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I am gearing up to do a 750/850 swap, so there must be another N00b thread. Please, hold your applause. 
Anyway, my project started with some part number searches to see what fits. Shockingly, the main parts are easy. The first GS850 uses the same cylinder head as the 1979 GS750 (part no. 11100-45820). My 1978 has a different part no. for the cylinder head (11100-45813) but they appear to be identical, use VM26 carbs, etc.
Other than the part no., is there any difference between the 1979 GS750 head and my 1978 GS750 head?
The GS850 heads change after 1979, because of CV carbs, etc. The cylinder jugs (11210-45100), however, stay constant for several model years, 1979-81. So I should be able to use any cylinder jugs from those years for the project. I have been hunting parts on eBay. No one seems to offer jugs and pistons together. Since new pistons are about $70 each, I scored some used 850 pistons on eBay for about $25. They look OK and were listed as standard bore, but they'll need to be cleaned up and checked out. Fingers crossed.
There are plenty of jugs on the Internet, erm 850 cylinder jugs, but pricing is a bit scattered. Some are $30. Others are $150. The information in the listings does nothing to explain the price gaps. Some of the expensive ones have chipped fins or blurry photos.
$50 - Gets this, but cannot see squat in photo.
$30 - Gets this but the photo is even worse.
They also are weird about the bore specs. That $30 job claims a bore of 2.711. The service manual sets a range of 2.716 – 2.717. So these jugs have less wear than brand new ones?? Even the piston limit is 2.7118, so these sleeves are too narrow for over-worn pistons, according to the seller.
Other than badly damaged fins, wildly bad mileage (came from a bike with 500,000 mi.), etc., what should I look for in the pics and details when buying jugs? I know the jugs will need to be honed, and probably won't show any cross-hatching. Are there other marks or wear that honing cannot save?
Gaskets are another mystery. Since I am mating different jugs to cases and head, which gasket controls? In other words, although they use the same head, the head gasket for the 1979 GS750 (11141-45083) is not the same as the GS850 (11141-49002). I suppose the difference is the openings for the pistons. So should I use GS850 head and base gaskets?
So here we go for another wild ride . . .
Anyway, my project started with some part number searches to see what fits. Shockingly, the main parts are easy. The first GS850 uses the same cylinder head as the 1979 GS750 (part no. 11100-45820). My 1978 has a different part no. for the cylinder head (11100-45813) but they appear to be identical, use VM26 carbs, etc.
Other than the part no., is there any difference between the 1979 GS750 head and my 1978 GS750 head?
The GS850 heads change after 1979, because of CV carbs, etc. The cylinder jugs (11210-45100), however, stay constant for several model years, 1979-81. So I should be able to use any cylinder jugs from those years for the project. I have been hunting parts on eBay. No one seems to offer jugs and pistons together. Since new pistons are about $70 each, I scored some used 850 pistons on eBay for about $25. They look OK and were listed as standard bore, but they'll need to be cleaned up and checked out. Fingers crossed.
There are plenty of jugs on the Internet, erm 850 cylinder jugs, but pricing is a bit scattered. Some are $30. Others are $150. The information in the listings does nothing to explain the price gaps. Some of the expensive ones have chipped fins or blurry photos.
$50 - Gets this, but cannot see squat in photo.
$30 - Gets this but the photo is even worse.
They also are weird about the bore specs. That $30 job claims a bore of 2.711. The service manual sets a range of 2.716 – 2.717. So these jugs have less wear than brand new ones?? Even the piston limit is 2.7118, so these sleeves are too narrow for over-worn pistons, according to the seller.
Other than badly damaged fins, wildly bad mileage (came from a bike with 500,000 mi.), etc., what should I look for in the pics and details when buying jugs? I know the jugs will need to be honed, and probably won't show any cross-hatching. Are there other marks or wear that honing cannot save?
Gaskets are another mystery. Since I am mating different jugs to cases and head, which gasket controls? In other words, although they use the same head, the head gasket for the 1979 GS750 (11141-45083) is not the same as the GS850 (11141-49002). I suppose the difference is the openings for the pistons. So should I use GS850 head and base gaskets?
So here we go for another wild ride . . .
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