I was wondering what you guys are doing with the 750 kit, are you adding a cam? anything with the clutch? welded crank? larger capacity oil pump? any info is useful as in the future I will be wanting to do this mod to one of my engines on the bench. xsjohn feel free to weigh in heavy here and any other engine guru. thanks guys
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750 Big Bore kit questions?
- Thread starter bigpup
- Start date
It woud be 8-1 if it were mine.........and the cam could well make it sound like a can of marbles....and make it have to rev more.....with the ole pressed crank .
.....the mind is a terrible thing when thinking about building one of these..........and reality later is never what was expected.....guess it really only matters on how far you want to get down the road.....and then again 99.9 percent would disagree with me as usual................
xsjohn
.....the mind is a terrible thing when thinking about building one of these..........and reality later is never what was expected.....guess it really only matters on how far you want to get down the road.....and then again 99.9 percent would disagree with me as usual................xsjohn
Stock cam is not going to wake up the 750 kit. My choice has always been megacycle; of these 3 cams, (if this is your first build) I would go with the 250-20.
(1) 250-00 .420" 272° 110° OK with stock pistons & guides. Valve springs 103-Y 26 btc/66 abc .006"
.420" 272° 104° are recommended. Improved mid-range power. 60 bbc/32 atc .006"
(2) 250-20 .415" 250° 104° New all around street cam. OK with stock pistons & 21 btc/49 abc .010"
.400" 246° 104° guides. Springs # 103-Y recommended. Improved 47 bbc/19 atc .012"
mid-range power.
(3) 250-30 .440" 271° 103.5° Use modified pistons and springs #103-Y. Best all 32 btc/59 abc .005"
.440" 271° 103.5° around "torque"cam. Great throttle response and 59 bbc/32 atc .007"
strong top-end pull. Guide modification needed
My advice would be to stay away from MikesXS performance cam. Made in Taiwan, inferior product from all reports; as are a lot of Mikes XS parts; Don't go over 10.5 1 CR, unless you plan on rebuilding the top-end once, maybe twice a year depends on how hard you flog the motor. Make sure the rocker-arms are in spec.
Get the head ported. There are a few people out here that know how to make an XS head work. Run 34mm Mikuni round slides with spigots . Run Ampco valve guides (bronze) Buy good valves (kibbelwhite) Buy good rods; I run Falcon knife rods. Have the crank balanced/welded. Stock oil pumps seam to work well for most (although I don't rum them in my motors) run an oil cooler (your motor will love you long time. Buy a good ignition. MZ-B
Build a good clutch package.
Last but not least; cut/grind off, all the bullshit on the frame. They are heavy. Use fiberglass wherever you can. Put good brakes on it. You'll either go up in flames or live to tell your grandkids just how fast that old XS was........ hay, its a XS 650 Yamaha. they are cheep and everywhere. Go for it; life is too short NOT to build fast motors.
OR...... you can half ass it and be a pissed off old fuck riding a low CR motor talking bout how many miles to a gallon you get.
(read;Buy a Vespa, whatta hoot)All true.
BigJimmyW13
XS650 Guru
Stock cam is not going to wake up the 750 kit. My choice has always been megacycle; of these 3 cams, (if this is your first build) I would go with the 250-20.
(1) 250-00 .420" 272° 110° OK with stock pistons & guides. Valve springs 103-Y 26 btc/66 abc .006"
.420" 272° 104° are recommended. Improved mid-range power. 60 bbc/32 atc .006"
(2) 250-20 .415" 250° 104° New all around street cam. OK with stock pistons & 21 btc/49 abc .010"
.400" 246° 104° guides. Springs # 103-Y recommended. Improved 47 bbc/19 atc .012"
mid-range power.
(3) 250-30 .440" 271° 103.5° Use modified pistons and springs #103-Y. Best all 32 btc/59 abc .005"
.440" 271° 103.5° around "torque"cam. Great throttle response and 59 bbc/32 atc .007"
strong top-end pull. Guide modification needed
My advice would be to stay away from MikesXS performance cam. Made in Taiwan, inferior product from all reports; as are a lot of Mikes XS parts; Don't go over 10.5 1 CR, unless you plan on rebuilding the top-end once, maybe twice a year depends on how hard you flog the motor. Make sure the rocker-arms are in spec.
Get the head ported. There are a few people out here that know how to make an XS head work. Run 34mm Mikuni round slides with spigots . Run Ampco valve guides (bronze) Buy good valves (kibbelwhite) Buy good rods; I run Falcon knife rods. Have the crank balanced/welded. Stock oil pumps seam to work well for most (although I don't rum them in my motors) run an oil cooler (your motor will love you long time. Buy a good ignition. MZ-B
Build a good clutch package.
Last but not least; cut/grind off, all the bullshit on the frame. They are heavy. Use fiberglass wherever you can. Put good brakes on it. You'll either go up in flames or live to tell your grandkids just how fast that old XS was........ hay, its a XS 650 Yamaha. they are cheep and everywhere. Go for it; life is too short NOT to build fast motors.
OR...... you can half ass it and be a pissed off old fuck riding a low CR motor talking bout how many miles to a gallon you get.
All true.
Well alrighty! You lost me on wake up the 750, but welcome to the site anyway!
Sundie
Jabroni
Not really. Unless you type really slow.
But it *is* two different ways to look at it. High speed/performance vs longevity. hey, i personally accept both of them and hope to end up in the middle somewhere.
I don't play the devils advocate very well...........getting old I guess......maybe my problem is I just ride too much....and my small fairing lets me hear everything.....the less I hear the better I like it.......my son just screwed up his dirt bike by hoping it up........now he is hopping it up some more............xsjohn
....xsjohndrog
XS650 Addict
I'm just curious 0u812,exactly what kind of issues have you had,or "heard about" with Mike's cams? They have been in production and sold for a few years now and this is the first time that i have heard that they are not a good product.Jerry Heiden,of Heiden tuning uses them,so i think if there was a problem with the quality he would have made it known by now.I am building a 750 engine,(complete kustom frame,etc.), with this cam in it for a customer,so would appreciate any info on this that you may be able to provide.Thanks.
drog
XS650 Addict
I forgot to add that Mike's cam is the exact same grind as Megacycles.
Stock cam is not going to wake up the 750 kit. My choice has always been megacycle; of these 3 cams, (if this is your first build) I would go with the 250-20.
(1) 250-00 .420" 272° 110° OK with stock pistons & guides. Valve springs 103-Y 26 btc/66 abc .006"
.420" 272° 104° are recommended. Improved mid-range power. 60 bbc/32 atc .006"
(2) 250-20 .415" 250° 104° New all around street cam. OK with stock pistons & 21 btc/49 abc .010"
.400" 246° 104° guides. Springs # 103-Y recommended. Improved 47 bbc/19 atc .012"
mid-range power.
(3) 250-30 .440" 271° 103.5° Use modified pistons and springs #103-Y. Best all 32 btc/59 abc .005"
.440" 271° 103.5° around "torque"cam. Great throttle response and 59 bbc/32 atc .007"
strong top-end pull. Guide modification needed
My advice would be to stay away from MikesXS performance cam. Made in Taiwan, inferior product from all reports; as are a lot of Mikes XS parts; Don't go over 10.5 1 CR, unless you plan on rebuilding the top-end once, maybe twice a year depends on how hard you flog the motor. Make sure the rocker-arms are in spec.
Get the head ported. There are a few people out here that know how to make an XS head work. Run 34mm Mikuni round slides with spigots . Run Ampco valve guides (bronze) Buy good valves (kibbelwhite) Buy good rods; I run Falcon knife rods. Have the crank balanced/welded. Stock oil pumps seam to work well for most (although I don't rum them in my motors) run an oil cooler (your motor will love you long time. Buy a good ignition. MZ-B
Build a good clutch package.
Last but not least; cut/grind off, all the bullshit on the frame. They are heavy. Use fiberglass wherever you can. Put good brakes on it. You'll either go up in flames or live to tell your grandkids just how fast that old XS was........ hay, its a XS 650 Yamaha. they are cheep and everywhere. Go for it; life is too short NOT to build fast motors.
OR...... you can half ass it and be a pissed off old fuck riding a low CR motor talking bout how many miles to a gallon you get.
All true.
All true
If you want to increase the displacement that's fine but if it were me I'd forget about cam swapping and focus on head where you'll see the most gains for the dollar,period. The head is the key to plus performance,regardless what engine it is. The intake ports are some what oversized and with some filling to reduce port volumes to about 75CCs will yield excellent gains in the low lifts to pack the cylinders when combine with low lift cams. If you wanna swap cams, forget about Megacycles and dial in a Shell #1 or the stock 256 cam,either one will provide better street ability in the low to mid power range. As for valves forget the Kibblewhites and get the virago 750 valve and cut'em down to STOCK XS 650 dimensions for the thicker valve margins to aid in reducing resistance as the flow makes the turn to the cylinder and for a slight increase in CFM's. Good luck and choose wisely for the perfect combo.
yamaman
xs650 addict
- Messages
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Bigpup, my bike was 650cc when I got it. Std cam & valves, VM carbs, seems to be very slight polishing on the ports. All in all reasonably standard. When I realised my bores were kaput, I bought a set of jugs that had already been sleeved & a pair of TX 750 pistons, bolted it up & it's run beautifuly ever since! Less vibes & a lower note for sure with the bigger jugs. Quite possibly should have been 750 from the start!
Sundie
Jabroni
Jack: i'm with you on the 256 cam - the only part you probably should have mentioned is that it's not a direct swap in for the 477/533 motors - you'll have to press the gear off and put a 477/533 one on.
Yamaman..........relooked the xt750 pistons thing....somewhat flat topped....betting your compression ratio is less than 8-1 .....smooth as you said....did we ever decide what Toyota engine that might have a match for them........?
xsjohn
xsjohn
yamaman
xs650 addict
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Toyota search was fruitless John. Need to scour a wreckers for 80mm pistons (or even 75mm I guess). Do some side by side comparo's.
Looked into again myself, mine must be the pistons shown in those earlier posts (that I denied). Small dome on a flat top with small valve reliefs.
Looked into again myself, mine must be the pistons shown in those earlier posts (that I denied). Small dome on a flat top with small valve reliefs.
drog
XS650 Addict
Hey ou812,i'm still waiting for the info from you about Mike's "inferior" cams,whats up? I honestly need to know if there is really something faulty about them before we put this engine together,or were your comments just heresay thrown out here just to be negative about one of Mike's products? Before this i have not heard anyting bad about them.Thanks.
