650 swap to 750 or650/750

Heres the thing simply should I buy a bone yard 750 for 200 dallars and gain 10 HP by swapping out my 650 for the 750. Or should I throw the jugs and pistons on my engine hense 650/750. Or run my 650 till I can rebuild a 750 with a bore kit. How big can I go. What can I expect. I saw a post about this before but I cant seem to find it??? Also there was a post about step by step how to disassemble an engine. Lastly were canI get bore kits and how much they go for?

Wiseco will sell you a piston kit. APE Jay is a dealer for Wiseco, I am sure and perhaps Jeff at www.z1enterprises.com sells them. Perhaps other kzrider members are dealers selling them. Your question has been asked soooo many times I wish someone would write up an article on this subject. My take is that if there isn't anything wrong with your 650 engine, why upgrade? Looking for more power? Is your 650 engine running as well as it can? A good tune up can make a good deal of difference in power. Still not satisfied? Well, that $200 for 10 hp is about as cheap horsepower as you will come by... with properly set up carbs, airbox and pipes, you could get perhaps 15 or a tad more horsepower over a stock 650 which isn't all that bad... Once you start getting into the internal mods necessary to make big horsepower, you start adding to the cost of the bike quite a bit and it might be worthwhile at that point to consider just going to a larger displacement ride which offers the power you are looking for without all the extensive mods to your current ride...

if you look in the archives Dan6five0(old name) has a huge write up on this.

i was looking into big bore kits for my 650 but it's just not worth it. The kit from a store is about 350 i just found one on ebay that sold for 202! then u have to get the cylinders bored out which can be expensive.

if u swap over jugs and head, i believe the cam chain has some issues.

i would just drop the 750 and tune it up. make sure the valves are adjusted, carbs sync'ed, etc.

Thanks Derek for the mention.

Its pretty easy to swap the 750 in, bolts right up to everything. My problem was the wiring but it wasnt that bad, I made a bigger mess out of it than needed.

You can click the blue bike in my signature to get to the thread I had going about the bike.

Hi Wiredgeorge. I'm one of those guys searching for more info on the 650 upgrade and I have noticed the increased buzz on this topic in KZR. I say bring it on...the more guys we have digging for details the more info we will all have to draw from in making our maintenenance and h.p. upgrade decisions.

You are right about someone putting together a detailled overview of their 650/750 project. In fact there are a few in the archives already. Perhaps we should even have a performance engine upgrade topic added to the forum for those looking for specific info on this obvious segment of interest for all KZ's.

Thanks in great measure to the archives and member's input (including your own carb recommendation wisdom) I have settled on one more step-up from my 700 Wiseco kit- A Kz750 bored to 810 with bigger carbs in addition to the other uprgrade goodies I have already done.

Your point of a properly tuned 650 is definitely right on the mark in line with all of the other solid, valid advice I have read from you. There are probably a lot of KZ650's running around in less than ideal condition-carbs-ingition etc. Some TLC from an experienced KZ tweaker can go a long way to raising the bar on hidden h.p. This is no doubt less expensive than getting into the innards of the powerplant. In fact your jetting advice this past summer helped turn my 650 from a panting dog into a greyhound.

But with respect to just picking up a bigger bike, this is something that I am not considering. I'm 180 lbs, 5'11" and for me the 650 is the perfect size bike for me. I've driven lots of bigger bikes including Kz900/1000 and GPz 1100 and even a CBX (I traded it for an MGB-go figure!) Nothing feels as right for me as my 650 chassis. It's lightweight, great handling and packs a solid middleweight punch like Sugar Ray Leonard in his prime. For a bigger rider, the 650 might not cut it, sizewise or powerwise.

A correctly tuned, performance-built 650 should be able to run and maybe outrun a lot of bigger stock bikes in a straight line. But even in properly tuned form this would be a stretch for even a strong running stock 650 (unless you have the skills and body weight of Pee Wee Gleason-I have neither.) All things being equal, there is no replacement for displacement-right?

It is much easier and cheaper to build up a 650 that I already own, rebuilt and have kinda grown attached to as opposed to starting over again on a bigger bike. There is a lot to be said for a little sleeper that has the ability to wake up other bigger bike riders who look at the 650 numbers on the side cover and sneer...that is until you light 'er up and leave 'em behind!

Thanks again Wiredgeorge for all of your advice. You and some of the other regular, experienced posters have helped us KZr members a lot more than what you may think. When we ask (sometimes stupid) questions we rely on the advice of other members who help build this incredible resource tool we depend on to keep the marque alive and strong.

Cheers-Colin Firth Ontario-Canada

A GPz750 motor into a KZ650 is just a little more hassle, but provides an extra 11 hp over the KZ750 motor. I think the ideal combo would be an 810 fitted GPz750 motor in a KZ650, it would be cool to pull up next to a stock KZ900 or KZ1000 at a light then proceed to blow it away :laugh: :laugh:

I think Mark Wing has some experience with doing that

You're right Steell. That's the probably the best combo to go with. The only downside (from the sleeper angle) is that other KZ guys might recognize the missing mechanical tach gear and the different shape on the GPz jug's cooling fins. Aren't the GPz fins a little less rounded than the Kz750's cylinders?

How about this combo gang??? ...810 Wiseco kit, bored out Kz750 jugs, 750 intake valves, upgraded valve springs, Gpz intake cam , Kz750 exhaust cam-with factory tach drive, 650 cam sprockets as to retain original style cam chain, a milled and ported 650 head which has smaller combustion chambers, 34Mikunis(?) set up by our resident carb pro Wiredgeorge and a header pipe?

Get this combo turning a 14 tooth sprocket with a new chain and Barnett clutch and I think you might really have created an 1/8 mile ripper there-wouldn't you say?

This is the combo I've started collecting parts to build. Still looking for Kz750 jugs and maybe the GPz intake cam-any spares lying around out there?

Cheers-Colin Firth-Ontario Canada

Post edited by: reborn650, at: 2006/01/03 21:16

Reborn I think I like your style.
What would missmatching the cams bring out in the engine?? I herd from a guy on hear that the gpz cams have more top end (longer duration). Whjat will mixing that with a older exhaust cam (shorter duration) do?
What needs to be done with the 650 head to accomadate 750 valves??
I wonder what would happen if some one were to put the stock 650 head on a 750???? using the 750 cams of course:huh:

Thanks Snakebyte. I just got back from the big Toronto bike show with 500 exhibitors.

I will defer to Stever Darlington's experience to answer your question. By going with the Kz750 intake valves I will have to trim 0.015" off the top of the valve stems according to Steve who has tons of experience hopping up 550/650 and 750 Kz's for his vintage racing. I have already picked up the valves and GPz springs from Steve as well as the cams. I will be swapping my 650 cam sprockets onto the 750 cams and this will allow me to stick with the stock cam chain set up which apparently picks up the revs quicker than the heavier Kz750 cam chain. Of course, when I get into the case to accomodate the bigger cylinders I will inspect the cam chain at that time.

The Gpz cams are hotter than the Kz750 cams (a little more lift) but I have read that they move the power band up higher, losing some of the bottom end grunt, which I want to keep. I figure the 810 c.c. kit, shaving the head, bigger valves and putting on bigger carbs will make up for the low/high powerband discrepency between the Kz/Gpz intake cams. With the head shaved and higher compression pistons on the Wiseco 810 kit I am pretty sure I will be moving the pistons slightly deeper into the combustion chambers. I want to make sure that the valves aren't banging into the piston crown whcih is more likely to happen with the Gpz intake cam.

For me the only choice for the exhaust cam is the Kz750 which will allow me to retain the stock mechanical tach drive, unlike the GPz exhaust cam which would reqire the hooking up of an electronic tach.

I am sticking with the 650 head which I had already ported and lightly polished according to the experts (who have detailled in a paper) where and how much metal to (carefully) remove with a die grinder. I had a Kz racer friend of mine babysit me last winter when we were building this motor with the 700 Wiseco kit.

I learned from my buddy that getting these things to a mirror finish is a common mistake by some modifiers. It is best to leave a somewhat abrasive finish as to encourage good air swirl.

The 650 head has smaller intake runners and combustion chambers than the 750 head. From advice on Kzr other modifiers have posted that this head gives better intake velocity and slightly higher compression. In the world of performance this usually equates to more torque and power. Additionally this head choice will also retain the stock appearance in case I get an experienced Kz junkie who goes over my powerplant with a fine eye for detail. Of course I will have to figure out a way to affix the 650c.c. casting onto the 750 jugs.

Cheers-Colin Firth-Ontario Canada

Hi Guys,
My '79 650 has a 750 barrel with 810 kit, andrews #20 cams which are hot street cams (slightly hotter than the '83 GPZ750 - the uni trak model -, which I believe has the hottest cams of the 650/750 range) flowed head with gpz750 valves.
I have fitted the fuel injection system from a gpz1100 to the bike and am in the initial stages of tuning. I havee just got a diy tech edge W/B 02 kit that I must assemble that will make tuning much easier. If you have an early 650 you have to open up the top case for the 750 liners but if you have the later 650 ( Iknow that the model with the Hyvo cam chain they fit straight on). Hope this info helps

Cheers

DAve

Hey all! Complete novice here. I have a 77' KZ650B motor sitting in a modified 650C frame, seat was dropped about 2". First bike and I found the bike pretty powerful, considering I am 6' 2" and about 292lbs. Can anyone point me to the threads with the basic power increase info? I want more power but am not a super wrench. Thanks!

1977 KZ650B