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Can You For Sure Make a 920 an 1100? (Read 8964 times)
Chris Johnson(Guest)
Ex Member



Can You For Sure Make a 920 an 1100?
12.02.03 at 15:28:00
 
This was written by Lars Sandstrom:
"The crancase of XV-models 750-1100 is the same with the exeption of the final drive. The crancshaft of the XV1100 should fit the XV920 so if you cange cylinders and crancshaft you should get 1100 cc.
Best regards
Lars"
The key question has to do with models. I know the later 750 to 1100 are the same, the question really concerns the very early 920 (1981).
I want to put Virago 1100 crank and top end on my XV920RH. The above "should fit" I want to know if it "definitely will fit." Can anyone say for sure?
It would be very expensive for me to buy the `98 Virago 1100 engine I'm considering, only to have it not really fit. I can do some machining, but don't want a major redesign project because they do not truly interchange across all those years.
-Chris

 
 
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Ken Breazeale(Guest)
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Can You For Sure Make a 920 an 1100?
Reply #1 - 01.03.03 at 05:18:00
 
I have much experience with automobile engine build-ups, especially Chevy small block engines. I have bored and stroked them to various sizes. I presently own a 1981 Yamaha RH 920. It is chain drive, not shaft drive like the 1100 Virago. I have found that when you swap the crank you also need to swap the rods and pistons or the longer stroke may cause interference with the head. At least this is the way with auto engines. You need a piston that will accomodate the longer stroke. So, relying on my experience, I would say that in order to make the 920 into an 1100 you would need to swap the crankshaft, connecting rods and pistons and cylinders together. If using the 920 heads, the increase in bore size from 920 to 1100 will also raise compression. Personally, I would just go to 1000cc by using cylinders and pistons from a 1000cc Virago and do some mild head porting and a 3 angle valve job for increased flow. The only difference between a 1000cc and a 1100 is stroke. The 1000cc and 1100cc have the same bore size. The longer stroke will not rev as quickly, but you also will not need to turn it as high to build the same torque. I hope this helps.

 
 
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Jerry(Guest)
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Can You For Sure Make a 920 an 1100?
Reply #2 - 01.10.03 at 05:25:00
 
I run a 1981 920R that, due to a rather painful oil pump failure, is now 998 cc. It involved boring out a set of XV1000 cylinders and installing them. The spigot holes in the case must be bored out as well.  My other comment on this involves the starter. The early XV's have a wretched starting system. Increasing a 920 to 1100, especially if you increase the compression, will strain the starter, and may make it unreliable. (Mine starts great with a brand new starter on it when cold, but a hot start has to be caught on the first couple of cranks or you are screwed.) If going to 1100, I would get as much of the 1100 donor engine as possible, making sure you get the 1100 starting set up and the side cover, but check to see if the gears and etc. will line up with the 920 engine case. A simpler solution would be to change the entire engine in the Virago, unless you have the R model with the chain drive. Good luck.

 
 
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timothy starliper(Guest)
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Can You For Sure Make a 920 an 1100?
Reply #3 - 05.05.04 at 01:00:00
 
i would love to make my virago have more power and what im reading about the 1000cc cylinders and pistons in place of the 920s is great but i cant find the 1000cc cylinders the pistons and rings are available from yamaha still but not the cylinders does anyone have any and if so how much.................bigfoot

 
 
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