Few pics of how my seat is attached. Let me know if there's any that are too unclear (my photos are pretty dark) and I'll post more. http://motorbicycling.com/showpost.php?p=646515&postcount=277
Frame Rebuild for 212 Engine
- Thread starter Gbrebes
- Start date
Gilbert,
I've revved the motor past 5k but it's been a while and it was with a different carb (19mm slide carb) and my 2-speed is setup to limit RPMS to under 4800. I did however modify the carb by making it an adjustable jet; using a Tecumseh adjusting needle and modifying the bowl plug, and drilling out the jet to a .055" or so. Last night I did get the high rpm sputter but then leaned it up and it ran perfect.
Curtis, the starter cup is the stock predator cup modified. I cut it down to the bottom of the slots, then put two rope grooves in, and then cut the fan down to starter cup size as its required to prevent the rope getting caught between the flywheel and the cup.
I've revved the motor past 5k but it's been a while and it was with a different carb (19mm slide carb) and my 2-speed is setup to limit RPMS to under 4800. I did however modify the carb by making it an adjustable jet; using a Tecumseh adjusting needle and modifying the bowl plug, and drilling out the jet to a .055" or so. Last night I did get the high rpm sputter but then leaned it up and it ran perfect.
Curtis, the starter cup is the stock predator cup modified. I cut it down to the bottom of the slots, then put two rope grooves in, and then cut the fan down to starter cup size as its required to prevent the rope getting caught between the flywheel and the cup.
Congrats Gilbert on your 3rd place finish in the Midrange Class on your new 212 cc
After seeing the performance on the track a VM 16 Mikuni carb will be allowed
which will make attaching the throttle cable easy too without a linkage.
A more free flowing exhaust would be ok too. Make it loud like scotto's 212.
After seeing the performance on the track a VM 16 Mikuni carb will be allowed
which will make attaching the throttle cable easy too without a linkage.
A more free flowing exhaust would be ok too. Make it loud like scotto's 212.
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Thanks Neil,Congrats Gilbert on your 3rd place finish in the Midrange Class on your new 212 cc
After seeing the performance on the track a VM 16 Mikuni carb will be allowed
which will make attaching the throttle cable easy too without a linkage.
A more free flowing exhaust would be ok too. Make it loud like scotto's 212.
I will try a mikuni carb next time. As far as exhaust, not sure I can get more free flowing than a 12" length of 1" tube with no muffler that I was running. I am pretty sure what makes Scotto's and other's predator engines so loud are the performance cams.
Also, thanks Neil for putting on these races. They are always a good time.
Gilbert
One more action shot from the last SoCal Motorized Bicycle race a Grange race track.
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Are you looking on the evil Facebook?
If not you are missing out on most of the action.......
thanks to Gingi.......
139 photos Socal Motor Bicycle Racing at Grange Motor Circuit
Oct 22, 20016
https://flic.kr/s/aHskKnk8wb
HOLY $HIT MAN!! That is some serious leaning!! Those are 26" hookworms? What psi do you run to not wipeout like that?
I saved the pic and will be showing it to my friends.
Thanks for the compliment Tony. I do use 26" hookworms on the track, they grip really well.
I don't check the psi really close. I do bring a pump and adjust at the track by how the bike feels, but I would guess I'm around 40 psi. I basically try to get the tires a little squishy, but not so much to cause squirrelly handling in the turns.
Even though these tires handle great, it is still possible to lose traction, I have laid it down more than once on the track trying to get through the turn a little faster. I need to work on hanging off the bike more so the bike does not have to be at such an aggressive angle.
Gilbert
From my experience in moped racing, hanging off the side can result in frame flexing and distortion or cracking. I strongly recommend the use of reinforcing tubes between the front of the frame and the back wheel. Like this Honda.
http://www.vintagebike.co.uk/pictures/1954-honda-r125/#.WC2WjbKLTIU
http://www.vintagebike.co.uk/pictures/1954-honda-r125/#.WC2WjbKLTIU
Hey Guys,
I am not really superstitious, but lately I have felt like I am a bit jinxed with the engine usage in my motorized bicycle. I have personally killed at least 6 motors with this bike. I have to make a run to the metal recycler to drop off some of these carcasses soon, they are piling up.
A lot have been my own fault. I ran a Briggs 5 hp on too low of oil and scored the cylinder. On one of my GC190's the oil drain plug backed out, let out oil and I seized that engine. I snapped a valve once on another GC190, threw a rod on a different GC190, spun the timing gear on another GC190, etc.
I was really hoping my luck would change with the predator 212 engine. But the other night I was going for a ride and my muffler started smoking from oil getting on it. Another oil leak! One of the side cover bolts loosened and fell out and the engine case developed a crack near the gas tank mount, which I was using as a third motor mount. I guess that wasn't such a good idea. Somehow the stress of using this mount as an engine mount instead of its intended purpose caused the case to crack around it.
But then I looked at my replacement block, and it already has what appear to be stress cracks in this same area. The cracks to not appear on the inside of the case, but I am afraid to use this as a mount again. I might look into using the other gas tank mount, as it is located on the flywheel side of the case, not the open side. But I already cut that mount off of this replacement motor, so I will have to try that on the next engine.
Pictures included. First picture, cracked block that leaks. Picture two, new block with stress "cracks", third, inside of same block.
Have any other Predator users encountered this? Maybe I have not spilled enough blood in sacrifice to the Gods of internal combustion in the shop recently? I do not know, but I sure would like to have some engine configuration with a little more longevity.
Thank you for enduring my rant.
Gilbert
I am not really superstitious, but lately I have felt like I am a bit jinxed with the engine usage in my motorized bicycle. I have personally killed at least 6 motors with this bike. I have to make a run to the metal recycler to drop off some of these carcasses soon, they are piling up.
A lot have been my own fault. I ran a Briggs 5 hp on too low of oil and scored the cylinder. On one of my GC190's the oil drain plug backed out, let out oil and I seized that engine. I snapped a valve once on another GC190, threw a rod on a different GC190, spun the timing gear on another GC190, etc.
I was really hoping my luck would change with the predator 212 engine. But the other night I was going for a ride and my muffler started smoking from oil getting on it. Another oil leak! One of the side cover bolts loosened and fell out and the engine case developed a crack near the gas tank mount, which I was using as a third motor mount. I guess that wasn't such a good idea. Somehow the stress of using this mount as an engine mount instead of its intended purpose caused the case to crack around it.
But then I looked at my replacement block, and it already has what appear to be stress cracks in this same area. The cracks to not appear on the inside of the case, but I am afraid to use this as a mount again. I might look into using the other gas tank mount, as it is located on the flywheel side of the case, not the open side. But I already cut that mount off of this replacement motor, so I will have to try that on the next engine.
Pictures included. First picture, cracked block that leaks. Picture two, new block with stress "cracks", third, inside of same block.
Have any other Predator users encountered this? Maybe I have not spilled enough blood in sacrifice to the Gods of internal combustion in the shop recently? I do not know, but I sure would like to have some engine configuration with a little more longevity.
Thank you for enduring my rant.
Gilbert
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Oh $hit! I guess that is the kind of damage my buddy was talking about when he said not to use those mounts. I have only one left but I'll be removing the engine tomorrow to modify the engine mounts to drop it, and I'll get rid of it completely and use the cylinder mount. This engine definitely needs a front mount or head mount. My front mount tab on the frame has already broken once. I don't know where my buddy got his info, but it seems people have had this problem before.
The frame flexing effects & cracks not only the frame but engine attachment points as well...including cases not just brackets and fasteners. Of course frame mounts and appropriate connecting points on the 212 engine are somewhat limited, but good judgement needs to be applied when selecting any high load bearing points.
Course racing puts your bikes under extraordinary stresses that aren't often encountered in daily riding, considerations from racing experience could prove instructive. Rick C.
