GS 400E Bogs at highway speed, at 4-6 gear and at 6500 rpm

[Guest]

Hey everyone, long time no see eh.
I finally have gotten my bike on the road again after 4 years. I took it in into a shop where they cleaned and tuned the carbs.

I notice when I am on the highway that the bike struggles to reach past 100 kph, when I am in 4 gear and reach 6000-6500 rpm the bike loses power and bogs.
I am going on a trip to Kelowna, BC this week and I need this sorted out ASAP.

I did put in bad gas in it by accident when I got it running. My mechanic said to put 91 octane and injector cleaner to clear it out. I have only refueled once. When I refueled it I used mid grade fuel since gas is expensive where I am ($1.619/L, regular 89 octane)

What could this issue be caused by?
Carbs: I dont have time for the mechanic to take them out and check.
Fuel/Treatments: Is this a simple fix of using a certain cleaner and fuel?

Sidenote: Carbs were cleaned via ultrasonic cleaner.

[fbody_mike]

Try putting the petcock on pri (prime) and try again. It could just be the petcock not letting enough gas in during more load on the engine. Also, has anyone installed a filter on the fuel line? Those can cause these problems too.

[HAMMERHT]

There no filter for the fuel.
The petcock was rebuilt b/c it was leaking gas into the crankcase.

[fbody_mike]

The rebuilt part can cause this. Sometimes the spring the holds the diaphragm closed is stronger than the factory one. When the engine is under load the vacuum pressure decreases and the spring starts to close off the fuel supply. Putting it on pri lets the fuel run no matter the vacuum. Its a good test to rule out petcock problems.

[Tom R]

I’ve personally experienced this with a rebuild kit years ago...

[Rob S.]

...the bike struggles to reach past 100 kph, when I am in 4 gear and reach 6000-6500 rpm the bike loses power and bogs.

Call me Dr. Obvious, but if this is the way the mechanic returned the bike to you, he didn't do his job. Or worse.

[Rich82GS750TZ]

Call me Dr. Obvious, but if this is the way the mechanic returned the bike to you, he didn't do his job. Or worse.

/\ This!
What does the mechanic you paid good money to say about the bike not running right?

[Tom R]

Is it only at sustained speed? Can you wind through the gears to redline from a stop?
Whether or not the mechanic is going to fix it, it’s useful to point him In the right direction.

[trippivot]

a different test. when you go riding and you get to the situation where you know "the bogging" is happening -- open the enrichener/choke - see how it reacts- that is guide post if the problem is with main jet/ fuel level in carbs. no reaction? it already too rich up there - big reaction? get bigger main jets.

[HAMMERHT]

I brought it to him a second time. The mechanic says he re tuned the carbs (this was done on Saturday)
i tried on Sunday and it did the same thing, I don’t want to say his work is bad yet, he has done good work for me in the past.
I will check the petcock and choke checks before I go on my trip. I can’t use another vehicle and part of this trip is for my business; so I can’t cancel it.
The bike red lines from 1-3 gears, once I get close to 100 kph, 4th gear and 6-6500 rpm I feel it bogging.
In town and on smaller highways where the top speed is 90 kph it’s fine.

[Rob S.]

...I don’t want to say his work is bad yet...
The bike red lines from 1-3 gears, once I get close to 100 kph, 4th gear and 6-6500 rpm I feel it bogging.

You don't want to say it? I'll say it. If he doesn't have a dynamometer, the bike should be road tested before returning it to customer.

100 kph is only 62 mph. Your bike should do the buck (160 kph).

[Gorminrider]

open petcock to prime was mentioned... the flip side of fuel starvation is an air leak. Or maybe your chain is too tight. maybe a new spark plug...a few "quickies" to try

Failing a quick fix, teardown of carbs and checking slides-diaphragms too, checking of valves,compression, plugs et al is likely in your future.

My gsx400 runs fine on low octane but the chevron 94 really cleans those plugs!

If he doesn't have a dynamometer, the bike should be road tested before returning it to customer

haha.. it's kinda hard to get up to 60mph anywhere very near Victoria let alone expect a mechanic to shut down his shop, and make an outing of it on a 35 year old motorcycle.

PS this thread shoud probably be in the Technical/Twins forum