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GS1100 crank mod for GS750?

  • Thread starter Thread starter Cafe750
  • Start date Start date
C

Cafe750

Guest
Dear anybody,
I have an '82 GS750T 16V and was broken hearted to find that my motor is not a roller bearing crank/rod setup like the 8V 750's or the 16V 1100's. I have an opportunity to buy a roller bearing GS1100 crank, my question is, will this fit my motor? I know that I'll have to line bore the case to fit the big bearings and that's fine, but what about cylinder spacing? Can I make this crank fit with some machine work to the case?
 
Just wondering why you are so enamored of the roller crank over the one piece one?

Mark
 
You'd likely spend less money, if were even possible, swapping a 1100 16v motor into that frame. That IS a roller bearing crank, and you'd get more than just the bonus of the roller bearing crank out of it. There are already pre-manufactured brackets that make this swap easy to do, all you need do is find an 1100 motor, which again, would cost you less than having your 750 case set up to accept the 1100 crank (which i still dont think is possible anyway)

As to the 750 motor: The problem that seems to arise MOST in that design isnt about the crank, its about the oiling system. Changing out the crank wouldnt solve it, as it has nothing to do with it. The problem, it seems to me anyway, has to have something to do with the mapping or size of the delivery ports, and the location and chain of them. The one thing i have noticed about the motor that is different from MOST of the motors I have worked on is that the gallery seems to be, or at least the bolt to the gallery, located at the BOTTOM of the motor, below the contact breaker cover. The 16v 750 system is High pressure, low volume, so i wonder if the problem is mostly the result of poor upkeep of the sump, cleaning of the screen and regularity of oil changes, causing crap to be picked up and blockages to occur in the delivery ports. There are quite a few people who have these bikes, with these motors, that dont seem to ever have a problem. However, there are also quite a few people that have had issues including scoring of the cams from lack of oil, lockup, conrod bearing failures, conrod failures, and ive even seen shattered pistons, from the underside, signaling that the oil simply wasnt getting there. Again, I am only speculating on these causes, but, at least to me, it makes sense.
 
Last edited:
TheCafeKid said:
You'd likely spend less money, if were even possible, swapping a 1100 16v motor into that frame. That IS a roller bearing crank, and you'd get more than just the bonus of the roller bearing crank out of it. There are already pre-manufactured brackets that make this swap easy to do, all you need do is find an 1100 motor, which again, would cost you less than having your 750 case set up to accept the 1100 crank (which i still dont think is possible anyway)

As to the 750 motor: The problem that seems to arise MOST in that design isnt about the crank, its about the oiling system. Changing out the crank wouldnt solve it, as it has nothing to do with it. The problem, it seems to me anyway, has to have something to do with the mapping or size of the delivery ports, and the location and chain of them. The one thing i have noticed about the motor that is different from MOST of the motors I have worked on is that the gallery seems to be, or at least the bolt to the gallery, located at the BOTTOM of the motor, below the contact breaker cover. The 16v 750 system is High pressure, low volume, so i wonder if the problem is mostly the result of poor upkeep of the sump, cleaning of the screen and regularity of oil changes. There are quite a few people who have these bikes, with these motors, that dont seem to ever have a problem. However, there are also quite a few people that have had issues including scoring of the cams from lack of oil, lockup, conrod bearing failures, conrod failures, and ive even seen shattered pistons, from the underside, signaling that the oil simply wasnt getting there. Again, I am only speculating on these causes, but, at least to me, it makes sense.
Click to expand...


the only difference on the 750/1100 16v. motor mounts is the bottem triangles..
there not really needed anyways:)
the 80-82 750 16v. engines eats rod bearings(in my opinion)
if you think you hear loose valves...think again, thats the piston(s) hitting the head.
ive had several come in for really loose valves, not the case.
tick tick tick, click click click:eek:
 
blowerbike said:
the only difference on the 750/1100 16v. motor mounts is the bottem triangles..
there not really needed anyways:)
the 80-82 750 16v. engines eats rod bearings(in my opinion)
if you think you hear loose valves...think again, thats the piston(s) hitting the head.
ive had several come in for really loose valves, not the case.
tick tick tick, click click click:eek:
Click to expand...
Agreed, I have seen many cases of rod bearing failure, but its not due to the crank IMO. Its due to the oiling system failing FIRST. If that fails, of course the crank and rods are next...
 
TheCafeKid said:
Agreed, I have seen many cases of rod bearing failure, but its not due to the crank IMO. Its due to the oiling system failing FIRST. If that fails, of course the crank and rods are next...
Click to expand...


its due to dirty oil, gas in oil and plain over revving.
dont quote me or part number me but...
i think the 750 and 1100 have the same oil pumps..
the 750 gets differant ratio gears to up the volume.
 
blowerbike said:
its due to dirty oil, gas in oil and plain over revving.
dont quote me or part number me but...
i think the 750 and 1100 have the same oil pumps..
the 750 gets differant ratio gears to up the volume.
Click to expand...
Im pretty sure you're right as far as the pump goes. Common mod to the 1100 is to use 750 gears on the pump to up the flow. But as far as the 750, i think one part of the problem is the port size and location. I do believe with the redesign of the 750 motor in 83, one of the things that they did to combat these problems were to put oil jetting ports in line to spray oil onto the conrods and bearings directly. The 83 motor was a much better motor IMO than the 80-82 in many respects. In fact, I kinda wish i had one :)
 
TheCafeKid said:
Im pretty sure you're right as far as the pump goes. Common mod to the 1100 is to use 750 gears on the pump to up the flow. But as far as the 750, i think one part of the problem is the port size and location. I do believe with the redesign of the 750 motor in 83, one of the things that they did to combat these problems were to put oil jetting ports in line to spray oil onto the conrods and bearings directly. The 83 motor was a much better motor IMO than the 80-82 in many respects. In fact, I kinda wish i had one :)
Click to expand...

I have a spare one on a parts bike. Only about 12,000 miles on it, turns over fine.

If you want it, pm me....
 
blowerbike said:
its due to dirty oil, gas in oil and plain over revving.
dont quote me or part number me but...
i think the 750 and 1100 have the same oil pumps..
the 750 gets differant ratio gears to up the volume.
Click to expand...

Like TCK said in another thread, many of these engines have tens of thousands of miles on them without a problem.

Change your oil folks, and adjust your valves.....
 
Griffin said:
I have a spare one on a parts bike. Only about 12,000 miles on it, turns over fine.

If you want it, pm me....
Click to expand...
Dont have a frame to put it in..I kinda meant i wanted a WHOLE 83 700/750...LOL..BUT, I may have someone who is interested depending on what happens with the one I will be working on this winter...
 
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