Choke does nothing, can't find vacuum leak...

James Owens

New Member
Joined
Oct 20, 2017
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12
So I will preface this question by saying that I have had a lot go wrong with my bike lately and there may be multiple issues at play here...


So the problem that I am having is that the motor is idling high and when I start unscrewing the idle adjust screw, once I pass a certain point it goes from very high idle to barely running and then dies. There is a very specific point and I am not really getting anything in between.

In addition to this, I have found that my choke is doing absolutely nothing and the bike will idle fine (But high) with it either completely open or completely closed.

I initially thought it was an air leak so I took of the manifold and put a new gasket in and covered the end of it with high temp silicone before sliding the carb back on then I gooped on a bunch around where it slides on. (I know it's only a temporary solution and that it isn't gasoline resistant)


Doing this seems to have solved some other problems I was having (it was dieseling at idle at even higher rpms before I did this) but it still is idling high and the screw won't fix it and the choke still does nothing.

The choke flap thing (don't know what to call it) covers the hole completely and seems to be pretty flush with the opening when I have it closed. (I've been doing diagnostics with the air filter off so I can confirm this).

If I completely cover the area where the air filter would be with my hand though it starts to die as if the choke were actually engaged...

I have no idea what is up with it and plan to change out the carb as the next step as soon as I can either get one back from my buddy or find all the parts to reassemble one of my other spares.






Other problems I have had at the same time as this one (they may or may not have anything to do with the problem but they may explain some of the symptoms) would be as follows:


•In my way home last week the bike seemed to only be running at half power.

• Reexamined electrical and changed spark plug to no avail.

•I then noticed that one of the mounting brackets was missing a stud. Tried to put a new stud in then realised the the stud broke flush with the case.

•Tried to remove broken stud and failed. Drilled out stud hole and attempted to helicoil. Didn't hold the drill straight and couldn't get it tapped because of sloppy hole.

•Drilled bigger hole. Put in 8mm helicoil and stud. Remounted motor on bike.

•Tried to bend muffler so the pedals would stop hitting it so I wouldn't brake off another muffler at the weld.

• I broke the muffler at the weld.

•Needed the bike for transportation so ground the threads off a lawnmower muffler and shoved in in the muffler pipe, driving a bolt through both the pipe and the muffler to keep in in place.

•Tried to drive in in to work, engine was topping at 20-25 the same as it was before dismounting and remounting.

•Muffler broke off at the weld.

•Built new muffler at work at the hardware store out of some pipe fittings, a water heater supply line, and a lawnmower muffler.

•New muffler worked fine but still topped out around 25.

•Next day, motor started to diesel and idle high, still topped out at 25.

•Figured it must be compression, took off head, saw blown gasket.

•Changed base and head gasket, retorqued to spec.

•No compression at all now, noticeable leak around head.

•Took off head, retorqued, still had air leak in same spot (repeat 5x)

•Took off head, replaced head gasket with new one, took new (used) head and retorqued. Still had leak in same spot. (Repeat 1x)

•Pull out all of my hair and curse the bike I a way my mother would not be proud of

•Took off jug, lapped jug, replaced base gasket, put jug back on, torqued down head, still had leak.

•Though about throwing a match in the gas tank and being done with it

•Examined all three heads

•Realized I had three warped heads, lapped heads.

•Put head back on with new gasket, no more leak.

•Able to reach prior top speed with this motor again.

•Clutch cable snapped, replaced clutch cable and reajsted clutch.

•Still dieseling at idle, idle extremely high.

•Gas tank busted a leak. Attempted to use seal all, still had leak.

•Replaced gas tank.

•Took off manifold, replaced gasket, added silicon.

•No more dieseling, ran a bit smoother but still idling high.




It has been a very long week with this bike... I'd really like to get it running normally again, any help would be incredible appreciated...
 


James Owens

New Member
Joined
Oct 20, 2017
Messages
12
Also the throttle cable does not seem to be getting stuck.

Could the muffler have had anything to do with overheating/dieselingissues? I'm concerned that it's having trouble breathing now because I'm not getting a ton of pressure out of the end of it, it's just small puffs and the end of the muffler doesn't get that hot to the touch. I don't really see anywhere else exhaust could be coming out of though... blowing through the whole assembly seemed to be about the same pressure as blowing through a stock muffler. The diameter of the water heater supply line is roughly the same as the diameter of the stock muffler pipes pre-muffler.

Here's a picture of the bike with the improvised muffler on it...
20180408_191120.jpg
 

FurryOnTheInside

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Joined
Sep 23, 2013
Messages
3,637
I would put tape around where the throttle cable enters the top of the carb, just because it's so easy and cheap to try.
 

James Owens

New Member
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Oct 20, 2017
Messages
12
I did indeed have a warped head, but I lapped both it and the jug before posting this and the problem still persists.


I tried the tape tying before heading to school this morning and unfortunately it didn't help...

It also seems to still be dieseling after she warms up all the way, but not quite as badly as before...

I'm running put of ideas here... I guess I will try a different jug on it next and lap the head down a little more (the crush ring is flat but I see that the areas around it are still pretty warped and may be preventing it from tightening down as much as it should on the gasket.

This still doesn't seem to explain why the choke isn't doing anything though...
 

FurryOnTheInside

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Joined
Sep 23, 2013
Messages
3,637
I did indeed have a warped head, but I lapped both it and the jug before posting this and the problem still persists.


I tried the tape tying before heading to school this morning and unfortunately it didn't help...

It also seems to still be dieseling after she warms up all the way, but not quite as badly as before...

I'm running put of ideas here... I guess I will try a different jug on it next and lap the head down a little more (the crush ring is flat but I see that the areas around it are still pretty warped and may be preventing it from tightening down as much as it should on the gasket.
...
I would guess it probably is the pipe after all, and that you just can't physically blow down it fast enough to really notice the restriction on your exhaust. It is a very long header even if the diameter is the same.


This still doesn't seem to explain why the choke isn't doing anything though..
 

KCvale

Motorized Bicycle Vendor
Joined
Apr 18, 2010
Messages
3,518
The choke plate is connected to the lever with a screw you are apparently missing.
Easy fix.

Warped head and cylinder? Did you buy some $95 engine kit and expect something different?

Anyway, when you take the head off best have a torque wrench to put it back on as it crucial.

I torque my heads in an X pattern in 5# increments until all are at 20#.
I paint and flip head direction all the time and this work great for me.
 

James Owens

New Member
Joined
Oct 20, 2017
Messages
12
I would guess it probably is the pipe after all, and that you just can't physically blow down it fast enough to really notice the restriction on your exhaust. It is a very long header even if the diameter is the same.


This still doesn't seem to explain why the choke isn't doing anything though..
My welder buddy has my three broken mufflers at the moment, I will try one as soon as I get them back. Honestly though it should be about the same length as the poo poo pipe, should the header length make that big of a difference?


The choke plate is connected to the lever with a screw you are apparently missing.
Easy fix.

Warped head and cylinder? Did you buy some $95 engine kit and expect something different?

Anyway, when you take the head off best have a torque wrench to put it back on as it crucial.

I torque my heads in an X pattern in 5# increments until all are at 20#.
I paint and flip head direction all the time and this work great for me.
No. I completely expect this on a 95$ engine. Which I why I lapped them to fix the problem. And as stated I "torqued them to spec" i.e. with a torque wrench. I know how this works...

And no, the choke plate and lever are as they should be, the choke plate is completely covering the intake and flush when closed and completely off the intake when open. As previously stated. I have been doing diagnostics with the air filter off and I have specifically inspected this. This isn't my first rodeo bub
 

crassius

Well-Known Member
Joined
Jul 23, 2012
Messages
4,575
0nly thing you need to know is that choke doing nothing means it is getting air someplace else - fix that first.
 

Tyler6357

Active Member
Joined
Sep 28, 2011
Messages
728
When you start it, put your hand down around the head to see if you can feel any air shooting out around the head gasket to make sure it's sealed now.
 
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