I have a 1990 zilla that I have completly brought back to life. It wasn't until I have finished the the whole project, that I heard about the bushings for the main bearings. It this nessary that I might consider tearing the motor back down and having it done or can it wait until the next rebuild? How do you know that you need them other than grabbing the flywheel? Will the engine be damaged if left alone?

 

Do you have the motor running yet? One of the most tattletale signs is vibration when you rev the motor.
All Zilla's vibrate some, but if it really rattles the bars the crank may be loose & moving. If this is the case I would fix it as soon as possible.

 

if you can grab the flywheel and it moves up or down or side to side , it needs to be done . i think the main ones with that prob was the 87 , but not sure . i have heard that if you buy new suzuki cases it also fixes the prob because of a different grade alluminum . LRD did ny 87 .

 

All years will need the fix... the question is WHEN.
Any perceived motion of the flywheel (When grabbing it and trying to wiggle up and down) will require the fix.
What happens if you dont? The crank seals will eventually begin to leak, thus causing a lean condition, and ka-boom!

There is a fella by the name of Roger Irvin (Good friend of mine) that is a really sharp machinist.
If you can convince him to do the work, he is very quick, and has reasonable prices.
Fire him an email: roger_irvin@yahoo.com

Good luck!

 

Even if there is noticeable unwanted movement of the flywheel, that does not necessarily mean that the bearing bosses are bad. The problem could be in only the bearings themselves. If the bearings still fit tightly in the cases then the bosses haven't gone bad yet. I agree that most all Quadzilla's will require the case inserts after enough use but I wouldn't tear down a perfectly good motor to make the upgrade. Also, are you sure the upgrade hasn't been done already by a previous owner? It would be a real waste of time/money to rip everything apart and send in your cases just to be told by the shop that the existing bosses are new.

 

I totally rebuilt the whole motor myself. I noticed that the left crank bearing was not as hard to put in as the right one, but did not slide in easy either. I have all new bearings and seals in the motor now. I might tear down the motor in a year or so( depends on how much riding I do )and have them put in then. I was also wanting to port the cylinder this time. I have completly redone the whole bike at one time and I was happy just to see it run. I had been talking to Trinity Racing about it and they said they do it for around $300.00. I thought that the bearings would spin in the housing where they go when the cases were heated up. I dont ride that often, I work all week and try to squeeze in riding once a month, so I think it will be all right for a year or so. I dont live near dunes or anything cool like that. Real boring where I live.