650 engine mods

I know, I need to get the XJ CD. I do plan on getting it, just haven't gotten a chance yet.

Anyway, if what I've read is correct, the 650 can be turned into a 750 with 750 rods/crank/pistons. Now, I read somewhere else that the 900 is simply a 750 with a big bore kit. So, here's the big question. Can I safely take my 650 up to a 900? Or will I have to find a set of 900 jugs (if they have thicker sleeves or something). I've done a big bore kit on a GSX-R 1100, and I believe I took about .100" or so out to make it a 1297 (I run a machine shop). I just don't have any of the specs on the bore and stroke of the three motors. Can someone enlighten me please?

Also, where can I get pistons for these motors? I've seen several sets of 750 rotating assemblys go for cheap on ebay, but they don't include the pistons, and I've been having trouble sourcing new ones. Guess I could go to Yamaha as a last resort.

 

I have no idea, but the 650-750 is the only one I've heard. I don't think the 750 and 900 are upgradable that way. Pretty sure the bottom part of the engine block is different.

 

... and if they were it would probably be cheaper just to bolt a complete 750 or 900 into the 650s frame. ( See if you assume the bottom ends are the same then why not just use the bottom of the larger displacement engine in the first place)

650 to 750 might be possible... of course it's the subtle differences that will be the problem you'll get into when you do it.

 

All I have been able to find is for the 650 and 900.
650 bore and stroke 63mmx52.4mm
900 68.5mmx60.5mm
I could not find the 750 specs right now.Might want to check out the link section. It has a technical site that lists the bore, stroke, hp and torque values for a lot of the xj series.
Hope this helps.

 

Bore and stroke on a 1981 750 Seca is 65.0 x 56.4 mm
Compression ratio 9.2 : 1

 

Thanks for the help guys, I'll do some more research. The reason I'd rather build it myself is because I want to get some more experience working on motorcycle engines. I have a full machine shop at my disposal, and I have a hard time bringing myself to swap junkyard motors into any of my vehicles.

Sick, I know...

So anyone know a good place to get new internal engine parts? Bearings, rings, pistons, etc...

 

Where would I find the upgrade kit for this improvement? I have a 1981 XJ650H. Sounds like wintertime fun!

 

650 turbo bottom end will take a 900 crank with no modifications, but the rods will have to be bolted up with the bolts reversed to clear the cases. I would think the cases for the non-turbo 650 would have the same clearances. 650 turbo cases are the strongest of all the Secas (lots of extra webbing). 900 barrels will fit with some relieving with a dremel tool for the larger barrels. Anecdotal stories have mentioned 130 rwhp with a 650 turbo and 900 top end. Personally, if I was wanting more power I'd just drop in a complete 900 Seca engine and be done with it. Don't know what a turbo 900 would do. Still dreaming of a turbo Maxim X.

If you need XJ specs in a hurry, go to the German XJ riders group board XJ-IG site mentioned in the links section.

 

Thanks, that's definetly some food for thought!

130 whp! 8O 8O

If I happen to find a 750 or 900 motor for a decent price, I probably will pick it up, but they seem to be somewhat hard to come by. I have however seen the 750 rotating assemblys on ebay, which is why I asked. The 900 was only made for a few years in the US, right?

 

The thing is - if you seriously only wanted the horsepower - it would be cheaper to buy an early 90's sportbike. Even the mid to late 90's are getting to be dirt cheap.

Ok - I'm not suggesting that as the solution, as a higher powered maxim would be fun - however - if the goal is simply power (and not to create a sleeper) then I'd suggest a newer bike

That being said - I did go up to a bigger horsepower bike and I just got bored. ( This is where I can understand the more power in a maxim being of interest)

If I cruised the backroads on a sportbike I'd be bored. They handle so well that the speed limit is a snooze. So I did what any young male would do - ride until it felt fast again - ride until it felt as fast as it did on my maxim. Now I never got a speeding ticket doing this - but I came to realize that this lifestyle wasn't going to work in the long run. I wouldn't say I was a true calamari - but I would say that at the speeds I went to have fun that I didn't have a chance in stopping and that I would certainly be loosing my licence if I was ever seen.

So - my solution - keep the maxim and enjoy the lack of power ( not really a lack as we're still talking better than average car power ) and enjoy the weight of it's handling. Now I ride the maxim at sane speeds, feel like I'm flying and am proud that I'm riding this '24 year old dog' with the big boys... and having more fun than they are humping their gas tanks.

Oh sure - I'd love a TL1000R or a VTR for some fun twisty riding once in awhile - but if I owned one of those bikes again it would be a track only vehicle.

A tangential rant - but sometimes bigger isn't better... Hell - I'm considering going back to the 250 because really - only a real man can flog a 250 at race speeds... Seriously - that bike is a hoot because you really do have to ride it... and that's fun.

Woot.

 

I've ridden a Ninja 250 on several occasions - fun, fun bike!

In fact, we have several in our fleet where I teach. I have to be careful not to do stoppies in front of the students! :twisted:

 

lol - Dean you're an under cover squid

Anyone seriously considering a long distance ride -- I mean AZ is a long haul from here but if we're talking half way???

Maybe we can all ride some 250's...

Cheers,
woot.

 

The 900 was a one year only model here in Canada, probably in the US as well, but they soldiered on in Europe up until 93, when they were replaced by the 900 Diversion. They eventually got the larger fairing of the XJ750RL in Europe, as well as a slightly bigger motor than the 853cc engine we got over here.

I guess they didn't sell too well, as they came out the same year as the 750 Interceptor, which would certainly clean its clock performance wise (although the 900 didn't eat its top end, but that's another story...)

 

I have to agree with woot, I think you can only do so much before it's just not practical anymore. From what i've found out, puttinf a 750 into a 650 is not that difficult but the amount of proformance you will gain is not a whole hell of a lot. I personally would just go with a differnt bike

 

I think what you guys aren't understanding though, is I can't AFFORD to buy a newer bike, as much as I'd like to. I can do all the motor and machine work myself, and plan on doing all the rest of the work to the bike myself as well. Even if I have to rebuild most of the entire bike, I'll still have a basically brand new machine for less than I could even get a heap of a newer one. And as far as the engine mods go, I'm a hot rodder at heart, and figure as long as I'm going to be doing internals, why not upgrade? Won't cost much more.

And, just as an update, I bought an entire 750 rotating assembly and XJ900 cams to go in it when I rebuild. The 750 rotating assembly I bought for less than a new set of oversize 650 pistons would have cost, so I still get to start out with a nice fresh bore, and increase displacement for less than the cost of a stock rebuild.

 

sounds good... keep us up to date with this project...

as for myself? I found a zx7r for < $2000 US that is tempting me to no end... with a bit of paint I could flip it, or keep it as a second bike. Not at all the bike I'm looking for for a primary bike (hence the hesitation to buy it)

 

And what is wrong with squids Woot? Hummm? (you'd never notice me).

 

I like calamari, if that counts for anything? The sportier the bike you ride the harder it is to have 'fun' legally.

The 7r is a fun bike.... but it's not really a touring bike. I think everyone should ride one when they're ready... closed track and just get a feel for it at low track speeds.

 

Got good calamari down here at a place called Neptunes Net, just down the road on the Pacific Coast Highway. It's a little seafood (really?!) on the shore just above Santa Monica. Great fresh stuff, little pricey, but good eats. Perfect place to stop after comming down off of Muholand Drive (half a mile south of there). I understand you like to drag a peg or two through the twisties, yes? Do drop in!

 

Joel07 glad i read all the posts on here this time my current bike (82maxim 750) has 900cam's in it and is jetted up all though at about 65 if i pull the throttel all the way back the bike starts to flud i think the jet's that were put in it are 2 big all though i dont know what theay are and dont want to tear it all the way down i cyfan through all the paperwork i got witht he bike when i get it this week and try to give you some info about what parts were put on mine if any one dose know i would also like to know how big you can bore a 750 or what are the biggest jug's i can put on their with my head assembly.


I my self am looking at turbocharging the bike to get the added air needed for the jet up and some chrome turnout's id like to see what info you have found maby we can help each outher out with specs or ever one can relly help with specs as like you joel07 i have the time and tool's and knolage to do every thing just not spec's on what is theroticly possible

 

Problem with turbocharging is to do it properly, you really need a set of sealed carbs, like what come on the Seca Turbo, or do a draw through setup, which has it's own unique problems. If you're seriously thinking about going turbo, I would look get "Turbochargers" by Hugh MacInnes, or "Maximum Boost" by Corky Bell. "Turbochargers" has a little bit more info on carb'd turbo setups since it was written in the '80's, and actually has a short chapter on turbocharging motorcycles. There was also a book I saw in the Dennis Kirk catalog about turbocharged/supercharged/nitroused bikes, but can't remember the exact name of it, and I've never read it.

Anyway, the simplest and cleanest method of turboing this bike IMO, would be to get the complete setup off of a Seca Turbo. Love the way they routed everything to make it look nice and clean, can't even really tell the bike is turbo'd by looking at it. There was a complete turbo setup on ebay last week, it must have ended though. It was up to almost $200 when I saw it.

 

ya i talked to a guy in lacross that put nitrous turbo's and so froth on bikes and he said the only real problem is getting a pressurized carb or rebuilding the one that's on the bike he said easyest way would be to get the hole seca turbo carb setup or he said if i wanted to be the first or among the few to fule inject it and he gave me some stuff to read and fule injecting the bike would be nice but would envaluve a lot of work and some chunk of change

so i have decided to find a set of carbs for the bike and rebuild them in my spare time. working on getting a exaust manifold for the bike and the parts needed but short on monney for now so just getting info

im still with you joel07 i could go buy a really fast crochrocket for around $2k or i could stick about 800 into this one and have a more comfeterbil ride and have one heck of a sleaper and this way i can have somting to do in free time and somting to take to a bike show

 

I bought my seca 650 with the 750 motor all ready in it. I'm actually not all that impressed with it's performance and am probably going to put the stock 650 back into it(it came with the bike). The first Seca 650 I had seemed as fast if not faster....but that could be my alzheimers kicking in. I know I am not impressed with my 1/4 mile et's at Infineon with it. It is extremely consistent though; rareley deviates more than .05 seconds all night.

 

I guess some just don't get it. I understand completely. Anyone can go out and buy stuff and bolt it together (if you have the money) And then there's some of us who'd rather make stuff work for us. I think your alot like me in that you get the satisfaction out of making/fabricating things and making the necessary changes that work for you. I was always one who could never leave things as they are. I have alot of respect for those who insist on doing things like you do. Building engines is a great hobby and I'm all for it.
I hope your plan works out for you. It looks to me like your doing your homework and I'm sure you'll figure it out.

 

The only money I have to put into these bikes of mine ... gets exchanged for the gasoline needed to make them go.

Her Majesty is watching me like a Raptor needing a fresh kill to nourish a nest full of fledglings.

Like the Rainbow Trout that rises to investigate the disturbance of the streams surface tension, hoping for an insect ... unaware of the Bald Eagle soaring just above the trees; swim out from the shadows and become airborne in one fell swoop!

 

Okay Guys/Girls
I have owned 4 Turbo Bikes over the past 24 yrs. (3) Seca and (1) GPZ 750. I know that there is mad power in the 650 w/just a few mods such as an open air filter directly installed on the turbo. The next is a slip on or an aftermarket/stock exhaust from a later model motorocyle. This will enhance the the turbos spool capability. The best/ most rewarding mod is a bigger turbo. The T3 is the smallest turbo ever installed on a factory engine. (Car or Cycle) A T3/T4 Hybrid or a GT25/28 would prove satisfactorily with some mods. (i.e. Header, flange, intercooler.....) The overall performance of our "XJ's" is the way they are put together. Not everyone has access to a SECA 900 to build into a turbo beast. So most of us need to "Run what ya brung"! If a boost controller or BOV helps by all means spend the money. I will say this. The stock Turbo 650 will make 90+hp after 6k rpm. If you put on a direct intake air filter and block off all vacuum lines and disconect the waste gate valve, the stockk turbo will hit 15 psi all day long. This in turn hits the surge box wich has a 15psi BOV built in. My assessment is to add a BOV that will blow at 18+ and then you will defenitely make power from there. The Seca Turbo is a sweet machine with room to grow. It is capable of 200+ rwhp if built right. Lets see who does what from here on out.

 

My Turbo makes ~94rwhp @ 7800 rpm @ 17psi. It is running my own BOV, a working wastegate, an upgraded compressor wheel. I have a water injection system in the works.

And a 900 donor motor sitting at Rick's house (the shipping frame is almost ready Rick !!) as well as the bits for a Megasquirt EFI in the works.

Time is certainly at a premium with the other project going but eventually I'll stop modifying and call it good.

 

200+ rear wheel HP out of a 25 year old shaft drive 650?

That ain't gonna happen....

 

You have that right.

 

For those that have the itch, that only a turbo parts bike can scratch,
mine is for sale. PM me.

 

L&L Cycle in Dallas has a 650 turbo bike they would really like to get rid of... It looks like it is all there too...