No throttle response WOT

[nimblebee]

Search for "no throttle response" over forums yielded nil results, so I'll begin this thread:

Riding along somewhere between 20 and 29 mph, I released throttle but engine did not slow down. It was kind of like on cruise control: motor just kept going.

Not to worry: I just pressed kill switch, thinking I would adjust the throttle same way World War One biplane pilots (who had no throttle control) would "blip" their motor on and off, to slow down enough and land.

SNAFU, kill switch made no difference; engine continued running.

Oh boy? Oy! What next to do? wiggled throttle cable and moved around throttle twist control, but nothing made any difference.

No problemo! engaged clutch and began slowing down, but engine definitely didn't! Motor continued roaring really hot and heavy! Thought to myself: Do something quick, that motor could grenade!

My next idea was to slow down with brakes, & dump clutch, thinking that would stall out engine.

Catch 22! After braking and slowing for a bit, clutch was disengaged/released and bike, instead of stalling, motor continued to accelerate, still having no throttle control.

My next master plan was to fully engage caliper brakes as hard as I could, thinking: haha! that'll put enough drag on motor that I'll slow down and with clutch disengaged, I'll be able to stop.

That worked to an extent (clutch dragging?) taking way longer than it should imho, then when bike slowed enough, was finally able to dump clutch and stall motor.

Kind of crazy, when considering, test drive's original purpose was to determine why "no idle" and had "difficulty starting"

Here's the thing: for whatever reason, the kill switch did nothing. Later on during test drive, when throttle somewhat operational, kill switch was functioning once again.

I'm not even so sure kill switch wasn't operating all this time? Do I need an exorcist?!

Is it even possible (like with glow plug model airplane engines) that a motor can keep combusting even with no spark?‍

I decided to add a special accoutrement to my motorized bicycle, that I wanted to let everyone know about, just in case they find themselves on a runaway bike with no way to stop.

I tied some twine around spark plug boot and looped the other end up, tying onto frame of bike, so that in worst case scenario (when everything else has failed) can grab cordage and yank spark plug wire completely off spark plug.

FUBAR in case that doesn't work, only backup plan beyond this:

"Our Father, who art in heaven..." Hail Mary!

Needless saying, haven't lived such an exemplary life to anticipate divine intervention: therefore removing carburetor (clean up/inspect), replacing cable from throttle, disassemble/inspect/repair throttle assembly (already ordered replacement throttle).

Since I've always been prone getting everything inside out, upside down and backwards, I'm going to add a very large, visible arrow pointing alongside direction to twist throttle, labeled "More on" (thereby avoiding applying "gorilla strength" forcing throttle in opposite direction, breaking/causing who knows what internal havoc).

 

[curtisfox]

It is probable running lean and getting hot and desiling, like you said ( like your air plane )fuel shut off woulld of done it...........Curt

 

[nimblebee]

It is probable running lean and getting hot and desiling, like you said ( like your air plane )fuel shut off woulld of done it...........Curt

Good to have one more approach in dealing with a runaway motor.

I'm not so sure how long it would take to stop, if shutting fuel petcock off before carburetor exhausted it's fuel within?

Just for grins, once tried seeing how far could run with fuel cut off, and was astonished distance before motor quit, as carb was starved of fuel.

I'm fairly certain, when taking carb off today and replacing throttle cable, going to find there's something snagging, holding slide wide open inside carburetor.

Another possibility would be there's something inside twist throttle itself, that's not releasing throttle cable to carburetor, so slide can't wind back down into idle position.

If, as you suggest, motor is running lean, I'd best determine quickly, before lean condition destroys motor.

Your notion of getting rid of the gas if the motor is dieseling is a valid one.

Suck, squeeze, bang, blow does nothing, if there's no fuel to flow.

If dieseling, my "emergency stop" yank cord's removing spark plug lead from spark plug wouldn't stop dieseling motor, but fuel starvation definitely would stall motor.

My NT carburetor has flip valve on bottom of carburetor bowl, instead of typical screw stop to drain fuel from carburetor bowl.

If needs be, could turn fuel petcock off, and install another emergency stop yank cord, this time to the "flip valve" on bottom of carburetor fuel bowl.

In this scenario, would be having two "yank cords" in hand like horse's reins, yelling "Whoa Nelly"! ;->

 

[Venice Motor Bikes]

Raising the choke lever on the carb is a simple way of shutting off the engine

 

[nimblebee]

Raising the choke lever on the carb is a simple way of shutting off the engine

lol Why didn't I think of that? Once everything's sorted/repaired, will try "choke" method during WOT test drive. I've already got a long extension on the choke lever for ease of operation during riding.

lol it's a wooden "honey spoon" from thrift store, sanded/contoured fitting choke lever & JB Welded/tie wrapped into position.

 

[nimblebee]

Inspecting inside plastic twist throttle, could see where failure occurred.

Until ordered replacement twist throttle arrives, decided on reinforcing, making repairs and working with damaged throttle, so as to retain use of motorized bicycle while awaiting parts.

Corners inside of grip which are supposed to stop twist grip turning too far, were rounded and damaged, wherein JB Weld was used to build-up/reinforce damaged areas.

Where cable's metal threads interfaced into plastic grip, all plastic threads had stripped out.

Repairs made via utilizing JB Weld reforming threads into plastic grip. Metal threads on cable were used as mold in forming threads.

Q-tip was used (dipped in dishwashing liquid) rubbed all around metal threads to act as mold release.

Further protecting metal threads from adhering to JB Weld, cling wrap was wrapped around threads, and then metal cable threads were put in place into plastic throttle grip, secured with JB Weld.

Combination of plastic wrap and liquid dishwashing soap will prevent JB Weld from attaching to metal threads, but will allow metal threads to act as thread mold for JB Weld, thereby forming replacement threads into plastic twist throttle.

How long repairs will last is anybody's guess; I've no idea. Suspect JB Weld will make stronger thread than original manufactured plastic threads inside of twist throttle.

What caused carburetor slide to stick in WOT? Appears twist throttle went past internal rounded plastic stops, rendering throttle non-functional, as cable turning past the stops, had pushed cable out bottom of twist throttle, being as plastic threads holding cable into twist throttle failed catastrophically.

There were other damages which could have, on their own, either contributed to or completely caused WOT condition.

End cap on cable sheath had split in two, completely detached from sheath, yet remained mucking up and interfering with throttle cable movement.

This was resolved via removing interfering debris, replacing missing sheath end cap with provisional throttle sheath end cap (which was cobbled up on the spot), then JB weld affixed cap onto end of throttle cable's sheath.

Not wanting to wait four or five hours for JB Weld to set up, set oven to 150° and used cookie sheet holding plastic throttle parts inside the oven, in order to to quickly cure JB Weld, in about an hour.

This process is known to be somewhat less durable than traditional 5-hour set up time for JB Weld, yet good enough until replacement throttle parts arrive. Proverb: Perfect is the enemy of good enough.

Brand new carburetor arrived in the mail today, and was modified with extension to choke lever (easier choke operation while riding), and "yank/pull cord" added to "flip valve" on bowl of carburetor, so that if necessary, fuel could be released from carb float bowl, even while riding down the road.

Carb came with O-ring to make good seal, to prevent air leaks I'm adding to that high temperature "form a gasket" silicone to eliminate problematic air leaks.

Determining factory settings, discovered idle screw was three and one fifth turns out from idle screw bottoming out.

When I get to some place there is hardware (nearest hardware store to residence is 18 Mi away) plan on replacing acorn nuts holding down cylinder head/jug with regular nuts. Suspect acorn nuts bottoming out on studs, rendered incapable allowing proper head/cylinder torque.

Tossing acorn nuts into trash would eliminate that particular odius cause of air leakage, and explain oily residue outside on motor.

 

[nimblebee]

Semi successful test run after repairing twist throttle, modifications and installation of new NT carburetor.

New replacement twist throttle arrived via post today, and will be retained as spare, preferring to see how long provisional repairs made to throttle work out.

Motorized bicycle retains lots of problems, with "difficulty to start" particularly irksome. May have isolated one likely primary cause, however.

Believe it or not, relates to stripped woodruff key on clutch shaft. Pedaling, disengage clutch, suspect chain sprocket slipping on clutch shaft, because chain turning but motor isn't turning.

When taking clutch apart, woodruff key was missing. Slot where woodruff key was supposed to fit into shaft was completely dished/cratered out.

New clutch shaft and sprocket repair kit ordered, but parts arrived without woodruff key.

Made provisional repair to last while awaiting parts, which seemed to work temporarily, but now repair is leaning towards failure, and permanent fix is needed. Might need to order another disassembly tool for clutch, unless can figure out whereabouts of tool? Fortunately, these are quite cheap, so it's not worthwhile to spend a great deal of time trying to search out the tool. When I do find the tool it will just become a spare for the next time I forget what I do with this assembly tool. lol ;-@

Tomorrow on day off, riding motorized bicycle 18 miles to only remaining hardware store in the county, and hope they have woodruff keys fitting clutch shaft. If they don't have the woodruff key, then either I have to order them online, or travel another 30 miles beyond that to get to a bigger town actually having a real hardware store.

Replacing woodruff key and clutch shaft, hopefully sprocket turns motor (without shaft slippage) for easier starting.

Other elements of test drive worked out:

a) At WOT can kill engine (as suggested, thanks!) via fully engaging choke.

b) Turning off fuel petcock whilst releasing fuel from carburetor bowl via "fuel dump" pull cord works.

c) Pull/yank cord to remove spark plug lead and boot from spark plug works (with caveats).

While pull/yank cord will stop engine, bugs remain to eliminate:

1) System works, but takes hard pull on cord to remove plug wire.

2) boot wants to separate from plug wire.

3) my spark plug wire is decrepit and needs to be replaced (but it still works).

Reading through forums highlights variant opinions concerning replacement plug wires.

Would be nice, if link to purchase on Amazon/eBay at reasonable price, but that's not what I'm finding through searches.

Persons making up their own spark plug wires have to buy length of wire, special crimping tool, end pieces, boots.

Further annoyance results from hassling with super glue adhearing spark plug wire inside CDI, before new wire can be inserted onto screw.

One poster claimed using heat gun or hair dryer where wire goes into CDI will soften glue, making easier to twist wire off CDI's "screw" type connection.

Read up on methods dissolving super glue and bought nail polish remover (100% acetone) as one possibility, but searched lots of crazy things including: butter, apple cider vinegar, coconut oil and enough other ingredients you could probably cook dinner with.

Motorized bicycle sitting out over night, will straighten metal core wire, reinstall spark plug boot, and use high temperature silicone make-a-gasket to fill gaps in missing insulation on spark plug wire.

Should provide usable provisional repair, allowing use of bike, while sorting morass of opposing opinions on where to buy decent spark plug wire for replacement on motorized bicycle.

I've only found one decently priced link on Amazon, which might be for what is needed? Can't determine from description whether or not is solid metal/copper core, non-resistor wire/non-resistor boot?

I heard back from Amazon seller is non-resistor, copper core wire. Went ahead and ordered and will post how spark plug wire works out: if it's any good, and only time will tell, if insulation is any better than spark plug wires/boots shipping with kits.

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