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Motorized Bicycle General Discussion All topics regarding bicycles with engines.

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  #7711  
Old 01-18-2015, 04:29 PM
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mapbike mapbike is offline
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Default Re: what did you do to your motorized bicycle today?

well, got the air leak fixed on latest build and took it for a 7 miles round trip maiden run, running good.

was running smoother and stronger by the time I returned from the ride, I cruised most of the way @ 27-30mph.

I did open it up for just about 40-50yds and hit 39mph, then I slowed it down and never got over 30-31mph the rest of the ride.

I'm not seeing the near perfect" balance factor" with it so far but it's fairly nice running at 30mph

On the first start and run all of my dax lowers were smoother than this engine is so far, its better than my bgf engines but time will tell what it will be after about 50 or so more miles on it.

I really thinking these Half Breed engines need about .020-.025" milled off the jug to get the compression to where it needs to be.

It seems that the dax engines are not what they were, looks like they are GT5 engines now, a member just got one and told me after the jug was pulled he noticed first off that it has the high pin type B piston and jugven Duane says on his site it's a 38mm stroke engine.

This is disapointing to me if this is true since I like the Gen IV well balanced PK-80 engine lowers I've got from him, anyone know what the reason is for the change?
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  #7712  
Old 01-18-2015, 08:25 PM
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mapbike mapbike is offline
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Default Re: what did you do to your motorized bicycle today?

put another 15 miles on the "Half Breed" running a little better business no where near what I expected from what I was told to expect from it, but we all know these engines are a rap shoot and you may get one thats a good solid runner and another one just like it that is an under performer.

it smooths out nice at higher rpm at at 39-40 mph bus it wont run that speed on the flat, it steggles to reach 35 on the flat so far, and the vibes between 30-37 mph are fairly harsh, way more than anyone of the dax Gen IV lowers I've run.

I think the biggest issue with this engine is low compression as far as power is concerned.

(Edited) Without milling .060" (.025" as I said before is not enough to get piston and deck height matched up correctly) off the jug and correcting the port timing issues there just wont be much performance to get from these engines compared to the 40mm stroke engines that have a good balanced and true crank and better port timing.

Because of the lower compression, these engines may have good reliability since the lowerend is under less stress and being 38mm stroke also helps take some pressure off the upper and lower rod bearing.

I think raising the compression on this engine and going from a 30T up to maybe a 34 or 36T might help this shorter stroke engine since it just doesn't have quite as much grunt as the 40mm stroke engine.

Seems at least the one I have is balanced well for high rpms, its butter smooth to about 28mph but doesnt get that smooth again until around 39mph and up to the max I registered at 41mph, I think higher compression and a lower gear ratio would get this engine into its sweet spot and help it to get there much quicker.

But all said and done , I got to enjoy 22 miles of riding in the 60 degree weather today after watching the Seahawks get lucky and beat the Packers, I dont think they'll be so lucky when they play the Patriots though.....


Had a good ride and watched a nail biter football game the wife and I have our health we are truly blessed so yeah.... it's been a good day and I'll get this "Half Breed" running better, I just wanted to see what it would do with nothing removed from the jug and only some port cleaning with no piston mods.
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Last edited by mapbike; 01-19-2015 at 12:49 PM.
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  #7713  
Old 01-18-2015, 08:57 PM
joey1320 joey1320 is offline
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Default Re: what did you do to your motorized bicycle today?

I made some decals for the frame and number plates. i also found a plate at Home Depot which I believe I'll be able to use for my new fuel tank. I'll be using a 1960's vw beetle washer fluid reservoir as a tank
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  #7714  
Old 01-19-2015, 03:46 PM
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Default Re: what did you do to your motorized bicycle today?

I drove it for the first time!
then it died.
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  #7715  
Old 01-19-2015, 06:31 PM
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Davezilla Davezilla is offline
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Default Re: what did you do to your motorized bicycle today?

That first ride is always the coolest... What happened tho? why did it die?

For me, today I took mine up the street to my favorite taco resturaunt for breakfast, but didn't turn on the gps to record the top speed... just rode it to enjoy it.
Then I had a few free minutes at the shop so I took the front wheel off the new bike to chean up the bearings and re grease them, found a bit of roughness in the front bearing so I took it all the way apart and cleaned everything to see if it needed new balls or if the races needed replacement, luckily it's just a nick in one of the outer races and I got a few spares...
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  #7716  
Old 01-19-2015, 08:24 PM
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mapbike mapbike is offline
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Default Re: what did you do to your motorized bicycle today?

Quote:
Originally Posted by Davezilla View Post
That first ride is always the coolest... What happened tho? why did it die?

For me, today I took mine up the street to my favorite taco resturaunt for breakfast, but didn't turn on the gps to record the top speed... just rode it to enjoy it.
Then I had a few free minutes at the shop so I took the front wheel off the new bike to chean up the bearings and re grease them, found a bit of roughness in the front bearing so I took it all the way apart and cleaned everything to see if it needed new balls or if the races needed replacement, luckily it's just a nick in one of the outer races and I got a few spares...
sounds like fun Dave, only problem for me is that a quick run to the nearest taco shop for me is a 20 mile round trip ride....lol.!

I did ride about 22 or so miles yesterday on the new half breed mill but none today, just knocked .060 off of a jug deck and and then thought about all of it a bit more....
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  #7717  
Old 01-19-2015, 09:46 PM
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Davezilla Davezilla is offline
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Default Re: what did you do to your motorized bicycle today?

My problem is just the opposite since the taco shop I go to is only about a mile down the road... not even far enough to warm up teh engine so I usually have to sit at the shop and warm up the engine for about 10 minutes if i want to do a speed run, then while I'm in there waiting on the food it usually takes around 10 minutes to get the food so the engine has enough time to cool back down... What wuold be really nice is if I had a 4 to 5 mile stretch so I could get it nice and hot right before I get on the throttle, it does tend to run a lot better after it's fully warmed up and the 4 stroking goes away for the most part, just a little blubbering at around 20 to 25 mph then it cleans up and goes... I'l tune it better after this tank is done since it seems like the rings are seated pretty well already and the bike kinda leveled off at around 41 to 42mph on top. I did get to see it go from 35mph at best to 38mph, then to 40, then to 41 about 2 weeks ago and I'm about 3/4 the way thru my second tank so it's real close to time to properly tune it.

.060" sounds like a lot but I had to cut out .040 or so just to true mine up, then I went back in and cut out another .012 to get the squish clearance on my first engine, as well as another .040 off the base to get it trued up, it trued up somewhere around .037 if I remember right so I just cut it up to .040 so it would be easier to keep track of how much I cut off. Then when I transfered this jug to the Dax bottom end the piston was sticking up past the deck by about .040" but I made up for that by using a .040" spacer, then I ended up ditching the spacer in favor of 2 .025" copper gaskets glued together with a very thin layer of shellac right before final assembly and torquing along with a single .016 and a single .025" copper gasket sealed the same way up top to set the squish in range.
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  #7718  
Old 01-20-2015, 07:14 AM
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Default Re: what did you do to your motorized bicycle today?

Quote:
Originally Posted by Davezilla View Post
That first ride is always the coolest... What happened tho? why did it die?
not sure, but I think the clutch let go, maybe it needs tightening. didn't bother trying to figure it out yesterday because I had exhausted myself pedaling it back home.

planning on taking a better look later today.
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  #7719  
Old 01-20-2015, 02:59 PM
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Davezilla Davezilla is offline
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Default Re: what did you do to your motorized bicycle today?

Ouch... that happens to all of us... I learned to keep my maiden voyage close to home... as well as the next several rides just in case something went south on me.
Anyway, hope you get your clutch sorted out, on these things it could be anything from a loose cable to grease getting slung up from who knows where and onto the clutch pads, could also be the flower nut wasn't locked down and backed out some... but you'll find it, these things are at least simple enough for quick fixes.

For me... Today has been unbeleivably slow and boring here at the shop so I set up the bearings on the new rim with the disc brakes, cleaned and lubed with Kendall Super blue which is an ultra heavy duty bearing grease I use on big truck bearings, but also use on anything else that needs grease, this stuff is slick, it stays put, and will most likely outlast that wheel I just built up... Enough on that.. My next problem to overcome is getting the caliper mounted on the front fork lower... This is proving easier said than done so I went thru my calipers to see which one would be the easiest to adapt to a fork that's not set up for disc brakes. Caliper #1... came off the other bike, has little tiny pads, but they work good. This one would be the trickiest to adapt to my forks so back on the shelf it goes... Caliper #2... came off a pocketbike rear brake... very large pads and very well built, but too bulky, too much needs modified, and it really needs a thicker rotor. Caliper #3... came off a pocketbike front brake, this one has nice sized pads, about twice the size of the small round pads the bike came with, full floating design so I just need to make a single flat bracket and it'll tuck in nicely on the back side of the fork leg, looks good once installed... Yup... this is the one I'll be using... Soooo... if today continues to be slow and boring over here I might just fire up the plasma cutter and make me a bracket... I got the measurements and reinstalled the old front wheel so the bike can remain functional while I'm working this brake situation out.
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  #7720  
Old 01-20-2015, 03:13 PM
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Default Re: what did you do to your motorized bicycle today?

Davezilla, sounds like you are building a sick machine there, I hope your braking power is magnificent!

I did some further mucking around on the bike, I think there was no key holding the drive sprocket to the shaft. that or it turned to dust. either way I need a new one. considering finishing the takedown of the clutch assembly before calling the guy who sold me the bike.
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