GS425 losing power at high RPM + backfires

[mwootto]

In neutral backfiring is very common even at around 3 or 4k not so much when I'm in gear except at high rpms and I'm losing power and can't go over about 80-85ish. Just found out I should be using 90 octane or higher. Past few months I've been using 87 thinking that higher octane was bad for old small engines Is it likely that this is the only problem or is there something else more pressing going on? Maybe I should replace the intake boots and rings? Re sync carbs? Thanks in advance for any advice.

 

[Charlie G]

I had a 77 GS400 and it would do 105mph. Like has been said, I'm sure, bebuild the carbs by dipping in Berrymens 24 hours, with new o-rings in carbs and the intake boots. Adjust the valves to specification and make sure the air box is sealed up tight. Once you have done that you'll have a better shot figuring out what else it needs. Some site members kicked me in the rear to do just that and it worked out for me. I found that it had the wrong jets in my carbs, they were dirty and the air box was leaking. My 650 had the very same symptoms as yours. Start with these and go from there.

Charlie G

 

[GregT]

If it's still on points ignition, a check of the gaps and condition of the points followed by running a timing light on it wouldn't hurt.

Greg T

 

[duaneage]

Lean out condition. Likely leaking o rings on the boots or the boots themselves on the carbs to head are leaking. Could be fuel flow problems, stuck float, dirty jets in the carbs, etc.


" I'm losing power and can't go over about 80-85ish"

Of course, getting a 4 cylinder bike (like an 1100E) would give you a higher top speed.

 

[Nessism]

In neutral backfiring is very common even at around 3 or 4k not so much when I'm in gear except at high rpms and I'm losing power and can't go over about 80-85ish. Just found out I should be using 90 octane or higher. Past few months I've been using 87 thinking that higher octane was bad for old small engines Is it likely that this is the only problem or is there something else more pressing going on? Maybe I should replace the intake boots and rings? Re sync carbs? Thanks in advance for any advice.

Regular gas is fine. What makes you think you need 90 octane of higher?

 

[Guest]

Are the carbs clean?
Are the valves adjusted?
Is the airbox fitted?
It the ignition igniting?
What's the compression numbers?

 

[mwootto]

ok i just need to stop being lazy and dip the carbs, replace o-rings and probably boots check the airbox, and sync the valves, I've known I should do that just been putting it off, then I'll go from there.

duaneage - yeah a bigger bike would be nice, but I know mine can get up to about 100 when it's working properly at the very least it was doing 90 with ease when i first got it

ed - i've always heard regular is fine but clymer's says 90 or higher. i can spare the few extra bucks

 

[skizm]

Where does one find boots for a bike this old? I have a gs1000g and can't seem to find them anywhere.

 

[80GS1000]

Where does one find boots for a bike this old? I have a gs1000g and can't seem to find them anywhere.

Check the OEM parts catalog on bikebandit.com. Fast service and decent prices, way less than your local dealer would charge.