GS1000G mods- big bore and fuel injection

[tkent02]

Looks like you only need to adjust the length of the fuel rail? Or is there more?

 

[GS1000G Shopper]

From my preliminary disassembly of the units and some measuring with them sitting in place, at least three things will need to be done:
1. Insert 19mm wide spacers where the long 6mm bolts go through. (McMaster sells these) (updated from 12-13mm to 19m 6/13/15)
2. Extend the throttle connection from the #3 to #2 throttle body. (Update: welded a 3/8" block onto the #3 TB)
3. Extend the fuel rail. Since I want to add a pressure regulator to the other end, I will likely cut it and see if the interior is round or oblong. If it is round, and based on the plug in the far end it is, I can slip in some aluminum tubing and have it welded so the proper spacing is achieved. Update: Cut it and drilled the openings to 3/8 and brazed in some 3/8" OD aluminum fuel line.

The fuel inlet fitting is similar to the late model GM fuel injected cars I've worked on- it is a plastic clip over a metal nozzle, and a plastic fitting on the inlet hose. I know Summit sells adapters for these to AN fittings.

EDIT
I forgot to add the secondary throttle shaft holes, which must be sealed. The quick & easy way here is to just tap them for 1/8 pipe- no drilling required as they are just shy of 3/8" in diameter. They can then be plugged with pipe plugs.

I have some more pics for some of this and will upload them later.

 

[GS1000G Shopper]

More pictures:
Fuel inlet fitting with hose removed:

Throttle body tab gap:

Spacer gap: UPDATE- I used a 19mm wide spacer after using the center linkage setup.

Test fit:

 

[GS1000G Shopper]

Fuel rail cut in half, inner diameter is about 1/4".
UPDATE:
I originally had used 3/8 OD fuel line and JB Weld but rethought this. I ended up using the same 3/8" aluminum fuel line that has a .245" ID. I drilled out the halves of the rail to 3/8" and then brazed the line into them.

These should allow the TB units to be seated and spaced properly.

 

[GS1000G Shopper]

UPDATE- Avoided this tab extension by using coombehouse's center linkage with my mod. When I removed the throttle plate it never realigned properly, and I believe this caused the high idle when I started the bike. The center linkage is a better way to accomplish this task.

While I had the rail off, I drilled out the brass plug on the far end. The opening is just slightly larger than 7/16, so it threaded as-is for 1/4 pipe. In the picture below, I have a 90 degree pipe adapter in it. I'll plumb the pressure gauge here.

1/4 pipe fitting at end of rail:

 

[ArttuH]

It's advisable to have a filter between the pump and injectors. It's not a bad idea have some kind coarse pre-filter on intake side of the pump too but probably the screen in the tank is enough for that. The filter before injectors should be "injection grade" i.e. fine filter, less than 10 microns.

 

[Guest]

Note

Note

A small comment. I like what you did with everything only, why not see if you could wedge the GSXR TB's into the stock GS1100 intake booties? They may be, at the most 2mm bigger than the 34mm cv carbs are but I believe, as I do have a set of them as well, that maybe only 1 to 1.5 mm bigger. Arttu used the same ones on his GS1100.
Laters
Greg

 

[GS1000G Shopper]

As difficult as it would be with the head fully accessible, trying to wedge them on after it was installed would be really difficult. I'd rather spend some time with a file (boot) and Dremel (intake) and have something that is easy to maintain. I have a big chip on my shoulder as far as carb installations go- anyone that has had to do this on an 80's V4 Honda engine can likely relate.

I've observed many a time in working on vehicles that the people that design them never work on them (the Sabre and my Gen 4 Trans Am are outstanding examples), so when I am designing something, maintenance is always in mind. The fewer battles there are to fight doing routine work the better.

That's why.

 

[GS1000G Shopper]

It's advisable to have a filter between the pump and injectors. It's not a bad idea have some kind coarse pre-filter on intake side of the pump too but probably the screen in the tank is enough for that. The filter before injectors should be "injection grade" i.e. fine filter, less than 10 microns.

Thanks, I'll look into it. I originally had an AN6 filter inline but it occurred to me I could use a barb one since the suction side does not need the expensive fittings. The GSX-G uses just those screens as its sole filtration system, and I've added an inline filter before & after the pump. I need to look at the GSXR-600 and see what it does.

 

[GS1000G Shopper]

Pulled the tank today. Preliminary sizing shows the GS1000G petcock and GSX1100G tank fittings are the same size for mounting. It looks like I may be able to use the GSX-G tank fitting. For the return side it has a long brass tube and also a small screen at the lowest level for the supply side. There will be no reserve function, but that is what a gas gauge and trip odometer are for, right?

Pics will follow if this is viable.

 

[willie]

Personally, I'm very impressed with all you've done on this project. I wish you the best of luck and will continue to follow your progress. I'm really looking forward to learning how it turns out.
Willie

 

[GS1000G Shopper]

It looks like a simple solution is at hand for the fuel fitting at the tank. After drilling & tapping the junk GSX-G fitting I had, the fittings would hit the GS airbox, which I hope to retain. Since barbed fittings are all that is needed here, and the GSX-G has these fittings, it looks like the GSX-G piece could be used. The trick is to find 5/16 hose wityh a 90 degree bend. When I looked at the old hoses I pulled off my GSX-G project, one has two 90 degree bends and could be cut in half.

I did confirm that the GSX-G fitting with the tube re-bent will bolt up to the GS tank. It's a little taller than the GS feed fitting, so it will be excellent for a return line.

Here is a picture of the part with the added part numbers, all of which are available. They are about $70 or so from the looks of things. The "gasket" is the circular one for the bolt, not the one between the tank & fitting.

 

[GS1000G Shopper]

I pulled the airbox from the bike today and no surprise, the boots line up perfectly with the throttle bodies. The bad news is the boots are way too large for the throttle bodies. If you reverse the boots, they are a decent fit, but too long. They could possibly be trimmed, but they are also pretty hard due to age, so I'm thinking a plan B is needed. I need to find out the airbox opening diameter of the GSXR600. If it is the same or close to the GS1000, they would likely work as-is. The TB OD is 45mm. The airbox opening is about 52mm+. Here are some test fit pics:

Stock position:

Reversed:

I'm also looking into re-wiring the fuse panel area, as the MS needs several fuses and relays. I found a relatively small (about 3.5" x 4.5") rear terminal panel at Waytek Wire (Bussmann 15303-2-2-4) that allows the use of several relays and 10 fused circuits. From what I can tell, it does not have a common or split bus design like some of their other panels (I have one on my 1975 280Z and 1988 Toyota Supra). A split bus is ideal for circuits that need battery power and others that need switched power. I can overcome this by wiring the terminals to create a bus, just a little more work.

The GS1000G has a steel plate that houses the fuse box, ignitor, and starter solenoid. I took it all apart today and used a cardboard template. The ignitor has a good bit of extra wiring, so I think it can be relocated.

To assess the idea, I cut out a piece of cardboard larger than the plate and marked an area where the fuse panel would be located. Allowing room for the solenoid, it appears I'll be able to use 3 of the 4 fuse panel mounting points. The GS uses a tab in the plate to hold it in place on the bottom. I won't be able to use this as the fuse panel will be in that area, but it looks like I can add a short piece of angle to the slot in the battery tray and extend the mounting point away from the panel. There is a good bit more work to do here, and of course I need to have a panel in hand to try it.

Here's a pic of the old plate with the solenoid and ignitor:

 

[GS1000G Shopper]

I have cleaned the airbox but it looks like I won't be able to find boots that go from 52mm to 45mm. An eBay seller was kind enough to measure his GSXR600 airbox and the opening are 45mm.

There are at least two things I can do here. One is to run pod air filters. I don't like this idea for two reasons- it takes away from the stock appearance, plus operationally I need to mount an intake air temp sensor. Using pods, I could only get the temp from one pod. I'd also have to plumb in a line to the breather.

The second option seems overly simple, but is more appealing. Reading about silicone hose, the 1.75" ID (45mm) hose is a little over 2" OD. Measuring the openings in the airbox, I get about 2.06". It looks like I can simply get a foot of the silicone hose and cut it into 4 pieces the same length as the GS1000 boots, run each one into the airbox, and then install the airbox, clamping the inside hoses first and the outer ones last. The boots on there now are not 100% sealing, so this would actually be an improvement. I bought a set of used clamps for the GSXR600 airbox boots.

I'm also looking at how to mount the air temp sensor on the GS1000 airbox. I'll likely weld on a small piece of steel and tap it for 3/8 pipe so I can use the GM sensor.

After reading descriptions of the fuse panels, I ended up buying the 15303-6-2-4, which has a buss on the relay side only. I need to have the fuses split onto 3 busses. I found an old panel from a GM truck leftover from an older project that is loaded with mini fuses and mini & micro relays, so that part will not be an expense.

The GS1000 fuse box connector is easy to take apart and replace with better quality wires. I did so on my blue bike after it arrived due to a green fuse for the headlight. It is using two ATC type fuse panels of 4 circuits each. The ATM style I'm planning here will be a much better setup.

I drew up the 15303-6-2-4 panel and applied it to what I'm doing:

 

[Big T]

3rd possibility, a 79 GS 850 airbox

 

[GS1000G Shopper]

Are the openings smaller? My airbox is ambiguous- it is stamped GS1000G on one side, and on the other GS750 GS850 DGM31773S GS850G DGM355854S

If this can be confirmed, or if the 850 uses smaller boots at the carb, that may be an easier path.

EDIT
Various part numbers, all show as current:

1979 GS850G boots
HOSE AIR CLEANE
13728-45010


1981 GS1000G boots
HOSE RH
13881-45050

HOSE LH
13882-45050


1981 GS850G boots
HOSE RH
13881-45030

HOSE LH
13882-45030

eBay auction info:

APPROXIMATE DIMENSIONS FOR REFERENCE:​

​

​

LENGTH: 58mm​

​

​

I.D. AIR BOX END: 47mm​

​

​

I.D. CARBURETOR END: 54mm (too big)
​

​

FITS YEAR/MAKE/MODEL :

1982-1983 Suzuki GS850G

1981-1983 Suzuki GS850GL


CONDITION :New


SUZUKI PART # :

13881-49070 x4 (Boots)

APPROXIMATE DIMENSIONS FOR REFERENCE:​

​

​

LENGTH: 65mm​

​

​

I.D. AIR-BOX END: 40mm​

​

​

I.D. CARBURETOR END: 43mm (may stretch 2mm)
​

​

FITS YEAR/MAKE/MODEL :

1977-1979 Suzuki GS750 (Standard)

1979 Suzuki GS750L

1979 Suzuki GS850G


CONDITION :New


SUZUKI PART # :

13728-45010 x4 (Boots)

 

[GS1000G Shopper]

After doing a lot of reading about fuel pumps, it looks like the Walbro inline model GSL414 may be a winner, although expensive at $155. I'm attaching a flow/current graph for it. At around 40 PSI, it is only drawing 3 amps and flowing about 29 gallons/hour (GPH).

I also looked into some OEM fitments using 80's model cars such as the Honda Civic- which was how I got the thermostat and fuel pump for the Sabre. According to the listings, a 1985 Civic had a fuel injected motor and used an inline pump. The Walbro # is GCL616, and it is rated for 121 liters/hour (LPH, which equals 32 GPH) at 45 PSI. It is more reasonable at $110. No current chart was available. The GSL414 at 32 GPH is drawing about 4 amps, so I'd say they likely draw the same current.

EDIT
I found this writeup on another forum, and the builder is converting a 1975 GT250 bike to FI and using the GSL414 pump.

Updating the fuel pump info, I found a page (PDF) from Bosch that shows their pump data. The lowest amp (maximum) rating is 5.2 amps for the "911" pump- people refer to the Bosch pumps by the last 3 digits. The 044 pump is popular, but is a very high output pump and rated at 15.5 amps. The 070 pump is rated at 6.5 amps and 3 bar (pressure) and has 3/8 x 5/16 inlet/outlets. 3 bar is 43 PSI, so it may be too power-hungry for this application. The 911 pump is rated at 5.2 amps and 4 bar, so it may be within range, but would require adapter fittings, as it has a 1/2" barb inlet x 12x1.5 outlet fittings. Still looking for some actual test data for amp draw.

UPDATE
I found a page where a fellow has designed a pulse width modulation control circuit for a low-amp fuel pump (he used one from a GSXR600). The big advantage here is it works on a returnless system, just like the GS uses, so you can keep the petcock. The idea is it powers the pump to maintain a set pressure, which is sensed via an OEM type sensor. His page looks fairly detailed. I plan to inquire as to the cost of a completed board. Here is his high level graphic of how it works:

I found a price of $50 elsewhere on his site. The pressure sensors he references are not cheap. The least I could find one for was around $30. I'm not too sure about using an in-tank pump externally. He mentioned possible pump heating problems above 90 degrees. Being in Florida, that's like 10 months of the year.

I will likely stick with plan A.

 

[GS1000G Shopper]

More fuel math. I used the RC Engineering technical notes/sizing page to do some calculating, I recall using it in the past to size injectors for my Trans Am- which was the opposite of what I'm doing here- it has a 383 CID turbocharged motor, high pressure fuel pump, and an MSD boost-a-pump that increases voltage under boost.

The known factors for the GSXR600 system so far is 43 PSI and 39 gallons/hour (148 LPH) for the pump. From what I have read, the injectors are in the range of 225~240cc/minute at 43 PSI.

According to the RC page, to get 90 HP out of my 4 cylinder engine, I only need 149cc/m injectors at 43 PSI. Since the GSXR600 ones are much higher than this, I do not need to run the pressure as high to obtain the desired output. Lower pressure= less amps drawn by the pump (this is likely why other conversions have used 5 amp+ pumps and still worked). Using the RC page, to get 150cc/m out of my 225~240cc/m injectors, I only need to run about 17~20 PSI ideally. Allowing for variables, it looks like I can operate on under 30 PSI OK. Injector timing will be performed by the MS, and fuel pressure regulated by a regulator.

 

[GS1000G Shopper]

Next discovery: Fast idle
I was reading through some older FI threads here, and one problem was a lack of a fast idle for warmup. I noted the GSXR600 has a cable and linkage that operates much like a choke- except all it does is tweak the throttle open slightly via a cam on the linkage. The shop manual says it will raise the RPM from 1,300 to 3,000. It appears it may interface with the GS1000G choke cable, but I have not pulled the cable yet. My throttle bodies were complete with the linkage and short cable.

 

[ArttuH]

I wouldn't go too low on fuel pressure. The injectors need pressure for proper fuel atomization. I think sensible lower limit would be something like 37 psi.

The fast idle mechanism on GSXR600 TBs should work fine with choke lever and cable. I'm using the stock choke lever for that but I can't recall if I used stock cable or if I made new one. Not a big deal any ways.