Xs750 engine build - 896cc big bore.

datadavid

Over 1,000 Posts
Doing a major engine build this winter, using old boxes of parts from 3 different blown up engines, building everything from the ground up and trying to be serious about it..
Planned modifications are:
The big bore obviously.
Porting the head.
Maybe installing bigger exhaust valves, not sure if needed..
Race spec cams from Web cams.
(Needs stronger valve springs)

These mods involve boring out the case to accept bigger liners.

Some mods to increase reliability:
Undercutting gear dogs for the dodgy 2nd gear.
Modifying the stock oilpump
Installing oil cooler.

Sounds cheap and easy enough!
 
where are you sourcing the 896cc kit? (I ask because I'm interested lol)

second gear on these is usually easily "repaired" by pulling a small shim from behind 2nd gear and putting it just before the nut after putting 1st back in. takes about 30mins, I did it on two of my 5 triples.

other than that, I was unaware that Web Cams offered something for these engines, good to know....
 
I got the bigbore kit from cruzinimage, made in japan. Cast pistons from what i can tell, but looks alright to me. Put a 1200cc kit in an xs11 last summer, still havent ridden in yet because of some electrical/fuel gremlins so cant really say anything about quality.
Came across web cams on the american xs triples forum, not sure if they need a core cam to build from or if they make new cams, but the price is really good..
Some 500$ for street/strip cams and springs. They even offer three stages of performance!
 
datadavid said:
I got the bigbore kit from cruzinimage, made in japan. Cast pistons from what i can tell, but looks alright to me. Put a 1200cc kit in an xs11 last summer, still havent ridden in yet because of some electrical/fuel gremlins so cant really say anything about quality.
Came across web cams on the american xs triples forum, not sure if they need a core cam to build from or if they make new cams, but the price is really good..
Some 500$ for street/strip cams and springs. They even offer three stages of performance!

if you need cores let me know, I have a spare set I'd let go for $20 plus shipping....the catch is I'll need follow-up reviews on web cams work so I can consider sending mine out ;)
 
I got 2 pairs! If you're in the states it could be gold if you sent them to Web with instructions to forward to sweden. Save some postage you know :)
 
Quick question focusinprogress - have you been tinkering a lot with your Xs engines? I want to do a few mods for reliability, f.e the oil pump has a dodgy construction - the non return valve is held in place with a clip and o-ring against a small ledge. I wouldn't trust that to stay where it's supposed to.. heard stories of the o-rings falling out with zero oil pressure as result..
 
datadavid said:
Quick question focusinprogress - have you been tinkering a lot with your Xs engines? I want to do a few mods for reliability, f.e the oil pump has a dodgy construction - the non return valve is held in place with a clip and o-ring against a small ledge. I wouldn't trust that to stay where it's supposed to.. heard stories of the o-rings falling out with zero oil pressure as result..

I haven't done much more than a bore job on any of my triples, aside from the simple second gear fixes.
 
So this weekend a garage mate found by accident that the primary axle in the gearbox is bent.. 2/10ths of a millimeter.. practicing straightening it in the shop press. You tend to learn a lot when tinkering with old junk!
 
datadavid said:
So this weekend a garage mate found by accident that the primary axle in the gearbox is bent.. 2/10ths of a millimeter.. practicing straightening it in the shop press. You tend to learn a lot when tinkering with old junk!

if you can't save it I have a spare.
 
Straightened the axle out to within 4/100 of a mil last night. Probably close enough but i'm going to give it a final nudge this afternoon. After that i will check crank bearing play and hopefully i wont find anything off with the block thats been milled out to take the bigger liners..
Hey Focus, how much did you bore your engine? Did you have to change liners? I'm guessing here but something tells me there should be a slight space between block and liners for some oilcooling/heat expansion effect?
Gonna have a nice long discussion with my machinist when he returns from the states.
 
I just did 2nd oversize Pistons in stock liners, pretty straightforward. Never had the liners out, sorry I couldn't tell you more lol.
 

Shit getting cleaned - so the engine builder wont throw me out of his shop!

Shit that goes to the builder for balancing, boring, grinding etc..
 
if you discover you need ANYTHING engine related, PM me....I've contemplated scrapping a lot of this stuff....

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I've got a complete head and cams, rotating assembly, stator/mag, and a spare ignition pickup too
 
That double slotted middle gear... think i only got the early single slotted ones.. might be good as I'm aiming for 80 something rwhp
 
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