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Discussion Starter · #1 ·
Hello to present members and I'll try and keep the intro short. Any questions I ask regarding technical issues will probably need re- directing so suggestions please. Riding for 44 years (42 on road) UK based and besides aprilia and Triumph track bikes it's mostly been a mix of Hardtail and swingarm Harley and Triumph bobbers. I've ended up with a VT1100 frame circa 2000, after engineering a different front end the option was a chain drive rear but wanted the 1100 engine (see where this is a well trod path or worn out question!) I am new to this bike and 1100 heads on a 750 lower seems totally achievable. Anyway thanks for your patience and the deathtrap is pictured
 

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2001 Shadow Spirit 750
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Welcome to the forum from West Chester, PA. Really interesting build. I plan on following your progress. What is that front end from ?
 

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Discussion Starter · #3 ·
Hello, thanks for reading. Front end is a Triumph Daytona T595 with ST1300 tree, the shadow stem is pushed into Pan European alloy yoke but an alloy shim is inserted and welded to the base of the clamp/yoke. A hex grub screw is inserted (just in case!) Front tyre/tire is to go from a 70 series to 90 to lift it a bit but I used heavy fork oil and springs as it's only 5.5 inches off the ground. I put a gpz1000 engine in to see how it would balance out with the Tomcat 18" rear.
 

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'83 VT750C; ‘21 SV650A
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Not so much redirected, but only a few have done customizations at that level, let alone on a Shadow. Like head swaps, the bikes are so cheap in the US that most just swapped motors, rather than mixing/matching parts. For example, check out @makenzie71 ’s CAFE build.

So you’re in uncharted territory, and would find out a lot of stuff (good and bad) as you went along. Like the above build, when you get so far in, you might find that pretty swingarm doesn’t allow the chain/sprocket alignment that you want, for example. If you can get ahold of some cheap junkyard engines, you could try the 1100/750 fitment as far as bolt holes and coolant/oil passages go. It’s hard to find a good picture of the engine with the shaft drive differential removed, but from what I’ve seen… You might just be able to slap a sprocket on there and make the clearance for the chain… 🤔
 

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Discussion Starter · #5 ·
Hello Troy.
I totally understand what you have stated, ironically my brain is geared towards making all non sports V twins low and chain driven despite the odds, Honda put their efforts into day to day practically and ease of ownership and going against intended design is arrogance &/or stupidity. No Honda product exists without a great deal of thought but as my brain cells die......
Best wishes
 

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Discussion Starter · #8 ·
Found the 750 crankcases........... turned out to be shaft drive. Seems the vt750 chain drive models are scarcer than Rocking Horse s**# over here (I'll be corrected by UK owners no doubt). If I end up putting the shaft drive 1100 in this I'll be pissed off and the exercise will end up being a purely aesthetic one which wasn't the point. I put the shaft rear end on it to make an emergency design plan, I don't like the space between the shaft housing and the ground but probably due to rigid frame disease, the funny thing is that the detachable lower frame that was on the main frame is from an aero but it was a sabre model so foot rest points are conflicting, the "good condition tyre" that last saw service in Nevada has the shape of an arched eyebrow. A cheap Honda frame from Ohio seemed like a gift........
Bitching over.
 

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This is an interesting thread! 1100 heads on a 750 motor? why? I mean that as a serious question...why? why not just do some headwork on the 750 heads. I had a 1100 for 5 years. I know those heads are not going to line up with 750 barrel/head studs. You can get 1mm bigger valves. You can have the cans reground for a higher lift/longer duration. You can have one-off custom pistons made to increase the compression. If you cant find a crankcase/tranny from a DC (chain drive), you can replace to the countershaft from the shaft drive tranny to the chain drive(changes internal final tranny gearing and give you a chain sprocket instead of the shaft drive) You can use the earlier 36mm carb (single xarb) in place of the 34mm carb. I think you can still get a performance chip that will alter yourt timing curve. After doing all of this, you MIGHT gain 10Hp. But, then again...some things are just...maybe..maybe it will work...lets try it! After all, we wouldn't have spagetti if the Italians hadn't figured you that don't HAVE to use rice to make noodles! Following....
 

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OP’s talking the entire cylinder and up. Not just the ‘head’, so the engine would effectively be an 1100cc.
ok! Thats gonna get even more interesting trying to put a an 1100 crank in a 750 casing..sort of like putting 8 pounds in a 5 pound bag. It absolutely will not fit in a 750 case...length, width, throw is much larger on the 1100 crank. Furthermore, the 1100 crank is much heavier than the 750 crank and the 750 case bosses that the crank sits in would not handle the weight. They would crack in very short order. So, that means turning the 1100 crank counterweights down to make the width less, shortening the crank length on both ends to make it fit in the 750 case, turning down the ends to make them match up with the 750 bearings to match the bosses, and once that is done, will the gear on the crankshaft that drive the cam chain still mate up? Next issue will be that there isn't room in 750 casing to move the cylnder/heads studs so they line up for the 1100 cylinders. You can't just drill new holes. this is a water cooled engine and those bolt hole sleeves are water jackets. He has an 1100 frame and the best bet is to use an 1100 motor and custom make a countershaft that eliminates the drive shaft mate up and makes provisions for a sprocket and of course, that would also requires a different final gear for that crossshaft.....or...have the 1100 crossshaft modified to put a sprocket on it and then just experiement with rear wheel sprocket size until the bike will move...given the internal gearing differences between the chain drive and the shaft drive, that rear wheel sprocket will need to be about as big as the wheel itself. This project for any success is going to require dumping the Honda motor and going with a belt/chain drive motor from a Kawa or Yami...a lot easier to position new motor mounts. But using 750 cases and making an 1100 top end fit...nope. physically impossible.
 
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Which… would be why he was only ASKING if it could be done? 😉
A quick trip through the service manuals for both would have answered every one of his questions. I love projects like this...I have built many one-off custom bikes over the last 50 years....how about a 1200 GW motor supercharged and put in a drag bike?.... but some things are just a bit too far away from reality to ever see daylight...the OP has dreamed up a "you cant there from here" bike. He could solve all the problems by just dumping a Honda motor and going with a Kawa motor
 
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Discussion Starter · #16 ·
A quick trip through the service manuals for both would have answered every one of his questions. I love projects like this...I have built many one-off custom bikes over the last 50 years....how about a 1200 GW motor supercharged and put in a drag bike?.... but some things are just a bit too far away from reality to ever see daylight...the OP has dreamed up a "you cant there from here" bike. He could solve all the problems by just dumping a Honda motor and going with a Kawa motor
 

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Discussion Starter · #18 ·
Hello Again all!
Work and other bikes aside I read all replies and found interesting the various points of view, I appreciate the sage engineer as well as the F##@ it and try type! Last comment brought me back to the use of another make of engine question, it's a well made Panzer of a frame that I got for little so playing around with it is okay, a desert state motorcycle is a boon. I have a Honda cbx750 (was an oil in frame) sitting here which is a great engine with a cb750 bottom end and thought......but seriously a vn800 crossed my mind but then I shouldn't be here should I and I'm back in vt750 territory. 1000+ is the lucky number so it's going to be a hardtail 1100 using the basics of the xvs650 swingarm sitting here. If you look at the shaft design/length of the Yamaha it's plenty of work but stay tuned.
 
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