87 GSXR 750 fitting a B12 engine. - Suzuki GSX-R Motorcycle Forums Gixxer.com
 
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post #1 of 12 (permalink) Old 06-21-2010, 10:29 AM Thread Starter
Squid
 
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Location: Dundee, Scotland
Motorcycle: 1987 750 slabside, 1993 750 wp
Posts: 16
87 GSXR 750 fitting a B12 engine.

Hi all.
Im having a little bit of an issue at the moment with fitting a 1997 1200 Bandit engine into my '87 750 slabside.
As we all know, any gixxer oil boiler will drop into the frame with ease (done) but Im not sure if i need to change my carbs and cdi?
I know the old 750 slab had a 2 point pickup and the 1200 bandit has a single point pickup....do i need to use a bandit CDI??
Carb inlets are the same and i have been running stage 3 dynojet when I had the 750 motor in. Can i jet these to run the 1200 bandit or should i be giving it a set of GSXR 1100 or bandit 1200 carbs??
I tried to fire her up yesterday using the stock '87 750 cdi and dynoed carbs, had a spark on all 4 cylinders and plenty of fuel going through but she just wouldn't have it. In the end the starter motor gave up. Got a spare though!
Is the ignition timing different through the CDI from the slab to the bandit?
Any help and advice on the electrical side of things would be great.
Lee.

Last edited by gixxerjunkies; 06-21-2010 at 03:20 PM.
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post #2 of 12 (permalink) Old 06-21-2010, 12:43 PM
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Re: 87 GSXR 750 fitting a B12 engine.

Quote:
Originally Posted by gixxerjunkies View Post
Hi all.
Im having a little bit of an issue at the moment with fitting a 1997 1200 Bandit engine into my '87 750 slabside.
That's the exact combo I have.


Quote:
As we all know, any gixxer oil boiler will drop into the frame with ease (done) but Im not sure if i need to change my carbs and cdi?
I know the old 750 slab had a 2 point pickup and the 1200 bandit has a single point pickup....do i need to use a bandit CDI??
You can use the bandit CDI with the Bandit pickup or the 87 CDI with the two-coil pickup. Thats's what I did. B12 rev limit = 10,900 rpm, 87 750 rve limit = 11,500 rpm. Not much difference.


Quote:
Carb inlets are the same and i have been running stage 3 dynojet when I had the 750 motor in. Can i jet these to run the 1200 bandit or should i be giving it a set of GSXR 1100 or bandit 1200 carbs??
I used 750 carbs on mine - two different sets, 36mm from a '88 and 38mm from a '90. Both worked fine. You may have to upjet or move the needle, but I used 750 stage III needles in both. Larger pilots in the 36s, larger mains and lowered needles in the 38s

Quote:
I tried to fire her up yesterday using the stock '87 750 cdi and dynoed carbs, had a spark on all 4 cylinders and plenty of fuel going through but she just would'nt have it. In the end the starter maotor gave up. Got a spare though!
Is the ignition timing different through the CDI from the slab to the bandit?
Any help and advice on the electrical side of things would be great.
Lee.
Should not be but you need to have the 87 pickup not the Bandit one. The Bandit pickup won't fire half the coils.
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post #3 of 12 (permalink) Old 06-21-2010, 03:36 PM Thread Starter
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Re: 87 GSXR 750 fitting a B12 engine.

Thanks for that info, will need to get hold of a pick up from a 750 slabbie,its prob easier to put a slabbies pick up into the bandit lump rather than try to alter the loom? I've already sold the motor I took out. Im going to assume that the pickup will be a straight swap where as the loom would need to be modified for the bandit pickup and cdi.
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post #4 of 12 (permalink) Old 06-22-2010, 12:26 PM
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Re: 87 GSXR 750 fitting a B12 engine.

Quote:
Originally Posted by gixxerjunkies View Post
Thanks for that info, will need to get hold of a pick up from a 750 slabbie,its prob easier to put a slabbies pick up into the bandit lump rather than try to alter the loom? I've already sold the motor I took out. Im going to assume that the pickup will be a straight swap where as the loom would need to be modified for the bandit pickup and cdi.
Yes much easier to install 750 slabbie pickup and rotor (b12 rotor won't work).

Loom can be modified but you need the B12 plugs for the ignitor. I would sell the B12 box for a 750 pickup and rotor.
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post #5 of 12 (permalink) Old 07-04-2010, 07:27 AM Thread Starter
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Re: 87 GSXR 750 fitting a B12 engine.

Looking for a little more help guys.
Ok so i just put a 750 slabbie twin pick up and rotor into the B12 lump. I also found that I had not knacked the starter motor but managed to loosen off the starter clutch locknut. The starter gear came away and wasn't meshing with starter motor. Got that back together and with the slabbies pick up in I tried the firing her up again. Fired up but only ran on 1&4, nothing on 2&3. I trust that the rotor can only go on 1 way round because of the dowel so no prob there, firing fine on 1&4 says that it is a prob with 2&3 either being coil, plugs or pickup. I checked the wiring to the ignition coil to make sure it was ok, removed the plug cap on 3 and put in another plug, fired it up (running 1&4) and had a spark on the plug at 3 (proves coil and pickup ok). Plug cap back on and done the same for 2....now lets jump back a bit....when I went to turn her over, even after having sorted starter clutch lock nut only just half an hour previously...it comes off again. Ok so I never used any thread lock 'cos I've run out but it was tightened to torque as per book. Now i need to redo it and use some thread lock but then I should have gone and got some first time round, I'll take out the plugs from 2&3 to check gaps and condition. If when firing it back up again it wont run on 2&3, is there something else I should be looking at? The spark I got on 3 was constant and weak but that could be down to it being and old plug I keep for testing. Could it be possible that 2&3 are firing in reverse to each other? or is that a stupid suggestion?
Any more help would be appreciated.
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post #6 of 12 (permalink) Old 07-04-2010, 08:02 AM
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Re: 87 GSXR 750 fitting a B12 engine.

These engines have whats called a "wasted spark" system-

1 & 4 fire together and then 2 & 3 fire as a pair-
When 1 needs spark, 4 doesn't, but then when it's time for 4's spark, 1 doesn't need it(but it fires anyways)Same with 2 & 3-

So there's no way on your bike that 2 & 3 are out of time or anything, they both fire simultaneously-(ever tho only ONE cyl is on the "power stroke")

Have you verified you are getting spark on 2&3 coil?
(sorry if you said it already, but your post is LONG! LOL)
Check and verify you have the same voltage to both coils positive (orange) wires- I have seen one getting 11 when cranking and the other getting 8v due to bad/dirty plugs

Check ohms with a multi-meter (coils still in frame, with everything disconnected) across the coils 2 spade terminals- should be 3 to 5 ohms (and compare to other coil) also read ohms by sticking the test leads one in ea spark plug cap in pairs- should be 25,000 to 45,000 ohms[no less, no more] (1-4, then 2,3) They should be fairly close to each other-

When I first put my 86 together I was having all kinds of spark issues-
I had one coil ohm out at 19k across the plug leads and the other at 48k
(one too high, one too low)

I got a pair of coils off a 400 Bandit, (which ohm'd out the exact same, 30k)
and my bike has run GREAT ever since-


HOPE THAT HELPS BRO!
Cant wait to hear it run! GOOD LUCK!

GSXR Tony....
Thats how I roll-

Last edited by GSXR Tony; 07-04-2010 at 08:04 AM.
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post #7 of 12 (permalink) Old 07-04-2010, 09:21 AM
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Re: 87 GSXR 750 fitting a B12 engine.

Where did you get the 750 p/u and rotor from?
It is the correct rotor? should be stamp 27A0 or something like that
Should look like this
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post #8 of 12 (permalink) Old 07-04-2010, 09:24 AM Thread Starter
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Re: 87 GSXR 750 fitting a B12 engine.

[QUOTE=GSXR Tony;4582113]These engines have whats called a "wasted spark" system-

1 & 4 fire together and then 2 & 3 fire as a pair-
When 1 needs spark, 4 doesn't, but then when it's time for 4's spark, 1 doesn't need it(but it fires anyways)Same with 2 & 3-

Never knew about this, this will explain why the spark was constant then.


I will get this damned started clutch sorted first as im just back from the moyor store with a fresh tube of thread lock.
Will try testing the coils ohms once i've got the lump back together and see where I am from there.
Thanks again for the help.
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post #9 of 12 (permalink) Old 07-04-2010, 09:30 AM Thread Starter
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Re: 87 GSXR 750 fitting a B12 engine.

[QUOTE=87gix750;4582178]Where did you get the 750 p/u and rotor from?
It is the correct rotor? should be stamp 27A0 or something like that


Looks just the same, got it from good old ebay and as you say, it is stamped on the rotor 27A0.
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post #10 of 12 (permalink) Old 07-04-2010, 02:13 PM
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Re: 87 GSXR 750 fitting a B12 engine.

Quote:
Originally Posted by 87gix750 View Post
Where did you get the 750 p/u and rotor from?
It is the correct rotor? should be stamp 27A0 or something like that
Should look like this
My 86 750 rotor says a big "V & H" on it and its black, not bare cad-plated like ya'alls..... LOL
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post #11 of 12 (permalink) Old 07-04-2010, 03:09 PM Thread Starter
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Re: 87 GSXR 750 fitting a B12 engine.

Ok so here we are, I have measured both coils across the spade terminals looking for the 3-5 ohms. My multi meter reads 00.0 when across the terminals. It does this on both coils that are on the bike and the others that I have in my crates of parts. Im going to assume that its just not reading low enough (I think my meter reads x1000 by the looks of it) and i'll bring a meter home from work that will. Measuring the resistance between the plug caps on 1&4 i get 39.5 and on 2&3 i get 36.7 ohms. Im gonna assume that these readings are 39,500 & 36,700. Voltage on the orange terminals are 10.86v on each.
I've got the starter clutch back together hoping the torque is right, wound at 150NM as it says n the book but now the clutch aint slipping freely as it should (in one direction) its on with a ton of thread lock so it aint come undone again.
Gonna have to call ita day now though because my garage is under the babys bedroom and thats him down for the night now. Dont think the wife would appreciate me firing it up and waking the little one lol especially considering I was out there till 1am this morning and then back out at 9 lol
Again thanks for all the help and advise, if there is anyhting else I could be trying 2morrow eve then please feel free to let me know.

Lee.
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post #12 of 12 (permalink) Old 07-05-2010, 04:28 AM Thread Starter
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Re: 87 GSXR 750 fitting a B12 engine.

BUMP for the day.
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