XJ550 Restoration.

Just starting my Maxim 550 restoration and I’m at a bit of a crossroad. Before I took the thing apart I did the standard compression check and found a decent 125psi plus or minus 1-2lbs on all 4 clylinders dry and a huge jump to 185 on the wet test. Now I’m a licensed Suzuki tech by trade so all I know is Suzuki’s at this point. The engine had 64,000km with unknown service history. Where I m at a crossroad is should I even bother cracking this engine open or not. If it was a 4cly Suzuki I wouldn’t bother but I really don’t want to do a bunch of work on this thing only to have issues in the near future. At the end of the day I’d like a nice reliable bike for the weekends to take on road trips.
Depending on the model and kms on various types of Suzuki’s it would be easy for me to deside but Yamaha is a new animal to me.
Thanks so much guys.

 

your motor should be good to go at that mileage with those test numbers. spend the money on rebuilding the carbs replacing all the rubber seals .Throttle shaft seals. fuel rail o rings, fuel tee, needle valve o rings or complete needle valve setup (if the needle valves are rubber tipped you should replace them), mixture screw o rings and washers, seals on the enrichment plungers. you should be able to clean all the jets. Use your judgment on the main jet washer and needle valve washer.
Valve cover donuts first then if needed the valve cover seal.

other problem areas include the tach seals, crush washer on drain plug, possible o ring on oil level sensor , then get a good look at the shifter seal and output shaft seal

suziki mikuni carbs are very similar to Yamaha mikuni carbs

 

The 550 engine has nothing insde of it that would require attention unless compression is low.
Clean the outside nad run her. The comression may just be on the low side due to valves being out of adjustment and/or rings being stuck from sitting.
XJ engines from that era are among the best built in terms of reliability and longevity.

 

121psi is standard and 135psi is max for the 550’s.

 

Thanks so much guys. I was really hoping not to crack the engine open and consentrate on carbs and other issues I’ve found during my year down.
Much apretiated.

 

From the sound of your figures, your engine is in good condition, agree check valve clearance easy shim over bucket . A large zip tie or piece of Romex only "special tools" required.