Too high rpm

Colt sr

Colt sr

Member
What is the highest rpm you ran on a flatty before it let go? We were turning 7300+ and pretty sure the engine is toast.
 
A well built Flathead with a billet rod should be able to handle 7300. With a stock class cam it is probably not making much power up there.
 
Chipg56 said:
A well built Flathead with a billet rod should be able to handle 7300. With a stock class cam it is probably not making much power up there.
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It was smoking more than a mosquito fogger. And it has a 96-3 cam if I remember correctly. Long story short the guy who was to loan us a motor never showed so we put one of the engines I brought with me to sell on so we could at least run.
 
AD9700E3-F3E9-44D8-AFE7-0F14E6142B15.jpeg

Still alive … 👍🏻
 
I’ve had one at 10,400 and it stayed together. I’ve also had a few blow the cylinder off, break cranks and one split the block and chucked out the whole mag side crank bearing. All of those were turning in the 9,000 to 9,800 range.
 
7300 won't kill an engine, but you're not doing it any good (especially if it was not built for that.)
A 96-3 is done making usable power well before 7300. We generally peak them at 68-6900.
A lot depends on the lash, spring pressures, carb and pipe. YOu can move the powerband up or down with small changes, but I'd say as a general rule, 7300 is out of the powerband for your engine.
It could just have a ring stuck, valve guides need replaced, etc.
Good flathead stockers built with low tension rings smoke a good bit anyway (especially leaving the grid,) but once you're on the hammer, smoke shouldn't be seen on the track.

We still rebuild plenty of flatheads and have all parts in stock if you need. Just give us a call.
We're currently working on a 4-6 week turn-around however.

🏁Thanks and God bless,
Brian Carlson
Carlson Racing Engines
Vector Cutz
www.CarlsonMotorsports.com
Carlson Motorsports on Facebook
33 years of service to the karting industry ~ 1Cor 9:24
Linden, IN
765-339-4407
bcarlson@CarlsonMotorsports.com
 
Oil covered the whole engine and frame of the kart. This was on a Jr sportsman. We were supposed to get a loner clone but the guy never showed. I had brought this flatty to try to sell. We had to set it on a 7 degree mount. We put a gold plate on it with a 49 jet. I only had a 52 and 49 with me. I currently have 6 flathead engines here. It was a last minute throw on the kart and get him on the track situation.
 
Colt sr said:
Oil covered the whole engine and frame of the kart. This was on a Jr sportsman. We were supposed to get a loner clone but the guy never showed. I had brought this flatty to try to sell. We had to set it on a 7 degree mount. We put a gold plate on it with a 49 jet. I only had a 52 and 49 with me. I currently have 6 flathead engines here. It was a last minute throw on the kart and get him on the track situation.
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With the smoking I would suspect blowby and/or a bad sealing at the breather, bad rubber grommet likely. Much like a crank seal, the flywheel fan blows it every ware. Even a small amount can look like a serious disaster.
 
^ Could be. Easy way to check is to look where the oil is still clean after running. The dust will collect to the oil that is not moving - where the oil is leaking will constantly flush/clean the dust away. Wherever it's got clean wet oil, there's your leak.
Look all around the grommet and breather gasket (especially lower right hand corner.) If you don't see it there, likely coming from the oil seal.
 
I agree with Brian on the oil seal. I built a brand new open with brand new seals and the mag side seal leaked and blew oil everywhere.
 
Skidude said:
I agree with Brian on the oil seal. I built a brand new open with brand new seals and the mag side seal leaked and blew oil everywhere.
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Certainly could be, but changing that seal requires the flywheel being removed. I have been told that the seal can be changed without taking out the crank but I have never tried that. The breather is a simple repair and I certainly would check that first.
 
If you need to change the seal, pull the fly wheel, drill a small hole in the seal, put a sheet metal screw in the hole and pull the seal out. Then install your new seal.
 
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