KymcoForum.com
Scooters - 50cc => zx50 => Topic started by: sidthesloth on March 31, 2011, 11:57:14 AM
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G'day all, I have been at it again. Have managed to get some money together and buy some more bits for the scoot. I am still going to keep my exhaust, for now, but I have just fitted a new variator as the slides in the old one were worn. I have bought a new cylinder kit, 47mm and a 44mm crankshaft. Once I make up a crank puller I will strip the engine and see how this new gear goes together. Unfortunately I bought a cylinder kit that was made in China, so I may have made a mistake already, but will remain optimistic. With my previous crankcase work it should be ok. Hopefully.
cheers,
sid.
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Awesome Sid! I just finished up mine last night, initial impressions are great! Keep us posted, lots of pics! ;)
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Hey, that's cool, how did you go with the engine mount bushes? I have the crank puller sussed, just got to cut, weld, drill and hope for the best, after all, two spark plugs were sacrificed for it. :) When I get a chance, I will do a port map, the trans ports look rather small. Might be that I am used to the big ones of the 50mm kit.
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Haven't gotten to the bushings yet. I have to make a call and see about some bearings. It will probably be a project for next week. I can't wait to see this contraption your making! I'm not visualizing how you're using spark plugs to pull a crank. I'm sure it will be interesting. Send me your portmap and I'll run some #'s for you. I'm always curious to see different cylinders!
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Will do. I thought the spark plug reference would spark some interest. I don't kow if what I have in mind will be strong enough, but the crank is not in that tight, so it should be good enough.
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Sid, whats up man? good to see you. Hadnt heard from you in a bit.. Well, you have my interest already. 1 ? tho, why go down in size?... suppose to keep going up.. :D...That shoulda made it close to a 99cc with the 50mm.....i THINK... :D ::)
Cant wait to see this build. ;)
oh yeah, pics...pics..pics... :D
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G'day thebatman, yeah, coming back into the fold. I guess I was getting sick of banging my head on a wall, so I was looking for a kit I could afford, turns out it wasn't so cheap after all, seller wanted more than the quoted price for shipping, cost a little over $160. If it turns out to be no good, I can always go back to my 50mm kit with the 44mm crank. I will try to take lots of pics where I can.
Question for you batman, on each side of the engine, how far does the crankshaft protrude from the cases From memory, I think they are about flush, but would like to make sure before I make a tool that won't fit.
cheers,
sid.
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Good morning sid...well...here.. ::) :D
Do you mean from the seals? or looking "down" on the engine?.. YEah, looking "down" from top view, It protrudes approx. 1 inch.. I believe the right side is more "flush"(looking from the top) than the var side
I can measure for you if need be. I still have the var side open..
Can i ask where you ordered from?..carlos?
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G'day thebatman, the kit is from scrappydog scooters, only way to find out if any good is try it.
Carlos has a new batch of 50mm kits coming in, from the Honda/Sym OEM, $100.
No need to measure, I just couldn't remember if the shaft protrudes past the case or not, but if it is not too much I should be ok. I have made the tool, very crude but if it does the job, then all is well. Just have to drill the holes and cut the slots, will include a pic of it.
Shaka, will try to get a port map in the morning, will post on here and email a copy.
cheers,
sid.
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Oops, that pic was a bit bigger than I thought.
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Here is the port map of the 47mm cylinder.
The square window is the boost port inlet, the piston does not have a window in the skirt so I figure that window is below the piston skirt. With the 44mm stroke, the piston should clear the lowest point of the boost port. I forgot to write on the paper, the exhaust port is 25mm, left transfer 35mm, boost 34mm, right transfer 34mm.
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Ok, so I have stripped the engine, and see that the new variator is not using the full potential, there is a ring of about 2-3mm wide at the outer edge of the variator, this will be something to look at when running again. I have taken some pics as requested and will post them in the next couple of posts. Here is a pic of the variator.
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Using the homemade universal holder to remove the flywheel nut.
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Removing the flywheel, this tool was only $11 from scooter assassins.
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Splitting the crankcase with the rough as guts homemade puller.
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Removing the crankshaft. I also used this tool to remove the bearings, which did push it to its limit, unfortunately I didn't get any pics of this.
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Rightio, have got the crank in, while the case was split and the crank was in the first half, I put the cylinder on to check clearance between the conrod and front of case, I had already worked the rear section last time I had it opened. It is very close, but not touching.
Pic. Below.
Also, while I had it apart, I inserted recoils in the three head bolt holes that hadn't been done. I figured it was better to do this now, rather than as a repair. The first one was stripped the first time I pulled the cylinder off.
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Oh well, 50mm kit stays, the 47mm piston won't run on the 44mm crank.
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Why won't the 47mm piston fit? Is the skirt hitting on the crank at BDC? If so, just trim the bottom of the skirt.
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Yeah, the skirt is hitting the crank, but well before bdc. I thought about trimming the skirt, but wasn't game, so just went back to my original kit.
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Now you've got some time to cut on it. Always good to have a back-up top end! ;) I would try to even out your ports while you've got the time also.
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G'day Shaka, I will give that a go. What would you suggest for cutting the ports? I do have a die grinder, but don't know if that will get in there.
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The ports are going to be real hard to get at without a 90 deg. head. I have had good luck using emory board nail files for chamfering the ports. I have ones with a foam type core that is somewhat flexible. If you bend them they also hold the shape and they are relatively easy to cut with scissors. You can bend a slight curve in the end to get there a little better. If you spend some time with it you should be able to smooth the edges out, it will take forever to remove any real material though!
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Thanks for that Shaka. I will look around the hardware stores and see what I can find. The emory board sounds good for the champfer though.
Cheers,
sid.
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OK, an update. A couple of days ago, I was running the 50mm kit with 8.5 gram rollers. The scoot was running quite well, though the take off was rather lax once going it had a nice sort of pull right through the full range, top speed was about the same as previous, so no gain there from the 44mm crank. I did a bit of a check over, removed the flywheel to check all bolts were tight, retorqued head bolts, gained a 1/4 turn on each, saw no signs of leakage around head or base gaskets. As an experiment, I raised the carb needle 1 notch to the centre setting, test rode the scoot, it seemd a little off but thought I would see how it goes going to work and back. Being on afternoon shift I was hoping for an easier start at night (starting to get cool at night now). Going to work it was absolutely dismal, way too rich but struggled on and changed the needle setting back to where it was after work but, it was still as bad coming home. Pulled the jug off today and found there was leakage from the head gasket, but no other problems. As a trial I raised the cylinder approximately 1.5mm, this gave me exhaust port duration of 192 degrees and transfer port duration of 148 degrees.
From memory my port durations were ex. 188 and trans. 130 degrees. It is now running very poorly, struggling to make 60kmh.
I will have to go back and read Gordon Jennings' handbook again and try to work out what I should do with the port timings. I would now like to trim and fit the new kit, but I don't want to do that while I have an underlying problem. :(
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A small correction, I found my piece of paper and my previous port durations were ex. 184 and trans. 138.
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Don't know what happened with the post title above. Was logged on my phone and don't get the option to add or change title. Maybe a moderator can help??
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Not sure without doing some math, but those port durations sound a little off. I would just modify the piston to work with the 47mm kit. This 50mm has just never really worked properly it seems. Let me know if I can be of any help.
Ps. I got the bearing engine mount conversion all figured out. It seems to be working out great! ;)
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That's good, how did you go about holding them in position?
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Yeah, I want to get rid of the current problem before I run the other kit. I pulled the cdi this morning in case some water got in the join, was dry, but I soldered the other terminals on and used the original plug, still no good. Will try another spark plug.
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OK, I cut the piston and put the 47mm kit on. I didn't do anything with the ports, too easy to stuff it up. I finished up with port timings of Ex. open @ 86 degrees giving a duration of 188.
Transfer ports open at uneven times so going with the first one, it opens at the same time as the boost port, 115 degrees giving a duration of 130 degrees. Plug chops are going to be an awkward job as I have to remove the right hand side fan shroud to get the plug socket in.
I also had to bend my pipe to fit to the cylinder flange.
I have started the engine with the scoot still on the table and it still seems to be sick. Pulled the carby and cleaned the jets and passageways, no blockages, removed and checked the reeds and inlet, also checked ok. :( Not looking too good at the moment.
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OK, got the carb sorted out, was ok after a blow out with compressed air. After many hassles I forgot I tried the #107 jet and when I took it for it's first ride I suffered a soft seize. I have now gone back to the setup I was running previously, #125 main jet that has been drilled a little larger and the needle on the second lowest setting, the middle setting was just too rich. I am surprised at the initial pickup of this engine, for a chinese kit it seems to be very responsive up to about half throttle. i will wait a couple of days before I give it all. At the moment it looks like I might be able to put the 1,000rpm torque spring back in.
Before I put the 8 grm Dr. Pulley sliders in I weighed them and collectively they were just slighly heavier than the 8.5 gram rollers that came with the variator. I had ordered the sliders before starting this job and it turns out that they are not a bad choice for now. I go back to work on Friday night, so I will see how she goes over the weekend. :)
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Given that I was happy with today's overall result, I decided to fit the new rear tyre I picked up last week when we went to adelaide, a Michelin Pilot Sport. It was a bit of a bugger to fit, but it is on and balanced up a lot easier than the conti twist. The Conti Twist still had a few K's left on the tread but there was a bulge in the tyre. Once removed the bulge was inside as well, the tyre had delaminated. Continental tyres are no longer on my shopping list.
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Last week I weighed all of my rollers and thought I would post the results. I don't know if they will be of any use to anyone but, here they are.
SCOOTER ASSASSINS 6 GRAM ROLLERS Dr.PULLEY 6 GRAM SLIDERS
6.04 6.00
6.06 5.99
6.06 5.99
6.08 5.99
6.04 5.98
6.05 5.99
TOTAL TOTAL COLLECTIVE WEIGHT 35.91
36.33 35.94
SCOOTER ASSASSINS 8.5 GRAM ROLLERS Dr. PULLEY 8 GRAM SLIDERS
8.03 8.05
8.02 8.05
8.12 8.06
8.01 8.10
8.05 8.09
8.03 8.06
TOTAL COLLECTIVE WEIGHT 48.25 TOTAL COLLECTIVE WEIGHT 48.40
48.26 48.41
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Just put the 1,000 torque spring in and also changed the 45 pilot jet with a 48. Tried a 130 main jet but that was a bit too much so going back to the drilled 125.
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Ordered a set of pilot jets from Scooter Assassins, range from 32-50 sizes. Tried a 40 jet but not a whole lot better. Tonoght, I put in a 38 pilot jet and it is a lot more responsive from take off. took it for a run and it is much better, I don't want to adjust the needle yet until I get a bit more time to give another run, (last time I did without a test run, I had to take the scooter home and take the Boulevard to work).
Hopefully, I can now try tuning it a little better, including needle adjustment.
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It's interesting to hear how much better yours and Batman's scoots run with a smaller pj. You both have a different carb than I do, but I know that my pj is too big, somewhat intentionally. I may need to go a bit smaller, problem is I need a "1/2 size" Arreche only goes in increments of 5. I need about a 22.5, I initially had a 20 and ended up with a 25. With all of the humidity today she ran pretty sluggish and I kept getting the cylinder "loaded up" and having to "clear it out" sitting at stop lights today. I pretty much have come to the conclusion that I need 3 different jetting set-ups per year here in NC. One for the winter (cold and no humidity), Spring & Fall (Hot no humidity), Summer (Hot & Humid).