rev Limiter

[boediddly]

Bike just got a rebuild this winter good compression ,timing is good ,have been up and down the jet needle and jet in every possible configuration bike will idle great and pull hard till approximately 4 or 5 grand and then it stumbles bad like its hitting the rev limiter it also wont go over 70 mph(same thing) just checked tdc with a degree wheel and then checked the cams, all good .The rpm gauge is busted .The P.O. wrecked the bike.Thats why im wondering - is there a rev limiter on this bike? any suggestions?79 special has anybody had this problem?

[TopCatGr58]

Oh goody, I get to be first!

Nope, no rev limiter in the iggy box, so you have to be careful especially without a TACH! How do you know that it's APPROXIMATELY 4-5 grand with a busted tach???

Anyways, WHO did the rebuild..you or a shop? WHAT was rebuilt?

IF carbs..were Indy filter pods installed? If so, what brand...EMGO cheap ones?? They have a prominent LIP that inhibits airflow thru the ports on the intakes of the carbs, and can cause loss of power at the 5k mark.

Quick test, take the pods off and test run/ride, if revs climb to redline, then you've found the problem...several ways to fix it..see tech tips or search for velocity stacks and such!

T.C.

[XSokieSPECIAL]

Also, disconnect the vacuum line from the #2 carb body and see if it makes a difference.

Might be a bad pickup coil wire that is affected by the vacuum advance diaphragm moving the breaker plate.

[MindWebs]

hmm, sounds like he forgot to hook-up the vacuum retard unit....

(i just did that 2 days ago )

you wrap it up to 7 then it just stumbling and starts growling like a pissed off dog.

vacuum line comes from the left side case cover(back edge) and runs up to the #2 carb body brass port. (second from the left as you sit on the bike)

NOT one of the 4 sync ports!!! (sync ports are the brass ports on the rubber intake boots)

good luck!!
Webs

[WMarshy]

Webbs already took my idea... Sounds like a possible timing advance problem.

[XS1100 Newbie]

That sounds exactly how my bike ran. For a year i ran it that way, until i started getting tired of not being able to go over 5000 RPM, and 60 MPH up hill. It was all in the carb float level.

[DiverRay]

As everyone else failed to mention it, I will!
Check the fuel lines for kinks, and put the taps on "PRIME" and run it. If it runs well then, you have a fuel delivery problem. If that doesn't work, look at the float levels. If they are too low, you will starve the engine when you NEED the power. If it revs great on the center stand, but not on the road, check the fuel delivery.

[boediddly]

vacuum line is hooked up correctly. maybe advancer is bad itsself running pingle petcocks so carbs are definitely getting fuel .not the filters ,does it with or without the filters ,isnt the pickup coils unless the pair i swapped them with have the same problem (knock on wood)I think ill try the float level .any more ideas?

[fredintoon]

- - - ,isnt the pickup coils unless the pair i swapped them with have the same problem - - -

Hi Boe,
not the pickups themselves but the wires that go to them.
Those wires flex like a trombone every time the vacuum advance moves the ignition plate.
Some times the conductor wire breaks inside the insulation and gives intermittent spark failure.
There's a tech note on how to fix it.

[boediddly]

whats the float height everybody is changing to?

[boediddly]

like i asked whats the float height everybody is setting them at and is that measured from the gasket area with the gasket in place or not?

[motoman]

Might want to put what scoot and year you have. Would help, doesn't mean it would have original year carbs, but a start.

[petejw]

the early model carbs the float level is 25.7mm
and 23mm for the later carbs, the floats are checked
from the gasket area with the gasket removed.
while your in the carbys take note of the jet sizes
for reference in case theyve been changed from stock.

[Ken Talbot]

whats the float height everybody is changing to?

This really is hard to answer, because the early carbs are a bit different from the later carbs, there is a wide range of exhaust systems and main jets in use, some guys are running pod filters while others are still using the stock airbox, and every bike is at a different point in its life cycle.

The first thing you have to do is to get all four floats set to the same measurement, whatever that turns out to be. Just pick one of the floats and set all the others to the same amount. It really doesn't matter what the actual measurement is at this point, because you will be changing them all at least once more anyways.

When you have them all the same, whatever that is, run it for a bit and perform the "chop test" a few times to get a read for your particular situation. If it is running overly rich, you drop the floats a mm or two and test it all again. Likewise, if it is way lean, to raise the floats a mm or two.

There are so many variables that is is pretty much impossible to use somebody else's recommendation and get it right the first time.

[petejw]

after spending the past couple of weeks
messing around with different float levels,
ive found the best setting to be slightly on the rich side,

as little as .1mm makes a difference when riding,
the float levels affect acceleration,
if your acceleration is flat then the float heights are lean,
if the engine bogs down when accelerating your floats are to rich.

also be real particular with your mixture screw settings, i also found
that if your mixture screws are similar to the stock settings (1 and a quarter turns out) then your float levels should be pretty spot on.

ive read where the factory pro site states to lean the floats by a mm,
when i did that, i had to go up 6 sizes on the main jet and 1 size up
on the pilot jet to compensate for the lean float levels, then this created
a hole heap of other problems on the way,

using didgital callipers make small adjustments, .2 - .3mm either way
will make a big difference.