Engine cuts out at WOT

[ctraylor]

Has anyone ever had a problem with their bike cutting out at wot? Mine runs good up to reline as long as I don't go to wot. It feels like it has a rev limiter at about 5500 rpm. It has no jerking or missing just feels like it falls on its face. I have checked everything except this vacuum timing sensor. Where is it located?

 

Curtis Traylor

[hipshot]

i'll play your silly game, curtis!

 

 

what in the world does WOT, represent?

wide open throttle, maybe?

just jt:confused24:

[Dano]

Yep

[rhncue]

Yep

 

I would imagine "Wide open throttle".

 

Dick

[BradT]

I have checked everything except this vacuum timing sensor. Where is it located?

 

Curtis Traylor

 

NOt sure but the timing is not adjustable, manually. Also could it be starving for fuel, maybe a new fuel filter would help.

 

Brad

[Dano]

Yes, it is "wide open throttle". Perhaps there was a typo, the redline on my 84 is 7500, not 5500. I have heard from others that there is a rev-limiter on these bikes, but it comes in past 7500 somewhere. Does it happen in every gear? Consistently at the same rpm? Famous question, have you synched the carbs? Others have more info than me, I just know more dumb questions I haven't got figured out for myself, yet. Others will post......Squeeze knows EVERYTHING about these bikes!

 

Good luck, Dan

[Dano]

Haven't laid my eyes on it, but follow the vacuum line that comes off of carb #2 (front left), it comes off of the manifold below the carb (a small 1/8" line with a check valve in it), and it should lead to it. I suspect it's behind the battery box by the TCI unit. Hope this helps.

Dan

[ctraylor]

Yes my red line is 7500 also. It will run to red line and get there quick as long as I don't go to WOT. At WOT it will just fall on it's face at about 5500. I just made a 3000 mile trip with no problems and it wil cruise all day at 80 mph. That is what is puzzling, the problem only surfaces a WOT which is fine with me cause I hardly ever go there but I know the problem is there and it bugs me, if that makes sense to you.

[Dano]

Yes, I know what you mean. If you need it to be there, you want it there. Possibly not enough fuel feed for that. Perhaps too much air for the lower fuel flow (lean condition).

Dan

[Squeeze]

Hi,

 

how much Travel of the Handlebar Grip can you use to redline the Engine ?

 

If i understand right, your Problem is, when you twist the Wrist maybe 70 or 80 Percent of the complete Travel, the Bike roars and RpM goes up to redline. If you twist to full open, the Motor roars and starts like a Champ, accelerates fine but stops all Efforts at 5500 RpM ?

 

If so, what happens when you back off the Throttle a bit ?

 

 

 

btw

It may sound so sometimes, but i can assure you, i do not know everything about the Bike. I had my Lessons learned and i'm still learning every Day. I'm quite interrested and i want to move the Borders. Mine and those of the Bikes.

[Yammer Dan]

Fuel flow restriction? Sea-Foam soak.

[GeorgeS]

First time I ever heard of this.

 

I wonder if maby one cylinder quits fireing, at that RPM, maby a problem developing in the TCI,

 

You might consider opening up the TCI and checking the solder connections. Might be one of the Diodes in there going bad.

 

Might be due to moisture in the TCI.

 

Try a new set of Plugs, make sure the plug wires have good electrical connection at the Coils, and the Plug caps. Screw out the wires, and nip off about 1/4 inch of wire and screw them back in.

 

Clean Air Filter ???

 

I would Drain the Carb Bowls, might be a probem there.

 

??????????????????

[ctraylor]

Already replaced plugs and ran sea foam through twice. I can go to about 75% throttle and it does fine. If I go to WOT, it will stop pulling about 5500 and if I back off the throttle it will come back to life again. I figure it might not be advancing the timeing enough. That is why I was asking where the vacuum switch was. This bike runs great otherwise and I ride it daily, idles fine, does not miss at all. This one is puzzling me.

[Condor]

Has anyone ever had a problem with their bike cutting out at wot? Mine runs good up to reline as long as I don't go to wot. It feels like it has a rev limiter at about 5500 rpm. It has no jerking or missing just feels like it falls on its face. I have checked everything except this vacuum timing sensor. Where is it located?

 

Curtis Traylor

 

The boost sensor is located under the bracket that holds your coils. On your '83 the vacuum is pre-butterfly. Follow the vacuum line located between the #2 and #4 carbs (left front and right front). For your '86 the vacumm line comes off the bib at the base of the manifold for #2. Hope this helps...

[Gearhead]

Check the carb slide diaphragms. You have to pull one out to check it adequately, which is not hard to do.

 

As for the vac advance unit, it is under the battery bracket. Major PITA to get to. I haven't had mine out, but I did remove the battery and was able to access the connector plug. It was corroded and prevented it from working. You can check its operation without removal. You need to trigger the advance and see if the motor increases speed. Not sure on the 83, but here's how on the 86. First, the vac advance doesn't work at idle, so adjust the idle speed up to around 2000 rpm. Remove the hose from the carb boot and pull a vacuum on it. You can use a Mity Vac or even just suck on it with your mouth. The engine speed should increase. If not, the vac advance is not working.

 

However, the vac advance only comes in at high vacuum, cruise conditions. Not WOT. Therefore, I wouldn't think it is the problem for you.

 

Jeremy

[Squeeze]

Neither do i.

 

I've done a bit of Resarch in ctraylors previous Posts.

 

He mentioned a leak in one Cylinder dued to a somehow open Intake Valve. The Discussion ended open ? Also this Discussion here has a History.

 

I think a serious Carb-Maintainance is in order. Although the Diaphragm seem to renewed, there is a Lot more working inside the Carbs. Seafoam will help in most Cases, but some serious clogged Jets, can't be cleaned up with Chemistry only. Also, Seafoam isn't working on the Air Ducts, because Seafoam can touch these Parts in the Carbs. Maybe the Air Duct in the Carbs Throat is clogged that much that there is not enough Power to Lift the Slides enough. Other Thing could be is PAJ#2 is clogged partly and the Vacuum does not build up propely in a timely Manor. This can cause the Slides to stop moving before the End of their Travel is reached.

 

Other Thing could be, unlikly but nevertheless, there are Slides on the Market that limit the Power of the Bike. On the Maxxes, the Power on some Engines is limited to 98 DIN HP by such limited dead Stop Slides and the V-Boost unplugged. That's because of Insurance Issues.

 

Also, maybe just for me, is one Question open, does the Bike not reach Redline at all or just not under WOT Condition ? Even with 75 Percent open Throttle in lower Gear, the Engine should go up to Redline.

[ctraylor]

The engine will go to redline as long as you don't go to wide open throttle. The slides were replaced before I bought it and it belonged to a small man that was scared to ride it so the slides that reduce power make sence. This bike runs like hell as long as you don't go to WOT and then it feels exactly like it has a rev limiter on it no back fire no miss. The open valve issue was that I was checking compression without opening the throttle when I turned the motor. This guy would crank it under his carport and kill it and fouled the plugs. This thing runs great gets 40-42 mpg as long as I keep it around 60 mph.

[Gearhead]

I don't know but I would think that the special slides are only available overseas. In the US they don't use such methods for insurance reasons that I am aware of.

 

Jeremy

[fixit3546]

I may have overlooked it; but this sounds to me like fuel delivery problem (fuel filter) Maybe carb floats set too low.

[Squeeze]

I don't know but I would think that the special slides are only available overseas. In the US they don't use such methods for insurance reasons that I am aware of.

 

Jeremy

 

I agree 100 Percent.

 

 

but

 

1st off, the Carbs need to be checked and cleaned anyways. Maybe not right now, but latest at the Moment its bothering him more than just a bit.

 

2nd

my lifetime Lesson learned ....

 

if you're looking in a Problem, don't take anything as given or assume anything. CHECK IT. Period

 

Those Stoppers are just some Plastics on the End of the Slider's Tube. One could easily glue something in to prevent the Slides from opening to the full Travel.

 

I would check the Function of the Spark Advance Sensor by detaching it from the Manifold Tube and give it some Vacuum with a Mityvac or suck it with the Mouth. Idle Speed should change. If so, wouldn't give the Sensor or the CDI a second Thought for now. Next would be taking the Carbs out and check and clean them. Fuel Filter might be also a bit clogegd, but that wouldn't be my Favourite.

[Gearhead]

"if you're looking in a Problem, don't take anything as given or assume anything. CHECK IT. Period"

 

 

 

Good point.

 

When checking the vac advance as described above, you must get the engine up around 2k rpm before the vac advance will take effect. It doesn't work at idle, I'm pretty sure.

 

Jeremy

[mbrood]

As I understand it, the timing advance (pressure sensor) is driven by vacuum... most fail by not advancing (broke) or not advancing enough (leaky hose or bad sensor) but it COULD be that high vacuum drives the unit spastic. Electronics are funny that way.. not unheard of?

 

But my money is with fuel delivery.. either fuel filter or float level.

[ctraylor]

Thanks for all the help guys. I will take all this to heart and give you a shout back as to what I found.

[yooper]

Did your bike have a burp in it at times if so your TCI computer could be going thats what happened to mine finally it quit this fall . Got one on ebay for 137 bucks and it is working fine. Hopfully all will be ok. 73 Yoop

[lonestarmedic]

Backing off the throttle to regain power sounds like a lean condition. More air than fuel so to speak. If you run it up slow, I bet it will hit redline. If you ever put too light a spring on a set of vaccum secondaries in a 4 barrel, I bet it kinda acts like that. Start basic. Fuel filter, fuel lines, pump operation both pressure and flow. I would even check the tank pick-up. Then hit the plugs, wires and caps. Last, run a good sync and see where you are at. There might be a few pinholes in the rubber, but it sure doesn't sound like any major tears. I would have to look at the carb reakdown to verify the WOT circuit and flow. Might be a carb with a piece of debris in a tube.

 

JB