greenhuman
06-23-2009, 09:09 AM
I have been asked a couple of times to write about how the 200cc laydown engine conversion came about. I hope it doesn't bore everyone to death.
Back in 1984 while I was racing trikes very seriously, I came up with the idea that my racing friends and I should all get ATC70's and go on social rides on Wednesday nights in the dunes behind my house. This was supposed to be a way to relieve the pressure of racing and have some fun. The rules were simple. Stock 70's. There were around six of us on the first night but that soon turned into 14 -15. Some bright spark bent the rules and put on a bigger carb and pipe which ment all of us had to as well. New rule . Only slight mods allowed.
Of course someone else put in an ATC90 motor and the new rule was standard 90 motors. Lots of rule changes until the norm was 180cc.
A few of us were sitting around my shed after a Wednesday night ride in 1991discussing how to go faster and someone said its a pity a 200X engine wouldn't fit in a 70 frame because they are vertical and not horizontal. The one rule we maintained all along was 70 wheels, tank, fenders etc. They still had to basically look like a 70 but a 200 engine in a 70 would drag on the sand and look ugly to boot.
After everyone left for the night I got to thinking of a way to overcome this problem so I got a set of 200X cases off the shelf along with a head and cylinder and laid them on the floor. I laid the top end on the cases so it looked like a 90 motor and stood back and squinted a bit. It looked good!
I got out the angle grinder and cut the front engine mount lugs off the cases and it looked better. I roughed out a hole for the cylinder to slip into and sat the head in place and chocked it all up with wood and sockets etc till it all stayed in place and stood back and squinted again and NOW it looked like something. I got out the tape and measured the length and width and it turned out comparable to a 90 motor and thats when I thought we're in business here.
I had previously fitted Honda XL175 heads and cylinders to ATC90 cases but I sold my milling machine so compared to that mod this was easy.
The very next day I went around to a few machine shops. They all looked at me like I was a nut job and said it would never work. I finally went to the guy who used to do my rebores and he said he would give the machining a go. After a few days I got the very first set of cases back and started to put the engine together. Everything went together like stock except for modified center case gasket and an alloy plate to cover the old cylinder hole.
The next job was the frame mod. A couple of hours grinding away metal till the engine sat in place and two new engine bolt holes drilled. Originally I extended the frame tube one inch but settled on two inches after I noticed the front tire rubbing on the bottom rocker cover at high speed.
I was happy when the chain lined up perfectly and even happier when the 90 footpegs all but bolted up to the 200X cases. Next was a custom inlet manifold and a DG exhaust which went up and over the clutch cover. A 28mm CR80 carb, new cables and trimmed wiring harness got it ready to fire.
Three kicks was all it took and it sounded great. I threw on a seat, helmet and hit the paddock out back. This thing made the 180's feel like a standard 70.
New rule. Standard Project X's only. Wasn't long before the 64mm Powroll stroker, hot cam, ported head etc made the new rule 220cc's.
After getting my machinist to do a few more cases he said no more. I went and bought a new milling machine and I get Mart to weld the cases and I do all the machining. I have done this mod to the Chinese 200cc electric start OHC engines as well and they have proven to be a good alternative as the 200X engine are getting hard to find.
The next Project X is going to be a laydown ATC 350X engine in a 70 frame.
New rule. 460cc only.
Back in 1984 while I was racing trikes very seriously, I came up with the idea that my racing friends and I should all get ATC70's and go on social rides on Wednesday nights in the dunes behind my house. This was supposed to be a way to relieve the pressure of racing and have some fun. The rules were simple. Stock 70's. There were around six of us on the first night but that soon turned into 14 -15. Some bright spark bent the rules and put on a bigger carb and pipe which ment all of us had to as well. New rule . Only slight mods allowed.
Of course someone else put in an ATC90 motor and the new rule was standard 90 motors. Lots of rule changes until the norm was 180cc.
A few of us were sitting around my shed after a Wednesday night ride in 1991discussing how to go faster and someone said its a pity a 200X engine wouldn't fit in a 70 frame because they are vertical and not horizontal. The one rule we maintained all along was 70 wheels, tank, fenders etc. They still had to basically look like a 70 but a 200 engine in a 70 would drag on the sand and look ugly to boot.
After everyone left for the night I got to thinking of a way to overcome this problem so I got a set of 200X cases off the shelf along with a head and cylinder and laid them on the floor. I laid the top end on the cases so it looked like a 90 motor and stood back and squinted a bit. It looked good!
I got out the angle grinder and cut the front engine mount lugs off the cases and it looked better. I roughed out a hole for the cylinder to slip into and sat the head in place and chocked it all up with wood and sockets etc till it all stayed in place and stood back and squinted again and NOW it looked like something. I got out the tape and measured the length and width and it turned out comparable to a 90 motor and thats when I thought we're in business here.
I had previously fitted Honda XL175 heads and cylinders to ATC90 cases but I sold my milling machine so compared to that mod this was easy.
The very next day I went around to a few machine shops. They all looked at me like I was a nut job and said it would never work. I finally went to the guy who used to do my rebores and he said he would give the machining a go. After a few days I got the very first set of cases back and started to put the engine together. Everything went together like stock except for modified center case gasket and an alloy plate to cover the old cylinder hole.
The next job was the frame mod. A couple of hours grinding away metal till the engine sat in place and two new engine bolt holes drilled. Originally I extended the frame tube one inch but settled on two inches after I noticed the front tire rubbing on the bottom rocker cover at high speed.
I was happy when the chain lined up perfectly and even happier when the 90 footpegs all but bolted up to the 200X cases. Next was a custom inlet manifold and a DG exhaust which went up and over the clutch cover. A 28mm CR80 carb, new cables and trimmed wiring harness got it ready to fire.
Three kicks was all it took and it sounded great. I threw on a seat, helmet and hit the paddock out back. This thing made the 180's feel like a standard 70.
New rule. Standard Project X's only. Wasn't long before the 64mm Powroll stroker, hot cam, ported head etc made the new rule 220cc's.
After getting my machinist to do a few more cases he said no more. I went and bought a new milling machine and I get Mart to weld the cases and I do all the machining. I have done this mod to the Chinese 200cc electric start OHC engines as well and they have proven to be a good alternative as the 200X engine are getting hard to find.
The next Project X is going to be a laydown ATC 350X engine in a 70 frame.
New rule. 460cc only.