Bike is bogging when given full throttle

[ride_002000]

Hey guys, bike is a 1978 GS750E. Bought it a week and a half ago and rode it around my apartment complex for a couple mins before I bought it then started tearing into it replacing things and making it more my style.

As far as I know the carbs are stock, so what I know is what you guys know. Also has a 4 into 2 exhaust.

The airbox was trashed on it so I put all new weather striping, cleaned and re-oiled the K&N filter that was in there and made sure all was sealed up good.

I started it up the other day and it started right up, idled great I could rev it up slowly to full throttle just fine and sounded great, but when I give it full throttle during idle quickly it bogs until dies or I let off.

Havent pulled the plugs but the old plugs that were in there that I replaced were black, telling me it was running rich. I need to get the arm for the clutch back on and working so I can take it for a ride and analyze it more.

I did read on the forum that these bikes are common for bogging if given full throttle at low RPM, not sure if it was correct or not. Wondering if I should put on a stock filter rather than the K&N? Or any other ideas as to why it bogs?

Thanks

[Steve]

Is your 4 into 2 exhaust stock or aftermarket?

If it's aftermarket, the combination of that and the K&N filter might require a slight re-jetting in the carbs.

You should also be aware that NO carb likes to be snapped from closed (idle) to full open. There just isn't enough air speed through the throats to maintain fuel flow through the jets. That is one reason the CV-type carbs were introduced, to maintain the air flow that would prevent the bogging.

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[ride_002000]

Not sure if the exhaust is stock or aftermarket. I attached a pic below, I dont see any markings on them or anything. I would assume aftermarket just cuz they look fairly new, the chrome is clean and not pitted giving me the impression they havent been on the bike for too long. I really dont want to take the carbs off (it scares me and I dont have a place to do it) I live in an apartment and im scraping by doing the mods I am doing in my carport.

Would going to a different air filter help alittle?

And Im not used to these old bikes, I have had a 2000 Honda CBR600 (carbed) and a 2002 Yamaha R1 (Fuel injected) and could blast the throttle no problem but understand this is an old bike and wasnt sure if this is normal or not.

[Steve]

Not sure if the exhaust is stock or aftermarket.

Definitely NOT stock.

Here are some of the BEST-looking stock pipes I have seen in a long time, and they are on a '78 750E, to boot.







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[ride_002000]

Thanks Steve, The bike actually runs great. Took it out a few times and accelerates great, is very smooth and shifts perfect. Took it up to 9k rpms and was smooth the whole way.

I got my new shocks put on today and the tank wrapped (think I might paint it tho) and im changing the fork oil tomorrow. Then going to go for a nice long ride to see how she feels.