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Old 02-16-2015, 03:16 PM
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mapbike mapbike is offline
Motorized Bicycle Elite Member
Join Date: Mar 2010
Location: Central Texas
Posts: 5,379
Default Re: what did you do to your motorized bicycle today?

Worked on the Green machine bike build yesterday, still have a couple things to work out on it to get it where it needs to be, but its coming along good so far.

Had a strange thing happen to me on it yesterday though, first I found out the a standard NGK B6HS spark plug will not work with this type cylinder head when the cylinder deck has been shaved down to allow piston to reach optimal TDC.

Luckily I had a good Champion J8C laying around which worked out to be the perfect reach plug for my set up.

second thing that went sour was that the CDI and the mag coil went out after the second short ride, first time since 2009 I have had either of these two parts go bad on me, First I thought maybe it was just the CDI, I had an extra so I replaced it and still no fire, so I hooked the other CDi back up and pulled a mag off of one of my old broke down BGF engines, cleaned it up good and installed it, still no spark.... so I got the other new CDI and hooked it up again and bingo she busted right off and is running great.

I had kill switch hooked up Red wire to blue and Black wire to Black right where mag and CDi hook together, this was done with good sealed type crimp on spade connectors, engine was running fine, I pulled up out front of house hit kill switch, went in house for a few minutes to let it cool down some, then took off for another ride and she wouldn't hit a lick, so it seems that the last time I hit kill switch to shut it off is when they both fried.

Normally I always hook one wire from the kill switch to the Blue wire from CDI and the other to enginess rear mounting bolt as ground, never had an issue with it hooked up that way but the one and first time I hooked both kill switch wires to both of the CDI/Mag wires it knocked both of them out the second or third time I ran the bike..??????

Didn't imagine that would have caused an issue, but I wont do that again..LOL!

So, the engine is running great, best running engine I have had yet with a stock exhaust pipe on it, it does lack a little grunt power down low, but on the flat this engine really scoots even pulling the 41T rear sprocket I went with on this build, I'll have to check to know for sure with my GPS later but i think I'm getting upper 30's with this GT5 wtha stock exhaust that has been match ported to head as good as possible, a standard NT carb with jet drilled with #71 bit, the pedal Chopper type head, jug deck shaved to give .025" squish clearance between piston and heads small squish band and the 41T sprocket, it also has a "Fred Piston" that has small ramps machined in at the transfers and the skirt has been trimmed on the intake port side to allow the port to be open at TDC.

low vibes all the way through revs and the higher it revs the smoother it gets, this is the first GT5 long rod 38mm stroke engine I have had and I have to say that so far I'm really liking the way it runs, I think this engine will really come alive with a good free flowing exhaust taht will let it breathe like it needs to.

I'm thinking I will either keep this bike now or put a different engine on it and keep this GT5 for one of my other bikes, I was trying to set this bike up to be a good runner at 25-30mph and that is why I put the 41T sprocket on the rear and installed the stock kit type exhaust, yeah i did some other mods to help it out and hopefully make it a bit more reliable, but I didn't expect that it would possibly be a 40mph bike even with the stock muffler and a 41T!

I'm not gonna sell a 40mph china girl build to someone, if they wont to mod it up for that they can, but I'm not gonna sell one that way.

I'm thinking my old Huffy may end up being the bike for sale since it runs great in the 32-34mph range as max speed and is a very comfortably cruiser at 28-30mph.

in the 20's &30's F here today and I have to work the next two days so my bike work is on hold until warmer weather allows.

Happy safe riding all and those of you who may be a bit on the fence about the GT% geometry engines, I can tell you based on this one that I have just got going that it has real potential and is way smoother than I had expected it to be, I pleasantly pleased so far with how its acting.

I dont always ride WOT, but when I do..I do my best to keep the rubber side down..Ride safely my friends!
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