New bike with vintage flair

#1
I love the look of the RCF standard frames. They give off a nice retro vibe. Adding a flathead was a given. This one isn't too crazy. It has a slapper cam and a Chikuni carb. The bike is slowly getting to where I want it. I just mocked up the new forks and bars. I got some triple clamps from RPC to use with my GPS forks. The front tire looks much better with the narrower forks. I am in the process of making a headlight bracket. My goal is to eventually get it registered and titled as an assembled motorcycle. Along with the DOT tires I have a headlight and taillight with blinkers, mirror, horn and all the switches and wiring. I will be using a Dewalt battery to power it all. IMG_20220713_111203_623.jpg 20221118_131044.jpg 20221229_141256.jpg
 
#14
I just couldn't get that flathead to run the way I wanted. Since this isn't a vintage bike, I had no problem going to a predator. This hemi has been sitting new in the box on my shelf for a couple of years. I put a non hemi crank in it to use a clone cast aluminum flywheel. It has a Banzai .265 cam and a real Mikuni. The torque converter has a Juggernaut and a 10t sprocket. It wants to pull the front wheel up when you take off and I hit 46mph quickly on my first test run before I chickened out. My next run I was properly dressed for riding. I drove around a bit to warm her up before I let her rip. I never got any further. My side cover came loose and leaked oil everywhere. I had everything torqued correctly. This happened on the last predator I put together. The dozens of others I have had the cover off and on didn't have this problem. I decided to order a stud kit and not worry about it anymore. I ordered a 12t sprocket and a kickstand. Once that gets here and I weld it on I should be ready to paint and wire it up. 20230410_104427.jpg 20230412_191326.jpg
 
#15
I just couldn't get that flathead to run the way I wanted. Since this isn't a vintage bike, I had no problem going to a predator. This hemi has been sitting new in the box on my shelf for a couple of years. I put a non hemi crank in it to use a clone cast aluminum flywheel. It has a Banzai .265 cam and a real Mikuni. The torque converter has a Juggernaut and a 10t sprocket. It wants to pull the front wheel up when you take off and I hit 46mph quickly on my first test run before I chickened out. My next run I was properly dressed for riding. I drove around a bit to warm her up before I let her rip. I never got any further. My side cover came loose and leaked oil everywhere. I had everything torqued correctly. This happened on the last predator I put together. The dozens of others I have had the cover off and on didn't have this problem. I decided to order a stud kit and not worry about it anymore. I ordered a 12t sprocket and a kickstand. Once that gets here and I weld it on I should be ready to paint and wire it up. View attachment 300645 View attachment 300646
Loose side cover bolts is a sign of too much crankcase pressure. That stock valve/baffle, in valve cover can't keep up with that higher rpm, and it will hang open too long pulling in air, as the piston goes back to top of cylinder. Its only designed to operate around 4000 rpm.

I've installed a vacuum/ pressure gauge for testing crankcase pressure, using a billet side cover port, and seen a big burst of pressure all of a sudden, really fast, then back down to normal on the gauge, above 4000 rpm with the stock valve. It jumps over 10-15 psi, real fast, normal was 2-4 psi. This extra pressure will loosen side cover bolts. All that pressure under the piston slows it down, and rpm wont climb anymore.

if you remove the stock valve, the pressure goes even higher at lesser rpm.

I started installing 2) 1 way check valves outta the valve cover and removing the stock valve. I never see pressures over 8 psi at 5900 rpm anymore.

Give em a try, you will see.
 
#16
Finally had time to work on the bike. I put the cover back on and torqued to spec. I started her up and oil started leaking out again. I saw a crack in the bottom left of the sidecover. I figured it was damaged whed I dropped it off my workbench. I grabbed another sidecover and put it on. When I went to fill the engine with oil, it started leaking again. The new one had a crack in the same place. After investigating I found that there was no end play on the crank. I took everything apart and found that I would need 3 sidecover gaskets to make this work. I put it together with a new cover and when filling with oil I saw the same leak with a crack in the same place. The 3 stacked gaskets were perfect on the sealing surfaces but they didn't cover the ridge on the outside of the bolt hole. This caused the corner to bend in when tightened, cracking the cover. I am quickly running out of covers and gaskets. I think I will probably swap a hemi crank back in and run a stock flywheel for now.
 
#17
You should have an average negative pressure on a running engine either with the stock check valve or your own check valves. If you have an average positive pressure then either you have restricted vents or worn engine with too much blowby. 19495.jpg
 

Minimichael

Well-Known Member
#18
Finally had time to work on the bike. I put the cover back on and torqued to spec. I started her up and oil started leaking out again. I saw a crack in the bottom left of the sidecover. I figured it was damaged whed I dropped it off my workbench. I grabbed another sidecover and put it on. When I went to fill the engine with oil, it started leaking again. The new one had a crack in the same place. After investigating I found that there was no end play on the crank. I took everything apart and found that I would need 3 sidecover gaskets to make this work. I put it together with a new cover and when filling with oil I saw the same leak with a crack in the same place. The 3 stacked gaskets were perfect on the sealing surfaces but they didn't cover the ridge on the outside of the bolt hole. This caused the corner to bend in when tightened, cracking the cover. I am quickly running out of covers and gaskets. I think I will probably swap a hemi crank back in and run a stock flywheel for now.
Bummer. At least now you know.
 
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