@swebass
Active 7 jaar, 9 maanden geledenAangemaakte reacties
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Thanks for your kind words Martino! I had a lot of fun writing it. Haha, I was about to clean it, but then my dad walked by and said “young lad, you know that if you clean up the piston you might lose some compression”. So I laughed a bit to myself and left the carbon on top just to make him feel like he knew what he was talking about 😀
I will clean it one day tho, dont worry!
One more thing I might forgot to say is that after the modifications of the cylinder were done, it was not only the top speed that went up, but also the power in the upper rpm registry. All of a sudden it showed good acceleration even when I was close to full speed. And from that it made it super fun to ride on the tiny and curvy asphalt roads in the forests around where I live!
Happy days:
Also, the GPS measurements I used before was way off. It was an app in my phone. This time I have used a GPS for cars, so my speed measurents in this article are now correct. When I wrote before in my previous posts that I drove 54 km/h on a 105mm pulley I was wrong. It was actually 43 km/h with a real GPS. Sorry for that!
Hello again! Time has been short and I did work to many 12 hour shifts last week. Now I am done with my project. Please feel free to read about it here:
https://vespa-ciao.nl/forums/topic/the-50cc-road-racer-from-25km-h-to-65km-h-for-60e/#post-776130
Thanks a lot all you guys!
Guys, I absolutely don’t know why, but when I pressed Verzenden to publish this, something changed the word “gave” to “gift” and the word “of” to “or” in my text.
Thanks again Martino for great advice. And to the rest of you guys as well for being so helpfull! Now I have made a plan from all your input, from Graham Bell and from other great posts on this forum. I will give it a go next week and regardless of how it turns out, I will write an article about it in the project section when I am done.
Cheers guys!
AA-T, This was the answer I was looking for! Thank you for spending so much effort on the answer. I was also thinking that raising the cylinder and milling a bit of the top might be the better option in this case. I am going to measure how many mm’s the piston is covering the bottom of the exhaust port and then raise the cylinder accordingly with a home made aluminum gasket. At least if we are talking 3 mm, otherwise a few standars gaskets on top of each other might work?
Somehow you also managed to answer my question about raising the spark plug, I was wondering about it but forgot to ask!
As you say, it might be tricky to deepen the combustion chamber in my case, since my top is of the offset spark plug type. I guess I could win 2-5% extra power in the low-mid by increasing the compression, at least if one would trust Mr Graham on this:
“Two Stroke Performance Tuning
Heat is the enemy of two-stroke engines and stretching the compression ratio to
give a 10% power increase will possibly result in a 3% power rise at the most; the rest
will be lost in heat energy and pumping losses. However, at lower engine speeds the
cylinder will not be completely filled with fuel/air mixture and the power may jump by
5-6% because there is not such a heat loss. This is, in fact, the real benefit of raising the
compression ratio, not to increase maximum power but to pick up mid-range power
and possibly widen the power band.”I wonder if it is really worth the trouble trying to grind out and deepen the combustion chamber?
Thanks once again for a good answer!
I read Graham Bell again and realised I misunderstood the concept of a offset sparkplug totally, so forget what I said about that. But these two quote kinda confuces me a bit, especially the last part:
“Reducing the squish clearance is not easy, you can’t just machine 1mm, or
whatever, off the head as the compression ratio would end up many numbers too high.”“After the clay thickness is measured you can work out how far the head must be
machined to give the desired squish clearance. As mentioned previously, the combustion
chamber must also be machined deeper into the head to keep the compression ratio at
an acceptable level. If you wish to keep the compression ratio the same as standard, the
combustion chamber will have to be machined twice as deep as the amount skimmed
off to reduce the squish clearance, assuming a 50% squish band. Therefore if 0.9mm is
removed, the combustion chamber will have to be made 1.8mm deeper.”Any thoughts from you guys?
Also, where did you get those thick base gaskets? Did you craft them yourself or did you bought them somewhere?
Martino, thanks again for good answers!
That at least give hope when it comes to sanding down the cylinder head since I will not get my hands on a mill any time soon. Tho I read in the Graham Bell book that it is not adviced to mill the cylinderhead if your spark plug is not centered in the cylinder top, and my sparkplug is offset to the center. Any thoughts?
I know, this forum thread went a other direction, for the better in my opinion. I will keep you posted about my progress anyhow. Next week I am working a lot, but the week after that I am free, so then I know I will have time to work on this project for sure. If I remember to take pictures during the progress, I might even do a new thread for this project with some text, if it is of any value for this forum, and if it is okay if I “copy” your design?
Thanks again!
Martino, thank you for writing such infornative answers. I wish I had a mill to use to mill down the cylinder head and the cylinder top. But sadly I don’t.
- I know there are ways to flatten the cylinder top using sandpaper on a flat surface, but I do not know if that is adviced at all?
- For doing the ports, did you use a drill, a dremel and files? Or did you have any other valuable tools that you could recomend?
I will hopefully have a cylinder to work with on monday.
Thanks in advance!
Ritze, Thanks for your input. You are right in that sense, one would need a lot of knowledge to get things right. I have allready planned to read a book or two on two stroke tuning, and Graham Bell is definitly on my to-read-list.
Zevenenergie, thanks a lot for the link! Now I do not need to buy it from Amazon.
Martino, My guess is that Sweden in general is a bit more pricey. I have been in Holland at least 15 times, and prices of every day items like food is at least 30-40% cheaper than in Sweden. Anyhow.
Thank you for your detailt post! It gives me the urge to start experimenting. I have some questions if you feel like you want to help me out.
- What do you mean by raising the cylinder? Is that done with aluminum base gaskets stacked on top of each other?
- If the pistion is covering some of the exit in it’s bottom position, wouldn’t it be possible to just remove the covering bit from the piston?
- Have you done any modification to the piston at all?
- Did you do any modification to the crankshaft, to modify the inlet timings?
- What do you mean by raising the exhaust port by 1 mm and flowing it?
- Last but not least, do you think it would have been any difference in performance if you had done the supporting channels from the bost ports and transfer ports in the carter instead if the cylinder?
Thanks in advance!
Ritze, I looked in your post as you adviced. Thanks for the inspiration. I think I am sort of understanding what you did with the cylinder. You are probably right about practicing on a separate cylinder then the one I ride on currently.
Is 37€ a good deal for a complete cylinder kit, second hand in a top notch condition? In that case I might have a deal!
Cheers!
KillerNoway, thanks for the headsup. I bought nozzles from 60-72 to play around with, as soon as my package show up. Even tho I find the 66 to be giving good performance atm. I have no off sounds or weak spots in the acceleration. It just goes straight up to top speed and sounds perfect, with a good draw over the whole rpm registry. Colour of the spark is looking good, but I bought the nozzles because I wanted to see if it can be even better. At the end of the day I just enjoy to have a little bit more juice in the system than too little, to be on the safe side during this hot summer days. After some reading I find 64-68 being rather common with my setup.
I drive to Ciao out on the country side, so it is more about long roads at full speed then the start and stop driving required in a city environment.
At the moment the springs are probably the ones that came with the ciao from the store in the 90s. But I ordered new polini springs yesterday, the ones thst are not painted. I also ordered the Newfren clutch shoes.
Thanks!
Ritze, thank you for interesting input. I am indeed interested in modifying the stock cylinder. Do you have any pictures or any documentation on how you created those 4 ports? Maybe there is any good forum thread you could recomend? When you say 1,5 mm wider and higher, what do you mean by higher? Do you mean grinding some extra towards the top of the cylinder? Sorry for a lot of questions, I am just curious and enjoy the small details when it comes to stock tuning!
Thanks in advance!
