ZX50 Crankcase Tuning

[sidthesloth]

i managed to get the new seals but, unfortunately I cannot get the bearings locally, so I will have to look on the net, maybe buy a crankshaft. My stock crank is in good condition, the manual says service limit for conrod endfloat is 0.6mm, mine is 0.28. I have sent a message to an ebay seller asking if he would drop his price on a stroker crank, 43.2mm. I could run the existing bearings, which I might do, just to see the difference in the work already done, then look at the stroker crank. That will give a better idea of what change has had what effect. Here is a pic of the cylinder raised so you can see the rear opening lined up with the crankcase port.

[sidthesloth]

Last night when I put the cylinder back on, I used the degree wheel, first time. I got some readings but they don't mean much to me. They are as follows:

Exhaust start to open @    93°
Full open                  @    74°
Close                       @  192°

Transfer and Boost ports are at the same level:

Start to open             @  118°
Full open                   @  180°
Close                        @  245°
As I said, they don't mean much to me, so if anyone could offer any help, that would be appreciated.

I think I stuffed up the exhaust close, I think that should be 267°

[Hoolander2]

Nice looking work, Sid!  Do you expect to have to up-jet again now?  More plug chops, etc?  I hope to hear you have a real screamer on your hands there! 

[sidthesloth]

I honestly dont know, I have a range of jets up to 140, so I will be ok if I do. I would expect to stay the same though as I have not altered the air filter, just more flow same mix.?

[art]

  You hope. When i did the squish on the p50 I had to re jet quite abit bigger  Would not run off idle after mods. It's hard to say. 

[sidthesloth]

Well, I took her for a ride and it is not a whole lot different than before, a little better but not a lot. Haven't done a plug chop yet, do that tomorrow. I keep coming back to the exhaust, I think that is going to be the solution.

[Hoolander2]

"More flow" means more air into the same amt of gas.  Do those chops!    What are you contemplating doing more to the exaust?

[sidthesloth]

Being a two stroke I doubt there is much I can do to the exhaust. When I bought the carb kit, I also bought the exhaust, a YMS V8, I have my doubts about it. The only way to find out is to try, another couple hundred dollars and two week wait. Yes, will do a plug chop today. I was thinking that because the flow was increased after the mixing, carb, the mix would increase to suit, same size jet, same air filter.

[Hoolander2]

I think you'll have more air pouring through the carb which is why I say that.  If I'm right, that's a good thing!

[sidthesloth]

Yep, you hit the nail on the head Hoolander, I did take it for a ride today and I think the difference is a lot more than I thought yesterday. First plug chop looked tan on the mix ring, but the ground electrode was white, went to a 130 jet and the ring looked ok and the electrode was a little darker. Have put in a 132 jet and will run that for a while.

[Hoolander2]

Hey, great news!  I missed your last post when first posted.  How's it doing?  Will it raise the front wheel?   

[sidthesloth]

G'day Hoolander, no it won't raise the front wheel, not without considerable effort on my part. I tried adjusting the carb needle, but going up was too rich, so just for the trying I went down one notch from where it was, that put the needle at the bottom, it ran well but lost a little top and was a bit of a mongrel to start in the morning, (and I had finally sorted out my starting problems with the CDI). I have now put the needle back to second from lowest setting and gone back to the 130 main. Seems ok so I will leave it like this so I can see how it goes over time with normal use. When I do get either a new crankshaft or bearings, I will try some more trimming inside the cases. Funny thing is, I had more fun putting it back together on the bench than I think I do riding it.
So, in a nutshell, it is going well, with room for improvement.

[thebatman]

digging this thread sid...... man, those intake openings i thought would have made a big difference......well guess i was wrong, had to have helped tho....

[sidthesloth]

Yes, it has made a difference and I will do more next time I open it up. I was surprised at the size of the main bearings, heavier than I expected.

[thebatman]

yeah, theres no way to do that one while the motor is assembled..   that will be on my list WHENEVER i have to split the cases FOR SURE!!!.. i figured that may have been the take off issue.. at least it helps tho.