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Discussion Starter · #1 ·
Hey everyone,

Thought I’d chronicle my build so perhaps others can leverage what I experienced.

These oil cooled engines seem to be rarer and more appreciated every year (like a fine single malt?). Perhaps my experience can help someone else looking to appreciate the finer things.

Anyway, a bit of background; I’ve had my 88 GSXR750J since 2002 as second owner. It’s been many things along that journey from commuter to track rat, to endurance race bike (here and there) to sitting in the shed for an undeserved amount of time.

This is now the third complete nuts and bolts rebuild I’ve done on her since I’ve had her.

My objective is to bring her to race spec for a bit of bracket racing here in Aus, and depending on what covid does possibly road register. I’ve always wanted to do the 7/11 or 7/12 conversion and hoping it’ll give me a chance of spanking some of the other newer bikes like I used to be able to before technology developments brought bikes to the amazing kit they are.

Here some photos along her journey…
 

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Discussion Starter · #3 · (Edited)
The Engine

I spent considerable time researching old posts both here and OSS. Here are some of the more helpful ones (for me anyway):


I was on the lookout for a while and eventually acquired a 2005 B12 engine with low ks.

Here is the sequence of steps to get my 88 750J (dot) head onto it and ready to bolt into frame;
-Leakdown test completed and B12 block in good condition, so opted not to do work on the pistons and barrels
-head from my 88 750 was pretty shagged. Went through the manual and checked runout, wear etc, ended up replacing the valve train with new, except for valve guides. Considerable effort and time lapping the new valves in. I didn’t end up cutting the seats as was able to confirm seating surface was within tolerance. Finally passed the test filling chambers with petrol and not leaking through.
-Bolted the dot*head onto the B12 barrels. Used the cam chain guides and valve cover from the B12- except for the front small cam chain guide, had to reuse the 750J one. New 750J cam shafts and OEM 750J head gasket.
-Degree’d in the cams and fitted slotted APE B12 cam sprockets to achieve 103i and 108e timing - at least as a starting point till I play around on the track and optimise.
-I fitted a Dyna2000 ignition some time ago and set that up at static timing 40 deg. as a starting point
-checked the valve to piston clearances by winding in the rocker arm tappets to full stop and measuring the difference with some vernier calipers. Came out as 3.45mm on the inlet and 4.45mm on the exhaust.
-measured piston top to barrel height before bolting head on, then again checked ******** squish after bolted on by inserting a piece of nylon wipper snipper cord in through the sparked plug holes and rotating to TDC. Came out as 1.6mm.
-Used the B12 valve cover rather than the GSXR750J valve cover as it needs the b12 plastic cam chain guide screwed to the underside.
Cleaned up the engine and gave it a coat of hi temp matt black. Also grabbed some new NRC covers and made em look pretty to match too.


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Discussion Starter · #4 · (Edited)
The Frame

Being metallurgical engineer by trade, I’m a little wary of these frames. Some of the welds are pretty average.

In a past build I found I’d managed to crack one of the welds to steering stem with a big high speed stack at Eastern Creek.

I completely stripped the frame and visually check each weld for any evidence of cracking.
With it all good, sent off to be powdercoated.

here’s the end result…looks schmick!

note! If you blast and powdercoat your frame, give it a thorough wash out before getting it anywhere near any other moving parts. Some frame hollow sections were full of grit from blasting. Not great when trying to fit to an engine without the valve cover in place! 😬

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I braced the stock swing arm with a 97 Fireblade brace. Can read about it here;

The swing arm bearings were seized and had worn the races, so plan is to replace them with a Slinky Glide kit.

Steering stem bearings were also a little sloppy, so also throwing a new set of All Balls bearings and races.
 

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Discussion Starter · #5 ·
Electrics

Easiest way to deal with the electrics was to think about translating the B12 into the 88 750 frame and ditch the 750J harness altogether.

I sourced a complete harness from a 2001 B12 along with switch gear, then bought an automotive wiring plug kit on evilbay to connect all the aftermarket electronics.

I hate those dodgy auto connectors. They promote corrosion and subsequent headaches down the track, so every connector has rubber grommets and all pins were soldered as well rather than relying on just crimping.

For whatever reason it seems as though Suzuki changed the wiring colours for the bandit each year, so it took a bit of stuffing around checking schematics from various manuals to build a wiring schedule that mapped out what various plug pins needed to go to each colour.

I also sourced a 1250 right handlebar switch block and dual throttle, so wired up that to mesh into the harness.

Heres what it looked like;

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Discussion Starter · #6 ·
Here’s a little flatlay to show all the nice little bolt on upgrades accumulated over the years, and more recently with this build

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B12 engine with 88 750J head
-GSF1200 K1 wiring harness and switch gear
-Bandit 600 sprocket cover and cable clutch
-NRC covers (painted matt black)
-Yoshi top triple
-Black widow exhaust
-Earls curved cooler and lines
-Li-ion battery
-Custom battery box (riveted aluminium strap)
-oil catch can
-03 CBR600 rear shock (re-sprung for 85kg)
-Zx6r rear brake MC (to be bolted up to zx6r rearsets) and braided line
-Dyna2000 ignition and coils
-Engine Guard temperature monitor/alarm
-NHK ODM2000 steering damper
-Stock 88 750J swing arm with 97 Fireblade brace
-GSF1250 right handlebar dual cable throttle and switch block
-88 750 J frame grit blasted and matt black powdercoated
 

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Discussion Starter · #7 ·
A wise man once said “fit the frame to the engine”. It’s been soooo much easier doing it this way. I’ll be whipping the swing arm and front end off in the future when I need to pull the engine for sure.
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Still paranoid about last remnants of grit falling out of the frame. Glad wrap does the trick 🤞
 

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Discussion Starter · #8 ·
Fixed up the dyna coil mounting arrangement, so should have a nice clean run for the spark plug leads and a decluttered look above the engine.
Mounts were done with a little aluminium flat bar and using existing M6 frame tappings.

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Discussion Starter · #11 ·
Fitting the Valve Cover

Thought this deserves a post as it’s a serious pain! And of coursesomething to deal with every time the valve cover comes off…
So I had the engine fully bolted up thinking that even though it’s super tight, I could get the valve cover on. Turns out every mm counts. Ended up having to unbolt the engine just to get that extra 5mm. Also found it far easier to sit the valve cover gasket on the head rather that having it pressed into the cover and the cam shaft clamps continually pulling it out of the groove.

anyway, here is the sequence I followed with success:
1. Engine supported with everything removed including swing arm, front end, oil cooler, exhaust, etc
2. Engine supported and unbolted from frame except for bottom 180mm bolt, so you can pivot the frame back and forth easily
3. Valve cover gasket sitting on head with a few dabs of RTV sealant half cured to hold it in place
4. Inner valve cover gaskets (around spark plug holes) fitted to valve cover - with a couple or RTV dabs to hold in place
5. Carefully slide the valve cover in from the one of the sides
6. Once the valve cover is in, check the inner gaskets are still in place with a flash light
7. Work your way around the valve cover main gasket with a paddle pop stick to work it into the groove
8. Bolt it all down and torque to spec - note I couldn’t reach a couple valve cover bolts with my torque wrench and had to do those by feel

before rocking the frame back:
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success by
pivoting frame back

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Awesome build. I'm an Engineer as well so I appreciate the thoroughness of your build thread. What fill rod did use for bracing your arm? How did you keep it from warping/distorting during the process? I need to do my arm this winter.
 

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Discussion Starter · #15 ·
Awesome build. I'm an Engineer as well so I appreciate the thoroughness of your build thread. What fill rod did use for bracing your arm? How did you keep it from warping/distorting during the process? I need to do my arm this winter.
Thanks mate, still lots more things to share along the way. I’m currently trying to decide what to do with the crappy bandit clutch.

I’ll throw in some disclaimers for the brace…I’m a materials engineer but not a TIG welder and I haven’t tried to verify with a PMI gun, but my welder guy said he would use 5356 - given it was going to be powder coated anyway, and I wasn’t fussed about discolouration or trying to anodise.

I couldn’t find what material spec Suzuki built these frames to, being a ‘propriety’ composition. I did read somewhere people think they are a 5xxx alloy, so 5356 makes sense.

Welder is a boat builder with 40+ years experience and does known quality work. He mentioned he’d give it a decent chemical clean and preheat. idn’t go through any controlled annealing cycles. I figure if the brace cracks, it‘ll be at one of the welds HAZ and not all four at same time. I’ll be doing several careful laps and checking it over many times when the bike gets on the track.

Warping wise; he started at the shock mount end, then did the welds at the axle end last. I’ve checked it out and it’s all straight and good with brace fitted.

Hope that helps
 

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there is a great thread detailing bracing a 86 frame on here. obviously there are differences between the models but the materials and techniques are the same.


The early chassis that Suzuki was producing utilized a proprietary alloy similar to 7005. The main benefit of this is no need for heat treating, significantly lowering production costs. IIRC wouldn't be until the 90's that they started using heat treating in production.

Most 5xxx series filler rod will work well since its only for a brace and not critical. However, a 5183 or 5556 will be stronger than 5356. When I braced my frame I used 5556.



Ive braced quite a few steel and aluminum frames and swingarms over the years and have never used a jig. The secret to not warping is excellent fit-up,, good weld sequencing, and adding the bare minimum of filler rod. This is true even if you have a jig for that matter.

-Sorry to hijack -

PS. what are your plans for the clutch?
I recently went through the clutch pains on my B12 swapped 750 bunch of new parts in there, but my b12 is mostly stock. I have been toying with the idea of different head/cams etc but wondering what to do about the clutch with a big increase in power.
 

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Discussion Starter · #17 ·
there is a great thread detailing bracing a 86 frame on here. obviously there are differences between the models but the materials and techniques are the same.


The early chassis that Suzuki was producing utilized a proprietary alloy similar to 7005. The main benefit of this is no need for heat treating, significantly lowering production costs. IIRC wouldn't be until the 90's that they started using heat treating in production.

Most 5xxx series filler rod will work well since its only for a brace and not critical. However, a 5183 or 5556 will be stronger than 5356. When I braced my frame I used 5556.



Ive braced quite a few steel and aluminum frames and swingarms over the years and have never used a jig. The secret to not warping is excellent fit-up,, good weld sequencing, and adding the bare minimum of filler rod. This is true even if you have a jig for that matter.

-Sorry to hijack -

PS. what are your plans for the clutch?
I recently went through the clutch pains on my B12 swapped 750 bunch of new parts in there, but my b12 is mostly stock. I have been toying with the idea of different head/cams etc but wondering what to do about the clutch with a big increase in power.
legend! Thanks for the link to that post including the technical articles. Really nicely details the metallurgical considerations. I’m wishing now I’d spec’d 5556 filler rod, but I think 5356 will be ok in the end. Guess we’ll see.

For the clutch, I’m looking at going with the ‘UK Lee’ upgrade eg. 89-92 GSXR1100 outer clutch basket/ GSXR coil spring clutch:

but I’m also toying with using a Sigma slipper clutch inner upgrade. I’ve shot an email to the Sigma guys for their thoughts on whether they have a reasonable option to still retain the bandit outer basket to save some pennies given the the GSXR1100 baskets are no longer that common with breakers and are a horrendous lead time OEM (12+ wks due to covid here in Aus).

I used to race 250 2 strokes so I’m ok with feathering clutch, but I’d rather be focusing my limited mental capacity on the track on late braking and corner speed vs clutch feathering to settle the bike with heavy engine braking. How have found your bike with downshifting? Felt a pressing need for a slipper clutch?
 

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Nothing wrong with bandit clutches as long as they are in good working order and with one heavy spring they will take abuse
 

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Discussion Starter · #19 ·
Nothing wrong with bandit clutches as long as they are in good working order and with one heavy spring they will take abuse
Hey mate, roughly how many ponies through the bandit clutch in your experience with just one heavy spring? Also with good working order I’m guessing you mean within thickness spec?

I’ve been going on an assumption that GSXR1100 clutch mod is a must based on what I’ve read in this forum and others. I didn’t want to waste a day at the track or dyno finding it slips from the outset

thx
 

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I tried looking for a 1100 basket but gave up after a while bceasue i simply couldnt find any in decent shape at the time. Im running the stock B12 basket with a barnett clutch pack and their heavy duty spings. My b12 is probably making somewhere areound 115-120 at the wheel. Ive never truely ridden it in anger because ive never had it on a track so i cant tell you how it would handle that treatment. Right now stock clutch seems fine with me hooning around town and the back roads.
 
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