750 into 850

[Karstan]

Hey guys, newbie here... Longtime lurker but I think this is my first post.

I've got an '84 GS 750 EF that I'm playing around with. I'm doing some cosmetic stuff to it, but I'd like to know more about what kind of mods I can do to the engine, etc. I'm most interested in slapping the 850 barrell on and boring over.

I've searched the rest of the forums on this issue and I found a few posts about it but there are a bunch of holes so I have a few questions

1) Pat posted this (http://www.thegsresources.com/_forum/showthread.php?t=153925&highlight=overbore) that indicates the 750-850 is a pretty straightforward swap, but that has to do with the older 8-valve engines. And some of the other threads mention that there is further machining involved and it isn't a straight swap. I have an ?84 750. Can I put an ?80 850 top end on it (I found one cheap on ebay here: http://cgi.ebay.com/ebaymotors/ws/e...em=&sspagename=STRK:MEBOFFX:IT#ht_500wt_894)?

2) And then there?s this post (http://www.thegsresources.com/_forum/showthread.php?t=173939&highlight=overbore) that talks about it as well, but there doesn't seem to be much consensus on the subject. A few people mentioned swapping the 850 top end onto the 750 low end, and the boring over and throwing some stock 1000 pistons on. Is this possible?

So, tell me oh wise ones, what can I do? What are my options? I'm currently unemployed, so I have more time than money, which is why the 850 swap seems like my best bet for a quick and easy modification. But I'd like to know if I can take that just a wee bit further.

TIA
Karstan

 

[Nessism]

2 valve and 4 valve engines are totally different. Parts will not swap.

 

[tkent02]

I think the 1100 engine from a similar year bike will fit, if you can find one.

 

[SVSooke]

I think the 1100 engine from a similar year bike will fit, if you can find one.

Not into an 84 frame,That will work in the 80-82 gen.1100 Bandit engines work though.

 

[Guest]

Check out the oldschoolsuzki.info site. Any oil cooled gsxr motor will fit in that frame nicely. I'm rebuilding a short stroke 750 ('88-'89 gsxr or early gsx katana) motor for my '83 es. And when i get bored with that combo i'll swap a 1052 crank, pistons and cylinder block into it...

 

[Karstan]

Thanks for the feedback, guys! I'll keep on looking. So far, the late 80's GSX engines and larger bandit engines seem a bit out of my price range, but maybe I'll come across something.

 

[Karstan]

Holy Moly!

Holy Moly!

Right after I posted my last response, an '85 GS 850 engine shows up on Craigslist for $75!!! http://portland.craigslist.org/mlt/mcy/2344415674.html

So... is the 750 to 850 top end swap possible on this era?

 

[Steve]

Right after I posted my last response, an '85 GS 850 engine shows up on Craigslist for $75!!! http://portland.craigslist.org/mlt/mcy/2344415674.html

So... is the 750 to 850 top end swap possible on this era?

There are a couple of very important points you are missing here.

First, the ad is for an '84 850, not an '85.

Second, and most important, as Nessism said, the 2-valve and 4-valve engines will NOT swap any parts.

Look closely, your 750 is a 4-valve engine, the 850 is a 2-valve.

.

 

[Karstan]

Thanks Steve. For some reason, I thought the '83, '84, and '85 gs models were all 4 valve engines.

edit: Okay, is there a guide/chart somewhere for this so I can keep all this straight?