I think I have a timing problem?

Fletch

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My engine is running great, except when under heavy load going uphill for an extended time.

*expansion chamber

*no base or head gaskets

*no porting

After going uphill for a while at full throttle the engine starts to bog and then die. I don't have an air leak.

After it quits, I can hear the engine continue to rev in a few short bursts like, "rvvvvvv.....rvvvvvvv.....rvvvvvw." Once it does that I can restart the engine and go again. It's like it is clearing itself.

I'm not sure if this indicated too little timing or too much? I just read that under load the timing increases (or needs to).

I pulled my plug but it has been used at different settings (ie. it's already colored). the tan ring around the center electrode insulator only goes about half way around on the side of the side electrode. There's some carbon build up on one side of the center electrode. If someone is really good at reading the plugs in detail I can post some pics.

I'm wondering if I need to put a base gasket back in, or if I just need to tune the pipe? Maybe lengthen the copper adjustment tube?

By having no bottom gasket that should be good for intake but bad for exhaust right? Instead of raising the exhaust it is = to lowering it a little. I'm stuck on this one.
 
hey

hey
simple check your ignition wires some times they come loose when you rididng i use to have the same problem figured out it was my ignition coming looser and looser and if not check your spark plug if its looose
thnx and put gaskets how they were
 
hey
simple check your ignition wires some times they come loose when you rididng i use to have the same problem figured out it was my ignition coming looser and looser and if not check your spark plug if its looose
thnx and put gaskets how they were

Thanks for the tip. My wires are soldered so I don't think they're loose. My plug isn't loose, although maybe this is a good time to ask what the torque should be (in ft. lbs)?

If it was loose wiring/plug... why would it only happen under the conditions I described, and not randomly?

I'd really like to know if this could just be a tuning issue with my expansion chamber. Maybe I took too much length off? This would be the easiest fix.
 
Sounds to me like a fuel flow problem.
I would bet you're running your float bowl nearly empty
with sustained uphill wide open throttle.
After it sits for a moment it has a chance for the fuel level to recover
in the float bowl.
Here are some things to check:

BLOCKED OR PARTIALLY RESTRICTED TANK CAP VENT
Try running your bike under the same conditions you are having trouble with, but without the fuel cap on the tank. A clogged vent is like holding your thumb on the end of a soda straw, doesn't drain

BAD FUEL FLOW TO CARB
Clogged inlet screen on "in tank fuel petcock"
Restriction in fuel petcock itself... Pull off your fuel line at the carb and see how well the gas flows out with valve open, a small stream is enough, it doesn't gush but dripping in not enough.
The fuel valves have a very tiny crappy opening for fuel to flow thru.
SBP has a nice one.

CLOGGED IN- LINE FILTER
If it's see thru, it should be nearly fuel under all running conditions

I'm willing to bet it's one of these, or a combination of a few.
Don't be afraid to experiment by using the process of elimination, stating at the tank..
Good luck and check back in when you find the culprit..
TIM
 
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Sounds to me like a fuel flow problem.
I would bet you're running your float bowl nearly empty
with sustained uphill wide open throttle.
After it sits for a moment it has a chance for the fuel level to recover
in the float bowl.
Here are some things to check:

BLOCKED OR PARTIALLY RESTRICTED TANK CAP VENT
Try running your bike under the same conditions you are having trouble with, but without the fuel cap on the tank. A clogged vent is like holding your thumb on the end of a soda straw, doesn't drain

BAD FUEL FLOW TO CARB
Clogged inlet screen on "in tank fuel petcock"
Restriction in fuel petcock itself... Pull off your fuel line at the carb and see how well the gas flows out with valve open, a small stream is enough, it doesn't gush but dripping in not enough.
The fuel valves have a very tiny crappy opening for fuel to flow thru.
SBP has a nice one.

CLOGGED IN- LINE FILTER
If it's see thru, it should be nearly fuel under all running conditions

I'm willing to bet it's one of these, or a combination of a few.
Don't be afraid to experiment by using the process of elimination, stating at the tank..
Good luck and check back in when you find the culprit..
TIM

Tim,

Thanks man... My first thought was that it was fuel starvation too, but the revving after it dies threw me off that. I did wax the tank and cap so maybe it's blocked. I wasn't using the screen until recently, but the engine was doing this before I put it in.

THere's no chance that it has to do with my float level setting right?

Ok...No gas cap made no difference. Normal hills are fine, but the one I'm riding up is a monster! My filter is always full, and I really don't think it is a gas flow issue. I did lower the float a bit because I had some leaking out of the carb. Maybe I lowered it too much? That shouldn't matter though because going up a large hill is going to drain the bowl eventually right?

Maybe because the expansion chamber uses up more fuel, I need a larger carb (new Speed NT, or CNS) if I want to full throttle monster hills. I did try going up the hill half throttle and that was fine.
 
Last edited:
hey

honestly if it were me i would buy a new carb if you have the stock one get a speed carb thats all i can say
 
wackey101,


I bought a speed carb but the threads broke out where the air filter screws in using an aftermarket filter. I found out I had a broken rear mount stud so the vibration probably caused it.

I tried to recreate the Speed carb using a dremel on a standard carb. I haven't given it a go yet because I put all the jets and needles in the same bag and don't know which ones came from the speed carb. Do you know what the needle looks like? Is it shorter and thicker?

I think I just set my float too low, but I want a better carb anyway. I don't have good luck with them though... 3 broken CNS, 1 broken Speed.
 
e

the pin for the speed carb is shorter than the one on the stranded nt at least that like mine
 
Well i got similar problem on flat land if im running full throttle for over a minute it starts bogging down .And eventually dies and half to restart it. 1/4 mile is all i get at full throttle before it bogs down. And i dont see nothing on that carb to adjust beside the idle screw and that doesnt do much just idles it down or up what yah think is ours similiar or what?
 
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