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TC88 misfire at 4000 RPM

J

JimDDoss

New Member
I have a 99 Road Glide TC88 carburated that will start and idle fine but if you rev the engine it will cut out and misfire. If you remove the breather cover it will run fine. I have replaced the carb,MAP sensor and the ECM ???
 
Pure factory stock ignition system? If you were to have the bike in 3rd gear going 2000 RPM and nailed the throttle, would the bike pull hard without breaking up until the RPM reached 4K? The title of the thread says 4000 RPM. That is the magic number in all cases. Steady road speed under 4K has NO sign of misfire?
 
It runs strong until you hit 4000 RPM then it misfires

It is stock
 
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Since you replaced the map sensor & ICM, it sounds like your focused on it being electrical. I agree it does sound electrical to me also. The part I don't understand is when you remove the breather cover, it allows the engine to run fine.
That really happens. All your problems go away if you remove the breather cover?
I want to say the problem is the primary trigger in the nose cone. But I don't see a relationship of that to crankcase pressure.
 
Hoople said:
Since you replaced the map sensor & ICM, it sounds like your focused on it being electrical. I agree it does sound electrical to me also. The part I don't understand is when you remove the breather cover, it allows the engine to run fine.
That really happens. All your problems go away if you remove the breather cover?
I want to say the problem is the primary trigger in the nose cone. But I don't see a relationship of that to crankcase pressure.
Click to expand...

TC 88 stock ignition, crank sensor should be the trigger, but why does it run right with more air? Is this carb set right? Does it have adjustable push rods? Does this have any vacuum ports on the carb or intake that are not plugged up or have hoses on them?
 
IT is a STRRRRRRRReach, BUT is the carb all the way into the rubber gasket that it is held by?

That 4000 RPM and the fact that WHEN you remove the air cover it runs Strong PAST? 4000 RPM?

signed....BUBBIE
 
Just another after THOUGHT:small3d021:

Coud it be HITTING the rev-limiter???

4000 RPM might be MORE than thought,,, Or a problem with what ever decides the LIMIT?

BUT WHY when the air cover is OFF it is GOOD???
Module?

signed....BUBBIE
 
Has the carb been apart recently? If the diaphram is pinched or misinstalled the slide will not be able to raise correctly and will limit the RPM.
 
The stock air box can cause a fair bit of restriction in the air flow if the bike has been modified with cams ,carb,exhaust there may not be enough air getting through the air box to feed it
In that case an se setup would be the cure

Brian
 
If it is the carb (and not electrical) then it would appear it's high rpm range setting is a little rich and the increased flow of the breather being off eliminates the stumble.

When I was younger during the last ice age, we used to remove the linkage that went from the secondary barrel's butterfly air damper plate (on a 4 barrel cage carb). This would cause the secondary air damper to open all the way (sooner) from the increase flow vaccum alone, as you gave it more gas pedal. In it's normal mode there was a spring that kept it from opening too soon. If we were drag racing on the back roads this gave us an edge.

The problem was if we did not remove our air clearners (as we always did when we were drag racing), it would stumble when you stomped down on it.

But further I have a question, Hoople referred to -> crankcase pressure.

We are talking about the intake air breather and not a crankcase ventilator correct ? I'm confused on the crankcase pressure part ?
 
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