16v4nrbrgr
Active Member
keeps getting flagged by a jealous emmeffer, so heres another
http://sfbay.craigslist.org/nby/mcy/3932204732.html
http://sfbay.craigslist.org/nby/mcy/3932204732.html
The Raven
- Thread starter 16v4nrbrgr
- Start date
16v4nrbrgr
Active Member
Ugh I had to contact craigslist, the ad won't last 10 minutes. Apparently I have a stalker. 
16v4nrbrgr
Active Member
I keep riding and tuning the bike up better and better, I wanna sell the bike at her peak, but its gonna be a sad day when we part.
16v4nrbrgr
Active Member
I'm thinking about putting a 212cc Predator in this bike since I haven't gotten any serious responses to the sale ad, and I'm tired of the two stroke. I would like something mellower to be able to use the bike every day, instead of as a racing toy so I might just take the KTM clone out and sell it. The KTM has been inconsistent, and I can't rely on it.
16v4nrbrgr
Active Member
Okay, so I have mixed feelings about the KTM clone, so I'm giving it another go. Ordered a used genuine KTM XS head for it in hopes it will stay flat and cool.
http://i.ebayimg.com/t/engine-cylinder-head-2002-KTM-50-Senior-Adventure-50-SXR-OEM-/00/s/MTA2OFgxNjAw/z/8EAAAMXQ2q9Ra1V3/$T2eC16JHJHkFFljZ8DmhBR,1V2hk4w~~60_57.JPG
Gonna put a lower compression copper head gasket in with some copper spray to hopefully make this mellow out on 91 octane, it liked the 20 thou aluminum one before it blew, the 25 thou copper will squish down a thou or two as well so I think it will be good. Also bought some 12.9 KPa bolts to replace the original 8.8 head bolts.
Wondering if I should get yet another ignition stator since they're supposed to be 500+ ohms and this one is 366. Keeping the engine cool has been a problem because it tends toward self destruction unless you constantly keep up with it. I would equate it to a 9 HP china girl, which considering the power you get in the small package its a good race or toy motor. I wouldn't suggest this engine for a daily rider unless you have figured out the major electrical, clutch, and sealing issues which seem to drive people away from the KTM for peewee racing. I think I have the clutch worked out, it engages strong at a low rpm and doesn't slip a whole lot, from my inspection of the lack of case dust in the oil.
I'm gonna stick with it, and see what I can do for cooling mods if the next setup doesn't simmer down and run reliably. If it really ticks me off I'll try out the 212, but I'd rather see what this engine can do, it was really awesome last time before it had the latest problems.
http://i.ebayimg.com/t/engine-cylinder-head-2002-KTM-50-Senior-Adventure-50-SXR-OEM-/00/s/MTA2OFgxNjAw/z/8EAAAMXQ2q9Ra1V3/$T2eC16JHJHkFFljZ8DmhBR,1V2hk4w~~60_57.JPG
Gonna put a lower compression copper head gasket in with some copper spray to hopefully make this mellow out on 91 octane, it liked the 20 thou aluminum one before it blew, the 25 thou copper will squish down a thou or two as well so I think it will be good. Also bought some 12.9 KPa bolts to replace the original 8.8 head bolts.
Wondering if I should get yet another ignition stator since they're supposed to be 500+ ohms and this one is 366. Keeping the engine cool has been a problem because it tends toward self destruction unless you constantly keep up with it. I would equate it to a 9 HP china girl, which considering the power you get in the small package its a good race or toy motor. I wouldn't suggest this engine for a daily rider unless you have figured out the major electrical, clutch, and sealing issues which seem to drive people away from the KTM for peewee racing. I think I have the clutch worked out, it engages strong at a low rpm and doesn't slip a whole lot, from my inspection of the lack of case dust in the oil.
I'm gonna stick with it, and see what I can do for cooling mods if the next setup doesn't simmer down and run reliably. If it really ticks me off I'll try out the 212, but I'd rather see what this engine can do, it was really awesome last time before it had the latest problems.
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16v4nrbrgr
Active Member
Hi Rock Out,
Yeah the hydraulic brakes are very strong, you can stop from high speed with pinky pressure on the levers, and the rear can lock if you stomp it easily.
I'm getting really poor from this motorbicycle addiction, so I'm going to be selling this bike unfortunately.
Right now it just needs a piston ring, but I might do a full cylinder kit. I'm going to fix it before sale unless somebody makes me an offer I can't refuse.
I'm thinking about $800 is a fair price for the bike, its only got 16 hours on the build and with the top end rebuilt it will be ready to go.
Anybody interested, PM me, local sales would be preferred but I could probably get the bike packaged into box with the wheels off.
Yeah the hydraulic brakes are very strong, you can stop from high speed with pinky pressure on the levers, and the rear can lock if you stomp it easily.
I'm getting really poor from this motorbicycle addiction, so I'm going to be selling this bike unfortunately.
Right now it just needs a piston ring, but I might do a full cylinder kit. I'm going to fix it before sale unless somebody makes me an offer I can't refuse.
I'm thinking about $800 is a fair price for the bike, its only got 16 hours on the build and with the top end rebuilt it will be ready to go.
Anybody interested, PM me, local sales would be preferred but I could probably get the bike packaged into box with the wheels off.
16v4nrbrgr
Active Member
Naw, SF Bay unfortunately. I'm going to open up the motor and order parts when I get a chance.
I really wish I could keep this thing but having too many motorbikes has tied up cash, and this things a little too much for me with the way I've been feeling lately.
To Lab, I dunno, I think some hella jelly dipswitch thought it was a threat to their Happy Cranbrook for $600 advertisement or something, lol.
16v4nrbrgr
Active Member
It's a rear brake for a CRF50 style pit bike, it took a lot of custom fab and welding an adapter onto the hub to work, along with a ton of fitment modification and fiddling, but it works awesome. I would check out maybe adapting hydraulic bicycle disc brakes to yours, which will be a lot easier, but might cost a little more. I found Tektro hydraulic brakes on Ebay for reasonable prices a while back when I was gonna go that route, but decided on the pit bike brakes when I realized that the engine had enough power to do 60mph easy, and stopping from those speeds requires some reassuring brakes.
I'm thinking about opening up the motor this weekend and ordering the parts I need to get it running again, so I can sell it hopefully and make someone's Christmas a Ringadingdingding good time, and fill my belly with real food, lol!
I'm thinking about opening up the motor this weekend and ordering the parts I need to get it running again, so I can sell it hopefully and make someone's Christmas a Ringadingdingding good time, and fill my belly with real food, lol!
16v4nrbrgr
Active Member
I pulled off the cylinder today, taking note of any evidence or lean conditions which could have caused the loss of compression. Turns out the head gasket sealed great, no discernible base gasket or case leaks. What did fail was the locating pin for the piston ring, which allowed the ring to get stuck in halfway around the piston groove, causing the loss of compression. It all happened so quick that the bottom end didn't get fouled with crap fortunately, because I shut it down once it started flapping. The skirts of the piston are all galled up from running crooked with the stuck ring, but that's okay, it's going in the garbage, lol.
The cast iron cylinder looks great and will just need a scotch briting since it didn't get scored at all by the aluminum piston. So all I need to order is a piston kit and some gaskets and it should run good again. Namura makes a pretty sweet piston kit with anti-friction coated skirts.
One thing I'm wondering is if I should keep the thicker copper head gasket I made, which made it run way sweeter on this crap Cali 91 gas than the OEM high comp gasket. It is possible that the ring-piston interface failed because the squish tolerance was too high which may have cause too high ring pressures. The crown of the piston looks great however, with no burning or pitting or anything, it was actually on the rich side. The engine made more power with the thicker copper gasket than with the stock thin aluminum head gasket, which must have been causing a borderline pre-det condition before, which obviously wasn't too bad or the piston would have been burnt. It ran a lot cooler with the thicker gasket too, the original setup out of the box got too hot in my opinion before lowering the comp.
I guess I'm going to have to consult with some two stroke experts with regards to acceptable squish tolerance on these motors, it could be possible that limiting the pressure pulse to the center of the piston crown prevents premature ring failure. This is a Chinese clone of the KTM with 16 hours on it however, so it could have simply been time for a new piston anyways. Putting a KTM50 on a heavy bobber bicycle with an an adult obviously puts more strain on the motor than a 100 lb gromit on a motocross bike on loose surfaces with tiny 10" wheels, so there are a lot of factors to consider here.
These motorized bicycles are my first experience with tuning two strokes, so the learning curve has been steep for sure. Any input you guys have about the top end on this thing is welcome.
The cast iron cylinder looks great and will just need a scotch briting since it didn't get scored at all by the aluminum piston. So all I need to order is a piston kit and some gaskets and it should run good again. Namura makes a pretty sweet piston kit with anti-friction coated skirts.
One thing I'm wondering is if I should keep the thicker copper head gasket I made, which made it run way sweeter on this crap Cali 91 gas than the OEM high comp gasket. It is possible that the ring-piston interface failed because the squish tolerance was too high which may have cause too high ring pressures. The crown of the piston looks great however, with no burning or pitting or anything, it was actually on the rich side. The engine made more power with the thicker copper gasket than with the stock thin aluminum head gasket, which must have been causing a borderline pre-det condition before, which obviously wasn't too bad or the piston would have been burnt. It ran a lot cooler with the thicker gasket too, the original setup out of the box got too hot in my opinion before lowering the comp.
I guess I'm going to have to consult with some two stroke experts with regards to acceptable squish tolerance on these motors, it could be possible that limiting the pressure pulse to the center of the piston crown prevents premature ring failure. This is a Chinese clone of the KTM with 16 hours on it however, so it could have simply been time for a new piston anyways. Putting a KTM50 on a heavy bobber bicycle with an an adult obviously puts more strain on the motor than a 100 lb gromit on a motocross bike on loose surfaces with tiny 10" wheels, so there are a lot of factors to consider here.
These motorized bicycles are my first experience with tuning two strokes, so the learning curve has been steep for sure. Any input you guys have about the top end on this thing is welcome.
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16v4nrbrgr
Active Member
Bah, looks like the 39.36mm piston in this engine is kinda unique to the clone. The genuine KTM50 uses perfect fit pistons in a range of sizes stepped up from 39.46, so I'd have to hone the cylinder out quite a bit to use a Namura or Vertex piston in there. That's only worth doing when the cylinder walls are scored from a lot of hours, so maybe the clone piston is the choice here unless I can find something.
16v4nrbrgr
Active Member
Ah screw it, I ordered the clone piston because I know it won't seize up when it gets hot.
16v4nrbrgr
Active Member
Last night I honed the aluminum galling out of the cast iron cylinder, of which I was really impressed with its durability! I used some emory and scotch brite to get the big crap out and then honed a crosshatch back in with a wire wheel brush, which didn't have much effect since the iron is so tough, I had to do it for a long while! I also managed to wire wheel my wrist, doh! 
I put the cylinder back on with the thicker of the two base gaskets provided in the kit, to match what was on there, and measured the squish band clearance. Turns out that the stock aluminum stamped gasket (which have a habit of blowing out) with the clone engine and a genuine KTM head would have closed up the squish band to something ridiculous like 5 thousandths. When the motor heats up, the con-rod gets longer and the piston expands as well, so I put my custom copper head gasket in with copper spray, the squish tolerance with this combo is .035" cold, which is conservative, but it will close up to the optimal .030" when it all heats up for sure. This copper head gasket made phenomenal power last time I ran it before the ring stuck in the piston and it lost compression, so I think its a great combo. It also started easier and ran much more harmonious on this crap 91 premium California gas. Fortunately I haven't been riding much because of work and school, so I have a stash of summer blend premixed gasoline, which doesn't have butane in it like winter gas, which stores badly and runs like crap in ring-dingers comparatively.I used some split lock-washers and blue loctite on the head, so it will stay tight.
I used a piece of silicone hose to seal the expansion pipe pipe union where the rubber seal was before, but leaked, this should work a lot better.
So here Raven is, all back together in one piece. Later today when all the sealants are dry I'm gonna go for some rides to break-in the new piston ring with the honed cylinder. I'm excited, it was quite powerful with this head and gasket setup last time I rode it!
I put the cylinder back on with the thicker of the two base gaskets provided in the kit, to match what was on there, and measured the squish band clearance. Turns out that the stock aluminum stamped gasket (which have a habit of blowing out) with the clone engine and a genuine KTM head would have closed up the squish band to something ridiculous like 5 thousandths. When the motor heats up, the con-rod gets longer and the piston expands as well, so I put my custom copper head gasket in with copper spray, the squish tolerance with this combo is .035" cold, which is conservative, but it will close up to the optimal .030" when it all heats up for sure. This copper head gasket made phenomenal power last time I ran it before the ring stuck in the piston and it lost compression, so I think its a great combo. It also started easier and ran much more harmonious on this crap 91 premium California gas. Fortunately I haven't been riding much because of work and school, so I have a stash of summer blend premixed gasoline, which doesn't have butane in it like winter gas, which stores badly and runs like crap in ring-dingers comparatively.I used some split lock-washers and blue loctite on the head, so it will stay tight.
I used a piece of silicone hose to seal the expansion pipe pipe union where the rubber seal was before, but leaked, this should work a lot better.
So here Raven is, all back together in one piece. Later today when all the sealants are dry I'm gonna go for some rides to break-in the new piston ring with the honed cylinder. I'm excited, it was quite powerful with this head and gasket setup last time I rode it!
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16v4nrbrgr
Active Member
She runs! Makes good power too, takes off without pedaling and accelerates as fast a car. The carb is kinda being a pain though, gotta go through it because it was kinda inconsistent. I cleaned out the jets, but I think it needs a complete cleaning and maybe a leaner main jet, I think I was putting out the spark and fouling the plug a bit, it was cutting out at high revs, but it was reading rich.
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16v4nrbrgr
Active Member
I completely cleaned and rebuilt the carburetor and put a 80 main jet in to replace the drilled 87 that was in there, I noticed that it pulled clean until a couple seconds into the main jet circuit at full throttle when it would foul out. I looked in the cylinder and the piston top was washed by fuel, so it was obviously wayy too fat, that would explain the crappy restart and running right after it cut out, fouling. I've got a set of 5 jets from 65 to 85 in 5 size increments so I can lean it down and then maybe drill one out to fine tune it if it needs a half step. I decided to put some air filter foam in the vents for the float bowl on the sides of the carburetor, because its a great place for crap to get in the fuel and plug the tiny transition jets.
Here's the diagram for the carb, in case you gotta open up yours.
Here's the diagram for the carb, in case you gotta open up yours.
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16v4nrbrgr
Active Member
Well the 80 main was an improvement, although I think I've gotta try a leaner main, it still seems to foul at full throttle, but not nearly as bad as before, I can let off and it cleans up. I just did a plug chop so I'm gonna drop it down to a 75 if the plug looks fouly.
I had to put teflon tape on the idle mixture screw and throttle valve screws since the idle was bouncing all over the place, and I could see gas leaking from the mixture screw threads. That seemed to help a whole lot, and now the tuning of the idle mixture circuit for a clean takeoff is actually working now.
I had to put teflon tape on the idle mixture screw and throttle valve screws since the idle was bouncing all over the place, and I could see gas leaking from the mixture screw threads. That seemed to help a whole lot, and now the tuning of the idle mixture circuit for a clean takeoff is actually working now.
16v4nrbrgr
Active Member
Wow, high frequency vibration is a powerful force!
After the last short plug chop run with the 80 jet I brought her in, and noticed that the freeze plug that seals off the startup bypass circuit on the side of the carb was missing. I had to make a new one out of aluminum bar stock and a little craftiness using my drill press as a lathe with a file and a hack saw. I put it in with loctite red, hopepully it doesn't decide to harmonic itself out again! lol
After the last short plug chop run with the 80 jet I brought her in, and noticed that the freeze plug that seals off the startup bypass circuit on the side of the carb was missing. I had to make a new one out of aluminum bar stock and a little craftiness using my drill press as a lathe with a file and a hack saw. I put it in with loctite red, hopepully it doesn't decide to harmonic itself out again! lol