Suzuki GT750 Neuvo Retro Cafe Racer

[Suzukidave]

Excellent , you designed the look perfectly .. posed on the rear stand it looks bad ass .

[zk0ot]

That seat works so well. Geez. Can't wait for my 380 to come together this spring.

[CJF]

It's a killer bike...you should be proud. The best part about building a custom bike like this is knowing you will never pull up beside another one like it on the road.....ever!! You're going to get lots of looks with this one. Nice work!!

[Alan H]

That looks proffessional.

[Rassie]

Thank you gents for all the comments either good or bad. I realize it will not be to everyone's liking. I did ride it about 50 miles so far and all is not perfect. The gear ratios need to be tweaked since she runs out of steam at about 90mph. I think I need to get a 15 front sprocket one up from the 14 I have now. That should solve that problem. It also surges pretty badly under closed and partially open throttle, Ringding was riding with me yesterday and actually gave me some good advice on how to address that. I believe there is a mod that I can do but I will start by synching the carbs and then also lift the needles one more notch to set it in the highest position. It is one down from the highest now. If that does not work I will ask for more help here. However in the mean time any other advice will be welcome.

[Suzukidave]

Check out Service bulletin #36 http://www.oldjapanesebikes.com/mraxl_G ... etins.html" onclick="window.open(this.href);return false;

[Rassie]

Check out Service bulletin #36 http://www.oldjapanesebikes.com/mraxl_G ... etins.html" onclick="window.open(this.href);return false;" onclick="window.open(this.href);return false;

Printed it out so I can do it.

[Rassie]

The Threesome next to Ringding's very nicely done stock GT750 during our outing yesterday.

[tz375]

That is looking awesome.

I think that http://pinkpossum.com/GT750/carb/BS40carbs.htm" onclick="window.open(this.href);return false; has it covered too. The air jets are stock Mikuni and teh tap is available from your local hardware store with any luck.

[RING_DING]

Hey Rassie,
I dug up some notes I kept on surging. Came from posts on Kettle Clinick. Depending on a number of other possible root causes, the jury is out on whether the airjet mod on its own will magically make the surging go away. I still had it (not as bad but still unacceptable) even after doing the mod. The notes mention a number of things to check including sticking butterflies, carb sync, idle speed, etc. If I had to do it again I would only do the airjet mod as a last resort. If any of the other factors are at fault, the airjets may not help.
Hope this helps

[Rassie]

Thanks Ringding, printed it out and will study the materials I have gathered. I hope to attempt to address it next weekend.

[Rassie]

Just a quick update. This evening I lifted the needles one notch to their highest setting. Hopefully this will help with the surging I have been experiencing. It worked for Ringding on his silver bike. I plan to ride it over the weekend and then, once it is nice and warm to sync the carbs. I will report back how this worked out. To summarize:

Started with:

Pilots 145 - slight hesitation of the mark.
Mains 115 - revved out quite nicely through the gears with a strong powerband plugs were coffee color.
Needles second to highest setting (one up from bottom notch) -

Current setup:

Pilots 147.5 - feels good off the mark, no hesitation so I think these are correct.
Mains 120 - revs out quite nicely on the highway with a strong powerband but I have only gone up to about 90 mph so no WOT running yet. Plugs still coffee color so may end up going to 122.5's but will do a WOT plug chop first to confirm.
Needles Highest setting (bottom notch) - Not tested yet but they were on the second to last setting and midrange felt a little lean or flat with surging off throttle or on part throttle.

One other thing I may try is to richen up the idle screws a quarter or so turn as well. However I will take it one step at a time.

[Rassie]

I took the Threesome out for a quick 30 minute out and return spin, about 20 miles. The weather is so nice here in NC. Anyway I am happy to report that lifting the needles to the highest setting had the correct effect. The bucking is now much better than before and I can feel the mid range is a little stronger. I also synced the carbs using the method suggested by Ringding. It was really easy to do (took all of 10 minutes tops) and I did it without removing the gas tank, thanks to some nicely angled 10mm wrenches and a shorty screwdriver. The sync definitely cleaned up throttle response quite a bit and it just sounds and rides better. Idle is perfect now as well.

Since the needles are now at their highest setting I think I need to try a washer underneath the needles to see if it will clean up the bucking even further. Not sure if anyone here has tried to put washers under the needles to lift them beyond the highest setting. Would be interested to know if anyone did. I took a look at the washers I have and they would be equal to about halfway between notches. So 2 washers will be equal to one notch. Looking at it that way I cannot see any harm in trying one washer.

For some reason today the WOT felt a little weak, could be my imagination but I think I will go to 122.5 main jets as well to see how that works out. Also did a quick plug check and it looks a nice brown coffee color, sort of like coffee with just a dash of milk in it. So it seems I can richen it up a tad more. May also try adding just a tad more idle screw, maybe a quarter of a turn, but will do that as a last resort. So my next setting will be the following:

Pilots 47.5
Mains 122.5
Needles lowest notch with one washer underneath.

Will probably only be able to ride again Sunday due to bad weather approaching so will report back then what I find.

[tz375]

That's great feedback. Do you have any plans to strap the poor girl to a dyno to see what the mixture loos like?

I was looking at dyno charts the other day and comparing them to a video of the same runs and it looks to me as if the operator rolled the throttle on quite slowly. Assuming - and that's a huge assumption - that the slides lifted somewhat similarly to a slide carb, that means the lean spot in our runs corresponded to partly lifted slides.

With a 3 into 1 I was able to weld in an O2 sensor bung and fitted a wide band sensor and yesterday I worked out how to add a TPS. Next I need to order an Aux Box to track RPM, TPS and MAP against Air:Fuel ratios and see if I can make any sense out of the data.

That can all wait a while though. They are forecasting 5-7" of wide stuff over the next 24 hours with an inch of ice to top it off.

[Rassie]

No dyno runs are planned for the old lady. I am planning to just go seat of the pants for now, maybe later if I can find someone I can trust with a dyno. Interesting observation on your dyno runs, so the needle lift together with what you observed is a good indicator that the part throttle lean condition is real. If the extra washers under the needles clears up the bucking or further improves it then I guess we can confirm that. That makes me think though, that I should hold off on the larger main jets first so we can get a clear and unadulterated view on what the washers under the needles will do.