1981 gs750 (gs750e) Retro Racer project

[LarsKroghStea]

I want the bike to be easy to move around, so I'll start with throttle, clutch and brakes. I've ordered Domino XM2 Throttle with universal cable kit. It's a push/pull setup, but I will only be using one cable and block the other holde. Then I have on in reserve. The sleeves are teflon-lined for low friction, and the kit includes two small teflon tubes for the adjustable carburettor end. They will be cut to fit the adjuster of choice. The kit also include two small "lock-barrels" with set screws. I also ordered ODI grips.

The kit looks like this (the old throttle-cable is in the picture for comparison):

 

[LarsKroghStea]

The finish is great:


It seems like the barrel clamps down really well. When all is good, I'll fix it with locktite and keep a spare with me. I had to cut a couple of strands from the old cable, as the Domino cable is thinner.



Here's a test with some old gsx750 carbs:

The original cable had a bend in it, near the carbs, so I think I'll go with the prebent adjusters. Any advice (apart from cleaning the engine..:cower?

 

[LarsKroghStea]

Fitted the throttle today, and the wire is extremely smooth. The kit came with three different cams; green, white and red. The red cam gives fast resonse from the start, then tapers off. The white has a greater circumference all the way around, and requires less twist to full throttle. The green one is the mildest, and the one I'm choosing as I think it will be easier around town. The other two are mainly for racing.






The bends have separate teflon tubes:




The sleeve was about 22cm too long:




The bend at the carb end made for a pretty smooth installation, and a nice slope towards the frame:




This is with the handlebars pointing straight forwards:




And this is with the handlebars all the way to the left (more than all the way, as I haven't installed the stoppers yet):

 

[93Bandit]

Holy smokes the corrosion on the carbs in that image!

 

[LarsKroghStea]

Holy smokes the corrosion on the carbs in that image!

I know.. It breaks my heart
Luckily, I took off some of the parts before I put the bike away. The old shed where I kept the bike was more damp than I knew. I cleaned and refurbished the carbs and painted the engine the year before, and now it looks like crap. The aluminum surface of the engine has also corroded, and the paint is flaking off. I'm not sure how I can fix this, so I'll fockus on finishing the build first, then I'll have a go at the paint. I'm considereing buying a set of engine sidecovers and a valve cover to make the job easier. The carbs will be pretty easy to clean, but I'll probably wait until winter before I take them completely apart.

 

[LarsKroghStea]

Wired up the ignition to test if the engine would start. It didn't, and the left coil got extremely hot. I won't bother with any troubleshooting, as I've already bought a set of Dyna coils because of the worn out plug wires and bad looking OEM coils: Does anyone have any experience with Dyna coils? They came with plug wires that you have to cut and terminate yourself, but I guess I can just buy ready made plug wires with the right length? Do plug wires differ in resistance or anything like that?

Old vs. New:

 

[LarsKroghStea]

Wired up the coils and shortened the spark wires




Also bought new spark plugs:



The old ones where the plugs that are intednded for the 8valve engine. The main difference I could spot is that they have extra internal resistance for noise suppression. Does it matter which one I use?

 

[LarsKroghStea]

Btw, the reason that the bike didn't start yesterday was probably a bad connection from the egnition, leading to the coil not discharging. Probably got damaged while the bikes was in storage. Runs well now

 

[Grimly]

Wired up the coils and shortened the spark wires




Also bought new spark plugs:



The old ones where the plugs that are intednded for the 8valve engine. The main difference I could spot is that they have extra internal resistance for noise suppression. Does it matter which one I use?

If you're using unsuppressed leads and caps, it's probably better to use resistor plugs.
The ignition system was designed to work with 5Kohm of resistance per plug (or in the cap).
Now, some will say they're running without resistance at all, and that's fine for them, I don't like to take the chance of shortening the life of my ignitor by running with no resistance.

 

[LarsKroghStea]

If you're using unsuppressed leads and caps, it's probably better to use resistor plugs.
The ignition system was designed to work with 5Kohm of resistance per plug (or in the cap).
Now, some will say they're running without resistance at all, and that's fine for them, I don't like to take the chance of shortening the life of my ignitor by running with no resistance.

Does that apply to the gs750 E (16 valve) or GSX 750, as it's called in Europe? I couldn't find out if it did, as the gs750 (8 valve) originally came with R plug, and the gsx750 came with no risistance plugs. The service manual for my bike, lists D8EA as the right plug.

 

[Grimly]

The 8-valve didn't originally come with a resistor plug, as far as I know - it had resistor caps of 5Kohm. The plug was the fairly universal 14mm B8ES.
Plugs I find listed for the 16-valve engine are, as you say, non-resistor too (12mm D8EA), but I'd be surprised if there was no resistor in the caps.
I'd download a manual and find out for certain - you can run it any way you like and it might not cause a problem, but better to be sure.
Several members here are (or have) run them, so somebody who knows for sure can chime in.

 

[LarsKroghStea]

The 8-valve didn't originally come with a resistor plug, as far as I know - it had resistor caps of 5Kohm. The plug was the fairly universal 14mm B8ES.
Plugs I find listed for the 16-valve engine are, as you say, non-resistor too (12mm D8EA), but I'd be surprised if there was no resistor in the caps.
I'd download a manual and find out for certain - you can run it any way you like and it might not cause a problem, but better to be sure.
Several members here are (or have) run them, so somebody who knows for sure can chime in.

Checked the old caps, and they are 5Kohm NGKs. Descided to measure them, and this is the result:



35Kohm seems like the logical explanaition for the hot coil. The numbering is not cylinder-number, so both 8 and 35 could be on the same coil. Measured the new wires, and they are about 1Kohm, which I believe is pretty standard for about 30cm/1foot of wire. I'll run the new plugs for now, and buy resistor plugs later.

 

[LarsKroghStea]

These are the rearsets I made a few years back, and I'm looking forward to finally try them out:






I'll use the old gear lever at the front, and connect the linkage on the inside. At the back, I'll connect at the outside of the lever:

 

[Grimly]

Measured the new wires, and they are about 1Kohm, which I believe is pretty standard for about 30cm/1foot of wire. I'll run the new plugs for now, and buy resistor plugs later.

What type of ignition wire? If it's carbon-cored, be aware they tend to give up after a while, with bad results.
The standard wire is copper-cored, which is why the caps (or plugs) have the resistor included.
The 1K per foot makes me suspect those are resistance leads, so worth being aware of the state of them.

 

[LarsKroghStea]

What type of ignition wire? If it's carbon-cored, be aware they tend to give up after a while, with bad results.
The standard wire is copper-cored, which is why the caps (or plugs) have the resistor included.
The 1K per foot makes me suspect those are resistance leads, so worth being aware of the state of them.

The wires have a stranded copper core, and measure the same resistance with or without the Dynatek cap. From what I can see on the internet, 1Kohm pr foot is not uncommon for copper-core wires.

 

[Grimly]

The wires have a stranded copper core, and measure the same resistance with or without the Dynatek cap. From what I can see on the internet, 1Kohm pr foot is not uncommon for copper-core wires.

You're either measuring it wrong or you don't have copper-cored leads.
A proper resistance for copper-cored leads is less than 0.1Ohm per metre.
I've just measured 4m of lead and got 0.3Ohm.

 

[LarsKroghStea]

You're either measuring it wrong or you don't have copper-cored leads.
A proper resistance for copper-cored leads is less than 0.1Ohm per metre.
I've just measured 4m of lead and got 0.3Ohm.

I might have measured wrong, somehow. I agree with you that there's no reason for copper wire to have som much resistance. Either way, I'm leaving this for the time being. There's som many other things to do

 

[LarsKroghStea]

Today I mounted a new OEM clutch cable. The old one was so worn, that I almost had to use two hands to clamp down the lever.. The new cable was about 10cm shorter than the old one, so maybe one of them wasn't exactly the right cable. I needed a shorter one, so that suited me well anyway.

I noticed earlier that my rear master cylinder was leaking. Took it off today, and it has definitely reached end of life I searched the net for a replacement, but it seems that all the well known brands mostly produce them in 40mm and sometimes 50mm (center to center measurement for the mounting holes). I had another one lying around, which is also 40mm, and for now I'll make a bracket and mount that one.



I've also had some problems with the watherpack connectors I use. I replaced most of them with other automotive connector, but I wamt to be sure that some of the connecctions are waterproof (e.g ignitionc etc.). According to most people the newer DEUTSCH connectors are a much better option for weatherproofing. I allready have the tools, as I don't mind double-crimping.

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[LarsKroghStea]

I'm also contemplating on putting a hugger/rear fender on the swingarm, to keep mud and dirt from spraying all over. Did this on my old Kawasaki Ninja, and it makes a big difference. As it hugges the rear tyre pretty tight it doesn't take away too much from the design either. Does anyone now of any aftermarket fenders/huggers that will fit, or any second hand fenders that kan be modded and mounted on the swingarm?

 

[LarsKroghStea]

With the throttle and clutch going, I'm fokusing on brakes (standard order of priority ). The brake pads that came with my calipers are the EBC FA379HH Double-H Sintered pads. They are quality pads with good reviews, and I'll stick with them.

I have an unused set of steel braided brake lines that I bought for the original fork. It's a setup with three lines, and they are far too long for the new short fork and clip ons.
The two long ones measure 62cm, and that's enough for making a cross over setup, like this:


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I will route the front left brake line over the Ducati fender: It looks like this, but I've drilled out the rivets. I'll have to make new fender stands as my front tyre is 19" vs the Ducatis 17".

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