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I've always wondered if this was something anyone had done. I know it's possible, but supposedly very difficult for this bike. If so, what was the experience like?
 

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yeh it is because the cylinders are part of the block. you need to completely dissassemble the engine to do it. on allot of moto engines the cyclinder\s come away from the block and you can leave the crank in place but with our cx's the crank needs to come out
 

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Discussion Starter · #3 ·
yeh it is because the cylinders are part of the block. you need to completely dissassemble the engine to do it. on allot of moto engines the cyclinder\s come away from the block and you can leave the crank in place but with our cx's the crank needs to come out


Just out of curiosity, could you point to someone who did it?
 

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2021 Benelli Leoncino Trail - 2021 CSC SG400 - 2017 SSR Buccaneer 250i - Several CX project bikes
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It would be easier to just slap a 650 motor in your frame, along with the wiring from a GL500. I'm working on my secodn 650 conversion now, actually.



Charles.
 

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I've often wondered if it would be worth the trouble of casting an 850cc block setup like the CX.... forged crank/rods/pistons, 11:1 compression, full fuel injection, on a brand new frame, inverted fork front setup. Wonder if that would be a cool bike @ around 10k?
 

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2021 Benelli Leoncino Trail - 2021 CSC SG400 - 2017 SSR Buccaneer 250i - Several CX project bikes
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I've often wondered if it would be worth the trouble of casting an 850cc block setup like the CX.... forged crank/rods/pistons, 11:1 compression, full fuel injection, on a brand new frame, inverted fork front setup. Wonder if that would be a cool bike @ around 10k?


Well, that's kind of what I'm doing. I've got a GSXR front suspension, an SV 650 rear shock (for now) with the GL500 swingarm and monoshock setup, a GL1100 17" rear wheel and disc (so I can run 140/80/17 rubber), and a 650 (673cc) motor. I'm not building a new frame or boring the motor, that's a bit much. But the bike is on a severe diet too. It's going to be quite a machine.



Charles.
 

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Hi, folks, thought I'd comment here. I only went .020" overbore on my 650 engines. This takes them to 83mm bore and 680cc. Our problem is piston rings; we have to have pistons made to take 83mm minimum rings because the 82.5s are all gone. 83mm is Hayabusa, which is a great ring pack and handles high revs very well.



Regarding boring further; there is only enough liner to get another .020" safely. Add that to the headgasket issues (this is an open deck and the fire ring could get really small at big bores), and you can see why I'm studying crankshaft stroke or destroke to fit classes. It's easier (and cheaper) to build rods, than to cut blocks, fit new sleeves, build retainer inserts, and have head gaskets made. When I learn more about rods, I'll put up a post; we need to be able to use the Toyota Paseo rod bearings (Honda bearings are gone), and rods with the bearing notch moved in would work well. Narrower rod bearings, with Diesel 15W-40 oil, will allow some good hard running.



My 500 engines are at stock bore, because the engine is so close to class limit. The 500 has the same thin sleeve issue; Honda made sleeves AND stroked the crank when they made a 750 out of a 500....and it overheated while making 90HP.



The 650 in 500 chassis sounds good. Also, a possible carb setup would be the Mikuni VMs prejetted for 650 Yamaha "kit" (SUDCO is one supplier). This is not terribly expensive, and gets a lot more flow than the CV carbs. Frankly, I'm pretty amazed at how well my flat-slide Mikuni 38s idle, and these are not very expensive carbs (1/3rd the price of Keihins). I can post the final jet numbers, if anyone needs them.



JimL
 

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Forgot I had this. This is an interesting page with info on carb setups that have worked for various apps. Note that should you decide to order Mikunis, you can spec each item you want in the carb, and save buying a lot of extra internal bits. I used the 450 Racing numbers last year and was all good except the idle.....but now I'm on flat slides and better.



http://www.ohiocaferacers.com/MikuniJetting.html
 

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I've often wondered if it would be worth the trouble of casting an 850cc block setup like the CX.... forged crank/rods/pistons, 11:1 compression, full fuel injection, on a brand new frame, inverted fork front setup. Wonder if that would be a cool bike @ around 10k?


Yeah someone has already done pretty much that, they're from Lake Como Italy called Moto Guzzi. All kidding aside, I think the machine work could be done after all most atuomobile engines are crankcase and cylinders being integral. I would like to do a 750cc I'd use aluminum sleeves with nikasil (sp) coating. Better cooling, the same thermal coefficent of expansion as the block, lubrication friendly, and lighter. More cc would mean more HP thus more heat therefore requiring more radiator area. I would probably look at using a sportbike aluminum radiator. If they can cool engines producing 120 to 180 HP it would probably work on the CX. Oh, an oil cooler too.

Cheers, 50gary
 
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