Suzuki GT750 Neuvo Retro Cafe Racer

[Rassie]

Quick update on the chain issue. Turns out to be an alignment issue. I forgot to install a 2mm washer next to the sprocket hub and the wheel was not properly aligned. So problem solved.

PS: Also please see my last post on the previous page regarding jetting...

[tz375]

Timing:
All three are the same. The reason that they look different is because the outers are at an angle and the center plug is vertical. All three should fire at the same distance or angle BTDC It's 20 degrees or 22 I can't remember which. I set mine with a dial gauge before the head is fitted.

Jetting:
The stagger is not required with chambers. That was a function of the split center pipe on stock bikes. Other's have their own explanations as to why the center ran cooler or richer, but I'll stick with the pipe story.
I ran mine on the dyno with Jemco pipes, UNI 6" oiled filters, 115 mains, needle in the 4th clip and 47.5 pilots and it was too lean all the way up the range.

On stock pipes that set up was between 16:1 and 18:1, so way lean (some of that may have been because the probe was too close to the end of the tailpipe). With Jemco pipes it was lean at lower revs and got slightly richer as revs climbed. On mine I suspect that 120 would be OK at high revs but too lean still at mid throttle, so I'll try raising the needle to the bottom position and 117.5 mains and see how that looks.

If that is still lean at lower revs, I'll swap in a set of Z-6 needle jets and drop the needles back 1 notch. I may need to go with a larger main air jet - up from stock 0.5 to tilt the fuels slope back with that set up though.

For your bike I would start with #47.5 pilots, #120 mains and needles all the way up and come back from that if it proves to be too rich. Watch out for part throttle lean conditions though. WOT is rarely the issue.

[Rassie]

Timing:
All three are the same. The reason that they look different is because the outers are at an angle and the center plug is vertical. All three should fire at the same distance or angle BTDC It's 20 degrees or 22 I can't remember which. I set mine with a dial gauge before the head is fitted.

Jetting:
The stagger is not required with chambers. That was a function of the split center pipe on stock bikes. Other's have their own explanations as to why the center ran cooler or richer, but I'll stick with the pipe story.
I ran mine on the dyno with Jemco pipes, UNI 6" oiled filters, 115 mains, needle in the 4th clip and 47.5 pilots and it was too lean all the way up the range.

On stock pipes that set up was between 16:1 and 18:1, so way lean (some of that may have been because the probe was too close to the end of the tailpipe). With Jemco pipes it was lean at lower revs and got slightly richer as revs climbed. On mine I suspect that 120 would be OK at high revs but too lean still at mid throttle, so I'll try raising the needle to the bottom position and 117.5 mains and see how that looks.

If that is still lean at lower revs, I'll swap in a set of Z-6 needle jets and drop the needles back 1 notch. I may need to go with a larger main air jet - up from stock 0.5 to tilt the fuels slope back with that set up though.

For your bike I would start with #47.5 pilots, #120 mains and needles all the way up and come back from that if it proves to be too rich. Watch out for part throttle lean conditions though. WOT is rarely the issue.

Thanks for all that information. It sounds like it would be better then to start out rich and go leaner from there if required as you suggested. I started the bike today with #115 mains in it and the needles on the second notch. I will ride it tomorrow and see how it goes. If it feels like it is on the lean side I will go up to 120 , 47.5 and needles all the way up as you suggested and then work my way down.

[Rassie]

Here is a short video of the startup earlier this afternoon.

http://www.youtube.com/watch?v=qbd05H73 ... tube_gdata" onclick="window.open(this.href);return false;

[CJF]

Looking very nice . Can't wait to see it painted.

[Rassie]

Looking very nice . Can't wait to see it painted.

Yeah same here I am super excited about that, I think I nailed the design and scheme, but will keep it a secret for now. I was going to paint it myself but now having second thoughts. Temperatures are getting pretty low and I do not have a paint booth to heat up things. So I may end up doing some initial prep and then farm out the rest of the paint work. Also expecting things to get crazy at work so I will call my painter guy today and see what he says. I already have all the paint and the job is pretty straight forward so hopefully it will be in a reasonable price range.

[Rassie]

I rode the bike yesterday for about 6 miles, no issues, it runs great with the jetting the way it is set up. Not sure if it is lean, could be. I think I will go up to the next sizes as suggested earlier by tz375 and see if I can feel a difference.

Since I do not have access to a dyno or any other way of telling for sure I guess I will have to try all the options and keep careful records until I find the perfect setup. But having said that it did run just great yesterday with the low end about the same as it was but it now has some serious top end pull. The powerband is very noticeable now, where as before it was less prominent. Honestly I am very happy with the result, just worried about it being too lean and burning holes in the pistons.

[Suzukidave]

The list had a topic run about running CV carbs , pod filters and chambers .. seemed there was engine failures from holed pistons while holding higher rpm , part throttle cruising for some reason . There was some thought that maybe it could have something to do with the rubber part of the stock air box acting like velocity stacks .

[Rassie]

The list had a topic run about running CV carbs , pod filters and chambers .. seemed there was engine failures from holed pistons while holding higher rpm , part throttle cruising for some reason . There was some thought that maybe it could have something to do with the rubber part of the stock air box acting like velocity stacks .

Good to know. I will do some searching to see if I can find it. I went out for a longer ride today to my friend Johann's shop, about 10 miles. On the way there I noticed the temp going over normal if I went over 65 so I just slowed it down and when I got there we checked the plugs, coffee color so way too lean all over the place. I will now go the way tz375 suggested to 47.5 pilots and 120 mains.

Will also be tearing down the bike for paint tomorrow so it will be a good time to do the jets. Also checked the timing with a timing light and it was spot on so no issues there.

[tz375]

The issue that Dave was describing appears to be a part throttle light load situation where the slides are not fully open. One of these days, I'll try a set of larger needle jets to see if that fixes it. I recently purchased a good air:fuel meter and wide band Bosch UEGO sensor, but I have not had time to weld on teh bung, let alone test under real conditions.

[Rassie]

The issue that Dave was describing appears to be a part throttle light load situation where the slides are not fully open. One of these days, I'll try a set of larger needle jets to see if that fixes it. I recently purchased a good air:fuel meter and wide band Bosch UEGO sensor, but I have not had time to weld on teh bung, let alone test under real conditions.

Thanks for clarifying. That is a bit scary. Would appreciate you keeping me posted on your findings. The last thing I want to do is blow up my motor. I think I will also move my needles to the highest setting (in the lowest notch) as a precaution. Sounds like you have already tried this or am I mistaken?

BTW. I ordered main jets all the way up to 125 just in case and my K&N filters came in today so I will be ready to do some tuning soon. Focused on the paint right now.

[tz375]

My needles are in the 4th groove but I have larger pilot jets in and 117.5 or 120 mains (I don't remember which). My bike was buried in the back of the garage for months as we worked on house projects and had visitors.

It may be over 32 degrees today and it it doesn't snow I'll see if I can get it outside and fire it up.

[Rassie]

I have not posted in a while since the start of the New Year. Too many celebrations and functions. I also spent time updating my website which was in desperate need of an overhaul. Now the new year has kicked in and work is demanding all of my time. But hey I still get some time to play with bike stuff. I have since the last posting driven the bike for about 20 or so miles. I was running it with Jemco chambers and pod filters, with, stock 45 pilots, 115 (up from 110) main jets and the needles second slot from the bottom. It was running quite well and felt crisp right through the rev range. I checked the plugs and they are a light coffee color, not good for a 2-stroke and definitely lean. I have now gone up 1 size on the Pilot jets to 47.5 and and 2 sizes on the mains to 120. I have also installed the larger round K&N filters that offer about 4 times the filtering surface area. I am not able to ride it now though to check the jetting since I have stripped the bodywork off for paint. The color scheme is a bit of a secret still, let's just say if you are familiar with Wes Cooley you may have an inkling of what I have in mind. When riding it I also noticed the exhausts moving around a bit too much so I made some new stronger and stiffer exhaust hangers out of quarter inch aluminum. Some pictures below of the new hangers and the carbs with the new larger filters.

[Suzukidave]

Great job on all the details and it will be a super nice custom with the fresh paint You may have a problem with the way you hard mounted the rear hangers , with the vibrations from the engine if the pipes arnt allowed to swing with it cracks in the pipes may form .. mine did .. i had to find a way of soft mounting the pipes .

[Rassie]

Great job on all the details and it will be a super nice custom with the fresh paint You may have a problem with the way you hard mounted the rear hangers , with the vibrations from the engine if the pipes arnt allowed to swing with it cracks in the pipes may form .. mine did .. i had to find a way of soft mounting the pipes .

Gotcha, did think about that some. I thought since the exhausts are just slip on and held there with the spring there may be enough movement to stop that type of thing from happening. It will be easy enough to convert to a rubber mounts though. Just means I have to make another set of hangers.