Unresticted RPM's

B

BRE

Member
What are some of you guys turning and does carb make that much difference in RPM's??????
 
Jason, all the components, working well together, influence performance, and RPM's. The motor's simply an air pump, so volumetric efficiency is key, supported nicely by a well-matched carb. One of the more common mistakes made, is to wind a motor too high, past the power-curve. That said, RPM's vary from builder to builder, and motor to motor. Pro-gas class might see mid 7000, Alky, closer to 8k RPM's. Much has to do with cam profile, air flow, and how well the motor seals through each cycle. Something so simple as valve springs play a huge part in this process. Related to the carb, if you're too lean, or too rich, the motor will not build rpms as well as a finely-tuned engine.
 
Agree with all that I turn mine from 7300 7600 again depending on track size and condition.
 
I got a gold plate animal no matter what gear I put on the Cart it will not go over 5900 rpm is it the jets being that it is a stocker animal
 
Normally, after isolating three very important elements that help a motor run, the problem becomes obvious. Let's start w/ fuel. Float set @ .865-.875, then jets are clear, and correct? How about the carb metering rod on the slide in place? Secondly- The ignition timing is a focal point. Has the flywheel moved (take the starter nut off) on the crank? do a visual to insure it's correct. Third is compression, so valves adjusted to minimal lash, and with the equivalent of a tablespoon of oil through the sparkplug hole, then the plug reinserted, is there acceptable compression?

Sometimes a failure to return a hot motor to TDC leads to valve warping, and a measurable loss of power.
 
Out west, we run Junior l classes w/ gold plates on gas w/ 34 primary & 93 high-speed jets. On Methanol, only a guess, but thinking 38-40 primary, and 130-something main jets. Engine builders have forever debated the merits of RPM in restricted motors. I gotta ask.... what rpm did this motor rev previously, with the same configuration of components?

Also, kind of unusual to have a flywheel move on a crank, so was it lapped, and could it have moved again?
 
Not sure on fly wheel man told me it wouldn't slip again but I don't know when we put the plate in it never pick up rpms so I was thinking it has big jets that regular engines would run
 
What jets are in it? I'd seek out a local kart shop that can assist. There aren't many doctors that offer medical opinions over the phone/internet, motors can be thought of in the same way. Best of luck!
 
There are a lot of things that make a good motor.
We need more info than what you have given us.
Is this a blue printed motor or factory stock?
What are you torquing the flywheel nut to?
Is it a electric starter nut or the flimsy factory flywheel nut or the new HD flange nut that comes with the motors?
Are you using a key? Straight of offset?
What are the valves set at?
Are you using a muffler?
 
Bought in Georgia it has Tod miller stickers on it
electric start
flywheel nut not sure came on it
no fly wheel key I believe guy lock tights
valves dont know
yes muffler
 
Do you know or trust the guy you bought it from?
Just because it has someones decal on it doesn't mean that's what it is
The type of ignition it has determines how the timing should be set. Tell me what color the coil is.
I never build an engine with out a flywheel key. I do not use locktite.
What size socket do you use on the starter? Does the starter nut extend past the blower housing?
You need to know how to check the valve clearance / adjust the valves!
I have had mufflers with loose baffles that have rotated to restrict the exhaust severely.
 
If it has a blue PVL coil the straight aluminum key from Briggs will work just fine.
Remove the flywheel nut and make sure the key ways are lined up and put a key in it.
If it's not a HD flange nut either get one or put an extended starter nut on and tighten to 100 Foot pounds.
Remove the valve cover and put the piston at TDC compression and make sure you can turn the push rods with your fingers.
The valves should be adjusted to the point that you feel some resistance when you turn them with your fingers.
 
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