Sizing up the XJ750 crank and big end for new bearings

Dived down deeper than i have gone before on any bike I've owned, the dreaded, 'gotta split the cases' silence you get from people when you tell them.
Even my parts wrecker was like, 'oh the bottom on the XJ's are pretty strong why do you want to do that'... I could have just whacked the motor back together with a few shortcuts, but i don't want to rebuild the motor again in 12 months...

Am glad i did.
Straight away i found the starter chain guide had broken off the mounts, flopping around somehow without getting jammed for the last god knows how many K's.
Chain had been rubbing on the oil squirter tang sending fine metal everywhere.
[Voice in my head] 'For how bloody long'...........

Found i had the big bore kit as in '87 XJ900 pistons, but it needed a rebore anyway. So i found the last Wisco Big Bore kit for XJ750 on the planet and got another standard set of barrels to bore to suit.
Saved $$$ on what my local Yammy dealer could do..
Hooked up with Chacal for parts which works out a lot cheaper than most dealers, so check out his page if you need parts....

I Figured out my crank and big end codes, so if my crank is not worn, or out of round- i should just order the same color bearings that were in it, which match what was stamped on the crank minus the case numbers.
[i could still make out the paint on the bearings]

Once the new bearings are here, i assemble with plastigauge to find out the clearances. But, if the clearance are too large, will i need to put the next size bearing in?

Without having a range of new bearings to measure up, could someone tell me which color is the thickest of the range. Yellow?

Sooo many pictures, i don't know where to start, maybe next post..

 

Sorted the crank, not out of round or worn, so i went ahead and ordered new main and rod bearings.

Have tracked down all the internal parts i need thanks to Len and glorious Yamaha part numbers.. Need to rebuild her while it's fresh in the mind and parts don't start winding up as my kids play toys.

I was offered an unknown condition 1983 XJ750P from a friend for $250, i paid him off and started stripping it for a rebuild, was told motor was working when ridden to my friends place and died from a holed fuel tank.




How's the size of the pics, do they need to be smaller, anyone?

 

Rockerto, someone put a "turbo" front end, brakes and rims on that Police Special. Is that the Police saddle?
One of these days I'll split open an XJ. . .

 

I did not know that, i like the curved spoke rims better. The seat is not a hacked job as the tangs in the metal are there at the back of the saddle, Unfortunately the saddle base is nearly rusted out and i will have to make a custom low profile seat now.

-So got her back home, had been sitting in a shed for 7 years.
I started stripping it back to powder coat the frame, tank had major holes in it so i got a better one for $50 in later pics, the tires and front forks were shot and everything needed cleaning.



It's an ex-police bike from Western Australia, the plate says 1983, but my Yamaha dealer codes the frame as 1985

MODEL NAME: XJ750P
STREET NAME: 1983 XJ750 Police Special
MODEL ID CODE: 37H
FRAME ID: 37H
SERIAL NUMBER STARTS AT: 000101



I don't like the white frame, and she's very dirty.



Took the bits off, made a work frame for it to sit on while the wheels are off
Back from powder coating $165


Motor back in.

At this point getting ready to start it up, made my own carb gaskets as dealer wanted 8 dollars each. From that moment on i have tried to buy everything i need off someone else, i can get parts cheaper from the US including shipping and have spare change to spend on other parts, they must really rip us off here in OZ..


I got it all cleaned up and ready to fire up for the first time, after i found i had low compression this photo is the best it has looked.

How can i add a you tube vid, it does not seem to be working with the code?

[video=425,344]http://www.youtube.com/watch?v=LxCvjtAxCCw[/video]

Oh, it ran, but i could hear the primary chain doing something, turned out the guide was broken off the mounts, and low compression saw me taking the top end off for a look, i got my head reco'ed for $200, And it had XJ900 pistons installed @ 68.5mm. I got a new 65.5mm bore barrel for $170 and a Wisco big bore piston set for $425 to my door, boring is another $100 so the top end is sorted.
I try and involve my boy whenever i can, but you know kids- they don't like getting crap on their hands.





Here's where it starts to get ugly-





Get these torx bolts out before the cases can be split, drill out the peen on the bolt and use a proper tool as my small one is useless and my friend Evan lent me his good set. An impact driver to suit the 1/2 inch socket is helpful to loosen up the grip these screws have.



Showing the broken primary guide and next pic, the oil nozzle in the case had the primary chain rubbing on it, so the main/gearbox and rod bearings all need replacing.




Homemade crank run-out checking jig.



I have .003 inch clearance across the crank which new bearings should get me going again.

Everything cleaned and waiting on parts.



That's about it so far, I've thrown some money at this already, and i am yet to take it down the highway.
We would suppose that it has XJ900 cams in it, and that vid on you tube is with the bike running with pot 2 @ 60psi and the rest around 115-120 psi.

She sounds hot, and i can't wait to have it running again with the new parts i ordered so i can get on with the bolt on stuff.

 

OK - - you're scaring me !! You dove right in to that bike !! Good job.

I was wondering if your final drive unit was also from a turbo bike, having a rubber cush drive, or is it the "normal" unit? And the idea that you have a turbo front end means that your calipers, seals and other parts won't be for the Police Special. There were 2 different Turbo front ends, different by 1 MM of tube diameter. Hope that helps.

 

Time to Ride, mate, your scaring me but thanks for the heads up about the front end. I will look into it in detail now and order the right parts, would that mean the rear rim is XJ650Turbo too, diff brake shoes?

I have not seen a rubber final drive but mine is the spring job.

I don't know much of the history of the bike, but having the turbo parts on, the 900 cam and pistons means someone went rank with it at some stage in it's life.

I will measure up and ID the parts during the week, thanks again as i would never of picked it myself..

Oh, i had to dive in, i can't trust anything in unknown condition and i think the old girls worth it.

More pics of the rebuild in about a month when parts arrive.

 

I especially liked the way the sidecar frame was attached in the front using XJ900 rear shocks.

Unique gauge cluster, too..........

In one of your earliest photographs (2nd from top) the engine side covers have the unique finish combination that is normally seen on 900 engines....black outer rims with polished central sections......that, combined with the 900 cylinder size that you mentioned........have you double checked to make sure that is not in fact a 900 engine in there?

The engine cc's are cast into the cylinder jugs, front center top, just underneath where the jugs mate to the bottom of the cylinder head (under the cam chain tunnel).

You can also check to make sure that is the original engine out of that bike, the "shorty" VIN that is stamped into the engine case, on the flat pad behind the clutch cover, matches the frame serial number (assuming that Police engines followed the same ID protocol as all other bikes).

Cute kid.

 

I count 18 teeth on the "middle gear", 900's and 750's had different gearing. I'll look for it.
That's a 650 turbo rear rim. There was an odd 750 in a "turbo 650" chassis for the Japanese home market. Slight chance of that as the source of your "turbo" parts.
I've heard BOTH, that the brake shoes are the same, and that they're different. Rumors. . .
I have a '82 turbo, a 900, and a 750. You'll have one unique bike when you're done.

+1 on the engine VIN.

 

Save the photograph showing the broken hanger on the Chain Guide.

That's one of the sources of Transmission's getting Hung-up and not being able to get shifted when the Guide starts to deteriorate.

 

Hi
Just was searching for my vin number, and found your build. I am also playing with a 37H vin XJ750P
My bike also has the turbo wheels and different front end.
This seems to have been factory for some
Trying to work out what parts to order to rebuild the forks.

 

Hi Darkfibre, welcome to the forum.
Nice to see your bike, hope your rebuild goes well.
We have a great guy on the site called chacal who sells new XJ parts and has saved me a mint over my local dealer here in Queensland.

Forks, got some pics for you, and even tho my frame is 1983, the dealer says it's a 1985.... :?:

I have my tubes at


$150 each to re chrome and if they can't match bushes chacal can hook me up with the right ones as my dealer can't get them and aftermarket is not available.
Also chacal said if i ship a tube to the states i can get them copied and both tubes would be around $270 USD. $80 to ship one tube from my location.

One new tube to suit XJ750p 36.9mm 603mm long tubes which are totally different to all other XJ tubes from Yamaha Aust is $312 Aud.

Here's the bushes you would need to look at from chacal.

Here is a list of the upper (inner) fork tube bushings that we offer, tell me if any match your measurements. All ID and OD measurements listed below are with the bushing in it's fully compressed (closed) condition:

HCP10702
Aftermarket inner fork tube metal SLIDE #2
split bushing on bottom of inner tube
19.82mm tall 34.07mm ID 35.43mm OD

HCP10703
Aftermarket inner fork tube metal SLIDE #2
split bushing on bottom of inner tube
19.79mm tall 36.38mm ID 38.68mm OD

HCP8481
OEM inner fork tube metal SLIDE #2
split bushing on bottom of inner tube
19.74mm tall 33.88mm ID 36.77mm OD

HCP10705
Aftermarket inner fork tube metal SLIDE #2
split bushing on bottom of inner tube
19.72mm tall 36.36mm ID 37.50mm OD

Here is a list of the lower (outer) fork leg bushings that we offer, tell me if any match your measurements. All ID and OD measurements listed below are with the bushing in it's fully compressed (closed) condition:

HCP10706
Aftermarket lower fork tube metal SLIDE #1
11.86mm tall 36.11mm ID 40.09mm OD

HCP10707
Aftermarket lower fork tube metal SLIDE #1
Slider (lower) = 19.98mm tall 35.08mm ID 39.03mm OD used

HCP10707C
Aftermarket lower fork tube metal SLIDE #1
11.98mm tall 35.08mm ID 39.03mm OD used

HCP10710
Aftermarket lower fork tube metal SLIDE #1
7.99mm tall 35.92mm ID 39.95mm OD used

HCP3087
OEM lower fork tube metal SLIDE #1
11.93mm tall 38.15mm ID 41.95mm OD

HCP10708
Aftermarket lower fork tube metal SLIDE #1
11.93mm tall 38.15mm ID 41.95mm OD

HCP4259
OEM lower fork tube metal SLIDE #1
11.81mm tall 36.95mm ID 40.97mm OD

HCP10709
Aftermarket lower fork tube metal SLIDE #1
11.81mm tall 36.95mm ID 40.97mm OD

HCP10549
Aftermarket lower fork tube metal SLIDE #1
19.90mm tall 37.04mm ID 40.99mm OD

HCP10549C
Aftermarket lower fork tube metal SLIDE #1
14.90mm tall 37.04mm ID 40.99mm OD






That's about all i know, i am yet to hear back from Rad but it's only been a week.
My forks were shagged so i got a decent set from Maddington wreckers near you so i have spare parts which helps, my real concern was bushes but chacal to the rescue again...

Made better side covers and doing a custom seat as rust has left mine unsafe for the roads




Edit: Here's where the seat build went

 

Well here's an update.
If i was rich enough to employ someone else to work on my bikes i would hire him. Or buy a new bike of some sort- i don't wish this restoring stuff on anyone, what a pain..

Sorry, been a hard road..



The fork rebuild went well, [as the place i sent them too did a great job]

I just found a set of pannier crash bars and boxes off eBay, i wonder why some of you guys in OZ let these pass- I justify the $230 i paid delivered for the look.
You can see the center stand is on atm but it fouls the 4 into 1 pipes :?

I'm yet to finish the side covers.
Just got the front wheel on and very happy i got the bike off the work stand.

Just sorted out the anti dive units, looks like a yearly job to dismantle and clean the dust out of the breather holes, a spot of lube should keep the top plunger from freezing up.
The bottom valve on these units are easy to clean and rebuild but the top plunger is the key to proper activation.



Now to sort out the brakes



Tank is off, i gotta rejet my Mikuni's for the pods and pipes, i did get it going the other day but it looks like the fuel needle valves are shot.
The rejetting is for another topic , i have a trick i want to share soon.

From what i heard from the crank case, it will run nicely and overall i am happy that a total rebuild is going to pay off for a long life ahead again.

I have made a oil pressure gauge fitting that i can make for everyone else and will share this in another topic, suffice to say, i had 55psi at idle so get yourselfs a 100psi gauge with piping like in the next photo.



And pic showing the location of the gauge...



I can't thank everyone enough on this forum for their help and comments and to especially chacal for his spare parts guru like help.
When i get these blasted carb's sorted out i shall link the YouTube vid here for you all to listen to.
Old vid before rebuild

 

Hey Rockerto you is da man ....congrats on a ton of work, hope you have years of riding pleasure with th bike you have resurrected from a near death experience. :> :> No, i havn't split th cases...spose th dreaded chain guide will get me one day.

 

Thanks Bushy, at last an answer to my poll.

If you look after your motor it should be fine.
The last owner rode it on the redline all the time, knows everything but nothing.

I just had to rebuild it after seeing the internals. Worth the effort.
Total cost should be $3500 AUD
About $1100 went into the motor not including carb's {another story}
Cheers, Rob.

 

Good to see your progress.. Are you on the road yet?

Was Chacal your supplier for the anti dive unit seals? I have decided to face the forks on my build, but have yet to find listings for the orings etc for the anti dive units to order them.

 

Slow progress at that juggling family and work but thanks darkfibre.

No just replaced o rings for now, a good clean and everything looked good so i put them back together. I think luckily everything was still wet with fluid and protected from drying out.

I just got a set of valve needles and seats and a few main and pilot jets today in the post and tonight is supposed to be screw it in and do the levels.

I got it started the other week, but it didn't run properly and i don't know anything about carb's.

Just looking at everything i can read here about Mikuni tuning.

Pulling apart the rack is a daunting task but i might have to put an order in to Chacal if the butterfly shaft seals are shot. [i usually don't mess with stuff if it's in usable condition]

My wrecker friend thought my Mikuni's are not original for this bike as well, ill post a few pics later tonight if someone can help id them.

 

Ah- Mikuni type 1 cv carbs bs30?

Had a 92.5 main jet and 40 pilot jet from previous owner.

We got the bike started but very rough, it needed a bit of choke but idled for a short time once warm.
No throttle response.
Then it went a bit weird and surged a bit in the rpm's.
I installed new fuel needles and seats, and installed a size 100 main and 42.5 pilot but it won't start at all.
Had the 37.5 pilot jet in last time but that did not help ether.

If i had a proper starting point for these carb's it would help as i have
intake pods and a 4 into 1 system.

Are these original for this bike?

 

If you are talking about the '83-5 XJ750, then I don't think they are, that sideways sliding enrichment ???????

 

All the XJ750P models i've seen are Hitachi carbs, and by memory your Vin number is close to mine. Someone has changed the carbs on yours in the past.

 

Cheers, that's what my wrecker said, probobly off a GSX750..

Now i'm tying to tune without a standard reference point.

Thanks for that pic darkfibre, am on the lookout for a set of Hitachi carbs on ebay..

A mate is coming around soon with a can of 'start ya bastard'

Feels like there is not enough fuel getting inside the pots, i got plenty of spark and i had it running the other day, i thought a larger pilot jet would help it idle..

mmmm

 

Pity you need carbs right now. There is a 99% I wont be using mine after all the work that went into them. But I won't be letting them go for a month or so.

 

Really, i was going to say that those carbs have come up looking nice, no hurry here as it might give me time to pay off the credit card.
If i'm still having issues ill let you know.

We just got it started and it's 3 1/2 turns out on mixtures but it revs hard at start, still no throttle response and it won't settle down to idle before dieing.
I will pull them again, up a size to 45 pilot and increase the fuel in the bowls as it might be starving, as it surges a bit.

Going to book it in to my local bike mechanic and see if he can pin the problem for me if tomorrows effort fails.

 

Update guys, i got the bike running tonight....

Not original carb's but i went up a few jet sizes from what was in it before the rebuild, it seemed lean, so,,,

I thought, you need some restriction with those pods...

Well, i made up some copper cones out of some sheet to line the inside of the pods, with a few holes drilled into them to pass SOME air..

Blow me down, i tweaked the mixture screws and she fired up.

Now i got it running great, i am yet to do a sync and colortune.

Just do a bit of fine tuning (hours of tweaking) and tidy it up ready for a road test in a week or two..


I am soooooo stoked

YouTube video of starting.

Running a bit rich, will step down the pilot jet for a start..


I will post and link the pod mod for ya all soon..

 

Just finished assembling my forks and being the same as yours, what amount of fork oil did you end up using?
The part numbers of the fork parts lead me to believe yamaha used XJ750D (jap delivery injected model). 37mm dia forks
My local Yamaha dealer says 312ml of oil for the West Aust XJ750P.

Any ideas?


late edit; I thought all xj750's had progressive springs, this one doesn't.

 

Restricting the AIR Flow has always been a Top Priority for correcting the Lean Conditions Pods evoke.

Beyond restricting Intake Air Flow.

Using a tight-fitting Hose with a Sealant or Adhesive ... Bypass the Main AIR Jet from being in the Turbulent Intake Flow.
>Create a Bypass Line ISOLATING the Main AIR Jet from the Intake Flow.

This will allow the Main AIR Jet to be protected from the Pressure Drop around the AIR Jets orifices as Turbulent Intake Air crosses the opening for the Jet.

Once Isolated and protected from the Turbulent Intake Air ... The Main AIR Supply will RETURN and provide a Flow of Air through the Emulsion Tube carrying Fuel and Atomizing the Main FUEL Jet Supply for a move favorable AIR ~ FUEL Ratio to power the Engine, ... reducing the Lean Condition and bringing the Mixture closer to the Enriched Mixture needed for Power and safely running the Engine at high-speeds.

 

Hi Rockerto,
I've only just stumbled on to this thread. So someone had previously bored out 750 barrels to take pistons from an XJ900, (presumably 853 cc, perhaps even 891cc ?)

Can any of the wise men on this forum comment on this ? ie OK if done right or recipe for disaster ?

PS Splitting cases.....Rockerto goes where others fear to tread