Twin Pocket Bike Engines Build

GoldenMotor.com

MEASURE TWICE

Well-Known Member
Jul 13, 2010
2,744
1,221
113
CA
That's a tight fit.

How heavy is the engine?
Not sure exactly, older engines specs hard to find. About 30 lbs. I used to take the plug screw-on tip and Dremel it to half height along with thread at end of plug. Now I know how to angle the engine and with finesse and have even the slightly higher head and fins on the 3.5hp fit I swapped in place of the 3hp. 80000 3hp an a 90000 3.5hp series Briggs are practically interchangeable in all outer dimensions luckily. Unfortunately what I got in a good condition is a 90000 series 3.5hp was a short shaft 3/4 diameter. I made some changes but no longer have a 10 inch diameter pulley being used which allowed greater than 12:1 ratio. The 3.5hp is in so much better shape that 20:1 ratio I used prior is not needed so much for the hills doing trail riding. For the future a manufactured 125 trail bike, used condition, and my back problem sorted, and I find some way of finishing the parade cover for my motorbike build. The cover in stalled progress is California Sheeps Head Fish!
 

5-7HEAVEN

Well-Known Member
Aug 2, 2008
2,661
240
63
Looking forward to seeing your bike!

What gear ratio is good for a 3hp Briggs engine?
 

MEASURE TWICE

Well-Known Member
Jul 13, 2010
2,744
1,221
113
CA
I really need 4 or 5hp and also all chain since belts slip and heat up which lengthens them from expansion.

Still fun and I scout where I can go. Engine that is in good condition around 3.5 hp maybe 16:1 for overall best on trails not too steep.

Copy between the QUOTES and paste in new window to go to Vimeo Video of mine

QUOTEhttps://vimeo.com/130158715QUOTE Helmet Cam Video on Trails

QUOTEhttps://vimeo.com/203968501QUOTE MC OHV Park road riding

https://motorbicycling.com/threads/mendicino-national-forest-trail-riding.54926/ Still pics of camp and ride NorCal

https://motorbicycling.com/threads/los-padres-national-forest.53832/ Still pics of camp and ride Central CA

https://motorbicycling.com/threads/adapting-briggs-build-to-accept-bigger-engine.61684/ Replaced Briggs to 3.5

https://motorbicycling.com/threads/...bike-diyer-build-to-add-side-car-maybe.29678/ The beginning to almost to what it is now a trail bike
 
Last edited:

MEASURE TWICE

Well-Known Member
Jul 13, 2010
2,744
1,221
113
CA
You clicked on it and it stopped? I have all videos available for anyone to view. There is an option to allow specific sites to play the videos embedded on the other sites (ie like this MB) and I have not allowed that. Still I thought the link would open another window to Vimeo and it would play. That is what I see happen when I click it. When it open the new window at Vimeo I see that I am not logged in, so I would think then anyone could do the same. The old MB website did not show this, if that has something to do with it.

I found in this format the MB website does not show that statement, so I edited above post.

QUOTEhttps://vimeo.com/203968501QUOTE

https://motorbicycling.com/attachments/img_1723-jpg.68021/ Photo of the Bike seen through corral
 
Last edited:

MEASURE TWICE

Well-Known Member
Jul 13, 2010
2,744
1,221
113
CA
Are the engine mounts welded anywhere to the frame or is this a clamp mounting? Or maybe you were just jiging it up to see?

I used over head lines to hang my engine in near position. Used pulleys the raise up and down. Got all things almost square too. The foot peg mounts were off a hair. Never noticed till I switched to motorcycle fold back spring loaded ones. Since I decided to extend the pegs out further and the mounting was different for Honda used part, I nulled out the prior slight tilt, by taking that into account in the adapter brackets I made, that were necessary anyhow.

I have seen some milling done on some of the posted threads here for engine mounts. Pretty nice and ingenious how things can be done. I just went to angle iron and flat plate and welded.

I know what you mean about lifting the weight of heavy motor bike. I have a ramp for mine so I can get it in the vehicle to take to trails.
 

5-7HEAVEN

Well-Known Member
Aug 2, 2008
2,661
240
63
Yes, Im going with angle iron and flat plate, welded.

Still jiggling brackets around for a fit.

If I can mount the pocket bike engines in a "V" angle, i'll be super thrilled.

I might have to change to a wider frame.
It has to be a multispeed one, tho.

I won't settle for a single speed bike.
 
Last edited:

MEASURE TWICE

Well-Known Member
Jul 13, 2010
2,744
1,221
113
CA
My bike has gears, just takes 2 hours to switch. I would have made more room for the engine but at the time was not confident in welding. Even what I have done so far with structural welding was leave a rear drop out half intact and added channel steel to one side. It was to fit the wider sheave when it became apparent that white metal washing machine pulley is very limited time till it cracks. Back in the 70's washing machine parts were strong pressed stamped steel.

If you widen the gap, you can put some sheet metal gussets.
 

5-7HEAVEN

Well-Known Member
Aug 2, 2008
2,661
240
63
Yeah, Im shooting for a 60 degree angle between the engines.
Originally, I had the engines stacked atop each other in a horizontal position.

Good thing I didn't weld the motor mounts in. Just bolted the mounts into place.

Functional placement.
Not as exciting as a "v-twin" to look at.
 

5-7HEAVEN

Well-Known Member
Aug 2, 2008
2,661
240
63
I'm in Seattle for a wedding.

I brought 2 steel plates and a pocketbike engine and carb to have the motor mounts fabbed.

Al Book's Welding in Burien WA did an awesome job for a reasonable amount of time and $$.

All I need to do is bend the mounting tabs until I get the correct "V" angle on the baseplate in the bike's midframe.