ETZ 251 cylinder re-bore to 300

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ETZ 251 cylinder re-bore to 300

Postby JurassMz » Thu Apr 09, 2015 1:31 pm

Hello,

is it possible to just re-bore ETZ251 250ccm cylinder to 300ccm for ETZ301 piston?

Thanks
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Re: ETZ 251 cylinder re-bore to 300

Postby cezar82 » Thu Apr 16, 2015 4:46 pm

Below shows one of the possible approaches to the treatment so that in my opinion it was the hands and feet. You can take a different course, there are no strict rules. All downloads are below. For those determined there will be nothing to jump.
Word access - to the conversion to 300 are suitable only without combination of ET cylinders 250 due to the angle of the exit window which the recess 75 does not change its position significantly. When the diameter of the recess on the fire ring disappears and the piston at TDC of the cylinder liner extends its height. The project is part of the head into account.
The most important element is necessary to rewrite the head:
1) The volume of the combustion chamber must be chosen so as to keep the compression ratio of 10.5 - 11: 1 while maintaining squich distance from the bottom of 0.9 mm. Chamber volume in the traditional way to measure the syringe with the liquid for assembled engine. Often I meet with the measuring head on the table capacity. This is so abnormal that it does not take into account the curvature of the bottom which is not flat.
2) Cat squish area, pull out of the up, so that the angle formed between the top surface of the head and was a divergent 1 - 2 degrees in the direction of the combustion chamber and not convergent. The diameter of the surface must be at least equal to the dimension of the piston, ie 75.5. I did continue to the next cut was good.
3) the ratio of the areas is proposing to do - squish chamber 60/40.
4) alteration must manually start the match Squish, since the dimension of 0.9 mm, it is very important for the performance of this type of head. It is only matched by Squish dremlujemy having a chamber to obtain a distinguished capacity.
Cylinder:
Without philosophy. In my opinion, it is good to take a ring of fire, because in a system where the engine hangs on the head once, and it helps the two centers the head is always in the same place. edge proposes leave sharply. This will facilitate the production of the seal by tightening the screws with a sense of the seal ring 250. The sharp edge will cut beautiful album of aluminum and have gicio równótką seal after the removal of cut waste. Luz ALMOT piston assembly (Hall) 0.05 mm. Honować cylinder to give a thick dimension stone. Then you need to do a rock intermediate 2 - 3 jumps to alignment inequalities that will plow the ring. Between the cylinder and the head is necessary to give even one aluminum pad. Motion below assumes that the most typical after inserting a 0.5 mm should appear 0.9 - 1 mm gap.
Dwg file I threw a few drawings from comments. Geometry is the curvature of the bottom and the same head 3d, taking into account all the above-described. Using a model of the head of the design height of the fire ring must be performed on 1.5 mm. His average external +/- 79.80 mm. This should be from the machine and the ability to process a circle into segments. (Turning it regards not the case here) People in the subject will know what it is, and here it is not important. The head is to be included on the ring that hides inside.
Well, that's it, here are some photos of the comment and the necessary materials. If there are any questions, feel free.
The probe must be placed on a table so as to maintain the parallelism of the table in the vicinity of 0.05. You can safely do so properly by placing plates of different thicknesses

http://alarts.nazwa.pl/intrmot/forum/etz300/001.jpg
http://alarts.nazwa.pl/intrmot/forum/etz300/002.jpg
http://alarts.nazwa.pl/intrmot/forum/etz300/003.jpg
http://alarts.nazwa.pl/intrmot/forum/etz300/004.jpg
http://alarts.nazwa.pl/intrmot/forum/etz300/005.jpg
http://alarts.nazwa.pl/intrmot/forum/etz300/006.jpg
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Re: ETZ 251 cylinder re-bore to 300

Postby DAVID THOMPSON » Thu Apr 16, 2015 5:30 pm

thats some nice looking work'' but my milling machine and it owner are both past there prime

so i will stick to antenna mounts and fittings

dave
Dave 2002 MZ RT125+1995 Saxon Tour(500cc)
1997 MZ 660 Traveller+6/13/09 WV USA
"IN the end times the IDIOTS will be in charge
of everything"
"I like the road less traveled if it's PAVED!"
wd8cyv at yahoo dot com
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Re: ETZ 251 cylinder re-bore to 300

Postby cezar82 » Fri Apr 17, 2015 12:43 pm

if you need more information, you can write a message in English and assure that receive professional help ...there is one section for visitors from abroad where they can post messages ...
http://forum.mz-klub.pl/viewforum.php?f=33
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Re: ETZ 251 cylinder re-bore to 300

Postby cezar82 » Fri Apr 17, 2015 1:00 pm

http://intr-mot.sklep.pl/ the owner of this store wrote this article
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Re: ETZ 251 cylinder re-bore to 300

Postby intr » Mon Feb 27, 2017 6:29 pm

Hello, I see someone put here my concept of cylinder head convertion on cnc but I see it's google translator version of oryginal polish text. So I'll update it. Hope you wouldn't mind.

I made a video for Polish MZ riders because of mistakes that were fairly common in this cylinder heads from ETZ 250 conversions. It covers simple job with using a lathe and for more advanced users I made a complete 3d model in most common dxf format, that everyone could use on cnc milling machine. You'll find it all in movie description.

If you find it usefull feel free to use it. Any questions concerning 3d model and concept, feel free to ask.

Youtube video have english subtitles, the best I could made with my english. You have to turn it on.

https://youtu.be/sPmO-do0lhU

Regards
Intr
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