ZX50 Build,,, Again!!!

[sidthesloth]

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.

[sidthesloth]

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.

[sidthesloth]

Oh well, 50mm kit stays, the 47mm piston won't run on the 44mm crank.

[Shaka]

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.

[sidthesloth]

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.

[Shaka]

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.

[sidthesloth]

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.

[Shaka]

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!

[sidthesloth]

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.

[sidthesloth]

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.

[sidthesloth]

A small correction, I found my piece of paper and my previous port durations were ex. 184 and trans. 138.

[sidthesloth]

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??

[Shaka]

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!

[sidthesloth]

That's good, how did you go about holding them in position?

[sidthesloth]

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.