Kimjon

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Everything posted by Kimjon

  1. My wheels looked like something Jacques Cousteau found at the bottom of the sea. I forgot to take before photos, but they were near bin material...however new ones with tyres and tubes would be approximately $300 landed. So refurbishment was the only realistic choice to keep the cost down. I stuck the rim halves in the lathe and used sand paper to knock them back into shape. Then etch primed the centre's. Then I hand painted the spokes to try make them look like mini Simmons mags. I was going to go gold...but pussy'd out and took the safe road - black. For tyres; the wheels on hand trolleys will work. My tyres were 3.0-4 and the sack trolley tyres are 4.10/3.50-4. Both are suitable for 4" rims, but the sack trolley tyres will be slightly taller and wider. But considering I have some already...free!
  2. Really starting to look awesome! You have nailed the lines on that bike. It could be made of pure gold and still look like shit if the lines are wrong...but you've got it looking just right!
  3. Here it is mocked up: I've turned up some axle spacers to set the clearance. Looks like it should do the job.
  4. Waiting on frame, so trying to do all the little things. I brought a new gas tank, so made this sexy bracket to secure it to the goped: Roughed out, and next to the old bracket. I want it to sit flat, bringing the tank closer in. The old bracket was bent to clear the wheel...but someone put a huge sprocket there Finished.
  5. What about one of those bicycle kayak things (2 kayaks with a bike sitting on them)...but V-twinned!!!
  6. Here ít is finished. Gone from about a stock 5mm lead up to about an 8mm lead. Also while I had it apart, I installed a grommet and re routed the kill switch (wire to ground the coil, to stop the motor). This looks a lot tidier. You won't see it once motors back on the frame. Pictured above with new modifications.
  7. I was advised the stock tiny little HT lead (spark plug) doesn't transmit to well at higher rpm's. The solution is to remove it, and replace it with a larger non suppressed lead. This was a dummy fit on a dud coil to see if I could do it. I used a linisher to reduce the OD of the larger HT lead to fit into the white socket. On the real deal, there's a rubber boot covering it. Spark plug connector installed. Once again there's a rubber boot to go over it. Finished.
  8. Oh i do like that tacho...more information please?
  9. Yes, but way more work For 4 strokes, keeping heat in the pipes and out of the engine bay is a good thing. However for 2 strokes where you scavenge some of the air/fuel mix back from the exhaust system the cooler the better, as hotter air takes up more room (less dense) and therefore potentially losing power. The amount I've wrapped won't really have a huge bearing on power (loss). And its going to prevent third degree burns to my leg...and it does look cool So if coolness factor like stickers add +5hp, then that would surely offset real world loses?
  10. It the meantime I decided to machine the head for better squish. I found two slightly thicker copper gaskets, then shaved the tiniest amount off the top of the cylinder barrel. My OCD just couldn't rest knowing it wasn't right. Then I fully assembled motor including exhaust, "torqued the head down" (i.e. turn hard until it felt about right ) measured squish... and got 0.73mm. So very close to the 0.762mm (or 0.030")... happy with that, so it's going to stay like that. Then assembled the rest of the accessories and exhaust. Is now 100% ready to run/test. Boom!!!!
  11. Sounds good. Be keen to see what you come up with, as clearly imagination is not a limiting factor for you
  12. Then I made custom exhaust gasket to match the new porting. And wrapped the exhaust header in fiberglass exhaust wrap. I soaked this in warm water, then wrapped from the thickest end down. By soaking and wrapping it wet, it will shrink tighter onto the exhaust. And by wrapping thickest part and working down to the skinny end it will prevent it from unraveling. Once done, I tied it of with stainless steel bands. Wrapping an expansion chamber is normally a really bad idea. Trapping heat changes harmonics/air densities and is known to decrease performance. However burning the fuck out of your calf muscle is an even worse idea than losing a tiny bit of theoretical performance...So being pragmatic, I opted for self preservation. I only wrapped the header though, not the entire pipe. Seams like a fair compromise.
  13. I started assembling motor to final stage. Carbon fibre reeds. I swapped over my custom made reed block. Walbro style 15mm pumper/diaphragm carburetor and my custom manifold. This converts it to pump its own gas from a tank mounted below the carb, rather than gravity fed like the original. It also allows for more tune-ability (yes I know that's not a real word). Lightened flywheel, new coil and modifications done to the spark plug lead.
  14. Daves discount motors. Freight was $50USD... but spread over the total cost of the order it was still a "cheaper" way of getting exactly what I needed/wanted.
  15. Fuck yeah...best day ever! Seriously impressed...about 3 or 4 days ago I ordered some goped parts from the US. I now have those parts in my grubby (gigantic oversized) hands! Fucking unbelievable!
  16. Awesome! Thanks @Raizer great information you've been providing, much appreciated. I'm no expert, so every learning opportunity is genuinely appreciated. There so much information out there that sometimes you become paralysed with overload. I guess I just wanted to achieve a result...rather than getting bogged down in indecision. So I've been building this based on information mostly provided by a championship winning racer. Yeah, the logic part of my brain says go full circle crank...and I'm lucky to have 3 of them to choose from. However the advice I've received from a master builder of this specific motor is differing to mine (and your) logic? I have numerous windowed pistons, cranks, heads...all the performance parts. And after going through all these countless options...he says use: -The stock piston, because it will rev higher with no window. Just polish it, and slightly taper the ring groove on the top side (using fine sandpaper) so it seals better under load. -Use the stock crank, as they produce more power. The full circle is better when stroked, but mine aren't strokers. -Use the stock cylinder, because there's less chance of leaking. But change the port timing, area and add a single large boost port. So far I've followed his advice, however I did go with the two piece cylinder. I did this for practical reasons, as it was much easier to machine and set up in the mill without a head in the way. I'm getting pretty exited, as in theory the motor is done. But I can't run it until I get the frame back etc...So I'll have to wait. The good news is I still have enough parts to build 3 more motors. So I'll do them all differently next time, just to expand my own firsthand knowledge.
  17. Until I hear back, I've decided to carry on. With the huge head kit now fitted, I noticed the fan cover wasn't going to fit. So I marked it out, then set to work cutting the clearance required. Looking pretty tidy for now. I haven't decided the colour for the motor yet, but I'll figure something out soon.
  18. Onto setting the squish band. From all the reading I've recently geeked out on (mostly from pocket bike forums), the ideal squish is going to be somewhere between 0.030" - 0.035". To measure this, there are various techniques. The one I liked the most was this: Tape a bit of solder inline with the pin bearings. Assemble motor and turn it over, squishing the solder as it gets crushed by the piston (hence term squish, as it does this to the air/fuel mix too). Pull out the solder and measure its squished thickness. This was the extreme squish 0.2mm (pictured above). Now I got the following data using layers of copper head gaskets to adjust the gap between cylinder and head: I copper gasket = 0.2mm 2 copper gaskets = 0.5mm 3 copper gaskets = 0.85mm So comparing that to the ideal range of between 0.030" (= 0.762mm) and 0.035" (= 0.889mm). Using 3 copper head gaskets gets me into that desirable range. I've emailed a couple mates who are absolute gurus on these motors as I want to know if it's worth machining the cylinder to get tighter tolerances(?). Hopefully what I've got is good enough... but if they say it's not, then I'll tear it down and machine some off.
  19. I improvised a crude crankshaft balancer. Keep adding weights (nuts hung from a wire hook on the little bearing end of conrod). Once it stays put in any position, compare the added weight against the weight of the piston, pin and bearings. Then do some basic math and work a percentage. The goal was 55% (as that's what the internet said). To achieve this you remove weight from opposing areas until happy.
  20. I thought the same, but the guys racing the same motors in their pocket bikes are getting much better results from stock cranks V's full circle cranks. I have to credit these guys for all the learning that I've done lately for these specific motors. Apparently the Paloni (excuse spelling?) Motors benefit from the full circle crank which in effect is one way of stuffing a case, but these cag (Chinese) motors tend to go backwards in performance with a stuffed case. The Paloni takes its air/fuel from off to the side and very little actually goes around the actual crank case (bypasses). Versus the cag, which draws it in from the bottom of the crank case and it mostly goes through the middle of the reciprocating crank assembly. Through experimentation, the pocket bike guys have found that these cag motors benefit from increased crank case volume to overcome the poor flow and (restrictive) characteristics of this design. Basically at high revs the piston wants to draw air in...but there's to much shit in the way crammed into such a small space blocking it. On my goped motors, these are different and I've stuffed the cases with aluminum linings. Stuffing certainly increased performance on these.
  21. I need to get some bearings and oil seals. I actually brought some today using numbers gleaned off the internet...whoops, bit of a mistake trusting the internet :-), ended up with the wrong sizes. I'll go back tomorrow and get the right sizes, then it's a simple matter of putting it all back together. In the meantime, I dropped the frame off at a powder coaters. And did a bit of internet shopping on an American goped performance website. I figured it hadn't cost a lot of actual money to get to this stage...so splashing out at the end of the project is somewhat justifiable. it may be a couple weeks before I have anything to show for it, but I think it should look pretty sweet once done.
  22. My crankshaft received some grinder love...(okay I knew that would sound dodgy, but I had no idea how bad until reading it back!) Before After The idea is to smooth the rough rotating edges and slightly point them, so it cuts through the air faster. It also lightens the rotating assembly a tiny bit, plus increases crank case volume. Normally you want to "stuff" a case to decrease volume...but that's for a piston port with the intake on the cylinder. This motor has reeds on the crank case, so volume is small and the flow path is restricted by the whopping big crank stuck right in the way, so an increase in volume (I'm picking?) probably isn't a bad thing here.
  23. Checking port timing after porting. All measurements were taken from the top edge of the piston, when it reveled the opening to the port (not from the rings).I then put a dial guage on piston and turned it over both ways until it reached its highest point running in both directions. There is about 6 to 9° window of movement where the dial neither raised nor lowered the piston at TDC...so I split the difference and set the zero in the middle of this flat spot. I repeated this until I was happy with its consistency. With that done, I got the following results for the blueprinted 3 port cylinder. I did this test 3 times over and got exactly the same numbers each time.-Top of exhaust opened at 97° ATDC-Bottom of exhaust at 163° ATDC-Inlets x2, plus boost ports opened at 120° ATDC. -Blow down time 23°I didn't use a base gasket, I'm thinking I'll just use a sealant RTV type gasket maker there? Next up is to calculate the port area. Basically done by shoving a bit of paper in the cylinder, rub the paper with a pencil or dirty finger...leaving an impression on the paper. Do some basic math, and roughly I got the following areas: -Exhaust port area 269mm2 -Total intake area 294mm2 (2x intakes, 1x boost port) I ran those numbers via some experts and they feel only very minor improvements could be made on those results...so stoked! Going to leave it there and look at assembling with new gaskets, bearings and seals.