My First Project: Briggs 3 hp

[professor]

My 2 cents-
I have a HF 79 powered bike. Belt to jackshaft ( bought ball brg. pillow blocks from Mcmaster Carr - if you pay w/credit card. -no problem).
I used 1/2 inch size because I had some pulleys that size. No keyways. Grind a flat where the set-screw goes and lock it down real good and you are golden.
That jackshaft runs by # 25 scooter chain and sprockets to another jackshaft which IS (now) a 3 speed Stumery Archer hub.
The hub is bmx chain drive back to a HT sprocket (grind down or adapt a bike chain ring to it).

Your idea of going 35 mph with one gear will not work unless you pedal real good to get started and THEN engage the clutch. The 4 stroke doesn't rev like the china engines. It will be like you are trying to take off with a car in high gear.

The double jackshafts allow me to have a freewheel and smaller pulley sizes.

I stretched the bike frame 3 inches and put the engine up front.
I widened the one piece crank like it was mentioned before.
I run the stock governor and it is great- like cruise control.

 

[jbcruisin]

My 2 cents-
Your idea of going 35 mph with one gear will not work unless you pedal real good to get started and THEN engage the clutch. The 4 stroke doesn't rev like the china engines. It will be like you are trying to take off with a car in high gear.

My 49cc Hua sheng does 34mph tops without pedaling to start with no problem. For some reason Quenton's 49cc is faster than mine on the take off & goes 40mph. I rode Fossil's 79cc Harbor Freight at my rally Saturday & it had no problem taking off without pedaling & went 42 mph . This is all on flat roads with EZ Q matic drives.
Jay

 

[professor]

Jb- thinking about your comments, the Briggs is like my HF. Low rpm engines. I assume the engines you mentioned are good for more rpm.

 

[jbcruisin]

Jb- thinking about your comments, the Briggs is like my HF. Low rpm engines. I assume the engines you mentioned are good for more rpm.

The engines I talked about are all 4 strokes. The Huasheng 49cc cruises nice at 7200 RPM. I think the 79cc Harbor Freight tops at less than 5000 RPM. You had mentioned that 4 strokes have to be pedaled to start off if you want any kind of decent top end. That's why I posted my comments.

 

[discontinuuity]

Sorry If I haven't updated this in awhile, as I'm working full time now and can't work on the bike as much. I've reconsidered my plan for mounting, and I'm going to try welding motor mounts onto a steel frame. I borrowed a small stick welder from a friend, I have a small pile of scrap steel, and I'm looking for a cheap steel mountain bike on craigslist. Then the plan is to finish the welds with a TIG machine. I'll use the same TIG machine to sandwich a couple aluminum bike wheel rims together; one for the tire and one for the pulley. I'll have to cut apart and re-weld the rear forks to make this fit.

Thanks for the input, prof. I haven't decided what the gear ratio (and thus top speed) will be. I'll probably shoot for about 30 mph. My only experience with Briggs engines was a 5 hp minibike I once had, and that thing did 35 mph on level ground no problem, and still had enough torque to climb hills. This 3 hp motor of course won't give me the same torque or top speed, but I can still probably get around town with one gear. I'd like to do belt drive with no jackshaft, but that probably isn't possible without putting the engine far to one side.

 

[bowljoman]

you might think Im crazy But I think you will get much farther and faster if you:
1 flip the motor, mount it on a rear luggage rack.

2 rip out the hub of a 3-speed wheel and use it as a friction drive. Grind down the spoke flanges and stuff it into a radiator hose for a rubber roller.

I did that as my 'second' motorized bike, and you will hit the 30+ you are after.

Yes the center of gravity is higher, but the big 4 strokes are notorious for cracking the frame over time. Its no fun to see them develop in the bottom bracket compared to seeing them on a rear rack.

3-rd gear in a friction drive slips a whole bunch, but I think you'll be rolling much sooner and faster. The key to speed besides raw torque and RPM capability is the overall weight of the drive train, and how much it has to move. Imagine a short chain running to a roller drum ,rather than jack shafts, long belt, and large pully.

You may figure that you can hit 30 mph with a single gear, but how long can you enjoy riding with that big 4-stroke at 4500-5000 rpm? These briggs motors are more brutal than the cute little 4-strokes.

P.S. carry extra chain and tools. The chain stretches and destroys your sprockets/derails easier, and the vibrations at WOT loosen everything else.

 

[discontinuuity]

I'd rather do an in-frame mount because I'd like to have the rear cargo rack open for carrying stuff. I'd rather not have a friction drive because of slipping and tire wear. The 3-speed hub idea is interesting; I might try something like that later.

 

[MEASURE TWICE]

I have done similar to back in the olden days and maybe also current, I don't know if Whizzer (sp?) is still around and as well connects a large v-belt type pulley to the rear wheel.

The way they did it was with some kind of clips to the pulley to all spokes on one side, I think from a picture I saw from one in the 20's era. It was real neat they also had two opposed cylinders and two separate carbs in the sweet spot of the frame (the triangle area forward of seat post and below).

I have an am again am using a washing machine pulley with the center cut out, but leaving the 6 tabs to help mount the pulley. I put 3 pieces of wood (later used resorcinol glue and paint over the parts to help preserve) on the inside of the spokes.

Two tabs per each of the 3 inner spoke wooden parts. Then I put a thin piece of wood cut out in a donut shape ring to sandwich over the outside of the spokes. Then finally on the outside of that I put the washing machine pulley and have holes drilled through all to tighten all together. All stainless steel 8-32 with two nut and split locking washers for each to set the tension or there can be a wobble. That can be tricky and has to minimize.

The centering on the other axis for the washing machine pulley allows for movement in all directions, but there has to be accounted for the screw not to be hitting the spokes. I made some slight error and ending up slotting some of the holes to get it right.

An easier way may be if you can get just the clamp on to the inside of the hub type thingamajig that some guy had on his motorized bike, but that was for a chain and sprocket. You might look to see what one of these things looks like and make one yourself and with pulley if you think it is worth a try. Come to think of it my way has been a bit tedious.

Some people suggested that I weld directly to the hub, but am not sure how that would look and hold up. I imagine that the metal is thin and melts away quickly when welding and felt I was not that good a welder to do that kind of stuff. I had problem with trying to weld thin to thick and it get to be a hassle. I did my best where that was necessary and tried heating the thicker part first and waiving the tip back and forth. Flame welding with oxy act may be easier for that type of problem, but the check out lesson for that at the center cost a lot and I already took MIG class too.

I guess an cheap import mini bike is one way to go, but I had fun getting time welding and doing powder coat. The bike will be spray can paint, the oven is too small.

The only thing different this time around I got the engine weighted better and volumetrically pretty close to center as well. I TIGed the steel angle iron to frame. AZ1826-12 Jackshaft kit 5/8 by 12 from Azusa Engineering Incorporated from a go cart shop nearby for only $32.95.

It had what I needed and the only slightly trick part is using the mount that accept the bearings to hold the shaft, either weld or drill and mount to what I already welded to the frame. I decided to do the second since I slotted the mount holes and can move the shaft forward and aft to adjust the v-belt which goes to the washing machine pulley.

So I have a small v-belt pulley on the jack shaft. Then I used the larger of the two sprockets that came with the jackshaft kit and ran it forward and off to the side to meet a slightly smaller sprocket part of a mini bike centrifugal clutch. This is to gear down and as I calculated the same type engine a 3hp size but with now 26 wheels will be the same as the 24 inch wheels due to the addition gearing down from the two sprockets forward connect to jack shaft.

I am getting to see how it will turn out soon, but have been working on getting a carb air filter snout hose to grab air up high away from dust while riding. See the hardware store for all kind of stuff in the heating and ventilation area and use it for what it was not intended. Even better a thrown out in the dumpster hose from a vacuum cleaner as part of the mod.

Measure Twice

I'd rather do an in-frame mount because I'd like to have the rear cargo rack open for carrying stuff. I'd rather not have a friction drive because of slipping and tire wear. The 3-speed hub idea is interesting; I might try something like that later.

 

[MEASURE TWICE]

I got to tightening the parts after painting them for this rear wheel pulley and found that unlike before where when in the past I had bent the tabs on washing machine pulley to make up the difference for the spoke angle I have a problem. I didn't know this problem was going to happen and I like the idea better to not make a two part bent in the tabs on the washing machine pulley like what had worked before, becuase I thought for long lasting results of the attaqched pulley, you do not do as such.

The problem was not before since I did not have the washing machine pulley fully contacting the surface of the wood spoke sandwich, ie. the bending of the pulley tabs had it offset.

Since I am spanning across I think about 8 spokes for each of the three wood spoke sandwiches to hold the washing machine pulley on, there needs to be varying degrees of shims added to the wood on the inside of the spokes wooden part.

The outer wooden part is a thin ring that flexes. The washing machine pulley does not get bent with the wood except for the tab of the washing machine pulley and not too much at that. The v-belt groove area of the pulley is only about an inch deep and rest on the wood ring. It is not spanning much distance from the spoke angle from the wheel rim to the hub.

The problem comes from when I tighten down the screws that cinch the whole sandwich together. If I were to have screws only at the ends of two spokes and not span across a 3rd middle spoke or more, like the 6 spokes in the middle I am currently having to span, there would be no problem.

The 8 spokes for each sandwich now have a gap in the middle that make the tightening pressure a problem there. The end spoke areas quickly bottom out the screw and nut and start tensioning statically. The inner 6 spokes have a need for more tightening the closer they are to the middle and cause the washing machine pulley to be bent inward and causing a wobble.

This is not a wobble that would cause the v-belt to become tighter and looser as the wheel spins, that is centering which I have ample adjustment and have gotten right. No, it is a side to side wobble that goes back and forth 6 times as it rotates. I looked at the distance it moves and cannot accept it as OK.

There will be shims of either wood or epoxy putty I will add to the inner wooden sandwich parts that should fix the problem. I just had finished covering the wood parts with a strengthening and waterproofing and nice looking cover to protect the whole deal. I used the resorcinol glue 1st and then followed 2nd by Krylon Fusion spray paint.

Measure Twice

=========================================================================

I have done similar to back in the olden days and maybe also current, I don't know if Whizzer (sp?) is still around and as well connects a large v-belt type pulley to the rear wheel.

The way they did it was with some kind of clips to the pulley to all spokes on one side, I think from a picture I saw from one in the 20's era. It was real neat they also had two opposed cylinders and two separate carbs in the sweet spot of the frame (the triangle area forward of seat post and below).

I have an am again am using a washing machine pulley with the center cut out, but leaving the 6 tabs to help mount the pulley. I put 3 pieces of wood (later used resorcinol glue and paint over the parts to help preserve) on the inside of the spokes.

Two tabs per each of the 3 inner spoke wooden parts. Then I put a thin piece of wood cut out in a donut shape ring to sandwich over the outside of the spokes. Then finally on the outside of that I put the washing machine pulley and have holes drilled through all to tighten all together. All stainless steel 8-32 with two nut and split locking washers for each to set the tension or there can be a wobble. That can be tricky and has to minimize.

The centering on the other axis for the washing machine pulley allows for movement in all directions, but there has to be accounted for the screw not to be hitting the spokes. I made some slight error and ending up slotting some of the holes to get it right.

An easier way may be if you can get just the clamp on to the inside of the hub type thingamajig that some guy had on his motorized bike, but that was for a chain and sprocket. You might look to see what one of these things looks like and make one yourself and with pulley if you think it is worth a try. Come to think of it my way has been a bit tedious.

Some people suggested that I weld directly to the hub, but am not sure how that would look and hold up. I imagine that the metal is thin and melts away quickly when welding and felt I was not that good a welder to do that kind of stuff. I had problem with trying to weld thin to thick and it get to be a hassle. I did my best where that was necessary and tried heating the thicker part first and waiving the tip back and forth. Flame welding with oxy act may be easier for that type of problem, but the check out lesson for that at the center cost a lot and I already took MIG class too.

I guess an cheap import mini bike is one way to go, but I had fun getting time welding and doing powder coat. The bike will be spray can paint, the oven is too small.

The only thing different this time around I got the engine weighted better and volumetrically pretty close to center as well. I TIGed the steel angle iron to frame. AZ1826-12 Jackshaft kit 5/8 by 12 from Azusa Engineering Incorporated from a go cart shop nearby for only $32.95.

It had what I needed and the only slightly trick part is using the mount that accept the bearings to hold the shaft, either weld or drill and mount to what I already welded to the frame. I decided to do the second since I slotted the mount holes and can move the shaft forward and aft to adjust the v-belt which goes to the washing machine pulley.

So I have a small v-belt pulley on the jack shaft. Then I used the larger of the two sprockets that came with the jackshaft kit and ran it forward and off to the side to meet a slightly smaller sprocket part of a mini bike centrifugal clutch. This is to gear down and as I calculated the same type engine a 3hp size but with now 26 wheels will be the same as the 24 inch wheels due to the addition gearing down from the two sprockets forward connect to jack shaft.

I am getting to see how it will turn out soon, but have been working on getting a carb air filter snout hose to grab air up high away from dust while riding. See the hardware store for all kind of stuff in the heating and ventilation area and use it for what it was not intended. Even better a thrown out in the dumpster hose from a vacuum cleaner as part of the mod.

Measure Twice

 

[discontinuuity]

I've worked a bit more on my motorbicycle.

First I got a steel frame bike:

Then I cut out some square tubes from an old broken barbecue ( you can see its remains in the photo above):

...made some ugly yet functional welds:

...ground them flat, and added mounting holes:

After a bit of tweaking I got the engine bolted up to the mounts and test-fit the engine in the frame. Currently I'm working on getting everything rigged up square and plumb before I weld the mounts to the bike frame.

Then I'll be ordering a clutch, bearings, jackshaft, pulleys, and miscellaneous other parts to get everything working. I might not need to cut and re-weld the rear frame after all, but we'll see. I'm going to school right now as well as working part time, but I'll keep working away at this project. Too bad it will probably start snowing by the time I'm done!

A couple questions:

1). Does anyone have a good source for a go-kart type clutch, as well as a jackshaft and bearings? The jackshaft only needs to be about 6 inches long.

2). The lawnmower carb I have needs a rebuild (all the gaskets are disintegrating). Am I better off fixing up the one I have or buying a carb for a 100cc scooter and trying to make it fit?

 

[MEASURE TWICE]

From Measure Twice:

Excerpt from above. I bought from Cambrian Gocarts in San Jose, CA. You can buy direct from the CA mfr and have them ship

AZ1826-12 Jackshaft kit 5/8 by 12 from Azusa Engineering Incorporated from a go cart shop nearby for only $32.95.

They have a PDF catalog you can down load 7.7mb from mfr; I found the one I got on page 36 of 50. Part 5/8 Jackshaft Kit. (see pdf for all contents) 1826-12 for the 12 inch jack shaft, they have 10 an 14 inch also. They have these in #35 type sprocket and a forth one if you need in #40 with 3/8 shaft, but that would mean you probably would have a bigger than 3hp to justify that.

Price I got was from the retail shop, so check with Azusa Engineering Incorporated for what they do when buying direct, could be different?

Azusa Engineering - Frequently Asked Questions

2. How do I buy Azusa Products?

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=====================================================

I am only suggesting this as I felt it was fairly good quality, but I still have not run the bike yet, I have a issue with the washing machine pulley I need to shim up to not be bent when I tighten it in place. I'll let you know when I get further with my project.

Measure Twice

 

[frostythesnowman]

I'm disabled and can't use the pedals on my bike anyways. I scrapping the pedals on my 5-horse chopper bicycle project. Welding large fender washers over the Cranktube openings, and routing tube steel thru the openinges int he wahsers. Welding the tube into place and attaching my footpegas to the tube. Right now, I'm busy assembling the rear hub and sprocket. Have to attach a larger sprcket on the left side of the rear wheel instead of the right, to line up with the output shaft of the 5 horse Tecumseh engine I'm using. Who needs pedals.... LOL!!

 

[bowljoman]

Who needs pedals.... LOL!!

Exactly!

In WA, they just changed the definition of moped/motorized bicycles to include cycles with no peddles.

 

[Dan]

I'm disabled and can't use the pedals on my bike anyways. I scrapping the pedals on my 5-horse chopper bicycle project. Welding large fender washers over the Cranktube openings, and routing tube steel thru the openinges int he wahsers. Welding the tube into place and attaching my footpegas to the tube. Right now, I'm busy assembling the rear hub and sprocket. Have to attach a larger sprcket on the left side of the rear wheel instead of the right, to line up with the output shaft of the 5 horse Tecumseh engine I'm using. Who needs pedals.... LOL!!

Very cool Frosty. Looking forward to seeing pics

 

[discontinuuity]

I'll probably run it without pedals for some time, until I can make the engine narrower or the pedals wider.

Which leads to the question, do any of you know how to get the pull start clutch off of the flywheel? If I can cut down the output shaft and machine the fan blades off the flywheel I could save a lot of width. Then I'll just need to cool it a different way, maybe with electric fans.

I've got the motor mounts in right now but I'm still working on the frame a bit. More photos and updates to come.

 

[discontinuuity]

So now that I have a little spare cash, it's time to buy parts. Hopefully I can put everything together around Christmas and get it on the road by the New Year.

I'm still planning on doing a belt drive, but I'll probably use a chain drive from the clutch to the jackshaft, since chain drive clutches are cheaper for whatever reason.

One question I have is whether I will have any trouble with the chain if I use small sprockets (about 10 teeth) on either end. Is there any chance that the chain will rattle against itself or would there be any other problems?

As for the belt drive, I'm planning on gluing two mountain bike wheel rims onto my back wheel: one for a spacer in order to clear the tire, and one for the pulley. Ideally I'd just get a Whizzer-type rear pulley or go with a two-stage chain drive, but I have about five spare bike wheels sitting around the house and those Whizzer pulleys are expensive. So unless someone in the Denver area wants to buy some bike wheels (both mountain and road bike type), I'll probably stick with what I got. I'll have to tweak the frame in order to make the clearance, but that shouldn't be too hard. But I thought I'd ask if I'm missing some easier/cheaper solution.

 

[discontinuuity]

I'm planning on using a Max-Torque go-kart clutch:
4-458 - 41 Chain 5/8" Bore Max Torque Clutch

I suppose the chain will be moving at the same speed as the engine, but if I understand correctly this is no different from how it works on a go kart or mini bike, except that instead of a big sprocket and a small sprocket I'd have two small sprockets.

So I'm not too worried about the chain flying apart from centrifugal force, but I am slightly worried about how I will keep it tensioned. I'm also worried about keeping the top and bottom of the chain from running into each other since they'll be rather close together.

 

[Dan]

YouTube - Homemade Mini-bike 2

This was pretty cool. More germane, if the chain can take this, great!

 

[discontinuuity]

Lol, that thing looks pretty fun, but also dangerous. I used to have a mini bike with a 5hp B&S engine, which was plenty powerful. That thing looks like an 8hp!

Also, I think I'll need a chain guard for my motorbike

 

[Dan]

LOL, I had posted bad information above so I wrote Discontinuity. Apologized and deleted my posts so as not to confuse any one. He's not really talking to him self.