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Post by 190mech on Mar 29, 2009 7:39:38 GMT -5
Wanting to build a pipe for my CPI Oliver City project.The pipe
calculators vary so much that I wonder who is right...Can you guys give me some dimensions from a pipe that works?Head
pipe dia and length(tapering?),difuser cone(first)length,spacer
dia and length,baffle cone(rear)length,stinger(tailpipe) length
and diameter.I'm using a cut down Honda CR80 pipe now and
it is too big for the little 50! THANKS! John
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Post by 90GTVert on Mar 29, 2009 9:55:11 GMT -5
I had made rough measurements with the pipe installed on the scoot before, but I was afraid they were inaccurate so I went out and snapped some pics and took some measurements of my MRP pipe for you. It worked well for me with an MRP 70cc kit, 4g rollers, 1000RPM torque spring, 2,000RPM clutch springs, and the stock carb/filter/jetting. It would hit pretty high in the RPM for me and carry me the rest of the way out to my max RPM (probably 11,000RPM or so). If anything looks a little off, I have had to make repairs to the pipe and some parts are still a little messed up from crashes and such.   Hopefully you can read and understand this. I separated the pipe into two parts to make it easier to draw/read. The head pipe section is drawn as if looking down on it and I drew the last section before the flange as straight insead of curving up to the cylinder to make it a little easier to illustrate. Obviously the drawing is crappy and not to scale.  Here's a closer version of each section.   I just noticed that I forgot the diameter of the stinger. It's 18mm O.D. or around 11/16. |
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Post by 190mech on Mar 29, 2009 16:44:22 GMT -5
Thank you!Thats just what I needed!I will post some pics when the project begins..
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Post by 90GTVert on Mar 29, 2009 16:49:57 GMT -5
YW. Looking forward to seeing your homemade pipe. You may wanna check out A. Graham Bell's "2 Stroke Performance Tuning". It has a lot of info on pipes.
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Post by 190mech on Apr 6, 2009 21:03:49 GMT -5
Sorry for not getting back here sooner,been working 7 days a week for months..Ive got a bunch of pix,but am having a bit of
trouble posting them,will try again in a few days,its lookin' good!
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Post by 190mech on Apr 7, 2009 20:54:03 GMT -5
OK, lets try this,here is the card board patterns; ![]() i639.photobucket.com/albums/uu112/190mech/cutout.jpg[/IMTransfer patterns to scrap sheet,old wash machine back,metal desk drawer  Pounding out cones on a steel rod with a hammer  Welding up the cones;  Head pipe and first difuser cut and fitted;  Fitting second difuser;  Final fit and weld;  Working on stinger,silencer,and mounts next!! |
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Post by rallyrrr on Apr 7, 2009 22:42:10 GMT -5
That is inspiring. That head pipe, with the curve and all, looks like it would have been a real challenge for me. I would love to build a pipe someday. I'm anxious to see the final results. Do you know the thickness or gage of that sheet metal?
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Post by 190mech on Apr 8, 2009 4:51:52 GMT -5
It is scrap metal,a back off of a washmachine and an old drawer!  |
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Post by 90GTVert on Apr 8, 2009 5:56:51 GMT -5
Great job so far. You take cost effectiveness to a new level. Very badass! Thank you for sharing. Keep us updated. +1 Bone
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Post by 2strokd on Apr 8, 2009 8:57:11 GMT -5
Looks good! Great job! +1
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Post by rallyrrr on Apr 8, 2009 10:24:17 GMT -5
Way to go. You are clever, man. Can't wait to see the rest.
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Post by 190mech on Apr 8, 2009 20:53:18 GMT -5
Stinger is 2 bends from an old shop light handle,silencer end caps are automotive freeze plugs(many sizes...)  Stinger and 'can' tacked on,hope to start on silencer core tomorrow...  |
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Post by rallyrrr on Apr 8, 2009 22:02:52 GMT -5
I was wondering what you were going to do for a stinger. Whether it would be u-shaped or straight. Rock on man!
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Post by 2strokd on Apr 9, 2009 7:31:32 GMT -5
No kiddin! That looks great 190mech. And i thought i was doing good just getting my pipe welded back together 3 times before i finally got it right lol. That is inspiring! Freeze plugs.?. Thats perfect, good thinking.
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Post by 90GTVert on Apr 9, 2009 7:34:19 GMT -5
I wouldn't have thought of freeze plugs. Cool idea. Looks great.
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Post by 190mech on Apr 10, 2009 20:42:33 GMT -5
Got the pipe finished tonight,here are some pix... End cap fabrication;  Silencer core finished:  All together and ready for prep and paint;  |
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Post by 190mech on Apr 10, 2009 20:48:39 GMT -5
Here it is painted and on the scoot;   Did not ride it tonight,but it sounds quite mean and will get 'on the pipe' while on the center stand!Next project is CVT tuning.70cc kit has been ordered from Autotech355... |
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Post by 90GTVert on Apr 10, 2009 20:50:08 GMT -5
Excellent work. You should be proud of that.
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Post by rallyrrr on Apr 11, 2009 0:46:09 GMT -5
190 Mech you are impressive. Nice work! May many happy hole shots be in your future! That was a nice pattern you laid out for him too Brent.
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Post by mopedjay on Apr 11, 2009 18:52:22 GMT -5
dude that came out awesome
i love it
i made a pipe but it came out like crap
!http://farm3.static.flickr.com/2188/2333665569_e51a2f290b.jpg?v=0!
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Post by mopedjay on Apr 11, 2009 18:53:33 GMT -5
crap i guess you cant post pics that same as on moped army
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Post by YellowScooter on Apr 12, 2009 8:54:22 GMT -5
Nice work on the pipe though... Truely nice work.  |
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Post by 190mech on Apr 17, 2009 21:11:33 GMT -5
Got hte 70cc kit from Autotech355,  Set up the degree wheel to check port timing,  Had to notch lower fin to clear oil pump,  Only grief was 2.5mm squish gap between piston and head,thought I'd try it anyhow,WOW!she got 54mph before starting a lean skip,seems to have 2 "on the pipe" bands too! I'll try some jetting and report back...THANKS GUYS!!!!! |
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Post by 90GTVert on Apr 17, 2009 21:19:57 GMT -5
Thanks for the update. Are you using a head gasket to get 2.5mm squish? If so, you may wanna try using copper coat instead of a gasket to tighten that clearance up a little.
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Post by dude on Apr 17, 2009 23:30:15 GMT -5
190 nice work. What did you use for the silencer core? I see 2 pistons with your kit, one looks better than the other.
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Post by rallyrrr on Apr 18, 2009 10:23:19 GMT -5
I hate to be critical but a lot of these kits don't seem to be designed to allow narrow squish clearances, at least for gasoline or street purposes. I believe you can witness to this 90GT, having had to have your combustion chamber recessed. I would almost guarantee that if 190Mech got his squish clearance down to that desired 0.5 - 0.7 mm range that he would have detonation problems just from my observation of the tiny size of that combustion chamber. What was that effective CR you wound up with after having your CC recessed 90GT? Somewhere around 6:1 wasn't it?
These squish-type heads on these kits seem to fairly useless w/o modification for street use.
A. Graham Bell advises not to worry that much with tight squish band clearances for play or street bikes anyway.
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Post by 90GTVert on Apr 18, 2009 10:40:30 GMT -5
That's a good point rally. I ended up at 6.2:1 effective compression to eliminate most of the spark knock. I've never taken the piston's crown into account, so it may be slightly higher. Those numbers are using effective cylinder volume and the cc of the head on a bench. I don't know that he wants to shoot for .5-.7mm as spec'd, but maybe less than 2.5mm. If he does have a head gasket in place, it's easy enough to remove the gasket and use a copper spray. My head gaskets usually end up being roughly .5mm once torqued, so perhaps he could try it at around 2.0mm to see if he gets any gain without machine work etc...
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Post by mopedjay on Apr 18, 2009 17:34:10 GMT -5
i wanna try an make a pipe like that but slightly modified to fit my jawa
how did you get the cardboard templates right im really bad with math and geometry if mobody explains this i will just screw it all up
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Post by 190mech on Apr 18, 2009 19:00:35 GMT -5
Yes,I used a head gasket,actually got to get in a short ride before sundown and am pleased with performance!I 'm installing a bicycle speedo now as they are very accurate and will post results.The silencer core is some perf sheet I robbed from a dumpster at a friends machine shop,have used perf from old dryer drums with good results also..The 2 different pistons are a 10mm pin piston and a 12mm pin piston,the 'shiney' one is the 12mm,seems cheaper made ,heavier and has no ports it the skirt,10mm unit'cast look'is better,but alas I've got a 12mm pin...
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Post by 190mech on Apr 18, 2009 19:12:38 GMT -5
 OK,I'll try to explain this,draw a side view of the cone(2"dia,83/4 long,4"dia),draw a center line thru the cone,next lay a ruler on the side of the cone and draw a line till it intersects the center line,this is the center point to draw the cone radius(a string and pencil works),then multiply the smaller diameter(2") by 3.14159,that is the length of the cone radius,lay ruler from center point to cone radius and draw a line,,NOW you have your pattern! |
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