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hey guys, just thought I'd start a build thread on my latest endeavor. Fitting a mildly modified Briggs inside an Electra Deluxe frame.
Let me start off by saying even though I'm still new to motorizing bicycles I have learned a lot already- mostly from dumb mistakes (actually started off the build by drilling holes in my frame.) :shock: Since then I've fixed that mistake and have been messaging a member on the motobicycling forum (msrfan) who races bicycles with a similar engine to make sure the build will hold up to the added stress. So far this has included moped forks, dual moped drum hubs laced with 12g spokes in the front and even bigger spokes in the rear (don't know what size yet.).... I realize my plan may be a bit overboard but I like to try and be unique. with that said if anyone has any input on how I can decrease my chances of disaster please feel free to chime in. Anyway, on to the build description.
Here's how the build started off.
The engine:
1972 206cc Briggs flathead- usually known as the 5hp Briggs or the Briggs model 13. I bought the engine from a member on oldminibikes that had been sitting for who knows how long. She was dirty inside and out but harbored a freshly honed cylinder under her head. First thing I did was gut it all the way down to bare block so I could take care of those nasty power robbing eyebrows, and figured while I had the dremel out I may as well cut off that rough casting in the ports. Then after the make over I flushed all the metal dust and sludge out with the solvent tank in my automotive class. Also threw in a stock length billet rod for ease of mind. Got her all built up and added a 'ghetto' pipe fitting header that I plan to hide in heat wrap, a Tecumseh h50 carb with a custom made intake and brace, a 4hp head for extra compression, and converted her to electyronic ignition.There are mixed arguments on the gains from the head because they tend to lack flow, but in my personal experience they lean more toward low/mid range more than the stock head so it should fit my needs just fine and if worse come to worse I can always get my hands on a cut stock head. :roll: And finally I decided to re-purpose an old trophy I found at the junk store into an oversize velocity stack.. It still needs some finishing touches if I decide to keep it (and don't worry, it WILL have a filter.)
And here's a running video:
http://www.youtube.com/watch?v=gbxWF195jhs
The Frame:
First and most important aspect I need to work on is frame strength. I've already removed the bad tubing with the drilled holes. We bent out a new one but it kinked a little bit, it shouldn't be an issue when the engine plate is in to tie the down tube to the seat tube though- it'll also be hidden from veiw :roll:. The down tube was sleeved before being welded and two brackets were welded in on the top and bottom of the crank area to make sure it holds- it could still use a little grinding I admit but it's all pretty solid. The next step is widening the rear to fit the Motobecane rear hub, any stretch will also be sleeved internally. Then I need to weld reinforcement tubes to tie the bottom and the top tubes of the rear together and add gussets in the headtube, kickstand, seat, and rear areas. After all that is said and done I should have a pretty solid frame. Also some pics of the Tomos forks and a headlight bracket I made.
the sleeve on the seat post tube is to cover up a hole I drilled.. ill grind it a little smoother one of these days.
The Drive system
The plan is to go direct belt drive from the engine to a jackshaft and then into a whizzer sheave on the rear wheel. The belt tension on the primary (engine) belt will be controlled with a hand lever made to look like a suicide shifter. I need to order a couple different pulleys to even out the gear ratio but most if it is all there. The rear jackshaft bearing hanger will be welded to the seat post tube and the front bearing will be held in place with a plate bolted to the engine that will also hold the bits and pieces of the lever... thats how I picture it in my head at least. Here's a mockup photo- in the pic I have a tiny vbelt pulley as the idler, but I have a flat idler pulley to use now. :wink:
Other:
The tank is off a Jesse james chopper bicycle, it's a fake tank my friend gave me but I bought a cap/bung set for it and I plan to weld it shut. I think it suits the bike nicely.
I also plan on running a headlight, taillight, brake light, front/rear signals, and a horn. Since a charging coil for my engine is extremely rare I decided to run everything off of a 12v 7ah (20hr) battery, and use a Harbor Freight float charger to keep it going... I'll just have to plug my bike in at night :?. I have most of my lights now but can't finish the wiring until I get a few more other tasks done, but for now the trailer taillight and Harbor Freight halogen work light make a good set up for my dark rides home from work. And it will all run to a combination switch on my handlebar. Also added an in-line fuse just in case
Oh and here's the battery box I made out of two failed engine mounts.
____________________________________________________________________________
I think that just about covers most of it so far, Thank you for tuning in to my kinda long build intro. I'm not the fastest builder on earth but I try and get things done when I can. Stay tuned in if you're interested, I can use all the criticism I can get. I hope to have updates soon.
-MGR
Let me start off by saying even though I'm still new to motorizing bicycles I have learned a lot already- mostly from dumb mistakes (actually started off the build by drilling holes in my frame.) :shock: Since then I've fixed that mistake and have been messaging a member on the motobicycling forum (msrfan) who races bicycles with a similar engine to make sure the build will hold up to the added stress. So far this has included moped forks, dual moped drum hubs laced with 12g spokes in the front and even bigger spokes in the rear (don't know what size yet.).... I realize my plan may be a bit overboard but I like to try and be unique. with that said if anyone has any input on how I can decrease my chances of disaster please feel free to chime in. Anyway, on to the build description.
Here's how the build started off.
The engine:
1972 206cc Briggs flathead- usually known as the 5hp Briggs or the Briggs model 13. I bought the engine from a member on oldminibikes that had been sitting for who knows how long. She was dirty inside and out but harbored a freshly honed cylinder under her head. First thing I did was gut it all the way down to bare block so I could take care of those nasty power robbing eyebrows, and figured while I had the dremel out I may as well cut off that rough casting in the ports. Then after the make over I flushed all the metal dust and sludge out with the solvent tank in my automotive class. Also threw in a stock length billet rod for ease of mind. Got her all built up and added a 'ghetto' pipe fitting header that I plan to hide in heat wrap, a Tecumseh h50 carb with a custom made intake and brace, a 4hp head for extra compression, and converted her to electyronic ignition.There are mixed arguments on the gains from the head because they tend to lack flow, but in my personal experience they lean more toward low/mid range more than the stock head so it should fit my needs just fine and if worse come to worse I can always get my hands on a cut stock head. :roll: And finally I decided to re-purpose an old trophy I found at the junk store into an oversize velocity stack.. It still needs some finishing touches if I decide to keep it (and don't worry, it WILL have a filter.)
And here's a running video:
http://www.youtube.com/watch?v=gbxWF195jhs
The Frame:
First and most important aspect I need to work on is frame strength. I've already removed the bad tubing with the drilled holes. We bent out a new one but it kinked a little bit, it shouldn't be an issue when the engine plate is in to tie the down tube to the seat tube though- it'll also be hidden from veiw :roll:. The down tube was sleeved before being welded and two brackets were welded in on the top and bottom of the crank area to make sure it holds- it could still use a little grinding I admit but it's all pretty solid. The next step is widening the rear to fit the Motobecane rear hub, any stretch will also be sleeved internally. Then I need to weld reinforcement tubes to tie the bottom and the top tubes of the rear together and add gussets in the headtube, kickstand, seat, and rear areas. After all that is said and done I should have a pretty solid frame. Also some pics of the Tomos forks and a headlight bracket I made.
the sleeve on the seat post tube is to cover up a hole I drilled.. ill grind it a little smoother one of these days.
The Drive system
The plan is to go direct belt drive from the engine to a jackshaft and then into a whizzer sheave on the rear wheel. The belt tension on the primary (engine) belt will be controlled with a hand lever made to look like a suicide shifter. I need to order a couple different pulleys to even out the gear ratio but most if it is all there. The rear jackshaft bearing hanger will be welded to the seat post tube and the front bearing will be held in place with a plate bolted to the engine that will also hold the bits and pieces of the lever... thats how I picture it in my head at least. Here's a mockup photo- in the pic I have a tiny vbelt pulley as the idler, but I have a flat idler pulley to use now. :wink:
Other:
The tank is off a Jesse james chopper bicycle, it's a fake tank my friend gave me but I bought a cap/bung set for it and I plan to weld it shut. I think it suits the bike nicely.
I also plan on running a headlight, taillight, brake light, front/rear signals, and a horn. Since a charging coil for my engine is extremely rare I decided to run everything off of a 12v 7ah (20hr) battery, and use a Harbor Freight float charger to keep it going... I'll just have to plug my bike in at night :?. I have most of my lights now but can't finish the wiring until I get a few more other tasks done, but for now the trailer taillight and Harbor Freight halogen work light make a good set up for my dark rides home from work. And it will all run to a combination switch on my handlebar. Also added an in-line fuse just in case
Oh and here's the battery box I made out of two failed engine mounts.
____________________________________________________________________________
I think that just about covers most of it so far, Thank you for tuning in to my kinda long build intro. I'm not the fastest builder on earth but I try and get things done when I can. Stay tuned in if you're interested, I can use all the criticism I can get. I hope to have updates soon.
-MGR