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Post by pitobread on Jan 26, 2019 11:43:26 GMT -5
Started this the other day, It is a engine without a home currently but I want to get some parts bolted to other parts in the shop. It is a Honda AF18 cases I bought off Yahoo Japan a while back, Current plans are stock crank, Peugeot Speedfight 2 Stage6 Racing Modular cylinder, Polini Evo Piaggio bearings, Moto Tassinari KX65 Reed block in a CT intake and half a Polini OTT pipe. I made a short video about the basic prep of figuring out what was needed to mount the cylinder. So the piston stroke of the Honda is 41.4, Piston is 39mm The stroke of the Peugeot is 39.1, Piston is 40mm This gives about an 74cc Displacment when you combine the Peugeot 48mm piston of the Stage6 Cylinder and Honda 41.4 Crank. So I needed to make up for the difference in stroke, by adding a .5mm base gasket I had the transfers around 130, boost at 133 and ex was low at 194 but the exhaust is easier to move up than trying to make the transfers move down.  This left about 1-1.5mm above deck that needs to go. After this I figured I needed to remove .080" from the dome to hit about a .07 Squish and allow the piston crown to travel up into the combustion chamber. After that I realized that I needed to somehow align the head to keep the piston centered in the dome. I whipped up some simple steel 7mm OD alignment dowels that go into the cylinder stud holes to align the dome. Any bigger than that and it may have some issues with leaky O-rings.   And here is where I am stopped, waiting for bearings to start assembly.. |
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Post by gsx600racer on Jan 26, 2019 11:45:04 GMT -5
 I just have one request, can you take a picture of bottom dead center without any shim. This was the issue I had.  The piston was below the transfer/exhaust ports and if I raised the cyl, it just made it worse.
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Post by oldgeek on Jan 26, 2019 12:16:40 GMT -5
Great video!
Is there an easy way or trick to getting the head alignment pin holes placed in the cylinder and head, so that the head actually lines up correctly?
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Post by pitobread on Jan 26, 2019 14:20:22 GMT -5
 I just have one request, can you take a picture of bottom dead center without any shim. This was the issue I had. The piston was below the transfer/exhaust ports and if I raised the cyl, it just made it worse. Mine is the same, but that is an easy fix! some time with a porting tool and a diamond burr and you are all set! |
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Post by pitobread on Jan 26, 2019 14:21:39 GMT -5
Great video! Is there an easy way or trick to getting the head alignment pin holes placed in the cylinder and head, so that the head actually lines up correctly? Video part 2 shows exactly that... it should be up in an hour or so. |
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Post by pitobread on Jan 26, 2019 16:26:18 GMT -5
Here is part 2.
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Post by gsx600racer on Jan 27, 2019 0:55:39 GMT -5
I just have one request, can you take a picture of bottom dead center without any shim. This was the issue I had. The piston was below the transfer/exhaust ports and if I raised the cyl, it just made it worse. Mine is the same, but that is an easy fix! some time with a porting tool and a diamond burr and you are all set! So you can lower the bottoms of the all the ports to match the top of the piston @ bdc with no ill effect ? |
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Post by pitobread on Jan 27, 2019 2:38:23 GMT -5
Im going to make a educated guess and say this. The lip will cause turbulence, I Know from reading like 2000 pages of the ESE thread that you want the piston to be dead flush to the bottom of the ports @ BDC for cooling effect. Without being a wizard of math, I will blanket state that the lip will probably be a "low pressure" zone and disrupt your "Schnuerle Loop" at the lower end of the flow. I think that the downsides could be that by opening the port up you would loose some port velocity. Would also have to try and blend and maintain angles a bit. Would any of this matter? Probably not. And I don't have a Dyno (yet) to do some A-B comparisons. But then what is even more confusing? Athena/Stage 6 designed it this way. as the exhaust port goes even lower than the bottoms of the transfers by 2 ish mm. Every other cylinder I have seen they all line up at the bottom of the stroke.. why it was done this way, I don't know. There are people out there much smarter than I about this stuff.  |
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Post by harleyracer59 on Jan 27, 2019 13:30:55 GMT -5
hey Pitobread,
cool build. do you live in the us? and when you said you got these af18 cases on yahoo japan, did you mean buyee? how did you get them to ship it? I was under the impression they wont let you purchase engines. because of international shipping. also are these cases an af18 or an af18e? ive heard their are 2 af18 motors. one of them, I think the af18e has the thicker 14mm crankshaft arms/ shafts like the af16.
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Post by pitobread on Jan 27, 2019 14:23:48 GMT -5
I am Canadian.
I have a buyer, similar to Buyee. He is a home business importer/exporter who lives in Japan.
There are small crank and large crank engine, the small crank ones are not great. It's almost impossible to distinguish the 2 from a distance, there are some casting differences but it's really hard to tell.. It is impossible to get a performance small crank of any type.. only OE replacement.
I now buy only engines that are stripped down, so I can see if it is a large or small. You can tell by the webbing behind the variator, large crank have a larger seal and the casting is larger.
Jiangwayne used to sell a conversion seal so you could run a large crank in a small crank motor. That is really the only thing limiting you from doing so.
I have imported 3-4 engines now... no issues at all.
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Post by harleyracer59 on Jan 27, 2019 16:20:27 GMT -5
that's cool you have a guy like that! maybe you can ask if its ok for me to get his info, if it is you could shoot it to me in a PM? theres a few things id love to get my hands on that buyee wont let me buy... lol I really want an af01 motor, ta01 variated gyro 2t motor and someday I want a stream a flush and a dunk.... those are some weird looking scoots I wish they were sold here. but id be down to johnny cash them and build them 1 piece at a time!  I know that there is a large and small crank af18 I have a small crank af18. I also know were there is 10 of those special seals you speak of that are available to me for purchase. there was 12 but I already bought 2 for my future small crank af18 build. 1 for the build and 1 for back up. |
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Post by gsx600racer on Jan 27, 2019 21:45:42 GMT -5
You mentioned this, it made me rethink the port timing thing. You read where others say "I changed this, I made this wider, ect, ect". I never put much thought with the bottom of the ports other then they are fully open at bdc or close to it. The more I thought about this the more I realized my thinking was backwards.
I always "tuned" bottom to top, but after your post, tuning the ports top to bottom makes more sense. Openings,closings and durations are "shim-able"(best case) or dremel(worse case). Where the bottoms end up are trivial for the most part as long they are close to the top of the piston, that and they are not too low that the piston skirt doesn't open them up at tdc.
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Post by harleyracer59 on Jan 27, 2019 22:46:56 GMT -5
the second part of that is close except its not THEY. it only matters that the exhaust port doesn't clear the bottom of piston. then you loose the good charge out the exhaust. the transition ports and boost port(s) don't matter nearly as much if at all. |
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Post by pitobread on Jan 28, 2019 0:32:36 GMT -5
that's cool you have a guy like that! maybe you can ask if its ok for me to get his info, if it is you could shoot it to me in a PM? theres a few things id love to get my hands on that buyee wont let me buy... lol I really want an af01 motor, ta01 variated gyro 2t motor and someday I want a stream a flush and a dunk.... those are some weird looking scoots I wish they were sold here. but id be down to johnny cash them and build them 1 piece at a time!  I know that there is a large and small crank af18 I have a small crank af18. I also know were there is 10 of those special seals you speak of that are available to me for purchase. there was 12 but I already bought 2 for my future small crank af18 build. 1 for the build and 1 for back up. |
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Post by pitobread on Feb 1, 2019 20:20:04 GMT -5
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