timmyc
XS650 Member
I have been reading about the all the variations of the 650 engines. I have a 73 TX650 with the 366 engine. Is the 366 a 256 or a 447? Or something in between?
Thx!
Thx!
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For the most part, it's a 306 (XS2) engine.
Basically, the 70-73 engines share the '256' conrods, pistons/rings, cam and camchain.
The original '256' crank has no starter gearcuts, which were incorporated in the '306' crank, and supercedes (replaces) the '256' crank.
With the 306 (XS2) engine, many changes occurred, including the starter system (with reduced oil capacity), new left cover, new right cover and oilpump, new head/camcover, compression release, new lower 1st gear and matching kickstart gear, new 6-hole camchain tensioner parts, and cylinder block.
Pouring thru the 70-73 engine parts lists, including the separate '73 TX650 parts lists, I can find no '366' specific engine parts, it's mostly the same '306' parts, with a couple of sub-revision suffixes.
Sub-revisions occurred throughout the XS lifespan, often in mid-year. Significant ones were covered in Service and Parts bulletins, others were mysteriously slipped-in at various times, probably due to changes in vendor specifications or sourcing. You can find these in my albums:
http://www.xs650.com/forum/showthread.php?t=31022
The '366' numbers appear to apply to bodywork only...
Basically, the 70-73 engines share the '256' conrods, pistons/rings, cam and camchain.
The original '256' crank has no starter gearcuts, which were incorporated in the '306' crank, and supercedes (replaces) the '256' crank.
With the 306 (XS2) engine, many changes occurred, including the starter system (with reduced oil capacity), new left cover, new right cover and oilpump, new head/camcover, compression release, new lower 1st gear and matching kickstart gear, new 6-hole camchain tensioner parts, and cylinder block.
Pouring thru the 70-73 engine parts lists, including the separate '73 TX650 parts lists, I can find no '366' specific engine parts, it's mostly the same '306' parts, with a couple of sub-revision suffixes.
Sub-revisions occurred throughout the XS lifespan, often in mid-year. Significant ones were covered in Service and Parts bulletins, others were mysteriously slipped-in at various times, probably due to changes in vendor specifications or sourcing. You can find these in my albums:
http://www.xs650.com/forum/showthread.php?t=31022
The '366' numbers appear to apply to bodywork only...
timmyc
XS650 Member
Thanks for the info. 
After I posted my question I did a bit of research with the online parts finder at my local dealer. I did find that the 73 rods and pistons do carry the prefix of 256 and that changed to 447 in 74. I am building a café racer and have started looking into parts for engine mods. I think I know why I got the bike so cheep, oh well. After reading a great deal on the forum about the differences between the 256 and 447 it sounds like if I swap the crank, rods, pistons, cam with sprocket and chain I can use the 447 performance parts? I am very familiar with the Honda CB350, I have had one for years and am now trying to learn about the TX650. Of the aftermarket manuals, Haynes and Clymer which is the most accurate in covering the early engines? Thank you for your input!
Tim
After I posted my question I did a bit of research with the online parts finder at my local dealer. I did find that the 73 rods and pistons do carry the prefix of 256 and that changed to 447 in 74. I am building a café racer and have started looking into parts for engine mods. I think I know why I got the bike so cheep, oh well. After reading a great deal on the forum about the differences between the 256 and 447 it sounds like if I swap the crank, rods, pistons, cam with sprocket and chain I can use the 447 performance parts? I am very familiar with the Honda CB350, I have had one for years and am now trying to learn about the TX650. Of the aftermarket manuals, Haynes and Clymer which is the most accurate in covering the early engines? Thank you for your input!Tim
Ditto on the CB-350. The XS650 is quite similar, just on steroids.
Get all the manual's you can, including Craig Week's Performance Manual. Find links for these in the Tech Section: Manuals.
Sounds like you have a pretty good idea of what's involved, and a plan to upgrade your engine. Be aware of the camchain tensioner system with a 447 configuration. You'll need a later 447 cylinder block to get the tensioner to work right. Could look into the 750cc big fin kit...
Get all the manual's you can, including Craig Week's Performance Manual. Find links for these in the Tech Section: Manuals.
Sounds like you have a pretty good idea of what's involved, and a plan to upgrade your engine. Be aware of the camchain tensioner system with a 447 configuration. You'll need a later 447 cylinder block to get the tensioner to work right. Could look into the 750cc big fin kit...
timmyc
XS650 Member
I have given some thought to the big bore kit, but it seems like the $'s to HP ratio is not very good? I am thinking about a rephrase engine with higher compression pistons, large bore carbs, electronic ignition, high flow exhaust and a high lift cam might be the better way to go? You would do all of that with the big bore kit but does additional displacement really make the difference?
Tim
Tim
By itself, no. Only about a 14% displacement increase. It's just a means to an end, solve the tensioner issue while opening the door to more performance potential.
Something you might consider is using the 256 cam since you have it. It's a bit hotter than the 447 cam. It involves changing the 256 cam sprocket to one off a 447 cam. Here's a thread .....
http://www.xs650.com/forum/showthread.php?t=29831
http://www.xs650.com/forum/showthread.php?t=29831
timmyc
XS650 Member
Thank you for all the great information! When I get further into the build I will post some pic's and info.
Tim
Tim
weaselbeak
XS650 Junkie
If dollars to HP is an issue, why rephase? Pretty expensive isn't it?
timmyc
XS650 Member
For me the major upside of doing a rephase is less vibration at higher RPM's. My plan for the bike is to ride the back road of northern Michigan so high RPM is realy not needed. What I don't like the side effect of making the bike sound like a V-Twin (no offense to those who do) if I wanted that I would buy a V-Twin. I realy like the sound of the inline twins, so I am not sure if it's worth the effort. So I will keep reading and building, besides there won't be much of the original bike left when it is complete.
Thanks
Tim
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shawn00sa
XS650 Addict
Tim.....I am in Michigan and doing the exact same thing also. I am not looking to rephase either. I'm thinking about going the 700 cc route.
timmyc
XS650 Member
Great! When you say the "700 route" are you planning to over bore the stock cylinders? If so who makes the larger pistons?
Tim
PS is Jonesville near Coldwater?
Tim
PS is Jonesville near Coldwater?
shawn00sa
XS650 Addict
Hoos racing makes them. I would have my stock cylinders bored. http://www.hoosracing.com/650enginepartsprice.html
Coldwater is very close. About 15 miles. I also have a cabin in baldwin and plan on roding up north also.
Coldwater is very close. About 15 miles. I also have a cabin in baldwin and plan on roding up north also.
timmyc
XS650 Member
You are correct, thx! That makes a lot of sense. What other mods are you planning ?
shawn00sa
XS650 Addict
I'm not sure right now. I'm actually a little torn. Thinking about head porting, cam, 700 Pistons, electronic ignition, Mikuni 34mm carbs
timmyc
XS650 Member
I am adding a front end from a 2012 R6 and have been contemplating a mono shock rear suspension. Also in my quest to have spokes and disk brakes front and rear I have a swing arm and hub that will meet that goal. Please let me know what mods you tackle over the coming months.
thx!
tim
thx!
tim
