Upgrading carbs, Full tank vs low tank top speed, Shift kit questions

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Sambino

New Member
May 12, 2011
15
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0
Washington (USA)
I have a couple of questions- If you know of a thread that addressed them already, that I missed in the search, please link me! If not, answers are appreciated too, of course.

1 -- My bike idles a lot higher, and runs faster when the tank is full, I assume this is because the extra fuel helps with the gravity fed fuel tank, is there any way to keep the motor running as well as it does with a full tank when its running low?
2 -- What benefits would a dellorto carb (over stock) provide? Would one of them be helping with the first question?
3 -- I installed the SPB shift kit recently, and the chain that connects the motor to the kit (not the kit to the bike gears) is pretty loose, I built a chain tensioner that helps when the bike is running, but when I'm starting the motor, the tension is on the other side, and the chain gets jammed in the motor. The chain is slowly stretching out to the point where I can remove the half link, but right now, it's just too short without it. - Any ideas other than building a new tensioner for the other side? Starting techniques perhaps?

Thanks in advance guys!
 
Dave31

Dave31

Active Member
Mar 1, 2008
11,199
47
38
Aztlán, Arizona
Hey Sabino,

1- Hmmm, Ive never encountered that problem but my best guess would be a gas cap that does not vent properly. A fuel petcock or the screen that maybe slowing the flow of fuel. Maybe others will have some better advice on this. Usually a Higher idle is caused by a vacuum leak.

2- I've used the Dellorto and in my opinion all it does is allow you better adjustments. I have a few Dellorto's but I save them for customers bikes. All my bikes I use the speed carb.

3- Never used or messed with SBP Shifter kit so someone who actually has one would probably be better to help you out.
 
Jbomb

Jbomb

New Member
May 19, 2012
19
0
0
Wichita, KS.
I have an RT carb from thatsdax.com that is a Dellorto clone. I got it to replace the stock CNS carb, which was a P.O.S. It made my engine run much smoother and quieter, and gave me more low end torque and higher top speed. I also got a billet aluminum intake with matched port for it. In my experience, that carb is the single best upgrade from stock that a person can do. It should help with the full vs low tank level idle issues too. At 30 bucks, it is well worth every single cent. I have no experience with shift kits yet.
 
M

midwestmayhem

New Member
Dec 23, 2011
79
2
0
southeast S.D.
I made my own shift kit, and when the chain was new it was all well and good. After it got some hours on it it stretched. I ended up making a shim that slides in next to the spacer between the motor and the shift kit plate/bearing hanger. This slightly increases the distance from the motor sprocket and the jackshaft, therefore tightening the chain. Depending on the thickness of the shim or shims I was able to "fine tune" the tension.

The shim itself looks like a T. The width of the vertical stem being the distance between the inside of the two motor mount bolts, about 1 1/4. The horizontal part of the T was there just so I could slide in the shim from the top and not have it fall out before I could tighten it. I have seen sbp kits, my custom kit is similar to it. And even though the one I have I made, I can't think of any reason why the shim wouldn't work on yours.
 
2door

2door

Moderator
Staff member
Sep 15, 2008
16,302
175
63
Littleton, Colorado
Can't help you with shift kit problems, I don't use them.

If the float and float valve in the carburetor are adjusted and working properly, fuel level in the tank will have no effect on idle speed. I do know that the RT carb must be sealed to the intake manifold or you will experience high idle speeds which is a result of an air (vacuum) leak at that point. The plastic sleeve will not provide a good seal even if the clamp is tightened.
Any good sealer will work as long as it is compatible with gasoline. I like SealAll insted of the silicone based sealers, many of which are not gasoline compatible. Read the label of any product you plan to use.
Tom
 
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