problem starting... choke

murph · Posted: March 29, 2008, 12:11 am Post subject: problem starting... choke

Well my 81 will start fine... with the choke in..not out... So I pull it out after it's running... but the idle will not raise with the choke out? has anyone else experienced this?

xsjohn · Posted: March 29, 2008, 4:39 am Post subject: Re: problem starting... choke

I'm baffeled that murphs BS34's that won't fast idol when he pulls the choke out........murph does it get richer when you pull the choke....in that case it would be no extra air.........and if there was no fuel it seems it would lean if it was getting air and make it rev up some or just mess up idol........baffeled......??

xsjohn

jimdi · 650Rider Supporter Joined: Oct 27, 2005 Posts: 512

yes - I have had this happen- especially at intermittent times while fooling with mixtures -
y theory is that if the idle mixture is over-rich to start (past rich roll off) - the extra richness just puts it way.... over the "rich roll off point".

Often time I think you will find that people compensate for this by opening up the idle SPEED screw too far (to keep the bike running)

ie. - just at idle you are past rich roll off - so when choke adds more gas to the mix - it provides no noticible difference.

Usually when I lean back a little - I notice I get my fast idle back with chokes.

this is one example of why I am facinated by those on this forum who seem to be able to richen up their mixtures to no end - for me there has always been a definate "too rich" point. Especially when warm weather sets in.

I am curious to see what his plugs look like - they really tell the story of what is happening in their!!!!!

FYI I have two sets of carbs - on one set - this point "past rich roll off" can be reached at 2.5 turns out - on the other it takes up to 3.5 turns out on the idle mix screws. You can't always say 2.5-3 out should be good.

Jim

murph · Posted: March 30, 2008, 2:23 am Post subject: Re: problem starting... choke

I have my mixtures set at 2.8 out... maybe it's at this too rich point.... I occasionally get backfires when releasing the gas... on roll off.... but nothing that is problematic.... Don't even know if that is related...I will take some pics of my plugs soon.
Thanks for the input jim

jimdi · 650Rider Supporter Joined: Oct 27, 2005 Posts: 512

I have been where you are at - here's what I can tell you - in addition to what I posted above about being to rich:

Stumble on acceleration is usuallly too lean -
I have had a really over-rich mixture cause pipe backfire.

Over- rich can also be caused by floats set wrong -

Get a micrometer and set the floats - for 81+ 34's 22mm.

ake sure all of jets and passageways are clean and clear - (pull jets to clean them)

ake sure the choke plungers are clean

Check you diaphrams for tears / gasoline.

If you plugs are black and powdery on the tips - you're getting too much gas in there -

If not - check the choke circuit for obstructions in the passge ways from the bowls...

Good luck

xsjohn · Posted: March 30, 2008, 11:30 am Post subject: Re: problem starting... choke

Poppping on decel is usually the mixture screws...and their relationship to the pilot jet (and of course the airjet)......Used to have to set my 80 BS34's at almost 4 turns and there was only a tiny little place in there where I could excape the slight poping on decel......couldn't venture very far till it came back.......Tried the 45 pilot and the swing was better and gave me some more latitude good and bad that I could try before the poping.......think the 81 an up carbs were a bit richer so the 45 should be fine....every thing else remaining stock......

Finally got pissed with my 80's and took an exact .018 guitar string and forced the maybe .017 thou 45 pilot hole to become a .018 which is about a 46 pilot...at 2 turns now.....and then used a bit of valve grinding compound....the end of string has to be smoothed where it was cut.......can't make it pop on decel no matter where I set them now..........

Tried smaller air jets and I didn't care for them on the 80.....some people do.....it seemed to narrow and lower the portion of the throttle controled by the low speed circuit and make the cruise less smooth......and the thing didn't roll up as good for decent cruise when coming down from a heavier throttle .......And just because the string says 18 on the package means nothing.......have to measure it with a good micrometer......and I am not so sure those chinese ones are that exact......I have one of the old fashioned real micrometers ....... and they are on ebay pretty cheap since everybody thinks digital is so cool..........

Hope this helps someone .....it did me......and others........

And as far as stumbling.....can either be to rich or too lean.......easy to tell ....just listen.........rich is heavy and loud....lean is thin and quiet......huge main jets will cause lots of trouble and so will needles.....this I can contest to for sure......wore more tin top screws out that anyone else has I bet.......and don't use the small pods ....

xsjohn

murph · Posted: March 31, 2008, 12:22 am Post subject: Re: problem starting... choke

got a couple of pics...
this is after a nice ride today around the city... perfect outside.. 60 with a cool wind and plenty of sun. Went down to at&t park and checked out the giants game vs the A's... anyway, the bike had the same small issue with no raised idle with the choke out.

xsjohn · Posted: March 31, 2008, 12:36 am Post subject: Re: problem starting... choke

Murph......Just heard from someone that took his carbs apart and when he put them together it had no fast idol........when he gets back to me I will forward what he found.....did it fast idol before you took them apart...those look like the plugs in my buddies XS1100......not bad if they don't foul and it doesn't miss.........if they do I can send along a bit thinner shim..........every thing is doccumented on my end so I know what you have in there........

xsjohn

murph · Posted: May 19, 2008, 9:02 pm Post subject: Re: problem starting... choke

I've stepped up to buying the 91 octane and this has helped in starting and raising the idle... So... now it's about 12 bucks to fill the tank.ugh

nj1639 · Posted: May 20, 2008, 7:09 am Post subject: Re: problem starting... choke

Well there you go.
y mentor told me in no uncertain terms to ALWAYS use high test, and change oil every 2,000 miles. I'd never hear the end of it if I did anything less. I guess the first question asked to anyone having carb problems is 'are you using high octane?'

tweedy64 · Posted: May 20, 2008, 7:24 am Post subject: Re: problem starting... choke

12 bucks to fill a tank aint you lucky, here in the uk its double that.

Joseph · Full Member Joined: May 22, 2007 Posts: 767 Location: NY

I am also using custom pilots. can i get the same efect with a say 46 pilot and mix screw in as say a 40 with mix screw out?

y 80 doesnt need the choke for long sometimes not at all. If it is runing and i pull the choke it stalls. I use the idle adjusting method as it warms up turn i idle down. Because i broke the cast on the carb that holds the choke open. I have a clip now to hold it open so im going to try and leave the idol alone. Is it standard to take these carbs out in pairs? I think thats how i broke the cast i took them out 1 at a time , what a pain.

oldskoolcool · Full Member Joined: Sep 08, 2007 Posts: 372

my 78 will not fast idle long either, like 10 seconds maybe when it's real cold in the morning.

tacoswild · Posted: May 23, 2008, 5:50 pm Post subject: Re: problem starting... choke

My bike hated the choke until I replaced the old dead pods with K&Ns. It absolutely would not start or run with the choke on. My plugs looked dark like yours back then too, I think it just wasn't getting enough air. After the new filters it prefers choke on most mornings to start and gets tired of it in about one minute and the plugs were real white so I went up one on the main jet and everything seemed a lot happier.

oldskoolcool · Full Member Joined: Sep 08, 2007 Posts: 372

i have velocity stacks too...stock pilots.

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