Suzuki GN125 revving problem

khush

Bought a used GN 125 for my son. The bike's revs go very high - up to 5k even while idling at traffic junctions. The gear shifts aren't smooth due to high revving. Observed no issue with throttle cable and butterfly. Opened up the carb and cleaned it, it wasn't dirty anyway. However, I notice carbon deposit on the cylinder between the rubber part and the pin on diaphragm. This cylinder goes up and down in the carb like a piston. I have tried cleaning it with WD 40 w/o success. I think this is causing the high revving problem as the diaphragm may not be moving up and down freely between accelerating and de-accelerating.

Has anyone seen/fixed this problem? please share.

Thanks

Alkers

Can you adjust the idle screw or is the idle moving about the place?

khush

Hi,

I have checked that, does not seem to be the issue, let me explain the issue in detail;

When the bike is started, the revs are normal, 1-1.5 k. Driving up gears as revs climb, they stay up even when the throttle is fully released. Too much fuel appears to be going/released to the engine. The main jet and the pilot jet are fine, I can see through the tiny holes in light.

Cheers

CJhaughey

Check the inlet rubber for leaks, check diaphragm for leaks/holes as well.
To check inlet rubbers start bike and spray wd40 around the inlet rubber if the revs pick up its cracked and letting in air.

listermint

CJhaughey wrote: »

Check the inlet rubber for leaks, check diaphragm for leaks/holes as well.
To check inlet rubbers start bike and spray wd40 around the inlet rubber if the revs pick up its cracked and letting in air.

Ya this is most likely should be a plastic hose between carb and head might be plastic or rubber. Has to be slit.

khush

Hose boots were fine. It is a known problem with GN 125 if unused for prolonged periods. I bought this bike from a guy, who had not used it in the last 3-4 years. I opened up the carb and gave it a good clean; it was not dirty at all. I asked for advise on this helpful forum before putting the carb back on as I was not 100% sure if the cleaning would have fixed the problem. I put the carb back on over the weekend, the problem is 95% gone. Still some issues while idling, it would randomly stall even when the engine is well warmed up. GN 125 is a very affordable generic starter bike, it would have such small issues, other similar spec japs are expensive and are better quality. I have a Honda shadow as well, can swear by Honda's superior quality.

Thanks to all for feedback.

CJhaughey

khush wrote: »

Hose boots were fine. It is a known problem with GN 125 if unused for prolonged periods. I bought this bike from a guy, who had not used it in the last 3-4 years. I opened up the carb and gave it a good clean; it was not dirty at all. I asked for advise on this helpful forum before putting the carb back on as I was not 100% sure if the cleaning would have fixed the problem. I put the carb back on over the weekend, the problem is 95% gone. Still some issues while idling, it would randomly stall even when the engine is well warmed up. GN 125 is a very affordable generic starter bike, it would have such small issues, other similar spec japs are expensive and are better quality. I have a Honda shadow as well, can swear by Honda's superior quality.

Thanks to all for feedback.

You need to clean it ultrasonically to get it properly clean just spraying carb cleaner won't clean it properly as all the small passageways inside the carb body can get clogged with the scum that comes off modern petrol.

khush

Sure, that is a very good advise, will do it next time. Was bit stuck for time.