Author Topic: 1G 600 shimming issues (Read 2923 times)

Oldschooler · « **on:** April 02, 2006, 04:30:57 AM »

Ok,

I got a Scorpion slip-on about two months ago. I didn't have the money for a jet kit also but heard about others who shimmed the needles and adjusted the airscrews in the meantime. So yesterday I figured I dive into this project and squeeze some better performance out of it.

Prior to starting the project my bike ran ok. That is, it started well idled well and ran just fine lifting the front wheel about 6 inches through first with just throttle. Now if I continued to stand on it up thru fourth it would stumble at about 11,000rpm and speed up when I backed off of it a tad. I figured this was a lean problem.

I got some #4 shims and started with two shims on each needle. I had drilled the airscrew plugs out but didn't adjust them yet. I test drove it and it was very flat, almost boggy from about 3,500 on up. I drove home and figured I take the shims back out.

When I got the tank off I saw that I didn't get the tabs back in on the filter cover on the airbox. I fixed it and took another test drive. Now it was much better but it had no low end anymore. Requiring much more throttle input to start off. It also didn't quite pull as hard as it did. But it didn't have a problem running to 12,000 in 1st thru 5th ( I left off after shifting to 6th).

I thought the airscrews would correct this. When I checked them # 1 & 3 were only a half turn out and 2 & 4 were completely closed !!!!! I set them all to 2 1/2 turns out and took a ride. The bike idled fine and accelerated ok and actually better from around 8,000 to 12,000, but was still kind of flat feeling until 8,000. It accelerated hard but there was no way it was going to carry the front wheel like it was doing before anything was done.

I went home and turned the screws back in so they are now 1 1/2 turns out. This improved the lower rpm's a little but still lacked the punch it did have. So then I took the shims out but left the screws at 1 1/2 out since they were so out a whack to begin with.

So now I have the screws at 1 1/2 and no shims. I know the screw settings are better than they were but the bike doesn't run any better than it did when they were all screwed up. The shims only seemed to make the bike run worse. Every thing I have read everyone seems to notice a good improvement but on mine it only seemed to take the edge of the bikes punch.

Am I screwing something up here? What am I doing wrong?

Red01 · « **Reply #1 on:** April 03, 2006, 12:00:23 PM »

First of all, not every bike is the same. Due to manufacturing tolerances, altitude, humidity, wear and other factors, some bikes will need settings other that what is "average".

Did you ever try 1 shim?
How about opening the screws 1/2 turn at a time until you find the sweet spot?

Oldschooler · « **Reply #2 on:** April 03, 2006, 04:36:48 PM »

No I never did try 1 shim. I was a little intimidated taking the carbs off, drilling the plugs, and then shimming, because I had never done it and the bike was running well so I was afraid I might screw it up. That played into not trying one shim a little bit because I was getting anxious to get the bike back running good, thinking I had screwed it up and it was never gonna be right now! LOL.

Right now I have no shims and the screws out to 1 1/2 turns, bikes running well again. I'm probably right at or just below sea level here in central Florida and the temps are anywhere from upper 70's to lower 80's during the day.

I have to say I was amazed that my bike ran so well considering two of the air screws were completely closed and the other two were 1/2 turn out!

I'll have to try the one shim and play with the airscrews and report back.

Thanks for the response!

tacoman · « **Reply #3 on:** April 05, 2006, 01:48:56 PM »

I am running just one shim on mine, when I had 2 it ran too rich. I didn't even need the choke for cold starts. Runs much cleaner with 1. I believe I set my air mixture screws at 1 1/4 turns out. One more quick easy mod is to change the jets in carbs 1 & 4 to match 2&3.

Oldschooler · « **Reply #4 on:** April 05, 2006, 04:11:03 PM »

Quote

One more quick easy mod is to change the jets in carbs 1 & 4 to match 2&3.

They aren't all the same! I mean I know each individual carb has dif jets, but I thought they were all setup the same.
I figure if I'm gonna be doing any jet swapping I might as well drop a Holeshot jet kit in there.

So you’re running 1 shim. Is your Bandit also a 600? or a 1200?

99er · « **Reply #5 on:** April 07, 2006, 06:06:56 AM »

Dude!
If you add a pipe, you drive it leaner. You know this as full throttle has a lean symptom at high RPM. Shims are a cheap and inadequate solution. Order a set of main jets that are two steps higher and this will increase both full throttle AND midrange fuel flow. The main jet feeds fuel to the main circuit - read needle circuit. Shimming may not then be required. I would only do it if the bike goes flat around 5-7 with part throttle. You're just wasting lots of fuel otherwise. Dale at Holeshot used to say that one shim too many on the B12 represented 5MPG. The B12 is classic for this midrang stumble but at a lower RPM than the 6. Those idle screws are fine for idle, min throttle, and transitions. Once at about 1/4 throttle, they're out of the game.

Learn about them - factorypro.com. Click on Product Support on top and then CV Carb Tuning. Use the high RPM model. Great information!
Marc/Atlanta