1982 550 Maxim replacement cam and pistons

Hi guys - I am getting a 550 maxim from my FIL that has not run since the mid 90's I am interested in rebuilding it with my 8 year old son and I suspect we will have to install new pistons since the motor acts like it is seized. I cannot find factory replacement pistons and was wondering if you guys know of any. Also, would you guys know if the 550 block can be bored out to accept XJ650 or XJ750 pistons and if yes, where I might find these?

If I get inside the engine I would like to replace the cam with something a little hotter than stock. Are stock or performance cams available and if yes, where might I find these?

Thanks,
Tom B

 

I company called mega cycle makes a cam for the 550 I believe. A cheaper option is to run 2 fj600 intake cames. As far as fitting big block jugs you're going to have difficulty with. Only way it would be at all feasible is to bore out the 550 cases to fit the larger sleeves. Best bet is to find a 600 topend which does fit.

 

Before jumping to conclusions, what is telling you that the motor is siezed?

Have you put it in neutral, removed the crankshaft cover (left side), removed the spark plugs, and tried to turn the engine by hand?

Usuaally an engine that's stuck from sitting will not ned new pistons, but may need new rings and a light honing of the bore. But you won't know exactly what it needs until you:

1. determine that it is in fact seized.

2. Free it up (50/50 mix of automatic trnasmission fluid and acetone (or kerosene) down the plugh holes and let it soak for a week or three.

3. Do a compression test once freed up (sometimes a fella gets lucky and it's just barely siezed and can run once freed up).

4. Tear the engine down for inspection.

Only after that should you start shopping for parts.

 

Hi guys and thanks for your prompt reponse. The bike inquestion sat outside for years before it was unceremoniously parked in a storage shed. I think the tank took on some rainwater and then ran into the block. Plus, it has not been ridden or cranked since 1994. The tranny is stuck in gear and the rear wheel will not budge so im kind of convinced its locked up. The bike is all there and i have an interest in getting it back running and if i have to open it up i might as well add some performance. I amnot in love with the bike but free is free.

It sounds like there are no easy options for a piston replacement so if it is in fact locked up hard ill resort to parting it out.

 

Find an engine. They are usually not expensive in useable condition.

 

my bike sat out side for over ten years had to cut it out of the bushes that grew up around it and in it.

a little 50'50 mix freed it up. runs excelent.
hotter cam get a seca 550 head for it, rejet the carbs to seca spec. the cams have no bearings and the whole head is replaced as an assembly of the cam support journals are out of spec

free will cost about 600 to 1200$ to fix and run safely
find a used motor for it instead of rebuilding it you will not be dissapointed with the 550

 

Unless the motor was full of water, usually the aforementioned 50/50 mix and patience will free them up. Started a few old motors this way. Clutches have a tendency to stick too after sitting for that many years.

 

Did you try shifting it to neutral and then turning the engine via the timing boss under the left engine cover? Pull the plugs out, and use a 19mm wrench

 

The Nighthawk 650 I just resurrected had been sitting since 2007, water in the oil, engine seized and stuck in gear. Acetone ATF mixture did the trick in 3 days, flushed all fluids and removed, cleaned and reassembled the clutch slave cylinder before repeatedly popping it into first, (lurch and kill). Took about 15 attempts before it popped free. I'd save my money for the brakes and tires you'll definitely be needing. Good luck, it's a great feeling when it catches for the first time!