm gonna install a performance cam which my mechanic will custom make for me. should I be adding valves and lifters and push rods also should I buy a power commander (piggy bank ecu)

  28. Hey grant, know your pretty busy but advice would be godly. So I have a 5 hp tecumseh year 95-99, have about 1/4 inch or more play n the crankshaft. Can push on shaft OR flywheel and get the play. Any suggestions for problems or solutions to eliminate some. Also con rod has slight play. Really don't want to replace to much. How can I rig it just to somewhat safely move it on its own power. Does have are not liable for any of my actions whatsoever. just shoot ideas @ me please.

  29. Dyno CM cam or Isky Black Mamba for my clone
    Engine ?
    I'm looking for max power
    Throughout the rev range/
    /powerband .
    I have a BSP 196c.c. with
    22m.m. Mikuni (Jap.)
    Aluminium Flywheel
    # 20 lb. valve springs
    Thanks in advance !
    Frank from Connecticut

  30. Briggs Flathead 8hp… I can't find any performance parts for this engine. I would like to have (billet) flywheel and all the internals accept crank. If no parts are avalible does anyone know if the parts for the 5hp fit and are feasible

  31. Are the springs the same for int and exh or is the exhaust spring a different part number? I bought the #555060 for the intake and #555076 for the exhaust. Did I get the right exhaust valve spring? Briggs #133232.

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