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Discussion Starter #1
So, last year I changed the stock pipes for the cobra shotguns. I rejetted the carbs with a cobra stage 1 jet kit. Put everything back together and ever since every time I open the clutch to start and warm up the bike it shuts off.

I did everything myself so I know it's related to the carbs however I am not sure why. I wish I had an idea of what is it I did wrong so I can take it apart and fix it but knowing what to look for.

It's really hard to get it started when cold. Once it has warmed up it, say during a ride, it starts right up no issues.

Are there any videos or resources to try and figure out what's going on?

Thanks
 

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https://sites.google.com/site/vstar1100kb/home/new-owner-must-do-list.
be sure to read the proper starting procedure. also check out the mid shaft nut. the choke is an enrichener circuit, as long as the linkage is functioning correctly it shoud be fine.
you didnt need to buy a jet kit. if you only changed the pipes you could have upped the mains one size or turned the pms screws out a quarter turn.
read the section on tuning and performance everything you need is in there.
 

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Please clarify:

1.Are you starting the bike with clutch pulled in and when let it out it stalls?
2.Is your kick stand up or down.
3. Is chock full on.
4. What temperature are you calling cold.

Any other info would be helpful. Has the bike sat long? What size jets? We're pilot jets cleaned? Stock are filter?

Thanks.
 

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Discussion Starter #4
Hey Nick57,

Thanks for the awesome link. going through it right now.
As for the Jet Kit I just followed what I saw recommended almost everywhere. I even had some issues buying insurance

for the bike because they do not insure "modified engines"...anyways, I installed it last riding season and I honestly
do not see a huge difference other than the backfire frequency has decreased.

Will keep you updated of any progress. I can only work on the bike on weekends so bear with me.

https://sites.google.com/site/vstar1100kb/home/new-owner-must-do-list.
be sure to read the proper starting procedure. also check out the mid shaft nut. the choke is an enrichener circuit, as long as the linkage is functioning correctly it shoud be fine.
you didnt need to buy a jet kit. if you only changed the pipes you could have upped the mains one size or turned the pms screws out a quarter turn.
read the section on tuning and performance everything you need is in there.
 

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Discussion Starter #5
Hi Les,

here goes:

1. I open the choke then I press the starter button, in N with the kickstand down. it sometimes will "run" like this
for a few seconds and then it dies down. If I have already attempted to start it with the choke closed and it runs
and while running I open the choke, it shuts off. it almost feels as if i'm CLOSING the fuel supply when I open the choke up.
I know this would make no sense but that's how the bike responds.

2. kickstand down.

3. yes, full on.

4. I'm in Canada so, we're talking colder than in the states; although I only ride when its above 14 celcius (58 F)

5. The bike did sit in the garage all winter. it does that too overnight so it doesn't really need to sit long. Last year I rode from
Toronto down to Newark, NJ. Everything was fine. the next morning when I tried to start it, same thing and then after I go through the
process for like 6 mins of trying to start it, then it runs. its always the same. it seems it sustains combustion as the engine warms up so,
I start it cold it would just stall, then second attempt it would run for like 2 seconds, shuts off, then another attempt then it would run for 5 seconds and
shut off, then again and again until it doesn't shut off anymore. The jet size I'm not sure of an exact # but they are the Stage 1 Jet kit from Cobra.
I did clean everything, thoroughly when I switched the jets last year. the air filter is a KN performance air filter (not stock) which I also
changed because the engine was backfiring a lot when I purchased the bike, however; back then the choke worked as supposed to.


Please clarify:

1.Are you starting the bike with clutch pulled in and when let it out it stalls?
2.Is your kick stand up or down.
3. Is chock full on.
4. What temperature are you calling cold.

Any other info would be helpful. Has the bike sat long? What size jets? We're pilot jets cleaned? Stock are filter?

Thanks.
 

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When you start the bike pull the choke all the way out and dont give it any gas till it fires, then you can burp it just a bit.

As soon as the engine starts push the choke in a couple clicks (about half way) so the idle drops down to normal.

Let the bike warm up for a minute while you do your preflight check on lights and brakes...

then ride off - when you get about 1 km down the road push the choke in all the way.

If you are pushing the choke in all the was as soon as it starts, then yes: the engine will quit.
 

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Discussion Starter #7
Hi KCW,

after reading the start up procedure on the link Nick57 sent and what your posting here I have to say
that I've been starting the bike incorrectly for about a year now and its definitely something that
I will try to review this weekend.

Seeing this I'm surprised that I haven't screwed up the engine, I'm ashamed to say. :|

The only real difference I notice now vs when I first got it is that the bike wouldn't shut off
before if I left the choke open all the way after it fired. It does now. Having said that, I will try this procedure
because there may be no real "problem" after all, maybe since I did the re-jetting of the carbs I inadvertently
"adjusted" the choke and I'm just using it wrong.

I will update this Saturday right after I start the bike.


When you start the bike pull the choke all the way out and dont give it any gas till it fires, then you can burp it just a bit.

As soon as the engine starts push the choke in a couple clicks (about half way) so the idle drops down to normal.

Let the bike warm up for a minute while you do your preflight check on lights and brakes...

then ride off - when you get about 1 km down the road push the choke in all the way.

If you are pushing the choke in all the was as soon as it starts, then yes: the engine will quit.
 

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choke and throttle are both words that can be used in a confusing way

choke means to close off (restrict the air) Throttle means the same thing. When you throttle someone you squeeze their neck so they cannot breath.

To be clear, lets call it choked and normal, which is the control pulled all the way out, and pushed all the way in (for normal operation with a warm engine).

When you start the bike and you have it fully choked, if you leave it there the engine will high rev, maybe up to 2000 rpm. If you left it there as the bike warms up the mixture will get so rich the bike will bog down, and if you tried to ride it that way it would have reduced power. When you stopped for a light the engine would rev hi. Thats why you dont leave it fully choked after the bike starts, you push it in half way.

This is something that has been automated on cars all the way back to the early 1960s - there was a little heater element on the choke, and as the car warmed up it would roll the choke off as the car warmed up. If it was not matched very well to how the car warming up, the car would stall at red lights. On old aircooled VWs you had to adjust the choke in the late fall and again in summer, or it would not be matched to the engine temperature.

Dont feel bad if you are not familiar with how a manual choke is used - they have not been on cars since the 1950s, most people have no idea what it is.

I recommend you make it a ritual when you ride off on you bike, when you get to the same place in the morning about 1 km away, always push it in all the way at the same place. If you forget the bike will run rich and it will rainbow your exhaust pipes.

BTW, if your bike is not running right with the choke you may need to adjust the Pilot Main Screws (PMS). Most rejetting lists tell you how many turns to set them for the intake and exhaust you have on your bike, but that is really just the starting point. Search for PMS adjustment methods, you can dial them in a little better than just 2 or 2.5 or 3 turns out like it says in the tables.

EDIT: forgot to mention, you need to use the choke when the bike has sat overnight, no matter what the outside temperature is. When the engine is at room temperature the gas in the air mixture that goes in the engine condenses when it hits the metal parts inside the combustion chamber. That is why the mixture needs to be SO rich on the first piston firing. Once the top end of the engine gets hot, that does not happen anymore.

If you commute and park your bike for the day at work, even in the sun, you might still need to use half choke when you start the bike up at 5PM. If the temperature is cold (like 40F) all day you will need full choke.

Otherwise, when you are riding the bike all day, stopping for an hour to eat, hanging out for a couple hours, you do not need to use the choke each time you start it - the core of the engine retains its heat for a few hours.
 

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Discussion Starter #9
Awesome post!

Mine is definitely NOT running right because, it doesn't rev up if I leave it fully "engaged" (instead of "open", see what I did there? lol). it did before.

At this point my main suspicion is that, although I have not been using it correctly to start the bike, I did (out of laziness) not tinker with the PMS
when I did the re-jetting. I installed the needles and everything EXCEPT I did not drill out the PMS cap and left it at the factory setting so perhaps
that's where the problem lies.

If I'm understanding correctly how this works between the PMS as is (Stock setting) + choke fully engaged I should be
basically "drowning" the carbs and that's why it's dying down?? so, theoretically I should adjust the PMS to make the mixture "leaner" (turning it counter-clockwise 3 full turns according to Cobra) so when that's done and the carbs are sync'd + choke fully engaged the mixture would be "richer" so it WILL
rev up but not so rich that it will drown it???


choke and throttle are both words that can be used in a confusing way

choke means to close off (restrict the air) Throttle means the same thing. When you throttle someone you squeeze their neck so they cannot breath.

To be clear, lets call it choked and normal, which is the control pulled all the way out, and pushed all the way in (for normal operation with a warm engine).

When you start the bike and you have it fully choked, if you leave it there the engine will high rev, maybe up to 2000 rpm. If you left it there as the bike warms up the mixture will get so rich the bike will bog down, and if you tried to ride it that way it would have reduced power. When you stopped for a light the engine would rev hi. Thats why you dont leave it fully choked after the bike starts, you push it in half way.

This is something that has been automated on cars all the way back to the early 1960s - there was a little heater element on the choke, and as the car warmed up it would roll the choke off as the car warmed up. If it was not matched very well to how the car warming up, the car would stall at red lights. On old aircooled VWs you had to adjust the choke in the late fall and again in summer, or it would not be matched to the engine temperature.

Dont feel bad if you are not familiar with how a manual choke is used - they have not been on cars since the 1950s, most people have no idea what it is.

I recommend you make it a ritual when you ride off on you bike, when you get to the same place in the morning about 1 km away, always push it in all the way at the same place. If you forget the bike will run rich and it will rainbow your exhaust pipes.

BTW, if your bike is not running right with the choke you may need to adjust the Pilot Main Screws (PMS). Most rejetting lists tell you how many turns to set them for the intake and exhaust you have on your bike, but that is really just the starting point. Search for PMS adjustment methods, you can dial them in a little better than just 2 or 2.5 or 3 turns out like it says in the tables.

EDIT: forgot to mention, you need to use the choke when the bike has sat overnight, no matter what the outside temperature is. When the engine is at room temperature the gas in the air mixture that goes in the engine condenses when it hits the metal parts inside the combustion chamber. That is why the mixture needs to be SO rich on the first piston firing. Once the top end of the engine gets hot, that does not happen anymore.

If you commute and park your bike for the day at work, even in the sun, you might still need to use half choke when you start the bike up at 5PM. If the temperature is cold (like 40F) all day you will need full choke.

Otherwise, when you are riding the bike all day, stopping for an hour to eat, hanging out for a couple hours, you do not need to use the choke each time you start it - the core of the engine retains its heat for a few hours.
 

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My 650 is fully stock and I have never touched the carbs so I will refrain from giving advice on adjusting the PMS. There is a bit of an art to the adjustment, but the bottom line is for the bike to start up the mixture with the choke has a somewhat narrow window, otherwise it will either flood or not fire at all.

Also with the 1100 you want to be careful about starting the bike. I think the 1100 (maybe the 950?) has an issue with the starter clutch getting back-spun if you give it gas before the starter disengages.

If someone does not address this search on it, because having the starter clutch fail is an expensive PITA.
 

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There's really only one way to adjust the idle mixture screws and that's done with the bike thoroughly warmed up and idling at the correct rpms.
 

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Discussion Starter #12
No worries about the advice part. I'm just trying to figure out the basic problem in order to decide what to do
since I have to rent the time I spend at the shop I don't want to go in there, take stuff apart and not even have
an idea of what I'm looking for. I'm a DIY 'mechanic' so I can figure out stuff once I know the reasoning behind it.

I think now, I have a pretty good idea of what the issue is, if my previous logic is correct once I re-adjust the PMS to
the recommended Cobra settings, the cold start issues should be corrected. Sadly I dunno any way to test this
while everything is disassembled so only when I'm done and try to re-start I'll know the issue is fixed (or not).
I also do not have a tach installed so it might be tricky to do a precise PMS adjustment.

At any rate I highly appreciate the inputs and hopefully I can solve this issue over the weekend.

My 650 is fully stock and I have never touched the carbs so I will refrain from giving advice on adjusting the PMS. There is a bit of an art to the adjustment, but the bottom line is for the bike to start up the mixture with the choke has a somewhat narrow window, otherwise it will either flood or not fire at all.

Also with the 1100 you want to be careful about starting the bike. I think the 1100 (maybe the 950?) has an issue with the starter clutch getting back-spun if you give it gas before the starter disengages.

If someone does not address this search on it, because having the starter clutch fail is an expensive PITA.
 

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There's really only one way to adjust the idle mixture screws and that's done with the bike thoroughly warmed up and idling at the correct rpms.
i don't know how anyone can adjust a 650 PMS with the engine running, the air duct blocks the rear screw, unless you install the thumb screws you'll have to adjust then run it then adjust again until it feels right, i don't know how it's done at the factory on a gas analyzer unless they use some kind crazy driver to get on that back screw, i wonder if that boot air cleaner assembly can be installed reversed flipped up just for the adjustment, i'd love the hear some ideas on adjusting that rear oem screw with the engine running
 

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This is how I do it. Remember I said I was small.

 

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i don't know how anyone can adjust a 650 PMS with the engine running...
I didn't say it was easy on a 650, that's just the best way to do it. For me it involved removing the intake duct work to access the screws with the motor running, turn each screw 1/4 turn, reattach the ducts, blip the throttle and repeat the process until the highest revs were obtained.
 

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Great explanation on the choke KCW. Now it's my understanding that my 1100 does not have a choke. It's an enrichment circuit. So I am guessing that a choke restricts air so the motor gets more fuel while the enrichment pushed more fuel to give somewhat the same effect, Correct?

choke and throttle are both words that can be used in a confusing way

choke means to close off (restrict the air) Throttle means the same thing. When you throttle someone you squeeze their neck so they cannot breath.

To be clear, lets call it choked and normal, which is the control pulled all the way out, and pushed all the way in (for normal operation with a warm engine).

When you start the bike and you have it fully choked, if you leave it there the engine will high rev, maybe up to 2000 rpm. If you left it there as the bike warms up the mixture will get so rich the bike will bog down, and if you tried to ride it that way it would have reduced power. When you stopped for a light the engine would rev hi. Thats why you dont leave it fully choked after the bike starts, you push it in half way.
 

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So I am guessing that a choke restricts air so the motor gets more fuel while the enrichment pushed more fuel to give somewhat the same effect, Correct?

yes, I think the 650 carbs may work the same way - ive never pulled the carbs off my bike to play with them

A choke is sometimes an entire 2nd butterfly that closes across the intake, or it could be a stop point that lets the butterfly close further than normal.

On a fuel injected bike it just injects more fuel

anyway to make the mixture richer for starting, its all the same concept.
 

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I didn't say it was easy on a 650, that's just the best way to do it. For me it involved removing the intake duct work to access the screws with the motor running, turn each screw 1/4 turn, reattach the ducts, blip the throttle and repeat the process until the highest revs were obtained.
impossible, the engine won't idle with all the ducts and cleaner removed in fact it will hardly run, just removing the air cleaner element will cause a flat spot , the ducts and cleaner act like a choke causing fuel to be sucked in harder if the mixture isn't enriched it won't run with that stuff removed, it's like sticking a hypercharger on and not touching the jetting it's not going run right if at all. besides you can't any carb right with no air cleaner on that's exactly why special tools were made. To get on the adjusters with everything in place
 

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So I am guessing that a choke restricts air so the motor gets more fuel while the enrichment pushed more fuel to give somewhat the same effect, Correct?

yes, I think the 650 carbs may work the same way - ive never pulled the carbs off my bike to play with them

A choke is sometimes an entire 2nd butterfly that closes across the intake, or it could be a stop point that lets the butterfly close further than normal.

On a fuel injected bike it just injects more fuel

anyway to make the mixture richer for starting, its all the same concept.
the 650 uses a bystarter not a choke, it opens a valve that allows extra metered fuel in just for starting, the further you pull the knob the further the valve opens, there's no butterfly plate closing off air flow
 

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This is how I do it. Remember I said I was small.

maybe for the 1100 but an air duct blocks the rear carb screw on a 650, with max air screws it could be done on the 650 with everything in place, maybe a short driver like that bent just right might do it, but i think i'll get the max air screws someday if ever get around to it
 
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