77 GS 750 with Wiseco 844 kit

[Greenmachine]

I have a 77 GS750 that I picked up for cheap that seemed to be burning oil. I took apart the top end and found that the cylinder walls were pitted pretty badly.


I think my best option is to get the cylinders bored and use the wiseco 844 kit. I am planning on replacing the cam chain guides and chain as well.

Is there anything I need to do to the bottom end to run this and are there any other parts I should swap out while I'm in the motor? Any watch outs from you more experienced GS gurus?

[JGordon]

This is what happens when a motor sits for a while without being ran or turned over. Depending on how deep the pits are is whether it will clean up. I would probably try and get a used set in good shape.

[gearhead13]

You dont need to split the cases for the overbore. If the bottom end isnt leaking and is otherwise working fine (ie shifting). Unless your engine has 100k miles+ on it the chain should be fine. There are specs in the manual to measure it for stretch.

[sparki]

Depending on how deep the pits are is whether it will clean up. I would probably try and get a used set in good shape.

the OP want to bore it out... no need for another setup as i think the 844 wiseco kit is like 4mm over? - pretty sure the pitting won't be that deep

[Greenmachine]

Thanks for the advice guys. I brought the cylinders and pistons for the 844 kit to my machinist and he is nervous about doing it. His thoughts are that if he bores it enough for the 4mm over pistons there won't be enough material left on the sleeve and it will crack.

He suggested that I try to get in touch with someone who has done this to make sure that I am not compromising reliability too much. Anybody have the wiseco 844 kit in a 750, any issues?

I did some searching and a common mod seems to be to use GS 850 cylinders with stock 850 pistons. Can I use my wiseco 844 pistons with the GS 850 cylinders?

Sorry for the noob questions, I tried searching with no real luck. Thanks!

[Agemax]

try getting in touch with Wiseco, see what they recommend. whether the stock liners will work or you need a larger block to start with....

type wiseco 844 in the search and it brings up loads of related threads, like this one......

http://www.thegsresources.com/_forum/showthread.php?t=200749&highlight=wiseco+844

[gsrick]

Just find a good 850 top end(cylinders, pistons, head and carbs, and use it on the 750 bottom end, and you wont need any machine work. Use the 850 gasket set. Pre 80 if you want to stick with 26VM carbs or 80 and later for the bigger 32CV carbs.

[Greenmachine]

Picked up a set of 850 cylinders and had them honed. They mic out at 2.716" which is per the wiseco spec and .002" clearance. After the hone there is still some very small pitting in one of the cylinders. It isnt much, I cant catch a finger nail on it or anything. Should I me looking for another set,can i bore it a bitmore to say .0025 or .003" clearance and be ok, run it as is? Here's a pic of the pitting:


The lighting in the pic makes it look deeper than they feel in person.

Sorry for the noob questions, just don't want to mess this up.

Thanks

[tkent02]

On this cylinder the piston was all the way up as it sat outdoors for decades.
I think those holes will fill with carbon and it will be fine, it's not like the water jacket will spring a leak or anything.

But I'm not an engine expert.....

[fast pom]

Hi Greenmachine looks like you have decided to use the 850 Barrels . Just as a note i have built and raced several 750 using the 844 kit with no problems at all with the over bored Barrels. Good luck with your build.