Gk76a SP Questions

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mattiec321
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Gk76a SP Questions

Post by mattiec321 » Tue Jan 27, 2015 6:12 am

Morning all

Well having picked up the sp as a non runner last week, yesterday was the first time I managed to get out and play.

The bike had been fitted with modified non sp carbs but came with a set of sp's in the box.

I opened the float bowls all clean apart from #3 which was a little shitty with rust and the brass a little corroded but in any case with these carbs on ( what a faff ) and fresh fuel she didn't want to know.

Open the drain screws fuel in #4 not in any others. Tank off pour fuel into pipes, thumb starter and she burst into life purring like a kitten cleanly at 1100 rpm. Give a rev all good but not right out.

Now I thought this was due to not reconnecting the air box and the tank being off.

I've opened up the fuel tap and the diaphragm was stuck shut so that was fixed. There was some rubbish but nothing to bad. Refitted again all good but not revving out.

Eventually I left it ticking over and she started to die off finally refusing to start. Again I opened he drain screws and this time there was nothing in #3 but fuel in te rest. I still suspect the tap.

So I will take the carbs off and rebuild with a kit from Blair but the tap bothers me I can't seem to find a rebuild kit for that. Any alternatives?

While I'm in there I fancy changing for stick coils. Any idea of a suitable parts and where I'd get the plugs to make the loom?

Cheers sorry it's a long one

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Re: Gk76a SP Questions

Post by dobbslc » Tue Jan 27, 2015 10:11 am

Welcome to the world of GSXR carbs!
I spent weeks sorting out a couple of these bikes a few years ago and the carbs are a real pain in the arse.
You are lucky now Mr Blair is doing good repair kits as I didn't have that luxury back then!
If only #3 carb was dry its not the tap, it'll be a stuck fuel float valve or blockage in that carbs supply.
Probably best to wait for the Litetec stuff to arrive and sort it all out properly or you will go round in circles.
If the SP carbs are any good I have a set of SP rubbers somewhere if you're interested.
Good luck. :peace:

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Re: Gk76a SP Questions

Post by mattiec321 » Tue Jan 27, 2015 2:01 pm

Dobbs you have a pm

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Re: Gk76a SP Questions

Post by SevenThreeSeven » Tue Jan 27, 2015 2:40 pm

You mention SP (BST35?) and modified non-SP (BST33?) carbs in your post. Is there a Throttle Position Sensor on the modified non-SP carbs? Lack of a Throttle Position Sensor would mean there's also a different CDI installed on the bike, right?

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Re: Gk76a SP Questions

Post by Variablevalves suck » Tue Jan 27, 2015 10:51 pm

From previous posts it would seem that the 33 and 35 mm carbs are the same casting so if you have machine facilities available you can basically convert 33's to 35's.
TPS sensor can be swapped across.
Don't think the tap is serviceable but if it comes apart you may find a kit from a similar aged Suzuki, gsxr750 or gsx.

I used cbr6 stick coils on my 73a but found them too long to get in and out with the tank on so went back to oe.
As I understand it they are not as good as oe because they are only getting 6v not 12v due to the two sticks in series wiring needed to get them to work

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Re: Gk76a SP Questions

Post by SevenThreeSeven » Wed Jan 28, 2015 4:35 am

I'm also using stick coils on my 1993 Bandit 400. They're the '05 Honda CBR600RR "Shorty" coils.

Even being the shortest stick coils available they still stand up pretty high above the camshaft cover. If I want to change spark plugs I have to remove the fuel tank but I have the fuel lines set up with stainless steel quick disconnects so taking the fuel tank off is quick and clean (only a tiny drip of fuel comes out when you pop the disconnects).

Pictures from the rebuild this past summer and fall.

Image

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I'm firing the coils with a QuadSpark igniter box ("wasted spark" style, just like the OEM setup). This insures normal 12 volt power to each coil stick.

Image

I'm using 2.5 milliseconds of dwell right now. I don't know what the stock Honda CBR600 dwell time was, maybe some more internet research will give me the answer. I've read that people are using 2.8ms or even 3.0ms without overheating these coils, but if 2.5ms does the job throughout the bike's rev range I'll stick with that. Testing and tuning this coming springtime will tell the tale.

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Re: Gk76a SP Questions

Post by mattiec321 » Wed Jan 28, 2015 4:29 pm

SevenThreeSeven wrote:You mention SP (BST35?) and modified non-SP (BST33?) carbs in your post. Is there a Throttle Position Sensor on the modified non-SP carbs? Lack of a Throttle Position Sensor would mean there's also a different CDI installed on the bike, right?
You are right

The previous owner has a set of 33's modified to accept the TPS.

As there was a set of SP specific carbs in the box I felt this was the best way to start. The bike still wears its SP CDI

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Re: Gk76a SP Questions

Post by mattiec321 » Wed Jan 28, 2015 4:32 pm

Also did you get the specific loom for your stick coils or did you get your plugs from somewhere like Vehicle Wiring Products ?

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Re: Gk76a SP Questions

Post by SevenThreeSeven » Wed Jan 28, 2015 5:27 pm

mattiec321 wrote:Also did you get the specific loom for your stick coils or did you get your plugs from somewhere like Vehicle Wiring Products ?
I bought the CBR600 stick coils (Denso "shorty" coils) off of Ebay, cheap. I didn't get any wiring or connector plugs with them.

However, as part of the preparation for my Bandit 400 fuel injection conversion project (that's where these pictures come from) I'd also purchased a complete '09-'11 Kawasaki ZX-6R wiring harness (once again, from an Ebay bike breaker, really cheap).

I bought this complete wiring loom for the sole purpose of getting the wiring connectors for the ZX-6R's secondary injector array (the one that connects to the 4 injectors that are mounted in the bike's airbox). My project research told me that the ZX-6R's secondary injector array would be perfect for my Bandit 400 because the spacing on the injector array matches the bore-spacing of the Bandit's Mikuni BST32s and the injector's flow rate is spot-on for fueling the 100cc cylinders of the Bandit 400 all the way to the redline.

Here's what the ZX-6R's secondary injector array looks like:

Image

Image

And here's what the Bandit's rack of Mikuni BST32's looks like after being transformed from Carbs to Throttle Bodies (with the injectors mounted where the float bowls used to be).

Image

Image

Image

Image

Surprisingly, the Kawasaki ZX-6R wiring harness also contained the correct wiring connector plugs for the CBR600 Denso coils, and the correct wiring connector to fit the '13 Honda TRX500 Rancher fuel pump that I'm using to deliver fuel, and the correct wiring connector to fit the ’03-’04 Triumph Daytona 600 Throttle Position Sensor that I've installed on the #4 Mikuni throttle axis.

I guess that just shows how common it is for different motorcycle producers to have sub-contracted parts providers in common.

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Re: Gk76a SP Questions

Post by mattiec321 » Wed Jan 28, 2015 5:43 pm

WOW!

Now thats ingenuity.

That looks good. Well I'll have to look for some and the old issue of PS mag for the HOW TO........

Well theres a few bits to do first such as sort the carbs with a wash and rebuild.


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