GT750 with CV carb Needle Jet available

[tz375]

I don't remember but it has to be an early Suzuki item I suspect. I scanned a couple of pages a few years ago. I have no idea where the original hard copy is though. That's not 100% true. I haven't seen it in a while, but it has to be in one of about 4 places under a pile of other stuff.

As I'm typing I seem to recall buying it from someone on here so it's an early Suzuki carb manual. It was beige IIRC, but the date of publication etc escape me.

[Vintageman]

Update

In this post I stated I was getting ~ 30 MPG (USA). I want to add that my plugs were also a dark black color and #8 per stock heat range plugs for a 1975 (funny a 74 is #6 and two steps hotter plug?).

When I accelerated say 1/16 up to 3/16 throttle pos and held fixed each time, it would not have climbed from low rpm to high rpm smoothly. It may have stumbled and/or skipped once or twice as it climbed up, which it did. Always opening throttle a bit as I climb rpms climb was OK. Not what I like or call a good tune. As stated in this post I felt my exhaust fumes were too heavy of fuel IMO and 30 MPG seams poor

I was all stock jetting carbs for a 75 but, put the 0.8 air jet mod for bucking per Suz bulletin. The only thing not stock are the Jemcos 3 into 3. I have not reverted back to my stock exhaust ... almost did but now having good luck tuning

Here is what I have done since:

I pulled the pilot air jet addition out and as long as my idle fuels screws are a strong 3/4 open no bucking.

My 75 is supposed to have the needle clip third position. 76 and 77 Suz said 4th (richer). My bike was 4th when I got it and I just changed to third clip for too rich I believe. I also put new Needle Jets (originals had some oxidation but seen worse). Verified float heights and OK

So in summary and in order

1) Removed air jet 0.8
2) New needle jets
3) Clip from 4th to 3rd (still original needles and look OK).

Each step helped smoothness and fuel economy. The dang thing is getting very enjoyable to cruise around, were before it was too much of an effort to keep it purring along and found I was not riding it.

My last MPG was 38.3 and I was not riding too hard nor trying for best MPG.

It still may miss/stumble now and again uses method stated above. The more I try the less it stumbles (plugs warming up?).

I looked at plugs and L and R still a too dark, center plug lighter chocolate brown and close enough. since I ride mostly needle jet circuit I changed L and R clip to pos #2. Even smoother. I was also going to try #7 neat range plug (why is a 1974L a #6 heat range? No difference I can see with engine).

I went back to 3rd clip and #8 plugs. I ordered new needle jets and driving them through a back order where I just heard they are due 08/05/15 (not obsolete… we’ll see). Although my needles look OK by eye (not new of course) they must have some wear (19K miles). So I'll try that next.

The other idea are #7 plugs, #2 clip pos and/ or better ignition coils if new needle do not clean up too rich when running mostly off needle jet circuit

Just thought experience worth sharing

[tz375]

Just a word to the wise: Plug color on the nose at 1/2 throttle doesn't tell you much at all and if you try to jet to get it looking the "right" color on the needle jet, it will be way too lean.

The thing we all tend to forget is that plug color is a function of its temperature. At low to mid throttle the plugs are relatively cool and there is a carbon buildup. Open the taps and run it hard and plug temps go way up, even at the same A:F ratio. Plug reading is only really effective at wide open throttle under load. AT any less than that the plugs should look rich.

How rich they should look is a good question, so watch that water temperature gauge.