One or Three?

[Coyote]

Those that have been following my current GT550 saga know about the completely blown left side of the motor. Well the deal is, the other 2 pistons and cylinders are in excellent condition. I got compression results of 120 on the right and 125 on the center. My chepo status tells me to just replace the bad piston and have the cylinder bored. Then put it back together. I told the head mechanic at the bike shop of my plan and he acted as though it was a bad idea. Now I'm thinking about balance. Balance between pistons made in 1975 vs. new pistons. Also the might be a slight difference in power, but my real concern is weight. I suspect new pistons are lighter than the old originals and the difference might cause the bike to vibrate abnormally.
I can go either way One new one or all three new with fresh bores on all. Opinions please! Will I be sorry if I just replace one?

[yeadon_m]

Piston to piston weight variation even back in the day was quite substantial. I had a single cylinder spoiled with a broken ring 3 years back. On that GT750B, piston weights without pins were 232g, 235g, 238g. So, Suzuki were happy to run it with a 6g variation. Oversized pistons from the same maker may not differ much in average weight either so I would weigh what I had and ask the suppliers to weigh theirs. If the result is say no more than 2% weight variation, you cannot have a problem due to uneven weights. These are slow, under stressed motors.

saying all of this.....I chickened out and had all 3 pots overbored )

So much for theory.

Bloody thing still vibrated after, like Kettles do somewhat.

Have fun!
Mike

[tz375]

If it's possible to buy just 1 piston set, get it and weigh it and see how it compares to stock OEM. We can hypothesize as to what might theoretically be the outcome, but until we have numbers, it's not very productive.

I'd get one fit it and run it. It's not as if we're talking a 12,000 rpm race motor

[Craig380]

For what it's worth, my 380 has run happily for 15,000 miles and 8 years with one standard piston and two at 0.5mm O/S. As TZ said, it may make a difference on a high-strung race engine, but not on a street motor.

[CBWELLS]

My 2-cents (& it's worth every penny!): Get a decent used STANDARD LEFT jug from someone on this site or watch eBay for what you need. I would not pay more than $100 for it, nor would I waste any time or $ on your beat up jug. Just toss it out!

(FYI, I have a nice matched CENTER cylinder & piston with rings etc., but that won't do YOU any good!). There's a left jug on eBay right now; http://www.ebay.com/itm/Suzuki-GT550-GT ... e4&vxp=mtr" onclick="window.open(this.href);return false;

While you're looking for that cylinder, buy a full set of the cruisinimage pistons, rings, & wrist pins... also on ebay. Ya can't beat 'em for the price (~ $80 at your door!). With all the money you saved, also buy new upper (small end) bearings for all three. These should be less than $15 each. While waiting for all these parts, work on the rest of the bike & be patient... The left cylinder is out there & you will find it! When you get all the parts, hone all 3 jugs, then just puttin' it back together will be EASY!

Doing this will give you a virtually NEW complete top end (with no worries about weight differences) for probably less than $200, AND you will have a very nice used CENTER & RIGHT matched pistons, jugs, wrist pins, & bearings for eBay resale, or for your own spares stock. Chances are you would recover most of your $200 expense from eBay if you so choose. After all, someone out there is looking for cylinders & pistons!...RIGHT?!

By the way; That's pretty much how I ended up with my Center set! Both my LEFT & RIGHT jugs & pistons were toast!

Oh... One more thing; Let's hope your crank isn't contaminated with any crud from the wounded piston/jug! My guess is it's OK (call me an optimist!) .

You asked! Good Luck & keep us posted. We want to know! We're kinda freaky like that!