CX500 motor in a CX650C frame?

[Speedz]

Is it something that can be done with no custom work? I have a blown Engine in my 650.

Well at least I am pretty sure it is blown. It blows a bit of smoke and has much crankcase pressure. If you unscrew the oil fill cap it will shoot it across the garage as the threads pass the catch.

At one point I had a lawn tractor gas tank on it due to a bad tank for testing purposes. It ran great with this tank. But once I fixed the tank and used it, it ran horribly in general. Sometimes it would run ok but then start to run weak and die. It refused to start and sometimes wouldn't turn over till I release the pressure out of the oil cap. So I assume that its blown. Also think the tank fuel selector needs a clean out or replacement. The lack of power and eventual dieing acts like a fuel starvation issue that is also made worse by the crankcase pressure.

Is this idea even a good thing to try? Anything needed to know first? Any other good info appreciated.

Thanks

[what huh]

u would probably be better off getting that question answered here choppercharles.com/cs/

[robin1731]

Does your oil smell like gas? Do you park the bike with the fuel valve open? Is the fuel valve a vacuum operated one? The valve could be bad and letting gas continue to run through the carbs, past the rings and into the crankcase. Since you talked about it running fine with your test tank and acting up after you put the stock tank back on I am leaning towards that senario. Pull the oil fill cap off with the motor off and see if you can smell gas in the crankcase. You could also drain the oil and see if you get alot more out of the engine than it should normally hold. I have seen this before with other bikes. If that is it get the fuel valve/petcock rebuilt.

[the chef]

If you don't have a case of bad rings and you are getting blowby into the crankcase you may have a fuel in the oil problem ,,, you have to get in the habit of turning the gas off when parking and turning back on when starting .
Simply important.
Before I wrote it off do go get some fresh oil and change the oil making sure of the correct amount .
If your still getting pressurized crankcase then you need to do a rebuild . At least a hone and ring job.
If the engine is too damaged then it would be cheaper to get a new bike . For parts or vice versa...swapping.....

[Speedz]

I actually suspected the gas issue as well. Forgot to mention that, but no gas in the oil and I learned the gas lesson the hard way on my first GS550. Those lil buggers love to drink the gas when sitting. It does have a vacuum line to the valve I had to block it off when I ran a test tank.

I do think one issue is a bad valve, but even with the test tank I got bad smoke and pressure in the lower end.

Thanks for the replies

[guy plain]

has the bike ben sitting for awhile? maybe stuck rings?

[Speedz]

Its highly likely its bad rings. I'm thinking its way more than I wish to get into at this point tho.
Shame tho since its a nice lookin bike minus the temporary patch job on the rusted bottom of the gas tank.

I just got a nice GL500 Interstate from a neighbor that requires far less attention. Fully drivable but needs a coolant system flush.
I think this is far more my style anyway. So I guess I'll be posting the CX650 for sale as is at some point.

[Purken]

I once let the oil get too low in my '78 CX500 and fried the engine. I bought a CX650 engine at Bent Bike thinking it would be easy to plug in; it wasn't.

When all was said and done the bike ran great and I was amazed at the difference 150 CDs can make.

Good luck w the 500

Paul

[revolution]

If I remember well , abaut similar problem (650 IN 500 FRAME) problem is in front engine mount and ignition system. It can be done

[Sidecar Bob]

A CX500 motor would be too much work because too many things are different, but if you get a GL500 motor complete with front engine mounts & radiator it will bolt in with only one mod needed. The final shaft (the one that the u-joint connects to at the back of the motor) is different so you will have to remove the back cover and swap in the one from your 650 engine. Since the engine will be out anyway, this should not take long - the hardest part will be cleaning the old gasket off.

Before I changed the engine, I would try soaking the cylinders with Seafoam or something like that to see if it is only a stuck ring, and failing that, have the offending head's rocker cover off to see if you can see the problem - you might just have a valve problem or a cracked head or something that and a good used head will fix.

[jinbtown]

Is it something that can be done with no custom work? I have a blown Engine in my 650.

Well at least I am pretty sure it is blown. It blows a bit of smoke and has much crankcase pressure. If you unscrew the oil fill cap it will shoot it across the garage as the threads pass the catch.

At one point I had a lawn tractor gas tank on it due to a bad tank for testing purposes. It ran great with this tank. But once I fixed the tank and used it, it ran horribly in general. Sometimes it would run ok but then start to run weak and die. It refused to start and sometimes wouldn't turn over till I release the pressure out of the oil cap. So I assume that its blown. Also think the tank fuel selector needs a clean out or replacement. The lack of power and eventual dieing acts like a fuel starvation issue that is also made worse by the crankcase pressure.

Is this idea even a good thing to try? Anything needed to know first? Any other good info appreciated.

Thanks

The 500 engine will fit with extensive modification to mounting, as the frames are very different. The fellows (myself included) can answer this over at choppercharles.com probably better than here, but long story short, unless you are willing to do some fab work, no, you're better off finding a salvage 650 bike or parting out the rest of your 650

Alternatively, I believe the GL engine might fit as those also have similar mounting points. IIRC there are a few things to be done still when taking this route as well.

[Rat]

Yeah, we didn't mean this little forum to be an in depth resource for CXs.

Chopper Charles' is the PLACE for that.

Gord