Post by rvandyPost by Bike guy JoePost by Robert LaCasseCan you drive normally with the intake manifold blocked the way you
start it? I mean blocking it with a rag or something to see what happens
differently in the top end....
That would be the most horrific advice yet. If he's got to block the
intake to start it, there is no reason to ride it with something
blocking the carb, that's not going to help and may well get a rag
sucked down the intake.
haha, ok...I'm not going to do that, BUT...if I leave my hand on the
intake, it will die if I throttle up. The model is an 87 CH150 with
about 3k miles on it...I got it a year ago with 1k...cleaned the carb,
gas tank, replaced a fuel line, that's about it - it hadn't been
ridden much so I assume it had been sitting unused in a garage most of
its life. I'd say if it's about 60 degrees plus, it starts instantly,
no problem at all. The colder it gets, the harder it is to start, but
I've never had it not start on me at all (except the time the battery
died, ugh).
The thing with the bystarter is...I'm not too clear on how it
works...from what I've read, when cold it's open - so it's adding fuel
to the mixture, and then as it heats up it kind of "melts" and pushes
the pin down to close off as the engine warms up and doesn't need the
richer mixture anymore, so unless its melty properties are shot and
it's stuck in the "closed" position (which very well may be the
case)....wouldn't that mean it should still work on cold days? I'm
assuming the fuel/air mixture is off...but given how perfectly it
starts when it's warm out, I'm hesitant to fiddle with them. I'd also
say that my mechanical aptitude is about a D-, so I'm also worried
about screwing something up. If it ain't (that) broke, don't fix it,
right?
I guess my question would be: how did you clean the carb? There are
only two good ways as far as I know, one is with an ultrasound machine
but most shops don't have those, in fact most haven't even heard of
them. The other way is to dis-assemble the carb and soak the body and
jets in a carb cleaner for at least a few hours (not the rubber parts
such as the diaphragm nor plastic such as floats). When you take the
slow/idle/pilot jet out it is important to turn it in first, noting the
number of turns, eg., 2 1/2 so that you can match the turns when you put
the jet back in. The jet may be covered with a plastic or wax or
aluminum plug, if so, there is a good chance that nobody has ever taken
it out before and the number of turns will be the factory setting.
The tube around the main jet might need some tapping with a similar
diameter object to get it out.
After soaking, the carb needs to be blown out with air - this can be
done with a cheap blower nozzle that you can attach either to an air
tank or a small compressor or even a car tire.
Not saying you did this but (I think) trying to clean a carb without
removing the jets is a waste of time. Some of the orifices and passages
are too tiny to clean any other way.
Unfortunately, I don't know of an online version of the CH150 manual and
if I had no experience with similar engines, I wouldn't try working on
the carb without one. However, you may find that CH250 manual which has
been bootlegged in several places on the web helpful. There is a
resistance test (around 10 ohms is right), a pressure test and sometimes
a test with a battery but at the very least you could check that the
needle itself is not stuck by tapping it with your little finger.
I believe it is quite possible that the starter valve/bystarter/electric
choke needle is stuck, possibly because of gum in the passage meaning
the bystarter itself might be okay. A thorough carb cleaning might help
this. It makes sense that with so much sitting will have caused gum or
varnish build-up inside the carb.
Also, when the carb is mounted and the throttle cables connected, the
butterfly valve should be closed so that it is in-between the three or
four little holes on the bottom of the engine-side throat. Sometimes
people turn up their idle speed which causes all of the little holes to
operate at idle - they are not meant to, the inside holes are the
acceleration circuits and the carb isn't set up right if they are
exposed at idle. I suspect the most common reason for doing this is
that the idle circuit is dirty or plugged which cleaning can fix. Not
saying for sure that's your problem, but it does seem possible that an
engine that is idling with all the jet openings exposed might cause hard
starting when cold (fuel doesn't atomize and burn as well as it does
when warm) which might explain why you have to block some of the air
supply to start.