Gearing / Speed issues

[yoshisakan]

Hey all, I am trying to figure out what the deal is here. My gearing is way off base. Here are the specs:

1999 Bandit 1200 - Primary Drive Ratio: 1.565
116 Link 5/8 Chain
110/90-19 Front Pirelli - 26.8"130/90-16 Rear Pirelli
1996 GSF600 gauges

15T Front
44T Rear

With this gearing, I am at 7000rpm @62mph. The gauge actually reads 56mph, but its off due to the front tire diameter difference between the stock bandit and my wheel. I ran this all though this gearing calculator - http://www.gearingcommander.com/ and none of it adds up. I'm getting the rpm signal from a dyna 2000, so i'm fairly sure that's accurate, but I am going to call them today and see if I messed something up there. Am I missing something here?

 

[posplayr]

Rpm sounds like it is off by two. I guess you don't have a rpm meter. A cheap timing light typically might have one. Probably a dyna 2000 setup issue.

 

[yoshisakan]

posplayr - I am using an rpm gauge from a 1996 gsf600 bandit. I did notice by mistake the other day that the engine is making a lot of power beyond 12k on the meter. I missed a shift and it was still pulling like crazy. I'm going tocall Dyna in a bit and see if they can advise further.

 

[yoshisakan]

Dynatek says that I need to use the yellow wire for suzukis, their tachs read 1 pulse per rev instead of the green wire which reads 2. That means that my rpms are effectively doubled. Going to change to the other wire tonight and see the difference. This is an exciting mistake because that means i haven't even opened up the motor yet! I also need to unplug the tank breather valve, because its choking my engine at high speed. Dumb mistake on my part.

 

[Steve]

I also need to unplug the tank breather valve, because its choking my engine at high speed. Dumb mistake on my part.

What are you calling a "tank breather valve"?

The ONLY things that will "choke your engine" are the throttle butterfiles and the stock airbox.

 

[yoshisakan]

You know how there's a breather hose that comes from the bottom of the gas tank? Well I plugged that line so there's a large vacuum build up in the gas tank as fuel drains out and that makes the bike run lean at like 80mph if I gun it. It's not float height, and opening the choke doesn't improve this condition, so i'm pretty sure this has to be the cause of the problem. In 1st through 4th gear the motor runs good through the powerband, although that's questionable since I just learned my tach is off.

 

[gustovh]

The only thing that vents your gas tank is the cap. Pull it apart, it's only a couple screws, and make sure a spider has not taken up residence in there. The tube that you refer to coming from under the tank is a overflow hose in case the gas gauge sending unit springs a leak.

V

 

[JTGS850GL]

What are you calling a "tank breather valve"?

The ONLY things that will "choke your engine" are the throttle butterfiles and the stock airbox.

On the Bandit you have a tube that runs from the tank gas cap to below the tank and into a rubber tube. If that is blocked it will create a vacuum in the tank and stop fuel from getting to the carbs.

Yoshisakan: Why on earth did you block that tube in the first place?

 

[Steve]

Silly me, I missed the "Bandit" mention in the first post.

It's not in the "Other Bikes" section, so I assumed we were talking about a GS.

.

 

[yoshisakan]

This is a bandit motor in a GS frame. Turns out unblocking the tank overflow thing did nothing. I have a pingel If that matters. It seems at high speed, or in wind, the bike bogs down. Also noticed getting off the highway when I rev, the Rev holds before coming back down. Could these issues be related? What about the carb vent tubes, between each bank. I don't have hoses connected to them and they're pointing straight up.

The bike pulls so strong through first and second gear, power wheelie strong. I don't get it.

 

[Guest]

It seems at high speed, or in wind, the bike bogs down.

This sounds like you don't have a stock air box and it's running lean.

What about the carb vent tubes, between each bank. I don't have hoses connected to them and they're pointing straight up.

These broke off/went missing from my neighbour's B12 some years ago. Makes no difference. He's running with K&N pods and Dynojet stage 3 setup. It really has masses of low end power.

 

[yoshisakan]

I'm also running KN pods and a Dynojet stage 3 kit. I've switched every jet you could think of getting this thing to run. I think its a delivery problem rather than a jetting one.

 

[yoshisakan]

Besides, if it were a jetting issue, opening the choke would alleviate the problem, that either causes no difference or makes the problem worse.

 

[yoshisakan]

Does anyone have any other ideas here? What would cause a bike to run strong in 1-3 gears, and then bog down in high rpm 4th/5th. Also coming off the highway, when revving the revs come down slowly. Could any of this be due to ignition timing? One thing worth noting is that the vacuum hose flange on top of the valve cover is wide open. Maybe this is causing a lean condition at higher speeds? Can I block this off or do I need a breather filter?

 

[BigBodyBiker]

Does anyone have any other ideas here? What would cause a bike to run strong in 1-3 gears, and then bog down in high rpm 4th/5th. Also coming off the highway, when revving the revs come down slowly. Could any of this be due to ignition timing? One thing worth noting is that the vacuum hose flange on top of the valve cover is wide open. Maybe this is causing a lean condition at higher speeds? Can I block this off or do I need a breather filter?

Without knowing all the details of your build, I'll help you out. Any vacuum loss is bad. Your power loss at high speed is attributed to your vac going byebye. I'm not saying plug it up, but more find out if it's a kpa + or - first by rtfd'ing. (Read the ??@king directions) If you haven't already bought a Bandit factory service manual, do so now. Try finding another vac port and using it to create what you need. Make it suck more...
Boomshakalaka...fixed