Author Topic: 5000 rpm flatspot (Read 3876 times)

GK75A · « **on:** August 06, 2006, 06:20:39 AM »

bandit parked up 4 years , new battery, plugs, rebuilt carbs with new seals. air-screw out 2 & 1/4 turns out but it bogs down from 5-6 k. then it clears and takes off. any ideas?

PitterB4 · « **Reply #1 on:** August 06, 2006, 08:52:36 AM »

More info, please.

Is it just a slight hesitation or a real bad bog? Does it get better when it warms up? Mods - exhaust, air filter, jet kit?

GK75A · « **Reply #2 on:** August 06, 2006, 11:51:47 AM »

oops, my bad.
its a 92 uk spec bike, everythin is stock. i`ve balanced and re-checked the carbs but still the motor struggles to make any progress btwn 5-6k. once past 6k it clears itself and really takes off. i had set the air screw to 2 1/2turns out but this had a worse dip in power btwn 5-7k. it has improved by air screw at 2 1/4 turns but im concerned as to further adjustment because most other posts suggest 2 1/2 - 2 3/4 turns out.cheerz in advance for any help

BrianM · « **Reply #3 on:** August 06, 2006, 01:35:35 PM »

Well, that flat spot would be tied to the needle (height typically) more than anything else. It'd be worth popping off the diaphragm covers and pulling the needles to see what's going on there. If there are shims lifting the needle, then remove them and see how it goes. If there aren't any, put some (2.5mm washers are what I use ~ 2 or 3 of them tend to do the trick) under and again, see if that makes a difference.

They're quick and easy to get to, so you should be able to run a few tests in a typical day and see what's better and what's worse... then just keep going in the 'better' direction till it starts to get worse again, and then go back a step or two.

Best of luck.

gsxr400 racer · « **Reply #4 on:** August 06, 2006, 05:05:46 PM »

Dont you ever only use 1 washer cause you are just trying to go a half a stef on the needle 2 or 3 you might as well just move the clip

BrianM · « **Reply #5 on:** August 06, 2006, 08:59:14 PM »

Uhhhh... STOCK needles don't have clips Jay.

I've never found reason to spend the $100+ for a jet kit on any of my bikes, can't justify the return on investment.

gsxr400 racer · « **Reply #6 on:** August 06, 2006, 11:36:21 PM »

well the needle taper is what you pay for!

BrianM · « **Reply #7 on:** August 07, 2006, 12:49:48 AM »

Like I said, *I* can't justify the expense. I don't buy bikes and try to make them faster/more powerful (other than doing basic maintenance) because it'll Always be easier to just buy a bike that's faster/has more HP. Just a huge waste of money to gain a tiny percentage of HP.

Shimming the stock needle, putting in smaller main jets (I'll have 90's in the B4 shortly as 95's are too rich), and adjusting the A/F mix screw always solves the ills that hinder street riding. Actually, for once I'll need to put smaller pilot jets in too... but I haven't been at 6k feet in elevation with most of my previous rides.

To each their own, but I'll keep that $100+ in my pocket (and the $400 for a pipe too), or just toss that money at a rebuildable shock/cartridge forks.

GK75A · « **Reply #8 on:** August 07, 2006, 08:04:48 AM »

ive taken the air screws out to 3 turns and its gettin pretty close now, just a slight dip at 6k now.im gonna have another play next weekend.
cheerz