1980 GS550E + 2000 Katana 750

[scott s]

Got the washers for the petcock screws installed and got the tank back on. Adjusted the clutch a little bit and HOLY HELL, this thing will fly!!

There's a tiny bit of low speed blubber or stumble. I can probably attribute that to the pods. But it's minor enough that I think I can get used to it and learn to work around it with the throttle.

I still need to pull the sprocket cover and check the neutral switch wires. I'd like to have that figured out before the first oil change, just so I can have one on hand if I need to replace it.

 

[scott s]

Still have this one, still not on the road.

I definitely have some carb tuning/fuel delivery work ahead of me.
When riding at normal speeds, part throttle, I could feel a sort of surging. I figured the pilot jets and/or mixture screws needed tuning. It pulls like a banshee up top, but will sometimes stall after a WOT run. Running out of gas, maybe?

I was starting it weekly until I could get to the dyno, and now it won't start. I have spark, so I suspect the vacuum petcock may have failed. There is no PRIME position on this one. I know how to check it....just need to do it. I got really burned out.

I used a DynoJet Stage III kit and went with their 140 main jets (which they measure differently that Mikuni does), their needles and set the mixture screws to 2.5 turns out. I DID NOT drill and tap the slides for the plugs they use. I'm told that's only to slow down the rate of the slides raising.
Knowing what I know now, I would have gone with an assortment of Mikuni jets or the Factory Pro kit.

Plus, the choke cable came loose from the carbs. I need to have one made that is about 2-3" longer. Who does that? Motion Pro?

Any suggestions for a low profile, non vacuum petcock?

 

[doc_rot]

Motion pro does custom cables. but not cheap or fast. look at a bandit 6 or 12 for possible cable replacement. Despite what many people say its possible to get CV carbs to work well with pod filters, i suspect there are several issues in the carbs making it hard to diagnose your problem. Have you done any plug chops? Getting on a Dyno makes it dead easy with a good operator. What does your current petcock look like? screw on or bolt on?

 

[scott s]

Dyno tuning was on the to-do list when the bike decided to take a nap.

The petcock bolts on with two screws, about 44mm apart.

The DynoJet kit only came with needles and mains. I feel like a needle adjustment is in order. I also think the pilot jets could be changed, but I can't find crap for info about the pilot circuit or jet sizes and it's been a while since I was in the carbs. Don't remember what it looked like or what size they were (the pilot jets).

No plug chops yet.....nearly impossible to pull a plug without removing the tank. That engine is shoehorned in there!

 

[scott s]

Dug into the GS/Kat today. The petcock seems fine, fuel flowed like crazy when I sucked on the vacuum line. Plus, the petcock is actually a pretty good size, with a 6.5mm I.D. My guess is that it will flow just fine for the 750 engine. When I cross reference the Suzuki part number, the same cock was used on the GS1000.

 

[scott s]

I got the choke cable back in place. That's a fiddly little sucker, and I don't know what is gonna keep it from popping out again. It could stand to be about two inches longer, so it isn't so tight when it exits at the front of the tank and goes up to the handlebars. I looked at a Bandit 1200 cable, but I don't know if it's any longer, and it doesn't have the spring. I would REALLY be concerned with it coming loose without the spring.

 

[scott s]

I was about to hook up my IV fuel bottle and see if she'd start but decided to pull a plug real quick. They're basically impossible to pull with the tank in place. Last time, I checked for spark by taking a spare plug and laying it on the head.
Pulling the #4 plug revealed the cause of my issues.

Fouled all to crap. I will clean these and double check that it will run on the fuel bottle, but I've already ordered a set of 4 new plugs. At this point, I'm just going to leave the bodywork off until I can schedule some dyno time and carb tuning.

 

[doc_rot]

Its a pain in the ass to check the plugs on these engines. what coils/plugs/igintion are you using? there were ignition changes in the various years and its not all compatible. Its possible its breaking up at certain RPM. I have the same issue on my gsxr with the choke cable. If it pisses me off enough I will convert it to a simple pull on the carb rack

 

[scott s]

Stock '00 Kat 750 coils/wires/caps and NGK CR9EK plugs.

 

[scott s]

Here we are, nearly a year later, and I'm finally getting this thing on the dyno for some tuning. It's just been sitting ever since my last post. I really hope it won't take much to dial it in.



Any guesses on the numbers she puts down?



2000 GSX-750F

BST 36 carbs, DynoJet stage 3, RamAir filters

Stock header with a Yoshimura exhaust

Timing advancer slotted (currently stock US timing, will experiment with + 3-5 degrees)

 

[scott s]

I ended up selling this bike to my friend. He fiddled with it while he was healing from his moto accident and got it running, but tuning the carbs was being a PITA, so he installed some flat slides.
On the dyno, it made 86 RWHP and 45 lb/ft TQ. He said, in his experience, on his dyno, that's well over 95 HP at the crank. He believes there's more in it with some more jetting changes. He's also upgraded the ignition since then. He said the slotted timing adjuster made a difference in the mid-range.

He also commented that the suspension is really dialed in, which means a lot since my dad and I did it all at home with string and a plumb-bob. I always thought the swingarm was too long, but he says it's the same wheelbase as many Ducatis he works on. He also said it lifts the front wheel easily in 1st and 2nd gear!

I made him promise to give me first refusal if he decides to sell it.

 

[doc_rot]

I think stock the katana made something like 90-92 HP so thats a small increase from the flatslides. Probably alot better throttle response as well. Its a cool bike. Hopefully you get it back at some point. Thanks for the update.