Minor sputter under heavy acceleration

[flotsamandjetsam]

Hi Everyone,

I have a '98 zg1000 -

When I really get on the throttle, the bike kind of sputters a bit between 3,000-4,000rpms then it takes off and runs normally. It's not real bad, but noticeable. Other than this oddity, the bike runs fine. I usually only notice this behavior through the first couple of gears because buy the time I hit 4th, I am going so fast that I have back-off.

I have recently rebuilt carbs and sync'ed them.

Any ideas what might be causing this? Or how to diagnose?

I am thinking it could be something in the spark plugs, or wires, or the fuel delivery system?

 

[Denny in NJ]

I'm leaning towards an ignition issue but more information is needed. You rebuilt and sync'ed your carbs. Did the sputters happen immediately afterwards or much later? When was the last time that valves were adjusted? Did the sputters happen immediately afterwards? Assuming your work on the carbs was correct as well as recent valve adjustments then I would check your ignition system as follows:
1.) Check electrical resistance levels in primary coils are in spec. 2.) Check resistance levels in pickup coils are in spec. 3.) Check air gaps in pickup coils are in spec. and adjust if necessary. If resistance levels out of spec., replace unit(s). These tests are outlined in the Clymer manual or factory manual. I prefer the Clymer manual. I had a sputter at idle on my '02 that was fixed with new pickup coils. Hope this helps.

 

[flotsamandjetsam]

I'm leaning towards an ignition issue but more information is needed. You rebuilt and sync'ed your carbs. Did the sputters happen immediately afterwards or much later? When was the last time that valves were adjusted? Did the sputters happen immediately afterwards? Assuming your work on the carbs was correct as well as recent valve adjustments then I would check your ignition system as follows:
1.) Check electrical resistance levels in primary coils are in spec. 2.) Check resistance levels in pickup coils are in spec. 3.) Check air gaps in pickup coils are in spec. and adjust if necessary. If resistance levels out of spec., replace unit(s). These tests are outlined in the Clymer manual or factory manual. I prefer the Clymer manual. I had a sputter at idle on my '02 that was fixed with new pickup coils. Hope this helps.

Thank you for the reply. I am suspecting the ignition system as well.

I inherited this bike as a project and it needed quite a bit of work, I am so happy that I have it running as well as it does, that I didn't really pay much attention to some of the finer details at first. Before the carb rebuild, it would barely idle and was running rugged all over, afterwards, it was a new bike.

Now that I have more time in the saddle on this bike, I am starting really get a feel for its personality. I have ridden it about 500 miles now and noticed this sputter at around the 200 mile mark. It's not bad enough to stop riding, but possibly an indicator of something not quite right or a component going bad. I am also wondering if this is affecting my fuel economy, I am getting around 34mpg. (not sure if that is about normal or not)

I know that the person that gifted me this project had 1 cylinder that wasn't firing and replaced the plug wire and that corrected the issue. As far as a I know these are the original coils, so anything is possible. He replaced it with some used stuff from eBay. (So I actually have 2 sets of ignition coils) I also need to check with him if he put in new spark plugs.

I will start testing the coils when I get a chance and see if it helps and provide an update.