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78 GS550FI (Fuel Injected).. carb rebuild turned EFI Conversion

  • Thread starter Thread starter hkeni
  • Start date Start date
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hkeni

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The story.

I am embarked on an epic journey the day I installed a pair of aftermarket pipes (MAC Paipes) on my stock 78 GS550. That opened the pandoras box. Started backfiring and losing power at all throttle positions. So I decided that I needed to rejet my carbs.


Having never done that before, I ordered a set of carb rebuild kits, tore up the carbs, cleaned everything and started to wait for the kit to arrive.
The bike was just sitting there, staring at me demanding more attention, I just couldnt say no. That is when i decided to repaint my bike.

Having never done that earlier, I walked into the nearest sherwin-williams autopaint and started asking questions. The more I asked the more I got confused. So I decided to try the hands on learning technique and bought all the paint stuff.


Harbour Freight is just 2 minutes away from home, I have forgotten how many times i have run to the store. There i bought a 8 gln compressor, $15 mini detail paint gun, and many other things to paint the bike with.

Sanded, Painted, Clear Coated with fair amount of success.Will post that story elsewhere. Oh..I also Kreem lined the tank.

Meanwhile my carb kit arrived. So I rebuilt the carbs. Rejet to 90 Main, and 17.5 pilots. I had no scentific way to guess the size of the jets with out the bike starting so I used a formula I found somewhere which said 3 sizes up the main and 1 size up the pilot for an aftermarket exhaust.
Tried starting the bike, would backfire through the carbs while starting , and through pipes while running.


Tried changing to DYNA S ignition and Coils, thinking that it was an ignition issue. (the stock coils had a bad plug boot). No amount of fiddleling made the bike start or run correctly.

That was when i decided to go EFI.

The electronic engineer in me sure does understand the circuits and it had been a while since I had used my education for something, (I am an IT consultant, dont have much to do with electrical engineering at work).

Found a set of Kawa GPZ1100 Throttle Boddies and injectors on ebay for $150..I hear that they are a perfect match for the GS550. I have also ordered MS1 V2.2 (Microsquirt kit), which I will start building as soon as it arrives.

In the mean time, I am digging around to see what other people have done and get some ideas.

What has me bogged down is how to modify the fuel system to accomodate fuel return...any answers anyone.
 
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What has me bogged down is how to modify the fuel system to accomodate fuel return...any answers anyone.

You can try to add a t-branch on hose between the tank and intake side of the pump and connect return to it. I used this solution for couple of years without any problems.
 
Pingel has adapter plates to convert over to a manual petcock; one of those might make plumbing the return easier.
 
I would think that either the pingal adapter plate would be a good fix or making your own adapet plate out of a peice of 1/4 inch steel.

Looking forward to see where this project goes. And as always pictures are a good thing.\\:D/
 
hit a roadblock yet another time..this time, the GPZ1100 throttle bodies that I ordered off of ebay arrived. They will not fit because the are GPZ1100 B1 throttle bodies, I needed B2. B2's have the injectors mounted on the TBI itself. It is not the case with B1. Dont know if I should keep looking to find B2 throttle bodies or should look at some other throttle body, for eg. the gixxer. Any suggestion guys..
 
I guess that the GPZ throttle bodies are almost only option with correct spacing. TBs from a gixxer and other modern bikes will always need re-spacing. The GPZ bodies are also most likely quite well sized for your bike. Modern ones tend to be slightly larger, typically 38-42mm. This isn't as critical than with the carbs but too large TBs will make throttle response very jumpy.
 
Check out Jenvey. They are in the UK. Although, I'm not sure you want to pay the price for the throttle bodies. They make them to spec. So you can get whatever you want. I don't know how different the spacing is, but have you considered something from say, a Honda CBR600?
 
An old texas farm term " plowing up snakes " comes to mind. An old Japanese term also applies "rots of ruck ". However I am interested in your old point plate and points & cond.
 
reddy...not sure if I still have the points plate. I will look around and if I find it I will be glad send it to you if you can pay for the shipping.
 
Finally got around to build the Microsquirt ECU today. took me the whole day but I managed to build and test the unit completely. Hurray.....I found the correct B2 throttle bodies on ebay. Its a matter of time before they arrive. Will go around shopping for sensors tomorrow. I have decided to go narrow band o2 for now. Once I have everything setup, I will think about going wideband o2.
 
Did you sort out your fuel pump question? I'm curious to know what you're using. Most of what I have seen are the internal type that need to be submerged in the fuel tank.
 
narrowband won't be a great choice, especially if you get stuck in traffic much

edit: also, you may have power consumption issues
 
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Did you sort out your fuel pump question? I'm curious to know what you're using. Most of what I have seen are the internal type that need to be submerged in the fuel tank.




I found one on ebay for $70 including shipping. I think it is Made in China and is a direct replacement for Mecr, Audi , VW Bosch pumps. It was rated at 4 bar (58PSI)which is sufficient for my use. Also I found FP regulator on ebay for $30..
 
narrowband won't be a great choice, especially if you get stuck in traffic much

edit: also, you may have power consumption issues



I am not going to use o2 at all for now. Once I have the baseline set on V3.0, I will upgrade to MSnE and include timing. The next upgrade will be to MSII with wideband. That should give me some time to figure out about the power consumption and its work arounds.
 
Restarted this project

Restarted this project

Well.. It has been 5 years since I last posted on this. I had to drop this project for all these years as I had to move in 2008. My MC was sitting in a friends house for 3 years and then I had it shipped from coast to coast and sat out in the elements for another two. I finally bought a home with a 2 car garage and now have the space to restart the project.
There are many rust issues to deal with now. I think I am going to do a frame off restoration.
 
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