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Scooters - 50cc => zx50 => Topic started by: sidthesloth on September 26, 2010, 11:40:03 PM
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Alright, I have bitten the bullet and ripped the engine out with a view to increase the inlet tract. I have never done this before, so I will be learning as I go, and hope to hell I don't muff it.
I will include some pics as I go. I have a couple of questions if anyone is able to help, I would really appreciate. Looking at one of the pics you will see where I have marked the aux. port. The existing one in the case is tiny, where the one on my cylinder is massive by comparison. How far can I go with this, without causing any problems? Or can I just go as far as I like while leaving a reasonable wall thickness.
Also, in the same pic, you can see two holes which I assume the fuel is forced through, to go to the transfer ports, should I increase these as well? The reason for doing this is that I have put on an 82cc cylinder kit, along with a 24mm carb and inlet to suit, at around half to three quarter throttle there is no more acceleration, only an increase in noise.
Any input welcome.
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You can do, sid...Good luck!!! :)
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...where th' hell's zombie...........
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You mean those two round holes in the bottom of the transfers? I think they're for letting some of the fuel/oil mix get to the crank bearings for lubrication. Don't know about other questions, sorry.
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And I wouldn't increase or change them in any way. Increasing them, I believe, would decrease amt of mix going up the transfers.
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Yes, thankyou Hoolander, I see that now. See, always learning.
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Your in over my head sid ;) Just a thought though. I believe this is about where I was at on my people 50 (before problems) I felt my real hold up was gearing. Your making noise but no more power to the ground because the tranny has hit it's peak.
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No, I don't think so art, I have now got the tranny at what should get her going. But right the way through setting up this cylinder, it has had nothing over half to three quarter throttle. I don't know if this is going to do any good, but the only way to find out is try.
I will put in a couple pics of where I am at so far.
The boost port has got me worried because I don't know whether to cut right the way down or not.
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This one is from outside the inlet with one opened up.
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I will try to put two pics on here, one from inside and one from outside. This is the inlet windows opened.
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Wow, sid, you have been busy. I see what you mean by "all in pieces" now. :o
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I'd go easy on that boost port on this first go round. Open up too many ccs below and you're not gonna force enough mix up. Oh well, can always fill back in with weld. ;D
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Does the boost port have it's own reed?
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G'day Hoolander, I took the safe option and opened the channel above the crank and left the casting near the crank as was. There is no reed there. Will put up pics when I get home.
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Here are the pics of the case after cutting out the boost port. The tabs you see at the bottom of the channel are the ones that caused me some concern. In the interests of playing it safe I left them as they were. I think this will utilise the carby a lot better than it was before.
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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.
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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°
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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!
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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.?
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;D 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.
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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.
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"More flow" means more air into the same amt of gas. Do those chops! ;) What are you contemplating doing more to the exaust?
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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.
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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! ;D
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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.
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Hey, great news! I missed your last post when first posted. How's it doing? Will it raise the front wheel? ;D
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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. :)
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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....
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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.
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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. ;)
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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°
Based on your numbers, your exhaust port duration is 174 degrees, and your transfers are 124 degrees. The "full open" on both should be 180 degrees from top dead center, as that is half of the crankshaft's rotation. The closing value is not required - using some simple math (outlined below) you can sort all that out.
I'm quoting off-site here, forgive me:
Can someone explain me how to measure squish and port timings. I calculate the timings by measuring from the top on cylinder to the top end on the port, but doesn't seems to me that they are correct timings. Can someone explain how to measure with degree wheel. I have not got that one but I'll make it or order it. Please someone?
Thanks
Jon's suggestion on using the piece of solder crushed between the piston and head works great.
To use a degree wheel isn't too tricky.
Bolt the degree wheel to your crankshaft. You'll want to also bolt on some manner of pointer or indicator. I like to use a small piece of thick wire, as it's easy to mount and move around.
(http://www.scooterinvasion.net/pics/mysuper9/block/1/IMG_0972.JPG)
In the above photo, you'll notice the piston stop.
Rotate the piston clockwise until it hits the piston stop. Take note of the reading on the degree wheel (where the indicator is pointing). Then rotate it all the way counter-clockwise until the piston stops, and take note of that reading. You can then adjust the degree wheel (or the pointer) so that your readings are symmetrical. For instance, the piston stops at 9 degrees ATDC and 9 degrees BTDC:
(http://www.scooterinvasion.net/pics/mysuper9/block/1/IMG_0974.JPG)
9 degrees BTDC when the piston stops.
(http://www.scooterinvasion.net/pics/mysuper9/block/1/IMG_0975.JPG)
9 degrees ATDC when it stops in the opposite direction.
At this point, you have your degree wheel "dialed in", and it will provide you with accurate readings. Remove the piston stop and you can rotate the engine to 0 degrees which will be true top dead center.
Now, if you rotate the engine slowly and watch for the exhaust port to be opened by the piston. Sometimes it helps to shine a flashlight into the port so that you can see it easier. Take note of the measurement on the degree wheel. This measurement (let's just say 80 degrees after top dead center) is your port "timing". The duration is the span that the port stays open for, which is also measured in degrees. To determine your port duration after discovering the timing:
80 degrees is multiplied by two to get 160.
Subtract 160 from 360 to get 200. The duration of the port that opens at 80 degrees ATDC is 200 degrees.
It may sound complicated at first, but really it's not. You know that in a complete revolution, the crankshaft turns 360 degrees. From top dead center to the opening of the exhaust port, the piston travels 80 degrees. It's going to cover that same distance on the upstroke, which is why you multiply by two. Then, subtracting all of the rotation of the engine that does not involve the exhaust port will leave you with nothing but the the duration of the exhaust.
The transfers are measured the same way. Remember though, you will pass the 90 degree mark often when measuring transfer timing. After you pass 90 degrees, you need to pretend the degree wheel goes on past that, instead of counting back down, you count back up. After passing the 90 degree mark, the next one was 80 degrees, but you will need to count up instead of back down so even though it says 80 you need to think "100" The next after is 110 degrees and so forth.
(http://www.scooterinvasion.net/pics/mysuper9/block/1/IMG_0992.JPG)
I may not have done the best job explaining it. If I can explain something better, let me know and I'll do my best to help.
~Josh
Don't forget to use a piston stop when setting up your degree wheel. Otherwise your measurements will be off. When you go for the higher-end tuning, it's very important to get these things right.
Furthermore, don't forget that at some point in your measuring, you will pass the 90 degree mark on the degree wheel, and instead of counting down, you'll be counting back up (90, 100, 110 etc, instead of 90, 80, 70). It looks like you may have read back down when getting your "full open" value on the exhaust port.
Now, measuring the timings isn't the hard part... deciding where to go, and what to do with them are! It gets to be a bit much to explain at 11:00 at night (I'm usually in bed an hour ago), but if you haven't picked up a copy of A. Graham Bell's "Two-Stroke Performance Tuning", I highly suggest it.
~Josh
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Thank you very much for this info Areomyst, I had never used a degree wheel before, and I did use it wrong. If I get a chance in the next couple of days I will change some rollers, so I might give it a try then, properly.:)
The readings I took were with the head off, so there is no way it could be accurate. Still learning.
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Thank you very much for this info Areomyst, I had never used a degree wheel before, and I did use it wrong. If I get a chance in the next couple of days I will change some rollers, so I might give it a try then, properly.:)
The readings I took were with the head off, so there is no way it could be accurate. Still learning.
How's it going sid? Running good?
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G'day all, I have finally put the degree wheel on the scoot using the piston stop and tgpe figures are, ex. open @88 degrees for a duration of 184, the trans. port open @ 115 for a duration of 130. As I said in an earlier post they don't mean much to me. I would appreciate any input anyone can give.
cheers,
sid.
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Back again, had the jug off yesterday, made some adjustments, was running crap after last time, too much compression loss. When I put it back together it was better, but , because of the increase in compression after the adjustments, it was suffering a lot of detonation, squish of 0.4mm. Today I have increased that to 0.5, though that may not be enough to eliminate the detonation, hopefully it will reduce it enough to run until my new cyl. kit arrives in a couple of weeks.
Yesterday I found my oil pump was loose and rattling around, so I made a small adjustment to fix it. I remember someone was asking about this a few months ago so thought I would put up a couple of pics to show what I did. The bracket that holds the pump in has a tab to push the pump into the crankcase, this tab just needed to be bent down a little to hold pressure on the pump. With mine, I also added two o~rings to the collar that the bolt goes through, just to hold it firm.
Here is the pic of the bracket
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In the picture above, the tab near the bolt hole is the one that needs to be bent down. The piston in the pic, the centre was starting to melt, caught it in time, before a hole formed. :)
Here is the pic of the oil pump with the two o~rings on the collar. I don't think it was nessecary, but added them anyway.
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G'day all, I have finally put the degree wheel on the scoot using the piston stop and tgpe figures are, ex. open @88 degrees for a duration of 184, the trans. port open @ 115 for a duration of 130. As I said in an earlier post they don't mean much to me. I would appreciate any input anyone can give.
cheers,
sid.
Sid, i know this old know, maybe shaka helped you but the #'s are looking good..(from what i'm learning on mine.) What was the boost duration?
Try the squish at about .6-.7???? .4 seems mighty small.