550 Bore?

[dzane]

Hi All, I am new to the forum. Been riding a 1980 GS550L since 1982 and have put on over 85000 miles. It is still in good condition but needs work and am considering a complete overhaul this off season. Can a 550 be bored to something like 650? Are parts available for this conversion? Thanks for all the great information on this forum! I also have a nearly complete 1981 GS550T for parts if anyone needs bits and pieces.

[Buffalo Bill]

I was thinking along the same lines…

Hi All, I am new to the forum. Been riding a 1980 GS550L since 1982 and have put on over 85000 miles. It is still in good condition but needs work and am considering a complete overhaul this off season. Can a 550 be bored to something like 650?

You can buy a GS650, don't ruin your 550. The GS650 is only 20 lb. heavier than the 550, but has 73 horsepower!.
I would be satisfied with a re-bore for replacement pistons. You can only overbore once because they don't make replacement sized overbore pistons.
There are some performance cams for the GS550 available at webcamshafts.com and for only $407 a set! You can build your GS550 to a stre$$ful high 60 HP level, but then you could just buy a GS650 with an easy 73 HP.
Bill

[TheBigRed]

Hi All, I am new to the forum. Been riding a 1980 GS550L since 1982 and have put on over 85000 miles. It is still in good condition but needs work and am considering a complete overhaul this off season. Can a 550 be bored to something like 650? Are parts available for this conversion? Thanks for all the great information on this forum! I also have a nearly complete 1981 GS550T for parts if anyone needs bits and pieces.

There are a couple of guys on here that have managed to squeeze a 650 top end onto a 650 bottom end. Quite a bit of work, and I'm not sure it is worth all the work unless you are redoing the engine anyway. I had the thought with my re-build, but didn't have the spare parts handy so stuck with 550.

Amos

[dzane]

Thanks guys!

I was only going to proceed if I heard something like: "Oh yeah, I've done it and it is easy and the parts are readily available and ..." I have enjoyed the bike for all these years and I will continue to enjoy it with a restoration this off season and possibly an engine rebuild. Fun little bike with lots of miles left in her. Buffalo Bill could you elaborate a bit on the "I would be satisfied with a re-bore for replacement pistons. You can only overbore once because they don't make replacement sized overbore pistons." statement you made? Thanks in advance.

[tkent02]

I have enjoyed the bike for all these years and I will continue to enjoy it with a restoration this off season and possibly an engine rebuild.

So you are going to make it a 650?

[TheBigRed]

I was only going to proceed if I heard something like: "Oh yeah, I've done it and it is easy and the parts are readily available and ..." I have enjoyed the bike for all these years and I will continue to enjoy it with a restoration this off season and possibly an engine rebuild. Fun little bike with lots of miles left in her. Buffalo Bill could you elaborate a bit on the "I would be satisfied with a re-bore for replacement pistons. You can only overbore once because they don't make replacement sized overbore pistons." statement you made? Thanks in advance.

I can't sai "Oh yeah, I've done it" but here is a thread you may find interesting:

http://www.thegsresources.com/_forum...hlight=6%2F550

Amos

PS. Someone else:

http://www.thegsresources.com/_forum/showthread.php?t=89845

[Buffalo Bill]

“If your going to do that, you might as well do…”

I was only going to proceed if I heard something like: "Oh yeah, I've done it and it is easy and the parts are readily available and ..." I have enjoyed the bike for all these years and I will continue to enjoy it with a restoration this off season and possibly an engine rebuild. Fun little bike with lots of miles left in her. Buffalo Bill could you elaborate a bit on the "I would be satisfied with a re-bore for replacement pistons. You can only overbore once because they don't make replacement sized overbore pistons." statement you made? Thanks in advance.

Good idea about not doing a 650 conversion, I read a thread about a basement project doing that, but no long term follow up , probably didn't work so well.
Replacement pistons come in 2 incremental oversizes, each just large enough for restoration of power in high mileage engines: 0.5mm, and 1.0mm. The cylinder is rebored to fit them. the pistons are purchased first so the machinist can measure them before he rebores the block. So your engine might be due for the first oversize rebore of 0.5mm, but it would have to be measured to know.
If you like (had money) you could consider: new oversize pistons, performance cams and valve springs with the piston tops cut to stay clear the valves. That would mean rejetting the carbs too, because the whole engine management system is connected like a chain, and all the changes will have to be tuned to work together as a unit. Interesting work if your up to it.
Bill

[TheBigRed]

Good idea about not doing a 650 conversion, I read a thread about a basement project doing that, but no long term follow up , probably didn't work so well.
Replacement pistons come in 2 incremental oversizes, each just large enough for restoration of power in high mileage engines: 0.5mm, and 1.0mm. The cylinder is rebored to fit them. the pistons are purchased first so the machinist can measure them before he rebores the block. So your engine might be due for the first oversize rebore of 0.5mm, but it would have to be measured to know.
If you like (had money) you could consider: new oversize pistons, performance cams and valve springs with the piston tops cut to stay clear the valves. That would mean rejetting the carbs too, because the whole engine management system is connected like a chain, and all the changes will have to be tuned to work together as a unit. Interesting work if your up to it.
Bill

As of late last year it was still running if memory serves. In fact the user was going to sell me a 650 top end to redo mine, but never got back to me on the cost to ship it, so I went with staying at 550 on my rebuild.

Maybe they will pop in and give an update on their thread sometime.

Amos

[dzane]

Keeping it 550

I'll be checking the engine to see if it needs to be overbored at all. It is a relatively hi-miler, but these engines well cared for, (mine has been), are 100K engines easy. I want the rebuild mainly for cosmetic reasons as the old girl has been through a lot including being parked in an open carport for a while. Other than those four years it has been garaged and it now has a home inside a shop when it isn't scooting around the Pacific Northwest. I like my bike!

[brveagle]

My gs550 is still running strong. I actually bored out the 650 cylinders to make it a 740cc, but it ran a little too warm for my liking, so I swapped it back to a 650 bore. Actually cc's is 673.

I raced a healthy running 850 and only lost by about 1-2 bikes.