XJ650 Revival

OK here we go I have owned this xj for 24 years and not ridden it for around 10years, it has around 300,000 Km on it and I used it as a courier bike in Melbourne in the late '80-early '90s averaging 200Km a day, and gave it a floging on weekends too, so its tired, i could feel the motor nipping up last time i went on a ride but it got me home and has been siting in the shed since then, i started it up a couple of months ago without to much trouble but thottle response below 3000rpm was woeful and there was a small amount of smoke so I pulled the carbys, all the diaphragms have holes worn right through, plastic retainers are split and throttle butterflys have clearance along the shaft axis (so air can pass along side when closed) so they are toast as i havent found throttle valves any where and diaphragms are a problem too. lukily Keihin make a set of 31mm cr slide carb (around $1000) so if going to spend that i may as well go all in.
This will be the rebuild story in no particular (or logica) order but i will tell what worked and didn't and where i got parts etc and post some pics along the way.
please feel free to comment, advise, ask question and tell me i have something wrong in the head to do this.
Steven

 

Wow, that's some serious miles!! Congrats for taking care of it to make it this far. You might find a much less expensive way to go getting a used rack off of fleabay or buying a "parts" rack and rebuild kits either from Brian at BDdesigns or here at XJ.

You're going to pull the heads for a valve job too? I'll be curious as how each of the valve facings look after so many miles. Just for kicks, can you check the valve clearences before pulling it apart so we can read the clearences? It will clarfiy the condition better if we know where the lash was for the past few thousadn miles.

jeff

 

I didn't check valve clearances before stripping as the head I knackerd (i'll get to that in a post soon) clearances would be close to correct as I did them three or four times a year when it was in regular use, I can let you know what shims were where if it's of value? As an aside, I can't find my shim tool and spare shims and it's driving me nuts, found one in Germany (louisfun.c ##.de) for €12 but all the shims will be the expense! I haven't checked out the sponsors on here yet but I will for sure.
As for head work I'll give you an idea where I'm upto; the crank has been ground .020" undersize and the cases linebored to suit some copper/lead bearings that can be made to work, rods cracktested and pins bored to take some steel backed bronze inserts and I have a set of forged Wiseco pistons (dynoman.c##) that will take it out to around 715cc.
Details to follow.

 

Welcome Hobbsy, thats a lot of k's ..you 2 must get on well ..
shims http://www.precisionshims.com.au/a/Prec ... -Australia
carbs would cost much less than a $1000 if you got 2nd hand from th usa, there are a lot more xj's there than here. xj4ever for th parts to make em new. I'm fairly sure another oz member has got new diaphragms from th u.s too, for an ok price

 

...and.. th carbs th carbs th carbs..always a must get right component of th project, they've gotta be one of th most discussed topics on here..seeing th light might just mean they need synching as it's basically = top and bottom.Apart from cleaning, new seals etc..

There are some excellent how to's if you search it.

 

Outta curiosity, how many times had you run into chain guide problems? All I hear about anything bigger than the 550s is the chain guide inevitably shredding up. With that many miles how many problems did it give you? Or did you actually take preventative measures?

 

Rudie, I'll bet a bike that's continually in use doesn't have the problem. I think it's all the sitting that most of these bikes have done that deals the death knell to the plastic; once it dries out, it will begin to break apart.

 

Will be interested to see more of this build. Says a lot for the bike that it's done such a mileage. I agree with Fitz - lots of use, with regular maintenance is probably the secret.

 

Yep, his bike never even cooled off!! Z1parts for shims....5 bucks and less apiece. If you assemble a list, I'll be glad to help you find them....I buy a couple of grand worth of parts each month so I have some decent connections. Anyone who has racked up 125K on one bike deserves the help!!

jeff

 

That could possibly be the highest mileage XJ in existence. Can't wait for this one to be reborn.

Just imagine how many km's it would have on it if it hadn't been parked for the last ten years.

 

Draging the chain;
I've never broken a cam chain guide or tensioner but i did break the primary chain guide a long time back ( and i have seen it in other bikes) the pieces tend to jam the gearbox ( i had to ride home in first that day) i then fished the pieces out via the side cover, i never replaced i up 'til now as its a full pulldown job ( it lives in the top of the crank case between the cylinder and altenator) i have done many thousands of kay's without it and woulden't pull an engine to replace it ,the mistake i made was not pulling the sump and cleaning out the oil pump. i'll post a pic of the wear marks when i have the case handy

 

would be glad of the help Jeff, i'll let you know about shims when I get to assembling the head

 

result of broken primary chain guide
View inside the cases

 

Got the barrels, crank and cases back from the machine shop, bore is now 66mm for a displacment of 717cc bigends 33.4mm and mains 33.9mm.
compression changes from claimed 9.2:1 (I mesured mine at 8.778:1) to a claimed 10.5:1 I'll have to do some maths to see if I need to get reprofiled cams or retard the inlet cam

 

And now to pistons I got these from dynoman.net (his second last set) as you can see they are a lot more modern with the rings higher in the piston for reduced dead space, acumulator groove to reduce ring lift and lateral gas ports to improve ring seal, the top ring is steel and coated middle is iron and oil is three piece, original rings are 1.1,1.45,2.75mm and new ones are .95,1.15,and 2.75mm, the pin is taperd and the skirt about 4.5mm shorter so weight was only up 4gm

 

gday hobbsy, i am watching this very closely, i gotta hand it to you but you know more about these in your big toe than i know all up, i read earlier you replaced your cam chain around about every 50 000 k's, my bike now has about 54 000k's on it and its always serviced and fresh oil and filter every 4000k,fresh final drive oil, spark plugs are always good, valves are always checked and carbs are always synced, the carbs are the only thing im not confident to do yet, but the old fella that does them has been a pro bike mechanic for around 40years, so its all good and is running spot on and never misses a beat, now i can get a genuine cam chain delivered at the door for around 50 bucks, but am hesatant to change it over because its running so well, what are thoughts on this and can you convince me to swap it? if yes what else would you do while you were at it? ive noticed on here a few of the experienced fellas reckon there good for around 50 000 miles (80 000k's), i dont want to start a debate or open a can of worms and am only after your opinion. i want to be riding this bike in 20 years time and think i will do another 100 000 ks by then, i will share the KMs with some other bikes.thanks in advance,kind regards ken from sunny old Brisbane

 

Okey, to judge how the cam chain is going; if you have a good ear ( and this is not common) you can compare with known good bikes ( low Kay's or relativley new chains) personally, I know how it should sound so the time I broke one was my fault 'cos I new it needed changing.
A more methodical way is next time you're doing the valve shims have a look at the guides have a feel of the chain tension and pull the tensioner off the back of the cylinders and see how far it is extended, more on this later when I dig up a tensioner.

 

Now to what's on my mind; has any one had any success porting the 650 head?
I've had a junk one on my bench for weeks and Yamaha did a good job but surely there's room for improvement?
I don't think larger valves are an option as the combustion chamber would need to be opened up to unshroud them and this would drop the extra compression of my new pistons and take hotter cams of the table.
So I checked port volume (45cc) witch is is right on the money, so I can't go wild or port velocity will drop and I'll lose bottom end.
Current thinking then; grooving the port floor (90° or 35° to air flow) to create a boundary layer therefor laminar flow ( researching this is giving me a pain). Widening and flattening the port floor ( 'though Yamaha have already done some of this), narrowing the guide boss ( 'though the port actually widens at this point to maintain volume.
The far side of the bowl is fairly shallow and I wonder if steepeng and grooving the wall above the seat might promote reatomisaton of wet flow?
Any opinions welcome

 

New carbs came yesterday, what can i say exept "phowar!"

 

nice, i bet they dont give tham away

 

Well I'm about 3 grand over budget so far ( most of it custom machine work), the carbs were part of the plan from the beginning and at around the price of a set of new diaphragms not bad value ( but not cheap admittedly )

 

well I found where the filings i've been getting on the magnetic drain plug for years came from, the primary chain has made a mess of it, and the middle gear shim looks like it may have been damaged on original assembly

 

One thing leads to another, the chips of primary chain guide in the oil pickup restricted flow, if I had cleaned it out earlier i might have saved some time and money now, still you live and........?

 

OMG! Can you post a link to the carbs?

 

Keep on posting. It's really fun and interesting to follow your project.
Thumbs up!

 

this is were i bought the carbs
http://www.showandgo.com.au/
i think http://www.dynoman.net/ can do them
saw them on motorcyclecarbs.com but havent dealt with them as they wouldent take credit card or PayPal and wiring money overseas for a one of is something i'm reluctant to do

 

Havent posted for a while so here we go, after some dithering I used Wurth Special 250 for sealing the cases, also around the cylinder liner base o rings and the camchain tunnel in the head gasket,

 

That's a nice start to a great build, can't wait to hear how it runs.

MN

 

skipped a few steps there but its together, cosmetics might be a project for next winter. started straight up. and after some carby fettling it runs well, ( lifted the needles 1 notch and isolated the starting circuits).
some issues though, the clutch won't hold above 7000rpm ( am considering the kevlar option from Chacal) and i have an ignition miss in the higher gears around 5500-6000rpm. has any one tried the Dyna coils Chacal has? (pickups, coils, plug caps, earths ( that's ground for you septics , [ i well remember the blank looks a a tech meeting in MN] all test good) im going to try a different tci tomorrow but mine looks ok inside.
power feels much sronger than it ever did before, but hard to judge i guess.
Comments please.

 

Very nicely done. Looks like you are a coat of paint and polish away from "Wow! Gorgeous!!"
Who/what are those pipes and mufflers? 4 into 1 or 4 into 2?

 

Thanks Fuller, pipes are 4 into one Marving "racing" ex Italy via wemoto.com, I chose them 'cause I like the flat 4into 1 merge and relatively large collector, it is loud though

 

so after geting my spare tci working, ( geting it back in the box being the hard part, especialy as it really didn't need to come out ) the bike runs exactly the same, so new more powerful coils it is!