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started CR500AF swap

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Got a few things done this weekend. For some background info I started with a 2003 CRF450R with a bad intake valve, and a 1989 CR500 that has been backyard engineered, jerry rigged, and then some. I got the frame cut, moved the Y up and welded in place. Welded the motor mounts in, got the headstay mocked up. Mounted the coil. Got alot of small parts coming this week to finish buttoning the motor up and make it look more like a bike. I was going to buy a whole new exhaust but the PC works pipe that was on it just needed surface rust removed. A couple hours with the wire wheel on the drill and it looks good enough to use.

Maybe in another month or so I will have it put together enough to fire it up. My main problem has been the CR motor seems to be a mix of various years parts. The cases are from a 1986, cylinder and head are from a 1996. Put a new .040" over piston in it. It has a hot rod crank for a 1996 which is the long rod. 1986 case is a short rod case so there is some kind of 5mm thick spacer between the cases and cylinder.IT doesnt look home made, but if it is I gotta give the guy props. It looks professional. The next step is to take the motor back out, clean everything up good and reassemble. Heres a couple pics of my booger welds and what I have so far.

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Got to work on the bike some more on my time off. My new work schedule of 6 on 3 off has given me some days off in the middle of the week. Im not used to that. Anyways I have the engine in the bike for good. Radiators are done. I only had to modify the bottom spout of the left rad. On the right rad I used a short hose with a 90* bend in it from the old CRF motor, and a Y from the CRF. fits nice and doesnt touch the pipe. Filled with engine ice, no leaks yet. My chain alignment looks perfect going by the swingarm chain guide. I used the 03 CR125 bushing on the right side, moved stock right bushing to the left. I didnt get a good pic of it but the stock expan'sion chamber mount lines up perfect with the stock hole in the frame that was used for the engine guard on the CRF. Only had to find a 1/2" spacer and longer bolt to space it out far enough to be straight. I mounted my CDI and pulled the plug and held it against the frame, has good spark. Tried to kick it over and it feels smooth, but man it makes my 450 seem easy to kick after kicking the 500. I wanted to start it but I have no air filter/air box made yet so I didnt. Heres some pics

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what air boot are you planing on using? i used a 97-99 cr 250 boot, 2000 might be worth a try

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I ordered a whole air box/boot from a 2000 cr250 on ebay. I also ordered a carb from a 94 cr500 because the carb that came with my 500 is a mikuni TM38 and the throttle cable is kinda too long for it, it doesnt want to go fully wide open even with the cable adjusted all the way out. Plus I dont want some oddball carb that I dont even know what its from. It looked to me like it had a real tiny pilot jet in it, main was a 370. I wouldnt know where to start with jetting the oddball carb.

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I'm not saying this is bad--but it looks like your engine is angled forward more than any other conversion I've ever seen. I know I have been trying to massage my conversion to get my engine lower, but it's about all I can do to get the "Honda" embossment on the clutch cover level with the frame rails. I hope my bike doesn't handle like James Stewart's old YZ450.

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I never really noticed how leaned forward it was, except for when I went to route the radiator hose from the left rad across to the right and there was no way there was enough room for a hose between the cylinder and the frame. Thats just how the motor fit in there. I really should have moved the frame Y up another 1/2" or so. The ears on the exhaust flange where the exhaust springs go are close to the frame. On the upside theres alot of room under the gas tank. I used the short BR8ECM plug and had no issues with clearance other than the fuel spout that comes out of the bottom of the tank, it angles forward and it hit the spark plug cap so I turned it around to point backwards and everything clears good now.

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Funny that came up I was going to ask how much of a PITA it was to get the engine angle correct on the 500. It's a pretty huge deal for the overall handling of the bike, and well everything.

You may be relieved to hear that the 500 motors do fit into a CRF frame much more naturally than a 250. I've heard a 250 is much much harder and requires a lot more work to get that angle just right.

This is my dream bike. I almost started one. Had a 04 CRF roller everything but motor and wheels for $150, but I passed after research. Was going to put my 250 in it. I still am going to build one of these sooner or later, but only difference I wanna use a GEN3 cr250 roller chassis, like this dudes. This is guy is the king of 500AF bikes IMO.

http://www.youtube.com/watch?v=4xW9KsxxelA&feature=fvwrel

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