New pics of my 77' XS750 build!
- Thread starter Mctweed123
- Start date
foundation982
Been Around the Block
pics of the engine up close please! I love me some yamaha porn
Swagger
Putting boot to ass since 1967!
I am HUGE fan of the Yamaha triple! My first 'big bike' and still own three and a half that will be built eventually. Looks like you're doing a fantastic job too so that's good.
Some advice though if you care to hear....
Ditch the front end, it is marginal for a bike 100lbs lighter. There's a 'hinge in the middle' of the XS750/850 from the factory, one half of that hinge is the front suspension, the other half is the swingarm.
Something around 40mm works well on that platform, you can pick up a great front end off ebay for $100 or less. Obviously the higher end the better. A pal has picked up a small pile of CBR600's for teardown recently and the front end on that is outstanding. There are lots of offerings out there.
For the rear you need a couple things: first and foremost the swinger is flexible and needs to be braced. The other thing the bike needs is a little more length to the swinger to bias some weight up front, they are tail heavy. A Virago 700/1100 (twin shock) swinger will mate up to your engine/frame and pumpkin and is a touch longer. Brace that one with a bottom loop and you've done yourself a favor. You can also juggle rear end parts to get spoked wheels on the bike but you'll have to run a drum out back but you'll likely still end up lighter than the stock cast wheels. Cool as they look (I dig'm!) they are heavy wheels.
Anyway, don't mean to clutter up your post but I have tons of info on this platform if you're interested.
Some advice though if you care to hear....
Ditch the front end, it is marginal for a bike 100lbs lighter. There's a 'hinge in the middle' of the XS750/850 from the factory, one half of that hinge is the front suspension, the other half is the swingarm.
Something around 40mm works well on that platform, you can pick up a great front end off ebay for $100 or less. Obviously the higher end the better. A pal has picked up a small pile of CBR600's for teardown recently and the front end on that is outstanding. There are lots of offerings out there.
For the rear you need a couple things: first and foremost the swinger is flexible and needs to be braced. The other thing the bike needs is a little more length to the swinger to bias some weight up front, they are tail heavy. A Virago 700/1100 (twin shock) swinger will mate up to your engine/frame and pumpkin and is a touch longer. Brace that one with a bottom loop and you've done yourself a favor. You can also juggle rear end parts to get spoked wheels on the bike but you'll have to run a drum out back but you'll likely still end up lighter than the stock cast wheels. Cool as they look (I dig'm!) they are heavy wheels.
Anyway, don't mean to clutter up your post but I have tons of info on this platform if you're interested.
Juggernaut
Been Around the Block
We need a Swagger knowledge fund. For some bucks he can let us in on all the dirty secrets about the triple. I imagine he would be putting a lot down.
Swagger
Putting boot to ass since 1967!
No funds needed amigo! I need to compile everything I have on file (paper and electric), I've been collecting info on these and several other bikes I dig for years.
Let's see......quick and dirty:
900cc can be had by using 3 of 4 overbore pistons for the XS1100 and is good for 8-10hp alone in this engine so long as the rest is in good nick. If i remember correctly the final compression ends up something like 10.25-1 so a nice boost. The 850 heads flow better, both air and oil, but the response to porting is amazing if the job is done well. Even a general port cleanup and match with a blend of the bowls and stem protrusion will yield pretty astounding results. Ditch the stock carbs if you do ANY tuning to the engine, they both suck and blow...but not in the good way. mid-90's Triumph triple carbs slip right in and are FAR more tunable, flow better and are more forgiving of pods. Better still would be a rack of VM34s.
Cams can be had and there's not a lot of drama involved in running them until you get to REALLY high lifts, but really a 'mild' regrind does great things in this case with that little bit of flow work. The later electronic ignition system is nearly bullet proof and makes a good spark but add a dyna booster and some hot coils if you're going to runs cams and higher compression, it's just good practice.
Unless you are going insane building it, don't go any larger than 1.5" diameter primaries on your header, primaries should be around 30-32" in length. If you merge them (3-1) use the smoothest longest merge you can and keep your post collector diameter to ~2" too big and it won't scavenge, too small and it'll won't resonate. Obviously if you're tuning it to 10/10ths then you'll want to do some serious calcs for the ultimate exh. for your engine but the above worked well for me.
2nd gear will pop out if you're working it hard, it's fairly normal with these bikes and can be cured with the removal of a shim easily accessed with the side cover off. There's several great write-ups on the yamaha triples website.
Barnett and ebc both make great clutch packs that I've had experience with though I'm sure there are other good performance options available.
If yours started off as a 'Special' check the rear shocks, they may well be adjustable Konis and very worth rebuilding and running. I've seen these same exact shocks used on racebikes with a threaded body pressed over the original lower steel portion. They work well.
adendum: My 100% stock '81 850 standard would do a GPS verifiable 125mph though from 110 up you need a long run out to get there. With simple port work, a 3-1 and a the take-off carbs from my Triumph jetted to suit and getting rid of some useless weight it pulled that same 125 WAY quicker and could have gone a tick faster but I was running out of road.
Chain drive is relatively simple to do on these but does take some fabrication work.
Let's see......quick and dirty:
900cc can be had by using 3 of 4 overbore pistons for the XS1100 and is good for 8-10hp alone in this engine so long as the rest is in good nick. If i remember correctly the final compression ends up something like 10.25-1 so a nice boost. The 850 heads flow better, both air and oil, but the response to porting is amazing if the job is done well. Even a general port cleanup and match with a blend of the bowls and stem protrusion will yield pretty astounding results. Ditch the stock carbs if you do ANY tuning to the engine, they both suck and blow...but not in the good way. mid-90's Triumph triple carbs slip right in and are FAR more tunable, flow better and are more forgiving of pods. Better still would be a rack of VM34s.
Cams can be had and there's not a lot of drama involved in running them until you get to REALLY high lifts, but really a 'mild' regrind does great things in this case with that little bit of flow work. The later electronic ignition system is nearly bullet proof and makes a good spark but add a dyna booster and some hot coils if you're going to runs cams and higher compression, it's just good practice.
Unless you are going insane building it, don't go any larger than 1.5" diameter primaries on your header, primaries should be around 30-32" in length. If you merge them (3-1) use the smoothest longest merge you can and keep your post collector diameter to ~2" too big and it won't scavenge, too small and it'll won't resonate. Obviously if you're tuning it to 10/10ths then you'll want to do some serious calcs for the ultimate exh. for your engine but the above worked well for me.
2nd gear will pop out if you're working it hard, it's fairly normal with these bikes and can be cured with the removal of a shim easily accessed with the side cover off. There's several great write-ups on the yamaha triples website.
Barnett and ebc both make great clutch packs that I've had experience with though I'm sure there are other good performance options available.
If yours started off as a 'Special' check the rear shocks, they may well be adjustable Konis and very worth rebuilding and running. I've seen these same exact shocks used on racebikes with a threaded body pressed over the original lower steel portion. They work well.
adendum: My 100% stock '81 850 standard would do a GPS verifiable 125mph though from 110 up you need a long run out to get there. With simple port work, a 3-1 and a the take-off carbs from my Triumph jetted to suit and getting rid of some useless weight it pulled that same 125 WAY quicker and could have gone a tick faster but I was running out of road.
Chain drive is relatively simple to do on these but does take some fabrication work.
Swagger
Putting boot to ass since 1967!
His setup was clean but kinda chunky and somewhat spendy at $450 IIRC.
As to your question of worth.....that all depends on you and what you wanna do with the bike.
For 90% of guys building/riding one, it's probably not. If however you're BUILDING one then yeah it's pretty worthwhile. You stand to drop a good bit of weight as gain the ability to gear it how you like. As well, you lose the tail-jacking that can be a problem with single joint shafties making big power. I will say that my 'hotrod' made loads of power and I never felt like it was ever unsettled. For purely performance building though...chain's where it's at; you can pick and choose your wheels to suit.
As to your question of worth.....that all depends on you and what you wanna do with the bike.
For 90% of guys building/riding one, it's probably not. If however you're BUILDING one then yeah it's pretty worthwhile. You stand to drop a good bit of weight as gain the ability to gear it how you like. As well, you lose the tail-jacking that can be a problem with single joint shafties making big power. I will say that my 'hotrod' made loads of power and I never felt like it was ever unsettled. For purely performance building though...chain's where it's at; you can pick and choose your wheels to suit.
Juggernaut
Been Around the Block
thanks Swagger. Great info.
