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Motorized Bicycle General Discussion All topics regarding bicycles with engines.

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  #7851  
Old 03-14-2015, 02:01 PM
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mapbike mapbike is offline
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Default Re: what did you do to your motorized bicycle today?

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Originally Posted by DRBS View Post
I also gave noticed the difference in the cylinders theres even a difference in the cranks ive noticed too. I bought a "high performance" crank and the diameter of the bearing shafts are different only buy a very small fraction buy there is a difference that must be why some shake more than others plus the difference in the ports would explain a lot LOL. ive been building these for going on 4 years and ive seen a lot of really messed up ones and a few that were fast right out of the box I should have kept one of the faster ones for myself LOL
The two main differen es Im seeing between the several type jugs I have is that first of all the jugs we're getting can be designed for three different engine geometries, even at that they're still very similar as far as height between base and deck with the one for the GT5 geometry being the shortest.

main big different is in height of transfers and intake port measuring from the base, the cylinder bore extends between 10mm & 11mm below the base on all the jugs Ive measured which doesn't make any difference, but I measure it and then subtract that amount from the distance between cylinder and bottom of transfer or intake and I have found as much as 5mm difference between jugs and that is huge in determining how the engine is gonna act as far as low down grunt or higher rpm capability.

Im thinking based on what Im seeing here that although port size is important, that isnt gonna matter much if the port timing is way off for what you're trying to achieve with the engine, A smaller port engine with correct port position for where you want the engine to run its best at is probably going to perform much better than an engine with huge ports that has then set way low or to high for the desire characteristics of the engine.

Im no expert on any of this but after close to 6 years of messing with these engines Im starting to dig into them a little deeper to see what parts I need to be looking for to get what I want out of them.
One thing Im definitely seeing is that the 40mm stroke geometry is by far the best, the pjugs just dont set well with these 38mm stroke engines, yeah they'll run ok, but for the average builder they will not run nearly as good as the 40mm stroke engine when its set up right, the PK80 engines have for less port timing issues just as Fred has stated in his videos and Im finding it to be completely accurate.

Ifeally hope Duane @ thatsdax will go back to the 40mm stroke GenIV engines, the cranks are better and for higher performance builds they are the winners above the GT5 geometry for me.
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  #7852  
Old 03-14-2015, 07:41 PM
TakeiT TakeiT is offline
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Default Re: what did you do to your motorized bicycle today?

Oh where do I start...My exhaust wouldn't stop leaking, no matter what I did. I pulled it off and wire wheeled it and found that the flange wasn't completely flat (Casting problem). So I ground that down, polished the whole pipe up, and put gasket sealer on it. There was oil dripping down the cylinder into the mag compartment, and when I removed the lowest bolt oil poured out. Pulled it apart, brake cleaner and compressed air cleaned it out. While I was at it, I cut the white wire off and the blue one, soldered a new one on that was long enough to go up to where I wanted my CDI. Also put a new clutch cable on and greased the wheel bearings, gave it a once over. I've been running 32:1 but will probably start going 40:1. Rebuilt the carb, changed the spark plug wire (Probably didn't have to, but for the $5 it cost for the wire and boot, might as well). Also trued up the rear wheel which I bent a spoke on last year and never fixed

Worked on it from 10am till 7pm. Going to probably make a wood "Tank" for the cruiser frame and stain it a dark color to hide the electronics in (Of course, make them accessible if need be), wire up the lights and horn.
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  #7853  
Old 03-15-2015, 02:43 AM
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Default Re: what did you do to your motorized bicycle today?

I just bought a step up transformer going to hook it to the white wire and run all my 12v lights off it and hook up a cigarette lighter socket to it so I can charge my phone ect on the bike also thinking about getting a small emergency light battery and hooking it up to run a car stereo don't know if it will charge the battery from the step up but worth trying ill let you all know how it works and if it works good ill be selling a box that you can hook up to the white wire and run 12v items on your bikes should get my hub adapter on Monday so I will find out how everything goes post pics on Tuesday
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  #7854  
Old 03-15-2015, 02:59 AM
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mapbike mapbike is offline
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Default Re: what did you do to your motorized bicycle today?

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Originally Posted by DRBS View Post
I just bought a step up transformer going to hook it to the white wire and run all my 12v lights off it and hook up a cigarette lighter socket to it so I can charge my phone ect on the bike also thinking about getting a small emergency light battery and hooking it up to run a car stereo don't know if it will charge the battery from the step up but worth trying ill let you all know how it works and if it works good ill be selling a box that you can hook up to the white wire and run 12v items on your bikes should get my hub adapter on Monday so I will find out how everything goes post pics on Tuesday
Cool, I'll be watching your results.
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  #7855  
Old 03-15-2015, 04:58 PM
TakeiT TakeiT is offline
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Default Re: what did you do to your motorized bicycle today?

just found out that the leak i mentioned above isn't the exhaust (Though that was leaking too) The head is leaking oil, the crank seal is bad and I haven't pulled it apart yet, was just out for a ride when I had less power than normal, going to pull it apart when it cools off
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  #7856  
Old 03-15-2015, 06:25 PM
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Davezilla Davezilla is offline
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Default Re: what did you do to your motorized bicycle today?

Got some free time at the shop today so I finished installing a new engine in a customer's bike but now I need to order a chain since his 415 chain rubs inside the front Sprocket housing, I may just go in and trim things to fit depending on how much free time I get this week but that's where I'm at with his bike now.

For mine I did the re jet on the stock carb and I'll test it out In the morning if the weather permits... got my 21mm carb in last week but I need to make an intake that angles it off to the side enough to clear the seat post before I can use it. I also scored last week on 2 kx65 pipes so I'm also in the process of making a thick flange and header to use one of these pipes.
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  #7857  
Old 03-15-2015, 06:25 PM
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Default Re: what did you do to your motorized bicycle today?

just a suggestion. when you put the head back on get 4 nuts that fit the cylinder bolts and tighten them down first then put the acorn nuts on. I have found that sometimes the nuts bottom out and you think that the head is torqued down to 12 foot pounds when really there not. I used allthread connectors as my bolts they work great and I put a small stud in and tighten the acorns to them they look like a taller acorn nut and your sure to get the right torque.
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  #7858  
Old 03-15-2015, 07:28 PM
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Davezilla Davezilla is offline
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Default Re: what did you do to your motorized bicycle today?

I've already done all that as well as a quick port cleanup, widened both intake and exhaust ports by 2mm, then I ramped the piston at the exhaust and transfers down 1mm and in 10mm to aim the transfer flow toad the intake side and help prevent short circuiting. This port job is by far not a hot setup for winning races but for typical street use on a 60lb bike and a 275lb rider I wanted to be sure this engine makes really good torque and still has the ability to Rev to around 7500 rim for a top speed over 30 but not past 35 or so... we definitely want more torque for this setup.
For the acorn nuts I kept them but used 2 washers and checked that there was more than enough clearance before torque the head down... I'll most likely put a Fred head and an expansion chamber on this one before he takes his bike back so this engine will be nice once those 2 upgrades are done. I just gotta remember how much this bike and it's rider weigh to keep it from being too sluggish at low speed. The option is also open for a reed valve which would give even more torque and I'll do the piston mods so it don't lose rim if I do reed valve it.
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  #7859  
Old 03-15-2015, 07:37 PM
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Default Re: what did you do to your motorized bicycle today?

you especially want the al thread connectors when you go to the fred head the regular nuts seem to "get lost" in the head since there is taller fins LOL just a suggestion
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  #7860  
Old 03-15-2015, 08:08 PM
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bluegoatwoods bluegoatwoods is offline
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Default Re: what did you do to your motorized bicycle today?

I started the day by changing my pedal chain. The old one had given me some trouble on Friday.

Then I swapped out my studded winter tires for some regular tires. Then I spent some time getting aggravated at the task of making sure that the various alignments were okay. It's a new bike so I'm still getting used to finding all of the sweet spots.

Then I tracked down a bit of fuel drip that I'd been noticing. I had thought that that came from the float bowl drain screw. But it turned out to be from the nipple at the top that accepts the fuel line. I didn't manage to fix it since I don't have the right clamp. But I know where to get them. So I'll do that tomorrow.

Then I moved the gas tank back to the top of the rear wheel. I kinda crave a bike that looks more like an old moped than a motorcycle. So this'll help in that respect. Plus the top tube location just wasn't convenient. The tank got in the way too much.

DSCN0432.JPG

Then, after a few shakedown cruises, I rode it uptown to get tacos and burritos for my daughter and myself.

Not a bad day, all in all.
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