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Motorized Cruiser Bicycles The beach cruiser has always been great bicycles to motorize. They just look good with a motor. Use this section to share and discuss about motorizing this classic.

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Old 12-11-2016, 08:08 PM
msrfan msrfan is offline
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Default Max's Phat Briggs Bike Build

This is Max with his Phat cruiser. He has a 3-4 hp Briggs motor for it and we made top and bottom mounts and had my grandson weld them in. He's looking for a fuel tank and has already purchased a 3D Motorsports clutch for it. He got the 428 (1/2'' pitch) sprocket and will use a hub adapter with sprocket on the rear. I sold him a front drum brake and had the button welded to hold the plate from rotating. Tons of work left to do, but he's made a good start.





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Old 01-16-2017, 12:06 PM
msrfan msrfan is offline
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Default Re: Max's Phat Briggs Bike Build

Max got a 4 stroke kit for Christmas and put it on the aluminum frame we were originally going to use for his Briggs build until we realized it wasn't steel. He got it running but had to work out some problems, like some orange junk it the fuel tank that made it's way into the carb. Wouldn't run without the choke on. He new it needed more fuel, so I told him how to clean the jets and it finally came to life. He rode it over to my house without brakes (about 6 miles) to get help hooking up the coaster brake arm to the frame. He had it bent way out to clear his sprocket and it was about an inch out of alignment. His vise at home is just screwed to a flimsy table, so using mine we straightened it until it lined up with the frame and of course now it rubbed the sprocket. I ground the square edges off the arm but didn't go far enough to weaken it. Then I started removing material from the inner diameter of the aluminum sprocket until it cleared. I used Dykem to check the rubbing areas and took off the high points.











I suggested axle adjusters and gave him washers to put under the nuts.




He showed me the belt on his motor was about 1/8'' out of alignment (which is considerable on such a short belt). We replaced the too thick spacer behind the large belt sprocket with a thinner one and now it wont wear out so fast. While we had the rear wheel off we widened the frame so the chain wouldn't rub anymore. We pounded a 2 X 4 in it until it was wider about 2'', then using Irwin clamps, squeezed it back together with the board still in it. That gave the desired clearance. He noticed some bolts missing from his POS kit supplied motor mount. I forgot to mention he never had a pedal chain on it because he knew what would happen if he tried to pedal backwards with the brake arm unattached. I cut sections out of the front and rear castings until they would swing enough to fit the frame squarely. We replaced the allen bolts with cap screws that had washer heads. Now the motor could be raised enough to clear the front pedal sprocket. Now his air filter (which he was running without) will fit without rubbing the frame. His spark plug was white, so I recommended putting his muffler back on and taking some more plug readings and compare with his friends with the same motors. With the engine higher his chain was too short. I didn't have any 415 chain to add to his, so I pieced together a 420 until we had the correct length. The pedal chain he brought had to be lengthened also. Luckily the length fit nicely when the drive chain was the right tension (without a tensioner).






I made a brake arm strap from some heavy banding I had and punched holes in it. He had removed the stock muffler in favor of a short curved pipe that hit the frame. I told him to add about 8 inches to the pipe and if he opened the mounting holes just a bit, he could twist it off the frame. We also replaced missing hardware on his seat so it wouldn't fall off. A small job of hooking up his rear brake became 3 hours of non stop repairs. Free parts, free labor. These kids have it too easy. Good thing I love to work on motor bikes. He texted me when he got home and said it was so much more solid and smoother riding than before. Max planned a long ride to Newport with a bunch of his buddies and decided to put his stock muffler and air filter back on. I told him to get a mirror and hook up some front brakes. He texted me again and said it had more torque and ran smoother in stock form. Still waiting to hear from him to see how his ride went. He'll probably come back over soon for the front brakes. I wonder what other repairs are in store for me.

Last edited by msrfan; 01-16-2017 at 12:12 PM.
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Old 01-16-2017, 08:04 PM
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culvercityclassic culvercityclassic is offline
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Default Re: Max's Phat Briggs Bike Build

Your a good guy for helping these kids, they may want to work with their hands someday for a living vs the boring desk job. You seem to keep busy being retired...lol

I have one of those motors on a bike and did not like the way it ran so I swapped out the carb for an NT from gas bike and wow what a difference, came with the intake manifold too.
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Old 01-16-2017, 10:45 PM
msrfan msrfan is offline
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Default Re: Max's Phat Briggs Bike Build

Yes, I'm twice as busy as when I worked for HB, but it's my own hours and I choose what I work on.
Max mentioned getting an NT carb when he was having trouble with his. I'll tell him it made a big difference for you. He says his is 49cc.
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Old 01-17-2017, 03:17 PM
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runnermike runnermike is offline
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Default Re: Max's Phat Briggs Bike Build

I think this is awesome! Teach them young. I have a lot of men that work for me that do not even know how to use simple hand tools.....crazy!
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Old 01-20-2017, 11:48 PM
msrfan msrfan is offline
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Default Re: Max's Phat Briggs Bike Build

I know what you mean Mike. I've dealt with educated engineers that couldn't come close to building what they design.

Max's little motor keeps sliding back on it's mount slacking the chain. The 4 6mm bolts securing it keep coming loose, so he put a block behind the motor and that helped until it fell out. He's trying shakeproof washers next. If it still moves, I'll have to make him a tensioner that will hold it in place.
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Old 01-21-2017, 12:31 AM
MEASURE TWICE MEASURE TWICE is offline
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Default Re: Max's Phat Briggs Bike Build

I use external star tooth washers backed up by a fender washer on the allen wrench drive bolt up from the bottom of engine platform. External star tooth washer grab very well in contact with the bottom of the engine platform.

The opposite side of the bolt with the threads I use a flat washer and a split lock washer and then the nut.

I also use this method on an adjustable height jackshaft where it sets chain tension between a dual jackshaft system. Using a belt and lots of tension it still held in position. I'm no longer using belt except from one of the jack shafts to a rear wheel sheave. Very small diameter belt drive with v-belts slip too much.

Last edited by MEASURE TWICE; 01-21-2017 at 12:36 AM.
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