surging at low speeds

[hawcer]

This is on my project bike (97 fzr600)....and it's still a project,LOL.

anyway, it would hardly start, ran like a turd and and had alternating, inconsistent cylinders cutting out or not firing at all.

So I rebuilt the carbs, retuned the idle mixture and syncronized them. It runs much better...Idles smooth and pulls strong. The only issue I have now is at low speeds. like putting from stop sign to stop sign in first or second gear it has a surge/lurch that can get quite annoying. Crack the throttle just a tad and it smooths right out...and also jumps you right over what I consider a safe speed for in town or neighborhood driving.

Do these just not like to be lugged around at slow speeds or do I need to investigate further and fix an actual problem? I can lug my GSX-R750 no problem in town and it doesn't even start to wake up until over 5,000 rpm.

I guess I'm asking if this is the nature of the beast or not.

Thanks!

[pnbell]

Simply the nature of the beast ... A few things that can make it worse though.

-Obviously Lean or Rich mixture at low RPMs (EX: pod air filters = bad) *Tuning required
-Loose or Worn drive chain
-Worn or hooked front sprocket
-Worn cush drive

but ultimately in my experience these bikes were not built for low speeds and do not perform well at them.

Feathering the Clutch tends to be the best solution.

Changing the final drive will help. Smaller front sprocket and/or larger rear sprocket; 14/47 520 conversion is very popular. I currently have a 14/45 setup which did help a bit with this low speed issue

[hawcer]

Changing the final drive helps too. Smaller front sprocket and/or larger rear sprocket; 14/47 520 conversion is very popular

I think this might have been done since the chain and sprocket set was new when I got it and the rear sprocket seem pretty large as well as the chain size, but I'll look into it when I get home.

Thanks!

[pnbell]

The rear sprocket will say the number of teeth right on it. A 520 chain would actually be smaller than the OEM 530 chain.

[hawcer]

It's a 530 gold chain with a 49 tooth rear sprocket. I didn't bother taking the front cover off to look at the front sprocket count.

I do have the rear wheel off to refinish it and replace the tire. A couple of the cush drives have cracks and could be the culprits....at least they are still in one piece.

[pnbell]

With a 49t rear sprocket should have some decent low end torque.

The cush drive are large chunks of rubber; when you say cracked like do you mean the have deep cracks in the rubber? If these are hard and or shrunk they probably aren't doing their job very well and might be causing this surging for sure.

It might be worth replacing them; $40 for the parts i think.

Also check the condition of your Front Sprocket. it's easy enough to do.

[hawcer]

The sprockets and chain are new...Have only been on the bike less than 100 miles when the front sprocket nut came off and screwed up the cover...thats how it was when I picked it up.

Yes, the rubber pieces of pie...have some cracking in the rubber on a couple. They seem hard and somewhat crunchy on one half of the drive sides and softer and normal looking on the other drive side.

I'll look into finding another set while i have it apart.

Thanks!

[navi7]

Hi Hawcer,
Im just wonder whether you have sorted out ur surge/lurch problem? I got the same problem with my 1990 fzr 600. I got the carbs cleaned and synchronized, new sprockets and 530 chain, but i didnt check the condition of the cush drive.
But as you said, the bike lurch at love speed and revs. I got slip on exhaust, never had original one on it, so cannot say whether the slip on can cause that.
Let me know whether you have sorted it out pls.

Cheers
Ive

[hawcer]

nope, never really did cure the problem. I sold the bike. Sorry

[Mikegeez]

I had the same problem with my fzr600 when I first got it. The emulsion tubes from factory pro helped virtually eliminate this problem for me. Still have to synch my carbs but I am still surprised at how much of a difference it made.

[stalin1221]

I just slightly engage my clutch when my bike starts surging at speeds too low for its revs. Stops it every single time


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