my journey begins and never ends

Hey thanks Chaz.

Crassius I'm intrigued, what do you mean about the piston?
it's my original zoom motor, which I believe is a pk80. I know your familiar because I remember reading that you thought they vibed at low rpm, but the A80 didn't and you prefered the a80. I am actually considering buying another engine from zoom. On their website it says and shows it completely disassembled. so I could clean up all the ports and transfers, and then assemble with better hardware. but mine does have a patch of vibes that are pretty intense in the mid-range.
Are you saying that is a characteristic of the pk80?

becuse I would have to rethink buying another because I would only buy another engine in hopes of not having a patch of wicked vibes anytime. other than that patch o vibes I love this engine.

However, I have "journey" developments. The back wheel is warped, so I have ordered a replacement from husky. and I decided I want jackshaft kit to go with my coming 3 spd internal hub. I understand that I will have to watch my throttle application as I change gears up and down. As I was checking out the bike closely I found a frame crack, again. So I stripped her down, and pulled out my other electra townie frame. when I wanted to use this frame before I couldn't because the engine chain just couldn't fit past the frame on the left side. but now with a jackshaft already in the scheme, she is back in play.

and I'm kinda happy about it. this is the 3rd crack in the other frame. in the picture below, the frame has orange lines where the first 2 cracks were, and the yellow is the new crack, so shes 3 strikes. although bad mount tightness maintenance is the fault of the first one by the seat stem.

the new frame has a couple benefits in the added strong points with the blue arrows. the seat tube is a little smaller, but I ordered the jackshaft after knowing I'm changing frames. I will still need my front mount modded, but thats fine. the other small bonus of the frame change it that this frame has a coaster brake, so it does not have v brake mount as does the cracked one. my new rear wheel is a drum brake as well, so I dont need or want the v brake mounts. new frame doesn't have through frame cable paths, but I don't care about that.

so that all being said, I'm thinking of a new engine because of the 3 cracks. and if all pk80s are suspect of intense mid range vibes...

Well I decided for a new zoom motor no kit. the individual motor is listed as sold completely disassembled, and a picture shows it that way. I called him and he told me he needs to change the website listing because it is actually 100% assembled. When I first saw it in pieces I thought "how convenient, I can clean it up and then build it with my own bearings/hardware". I decided to to pick it up anyways, Zoom is ehbc distributing and they are 15 minutes from my house. Zoom guy (I asked and have forgotten the guys name) assured me that all their stocked parts are for the engines they sell now. it wasn't always that way.

So I picked one up, and have decided to go with no mods to start. My first engine I tore apart and did all the work right off the bat, from what I've read 60 kph on a 44T sprocket, nt 66 jet, running 100:1 mix, modded stock muffler is not too bad. But as I've mentioned there were a bad patch of vibes, someone more experienced has told me he believes it to be crank balance issue. Also on that first engine I managed to actually break a piece out of the bottom of the crankcase, I used JB weld to fix it and my dremel to make sure inside was completely smoothed out with the case. It has held to this day and shows no signs on the exterior of fatigue. A new untouched engine will give me a better chance to learn more and understand it better in the end. I will mod step by step to see how it changes. that being said I am starting off with my nt carb 66 jet, which I can't remember what the stock jet was(66 stock?). I don't use an air filter, I use rain sock material across the intake so I think I am up a size or 2. this carb was running pretty good on a stock muffler, so I will start off there.

I'll have to see how everything comes together and if all goes well after break in I will start playing with my box of parts. I will continue my use of opti 2 at a 100:1, but for break in I will use whats left of my lean mix(oilier) that I've mentioned before.

I have a modded stock muffler and a long non performance one I like the look of. I also have a sha 15.15 with idle and a/f mixing screw, and a skyhawk cns to play with(I have a speed with the petcock attached that I doubt I'll touch). I like the idea of the cns using a seperate fuel system as a choke instead of choking off the air, sounds easier to tune as you can apply more or less fuel on test runs to see response. I have read alot about carbs, and I know there are some very experienced and knowledgeable members that believe a properly set up nt is as good as you'll get, but I have these things lying around and do enjoy tinkering. Also will play with intake length, and air collection ideas.

once I get the carb/intake and exhaust set up, I will look into the electrical system for strengthening spark and maybe improve timing. CDI harness and oz coil.

then I would think of modifying piston and compression adjustments (will I have to tune my whole my air/fuel system
again?). just saw a thread about stuffing the wrist pin that's interesting, greater compression, but greater piston mass? maybe as a last resort for compression increase? Also I've seen a brass bushing to replace the needle bearing, not sure if it's a fit for my motor but I could measure and email.

then opening up the cranckcase for clean up and maybe stuffing.

right now I'm waiting for my husky rear wheel, tires and tubes. and a sbp uhd jackshaft kit. the engine hardware is upgraded (external stuff so far), and I checked out the jug and piston. torques on the head were all around 150 in/lb, I use 110 which I read on a forum at some point. frame is repainted, a can of primer and a can of header paint. not a show piece, but it's black. engine too, no primer just header paint.

I'll try post photos after, but looks like photobucket is changing again today. may have to go back to my flickr account and upload the pics over there.

Rough sanding, dont have my crank tool I have one coming.



Out of the box, straight from China

Some hardware swapped out and painted.

JB Weld before it was even fired up.

So it's built, and running. Needs tuning on exhaust and carb to get it running well.

Between waiting for parts, getting a new front mount made and making it all work on a pedal forward frame was a predictable challenge and took awhile.

What I've done
I checked and repacked my front wheel cone and bearings
Installed sbp jackshaft, with wider bottom bracket
New rear end, wheel, 3 spd and drum brake
Wired a hard kill switch into cdi (toggle on/off) switch
New maxxis hookwarm tires with mr.tuffy liners and some super thick tubes from Japanese manufacturer.
New suspension seat post
And of course a new untouched motor

Next will be setting up my exhaust and getting the carb happy with it.

One thing I will mention, is holy #@$% it's a stiff kick now. There's no pedal along and drop the clutch and pedal stiffens a little to kick over the engine. Now when I drop the clutch I need to position the pedal in a spot to be able to kick down full force to start her up. And with the pedal forward frame it makes it a little harder as well I think.

I'll need some good enough weather to tune it, hopefully later this week. I'll post pics later

Oh I, when I had the frame stripped down I used some foam to fill the seat tube and lower frame tube where the engine mounts. I used a foam that is used for window sealing. It has very little expansion and cures soft not hard. I used some blockers to keep the foam in areas I wanted only. Haven't had enough time riding to notice if it's doing much.

My intention for doing this is not to strengthen the frame but to try absorb the high frequency vibes and dull them down.

Ya it does require air, so at first I blocked one end with old forks and the bottom end with the old cartridge. allowing it to cure up to the cable holes and mount holes on the frame with a fan blowing over it over night. then pulled out the blocks, some oozed and cured further at the bottom end, nothing came out the top end. cleaned out easy before the new cartridge went in. then gave it the poke test with long wooden kitchens skewers (long toothpicks essentially) through all available access points, came out dry and clean all over.

I know it's generally frowned upon, but that's the beauty of building your own bike. the only time I've seen it mentioned is always negative, but I figure with conservative use in the areas of the mounts it can reduce the sharp vibes.

and if it causes me grief I'll post that up too

well hopefully it helps and doesn't cause any grief, I didn't actually build the bike for a week or so after all that.

I gotta wait couple days before I can take it out and try it with a different exhaust I've mounted now, also received a few jets from aliexpress, so I can try a little tuning.

I also am using my punisher skull intake cover with a huge hole cut out of it, now the intake has a bit of protection from the direct rain.

I dont have the right side chain tensioner on in photo. I will run a tensioner and try stretch the chain a bit, right now with a half link it's just too tight.

Looks a little rough but works well. I'm hoping to switch to a half link after the chain stretches abit. The engine chain and the wheel chain are very close together, I don't know if I'll be able to run a 415 chain, buy I'd like to.

Here she is now, all 72 lbs of her. I had the right side plate from a Chinese jackshaft kit that I have used with another bearing to add right shaft support, and made another plate on the left side similar to the left side tensioner sbp sells. But I dont have a tensioner sprocket mounted right now, dont need it right now. So the sbp jackshaft is mounted to the seat tube and extra plates are bolted to the engine and sandwich the js sprockets. Just because I could and figure it adds support to the whole system.

Here's the killswitch wired into cdi

Here I'm using thick rubber and zap straps, holds up well and is quite quiet.

Build is all solid, but I'm still tuning. Just been busy lately, not alot of time right now.

finally had a chance and ok weather for tuning, was running very poorly. Did some drastic changes on the jet and it made no change, so I cleaned out the slide needle jet and the float needle seat. visually they looked gummed up, after cleaning them is was clear just how gummed up they were.

So she'll do 50 kph with a long pipe and empty can exhaust, and a 70 jet. Haven't even looked at the needle position yet, and haven't pushed it much in 3rd. Not a bad start.

Running in the high 3k rpm range, topped out just over 5k going down slight slope in 2nd. some room or improvement there I would think. Vibration seems low, but so are the rpm.

I miss bump starting though, it's alot easier to start with a couple hundred lbs rolling momentum than kick starting this beast after getting it up to half assed speed. I still need to check the compression, I will do that before putting on my new head, stock cc.

once it's broken in I will think about porting and doing jug/piston work. It would be nice to have my cheese motor cranked swapped into my motor I just took off. All the motors are pk80s I believe, I will measure and compare crank and rod when I break down the mid range vibey motor. then when I take this new motor off for work I could mount that one and see how it runs.

edit: disregard the rpm, I hadn't set up the tach yet.

so I have had a chance to get out a few times, tach set up now. First off, the only 50 kph I hit is downhill, on flats in 3rd i'm in the mid 40s. vibration is really low on the bike, I don't feel much until I'm hitting the upper 9k to 10k range. the tach is a nice thing to have, worth the $25 I think.

the jackshaft sandwich is running great, when going over everything I noticed one of the js sprockets set screw had loosened just a bit, but with my sandwich there is zero lateral movement. I did use normal strength thread locker but I guess I'll have to use the permanent stuff. I was trying to run the math on my rpm but came up with 58 kph at 5k rpm in 2nd gear, which sounds way too high. I'm running engine 10T, js in 17T, js out 10T, big crank 44T, smaller crank 36T, 3 spd 21T. apparently 2nd is 1:1, then 1st is 3/4 that and 3rd 4/3.

I also found finally found my neoprene handlebar boots I bought a couple years ago and never got to use, they're awesome. I don't have to wear big bulky gloves, and hand stay out of the rain and wind.

starting is a little better, I added an extension to the nt carbs choke so reaching down. Now I at least only have to start it once, but I need to look at the clutch. slips sometimes when kickstarting, and lever is well set, so I may have to adjust flower nut. I need to refresh myself on the clutch again anyways.

I ran on oily gas for the first bit, I don't know the ratio but definitely fuel lean compared to my usual 100:1. Now I have a new batch (just over 50 ml of opti2 to 5 L of gas). I know all the controversy over this, I have read the mega thread here or there (cant remember which site). I've read up a bit on the jennings 2 stroke book and other write ups on the subject. I do it because I can, it's a hobby for me. the only reason I have an mb is for fun, and that fun is not just saddle time. so tinkering and trying things out is apart of it all, and I've learned alot by just trying things. if I kill the topend on a ride, I will have to lock it up and come back for it (unless I'm close to home). a whole new topend is 15 min and $30ish away, I think it's a reasonable risk. and all that being said, the last motors latest topend ran 100:1 the whole time from day one. the pics showing the piston, show it's looking pretty good condition after many miles. still running strong, and that engine lived WOT. I never cruised part throttle, I did lend it out as a commuter for a few months and I don't know how many miles or how it was driven. I still plan on a crank swap for that engine to see if I can get rid of the midrange vibes.

this engine is getting better, but doesn't feel broken in yet. on the 70 jet and bottom notch until its broken in. running well, but I should do a chop. I'm also getting more used to riding with the js, feels like I would like a bigger spread of gearing but I'll see later. Intake is back to no cover at all, I'm using one of the stock filters plastic grids, cut be wide open in front of carb intake. that grid holds on a big hard rubber ring about a 1/2 deep that holds the rain sock material in place.

once it's broken in, I'll play with carb and exhaust. to be honest I really like my exhaust, to me it looks the part for my hobby bike. it runs well but I might drill a couple holes in the can to modify the putput sound of idle. the bike is quite quiet, I have to lean back and turn my head to hear the exhaust over the intake. the carb I will try the sha clone to see if I like it better, the choke has a cable to handlebar lever which is nice. intake length is tricky, not a lot of room for a longer one unless I go side ways. I've got a new cnc head waiting for break in as well, I will do a compression test on this one when I take it off, then do the new one to compare. I will also shorten my plug wire then, I also have a couple plugs lying around to try.

once I "finish" working on this one I can tear down the other engine to swap the crank. then put that on the bike so I can tear down the new engine and clean it up.

ok I read that the 66cc internal ratio is 4.1:1 (drive gear to clutch gear?), when I start with that and go through the numbers they look much more realistic.

well between weather and being sick, I didn't get alot of riding in december. broke in the top end and got impatient with lack luster performance, and swapped new top end for my modded previous top end. I also put on the new round aluminum head and shortened the plug wire.

with my modded top end and the cnc head she starts much easier, loss in compression? maybe. still tuning though. I have a 70 jet I feel is too small, but my next jet up is a 75. and I have carb plans in the works that will kick'n the nt out.

also felt the exhaust was too restrictive, so I drilled out the the little stinger output and drilled an extra hole in the end of the muffler can. I thought the can was empty, but I could see baffles through the hole I drilled. So I cut the end of the can right of, then it was wide open. took it out with the 75 jet, she was popp'n and bubbling and scared the neighborhood pets pretty good. but no good.

so I cut a couple more inches of the can of and installed my own silencer, turned out really well. I'll explain it with pics later. but allows me to experiment with baffle material, and how much. I dropped the jet back down to 70, and will try get out tonight for a run to see how it is.

this build has been very solid, very solid ride. but performance high and low is still not there, I have come close to 50 kph on flats, sitting up. I'm still not sure about my sturmey 3 spd(1st 75%, 2nd 100%, 3rd 133%, 22T), but too early to make final judgements. I like the drum brake, and can tell it's still breaking in. I tried a 3 spd thumb shifter/clutch lever, 3 spd jammed on first ride so I swapped back to twist.

I also am going to replace my right side chains with kmc k710 kool chains soon. left chain has stetched a touch so I will adjust shims for that which changes right side chain distances as well. good time to put on the new chains.

Also just picked up rockbros seat pad for my brooksbros seat, springs are great but the saddles just too hard for long rides. the new cover looks lame, but feels pretty good.

I used a piece of side support out of a neoprene knee brace as a muffler support, working out well. it has spring action, but is very stiff.

waiting on a carb and have plans for a custom intake to allow for it. over all the build is still disappointing because the thrill isn't there yet, but I gotta say the reliability has been awesome. much better than my previous build, I really can't complain. I just have to tune it