What kind of bhp available from a simple big bore setup?

Jake68 · 650Rider Supporter Joined: Mar 23, 2007 Posts: 841

Guys,

I am slowly putting together the parts to make a big bore motor for next year. To give me more cruising power and punch. Being able to cruise comfortably at 80 plus would be a real bonus as I plan to cover some distances next year...

I was planning standard 38CV carbs, free flowing exhaust, cam (perhaps you can recommend one for my purpose?) 750 kit on a 447 motor, with uprated oil pump and side oil cooling...perhaps a high performance rod kit. And a fresh crank. Perhaps you think a carb swap is a must also?

Do you think my wishes are realistic? And what kind of bhp would I expect from such a setup? Knowing this might give me an idea based around the power output and weight of more contemporary machines ..

Thanks Guys, hopefully it sponsors some good discussion as well Wink

yamaman

re sleeved mine for 80mm bore, used XS 750 pistons, straight in no worries. Just another option instead of wyseco. Not sure what HP gains, does go harder though for sure!
I would be interested what the weight of the HP rods is compared to std (they look heavy). Std rods in good nick are good enough unless you realy start pushing up the HP.
Std carbs means you can use std air box, so not a bad idea.
Probably save the cam $ and spend it on a bit of port work, easy to change the cam later if needed.
A bit of good reading for you here!
Cheers

www.xs650.org.au/improving.htm
www.xs650.org.au/tech_minton.html

Jake68 · 650Rider Supporter Joined: Mar 23, 2007 Posts: 841

Good Links mate Smile

So you used pistons from a triple? ..Did you do this with a 447 crank motor? This sounds interesting, also wondering where you got the pistons?

I guess you mean TX750 Pistons?

yamaman

Ahh roger, TX 750 pistons!

Jake68 · 650Rider Supporter Joined: Mar 23, 2007 Posts: 841

where did you get them from yamaman, original Yamaha?

yamaman

Yes, yamaha pistons. Got them off Peter Kommer. You can find him off the links I put up earlier. He supplied minus rings, I got chrome rings from repco to suit. You might prefer Moly or Iron. I think if you got from Yamaha they would be chrome
Yamaha ring part #'s
341-11610-11...1st o/s...TX750A
341-11610-31...3rd o/s...TX750A

Yamaha piston part #'s
341-11635-01...1st o/s...TX750
341-11637-22...3rd o/s...TX750

books.google.com.au/bo...t#PPA96,M1

Jake68 · 650Rider Supporter Joined: Mar 23, 2007 Posts: 841

Did these pistons go onto a 447 crank with 20mm wrist pins? and without any other mods?

yamaman

I dont recall gudgeon pin size (I will have a look at the old pistons next time I'm in the shed), but yes std 447 motor, no other mods. I dont recall clearance measurements but it all goes fine!
ake sure bores are done by a quality shop!!!!!

Also would be interested to know the weight difference between the Wyseco and Yamaha pistons!

One day I shall write in the book I have to record such things!!!!!!

yamaman

Not saying there is any drama with Mikes set up, just more than 1 way to skin a cat!

Like I said earlier, I'd like to know the weight difference between the Wyseco and Yamaha pistons, as well as the weight dif between the heavy duty con rods and std!

Jake68 · 650Rider Supporter Joined: Mar 23, 2007 Posts: 841

447's have the 20mm pins!...

I guess I'd need the pins from the TX750 as well..

ALthough you need machining work the megacycle setup looks VERY good value at around 400 US$

xs1961

Stick with the Wiseco kit Jake, its a straight forward ,cheap & lot less hassle ..Ive had three of them & would reccomend them over my 840 any day due too the ease of fitting & access to spares

Jake68 · 650Rider Supporter Joined: Mar 23, 2007 Posts: 841

The Megacycle deal is a Wiseco kit mate, they come complete with the spring kit and cam for 400US..just needs maching ...thats gotta be a good deal..

xs1961

Yeah,I had a couple from Megacycle..Speak to Barbara there ? - shes helpful..
Sometimes Sportingforless or Speedmoto flog the Megacycle Wiseco kits for less than Megacycle do ! Pity you missed mine on Ebay in June, full kit INCLUDING liners fitted & bored for £275 !! I shoulda kept it.. Crying or Very sad

Jake68 · 650Rider Supporter Joined: Mar 23, 2007 Posts: 841

I know geezer I was gutted...after my bores were mic'ed up it turns out they are OK...I am just gonna make the most of it until new year, later spring ...and try to get together some performance bits for another motor build around then..

xs1961

Same here..The missus & kids are bleeding me dry at the moment..bad year for my projects.. Crying or Very sad

xs1961

Yes, the sleeving & boring cost me £100 & that was done by an engineer mate of mine ! Shocked

Personally I'm going for Mikes 750 kit next year ( with my 533 rods probably) it may cost a bit more but I cant resist the look of those wide-finned barrels !

Jake68 · 650Rider Supporter Joined: Mar 23, 2007 Posts: 841

Yeah, I gotta say the big bore fins are almost as attractive as the big bore barrells and pistons Smile

The pistons "look" great quality, but I doubt they can rival wiseco? Or am I being too loyal..

I had a kit of theirs fitted by a previous owner in a Honda 4, and it was much much quicker than the standard bike I road at the time..and it was the only mod. The guy who had it done kept the old barrels as well for spare..quite an attractive prospect..

xs1961

Ive never had ANY issues with Wiseco pistons/kits , Ive used them since the late 1970's in GS1000's, GSX1100's , Kwacker Z1000 etc. great quality.
It really is the look of the barrel on mikes kit that I'm after, bit like the Morgo barrels we used to fit to bonnies..
Jake, did you know you can get the same( XS)Wiseco pistons over here ? My mate fits the identical slug to his racing BSA singles & to a big Kwack four !
Buy the liners from the L.A. Sleeve company & gaskets from650central & you save a few bob there too..

yamaman

It's all good 650skull Wink

I agree, Mikes kit looks great, in value and appearance.
Will probably go a set myself eventualy!
I wouldn't have known about the TX pistons except they were all I could get when I needed them in a hurry. They do work well. Just another option is all, more the better.
750cc is a good size for these engines (the 840's seem to have a few dramas), I must say, as others have told me, the engine (running open rev cone mega's) definatley sounds quieter in 750cc guise. Perhaps a lowering of frequency with the bigger jugs???? Anyone else notice this??

xs1961

Definitely , my 650's are a lot harsher than my 750/840's !

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Yamaha xs650