K&N Air Filter Replacement (Non-Pod) and Potential Exhaust upgrade for my GS750

[sam000lee]

My 1977 GS750 is basically stock and has been running great for the past few years. I've never replaced/cleaned the airbox filter but it's probably time. There's currently a UNI filter. Does anybody have experience with the K&N oem-style replacements? For my bike it's the SU-1200 - you can get it on amazon: https://www.amazon.com/1200-Suzuki-Performance-Replacement-Filter/dp/B000E2CUCK

Do I need to rejet for these or are they similar to the stock set up?

Secondly, I'm thinking about making some upgrades including a Delkavic 4-1. I've read through the threads about the V&H vs. Mac vs Delkavic and am feeling good about this option with the straight cans. Anything to consider here while I'm also going through the airbox?

Thanks as always.

 

[LAB3]

If you're carbs and intake are stock, keep 'em that way. The engineers that designed it have a better grasp and how to make a bike run right under a variety of conditions than most if not all of us do. There's no shortage of marketing claims that say "we're better" but in the end that's all they are, marketing claims.

 

[allojohn]

Carbs are fine as is in both cases. If you put pods on it all changes....
BTW, the Delkavic is a nice bit of kit.

 

[Nessism]

K&N's flow lots of air because they don't filter that well. There are tests available on the internet if you want to see more details. It's not a huge big deal since you are using the stock airbox but in my opinion I'd stay with the stock foam filter.

 

[sam000lee]

Reviving this thread - I've noticed more this summer that my bike is hesitating at close-to WOT throttle pulls. I pulled the UNI air filter to inspect, clean and re-oil and it essentially came apart in my hands as I was washing it. I bought the K&N SU-1200 replacement filter that should be arriving tomorrow. As far as I can tell no re-jetting is necessary. I'll post back once it's installed and I've had the chance to get the bike out. If all is well, I think I'm going to go for the delkavic, too.

 

[dorkburger]

I used a K&N drop in factory style in my 1150e years ago. Ran great before, ran great after.

 

[Big T]

I've been running a K&N drop in for 30 years in my 78. No problems

 

[sam000lee]

Well I dropped in the K&N after following the oiling instructions. Took it out on the highway and it was still bogging down at anything past 1/3-1/2 throttle. Pulled the carbs off and found THIS:

Needless to say the bike rips now after screwing that jet back in

I rebuilt the carbs before I went cross country on the bike a few years ago and have had them off the bike maybe once or twice since I got back. It must have worked its way out sometime this year.

Two things:

1. There's another issue that I noticed. When I pull hard on the throttle at close-to-WOT, the bike accelerates hard. Once it hits the power band and smoothes out, every once in a while the engine RPM's will suddenly shoot up as if I've pulled in the clutch and the acceleration will slow. If I let off the throttle a little bit and then ease back in, the engine speed will fall back to normal levels and accelerate as expected.

Could this be a clutch slippage under the (revived) power of the engine?

2. The main jet is a 102. My bike has a manufacture year of 1976 (as indicated on the neck). The basscliff chart has three bikes for the GS750 for those years:

1976 - GS750 - Main jet 105 - P1 Needle - Pilot 22.5
1977 -GS750B - Main jet 97.5 - O6 Needle - Pilot 27.5
1977 - GS750 - Main jet 105 - P1 Needle - Pilot 22.5

The bike feels great at everything up until the very top of the power band at WOT where I think it could be lacking just a little power. I should probably pull them off the bike again and see what the pilot jets and needle are as a point of reference (I'm kicking myself for not just looking yesterday) but assuming they're the P1 needle, should I bump the mains up to 105? I'm thinking about putting down for a Delkavic and would imagine if it's slightly lean now with the 102's, the K&N + Delkavic would warrant slightly larger main jets, even though either alone doesn't.

 

[chris]

What you described is a sign of clutch slippage. I think a clutch inspection is in order. About your exhaust, I had a Vance and Hines exhaust on my 1100e, it was a excellent performer but I had to weld it at least 4 times during 20 years of ownership, the first cracks appeared when it was only 3 years old. Maybe try the Delkavic, you can go to the Vance and Hines web sight to see if they have jetting specs . If I remember correctly they did at one time. A well jetted carb and free flowing exhaust is a nice combo.

 

[sam000lee]

I had bought clutch springs a while back and tossed them in a few days ago. Honestly it feels like a different bike coming out of first. Before as I let the clutch it would drag for a second and it engages quickly and smoothly now. Handles full throttle better, too. I had never messed with my clutch before so it was cool seeing up close how the friction mechanism works. Thanks for the help

For fun, here's a picture of my GS750 next to the GS550 I've been fixing up for the past few weeks.