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  #7731  
Old 01-21-2015, 06:01 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 IS a good price for that case....
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  #7732  
Old 01-21-2015, 07:32 PM
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Default Re: what did you do to your motorized bicycle today?

Quote:
Originally Posted by Davezilla View Post
That IS a good price for that case....
I need one myself so I can pull all the guts out of an older BGF engine that had the crank walk over and caused the mag rotor to eat up the seal and into the case on the mag side, been planning to get it apart to see if a main bear spun I the case and caused to problem or what actually happened, this was a smooth running engine at about 36-38 mph with nothing done to it but a well tuned NT carb and a free flowing exhaust pipe.

if crank is still good in it Id probably just chuck it up in lathe and get it as tdue as I can to help it even more and then slap all the guts in a new case, it has the round clutch pucks which I like better than the squarish ones they all have now, its easy to make really high quality round pucks that work better than the others I think.
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  #7733  
Old 01-21-2015, 07:50 PM
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Default Re: what did you do to your motorized bicycle today?

That's the same exact reason I originally tore into my first engine... it had about 1/8" of crank walk and I just happened to notice it one day when I had the mag cover off, the crank moved really freely then felt like it was locked up, then next time I tried to move the crank I noticed it was moving side to side a lot.
I took that one all the way apart to get the crank out and everything looked just fine, the crank was sliding side to side on the bearings, they were ok too, just felt a little rough due to being so cheap. After I trued the crank I put the bottom end back together temporarily to see what things were like and saw where the play was. I was going to make a few washers to keep the crank centered but at the time i had a lot of other stuff going on so I bought a new Dax lower and put my top half onto, bought a new jug but decided the old jug had better looking ports, the new one was one with smaller transfers that were slanted across the top instead of straight, and the old one already had the transfers cleaned as well as everything else opened up really nice so it would take less time to just make the old jug work on the Dax lower, the old jug only had about 30 minutes of run time on it anyway so it was practically new anyway...

What I think was going on with that setup was maybe they were relying on the crank being a tight fit on the bearings to keep it centered or they machined the steps off the crank or it was missing the spacers or washers... or who knows what they were thinking, and I was surprised it ran so well like that...
Hopefully yours is the same way and you find nothing wrong but the crank walk and can make or get some spacers for it, and also, when I temp installed it again with the crank straight and true it slid side to side even more freely...
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  #7734  
Old 01-21-2015, 10:54 PM
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mapbike mapbike is offline
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Default Re: what did you do to your motorized bicycle today?

Yeah I have two engines that do this, the latest to start this side to side mess is one of my dax engines, it's the one I actually ended up GPS'ing 52.0 mph out of on the old western flyer bike, I think I got it a little hot and trashed the temper in the rings because it lost power big time as if it had no compression, i pulled the jug and the cylinder bore and piston were both in good shape but the skirt on the piston is really oily black carboned up from the serious blow by from the lack of ring seal.

While I was looking at that issue I just happen to push the piston to the side and thats when I noticed the crank had all the side to side movement and I though, well this ain't good....!

I set that engine aside until I can take it down and see for sure what's going on, but i would imagine its just as you found with yours and the crank is just sliding in the bearings.

Maybe if I could find a brass bushing that had the right iD that was at least very close to the size if the shaft and not to thin, a fella could make a couple spacers for each side of crank between it and the bearing and resolve that problem.

I found out after it was a little late of the old BGF engine, I was on my way back from about a 10 mile ride, I was cruising smoothly at about 36 mph and all the sudden the engine had a slightly different sound, my first reaction was to let off the throttle, but much to my surprise when I released the throttle nothing happened,it's like I was stuck on cruise control, bike was just zipping right on down the road... I thought the carb slide had stuck wide open at first and just continued for maybe another mile or so, I reached down and even closed thr choke and it actually seemed to run a little better and thats when I knew what it was...HUGE air leak, long story short... I had to shut it down and peddle for about 5 miles up and down hills all the way home, and when I pulled the mag cover I saw aluminum shavings all in there, I pull the rotor and then seen where it had rubbed into the seal until it ruined it and there my HUGE air leak was.

Sad thing about all this was that this engine had just got to the point to where it was smoother running than ever and was such a pleasure to ride.

The case may actually be savable since it just barely shaved enough material until the rotor contacted the seal and ruined it, if I can save the case and reuse it that will be nice since it's a large from mount case and these sure work out nice on the cruiser frames.




Quote:
Originally Posted by Davezilla View Post
That's the same exact reason I originally tore into my first engine... it had about 1/8" of crank walk and I just happened to notice it one day when I had the mag cover off, the crank moved really freely then felt like it was locked up, then next time I tried to move the crank I noticed it was moving side to side a lot.
I took that one all the way apart to get the crank out and everything looked just fine, the crank was sliding side to side on the bearings, they were ok too, just felt a little rough due to being so cheap. After I trued the crank I put the bottom end back together temporarily to see what things were like and saw where the play was. I was going to make a few washers to keep the crank centered but at the time i had a lot of other stuff going on so I bought a new Dax lower and put my top half onto, bought a new jug but decided the old jug had better looking ports, the new one was one with smaller transfers that were slanted across the top instead of straight, and the old one already had the transfers cleaned as well as everything else opened up really nice so it would take less time to just make the old jug work on the Dax lower, the old jug only had about 30 minutes of run time on it anyway so it was practically new anyway...

What I think was going on with that setup was maybe they were relying on the crank being a tight fit on the bearings to keep it centered or they machined the steps off the crank or it was missing the spacers or washers... or who knows what they were thinking, and I was surprised it ran so well like that...
Hopefully yours is the same way and you find nothing wrong but the crank walk and can make or get some spacers for it, and also, when I temp installed it again with the crank straight and true it slid side to side even more freely...
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  #7735  
Old 01-21-2015, 11:20 PM
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Davezilla Davezilla is offline
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Default Re: what did you do to your motorized bicycle today?

What I was planning on doing was to try and find some brass washers that would slip over the crank that were like. 040" to. 050" thick to limit the side play to. 040" or .020" crank to bearing clearance on each side but any washer that would fit would also block off the fuel/oil mix from reaching the bearings so it was back to the drawing board and I need to make a mandrel that's the same diameter as the crank and then punch some small pieces of sheet brass in the right thickness then cut it so the outer diameter is the same as the bearing's inner race. That would eliminate the slop in the crank but also leave about .020" side play to keep it from going too tight after the engine is fully warmed up. I'm not sure how much the crank and all expands from heat fully warmed up compared to cold, but at .020" there should be plenty enough room but drastically reducing the side play. This side play as you saw can cut into the case, ruin the seals, or even short out the mag if enough tiny shavings are in there floating around when the engine is running which would just feel like a hickup or a small miss every now and then, but could eventually ruin a mag by shorting it out on and off while riding.
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  #7736  
Old 01-21-2015, 11:41 PM
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mapbike mapbike is offline
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Default Re: what did you do to your motorized bicycle today?

Using a brass bushing like I was thinking of and just chucking it up in the lathe and then slicing off the thickness you need for the right spacing wouldn't interfere with bearings getting lube since the OD would likely be roughly the same size as the bearings inner race OD, the spacer would just kinda act like and extension of the bearing inner bearing race that is on the crank shaft.

This was my thinking, instead of making a shim washer, this would be what I would call a spacer on the shaft.
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  #7737  
Old 01-21-2015, 11:47 PM
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mapbike mapbike is offline
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Default Re: what did you do to your motorized bicycle today?

since we both have a lathe handy how about just getting a piece of bronze bar, bore it to the correct ID turn it to the desired OD and then mark thickness needed and slice a couple spacer off and bingo...



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  #7738  
Old 01-22-2015, 12:07 AM
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Davezilla Davezilla is offline
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Default Re: what did you do to your motorized bicycle today?

That would work just as well... I think boring out the center hole first then slicing off the needed thickness would be the easiest way. The spacer needed in this case is more like a precicely sized ring than a washer because we need to make sure we don't block off the bearings from getting the proper amount of lube. Now if I can find a piece of silicon bronze bar stock that's about 1" diameter.... finding it isn't too hard but getting somebody to sell just a small piece of it like maybe 3" or so may be...
Brass or other types of bronze would work just fine too I'm sure, even annaluminum alloy like 6061 or 7075 T6 would work and hold it's shape for the life of the engine.
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  #7739  
Old 01-22-2015, 12:10 AM
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Davezilla Davezilla is offline
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Default Re: what did you do to your motorized bicycle today?

Now you got me thinking... brass tubing with the right id would be as easy as facing the end then slicing off what,s needed. It just needs a wall thickness of .080 to .120" to work.
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  #7740  
Old 01-22-2015, 12:14 AM
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mapbike mapbike is offline
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Default Re: what did you do to your motorized bicycle today?

http://www.ebay.com/itm/1-BRASS-C360...item53fc20f4a2

not expensive and enough to make the spacers and possibly other things that could be made for a bike build...

If nothing else just turn the rets of it down and make a nice punch.
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I dont always ride WOT, but when I do..I do my best to keep the rubber side down..Ride safely my friends!

Last edited by mapbike; 01-22-2015 at 12:16 AM.
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