Bonneville America Forums Forums Technical Forums General Tech Still not running right, backfiring, etc. HELP

All,

Here are the symptoms:
1. Starts great
2. Warms up with choke pulled out...there is a hiccup and it seems isolated to the left side-fuel will drip from plunger where choke enters carb when the choke is pulled all the way out.
3. Idles fine when chock pushed back in.... with no sign of the hiccup in the carbs. Revving engine sounds fine with a small backfire from left side when revving engine (much smaller than previous)
4. When pulling out the bike has NO power and is hard to get up to speed if at all....Seems worse when its warmed up completely

INFO:

1. Left side carb boot dryrotted. Both boots replaced. Utilized original clamps (they tightened really well-the replacement ones have not arrived-used ones from 2003 SM and this did not correct the problem)
2. All squirell condoms checked and ones from 2003 SM put on to test. No problems found.
3. Changed spark plugs
4. AI is still on the bike (anyway this could cause anything?)
5. Air Screws 3 1/2 turns out

I am about to take it into a dealership (but it is 3 hours away). If anyone has a suggestion to try prior to the trip PLEASE get back with me ASAP. ( I will be leaving around 930 AM tomorrow)

You may call my cell phone if typing something out will not get the point across. 304 360 4082

Thanks in advance

Steve

Almost sounds like a stuck float. Try smacking the carb bowl gently with the backside of a screwdriver and see if helps.

check the vacume line to the air pump and possibly the air pump diaphram. Could try to remove the vacume line and cap that port too.

One of the first I did....used to own an old chevy truck that I would have to beat the crap out of the carbs..

Think I may need to take the carbs totally off and clean? After finding the dryrotted boot I figured it wasnt dirty carbs.

couldn't hurt to make sure check that all the jets are clear too.Make sure all your electrical connections are good at the coils too including the sparkplug wires. I really thought you had it beat with that intake rubber.

I checked all connections on the plug wires when i Had the tank off.....no corrosion of any kind. still has grease on connections

Ok here is s stupid question I am sure but are you sure you didn't pinch the tank breather?

I checked and rechecked that when I put the tank back on...

I guess it could be pinched somewhere where it runs down to the bottom of the bike. I can check that

probably not, where the tank mounts is the most likely spot. check the tip over valve as well.

where and what is a tip over valve?

Well after readin the previous post i noticed the front and back part on the carb boots. Took them off again and put them on the correct way. Still having issues.
Tank vent ok, all other possible vacuum leaks have been checked. New clamps will arrive tomorrow so on the outside chance that is it I will replace them......

Any other ideas?

Could be a coil try swapping side to side and see if the problem moves with the coil. Since the bike sat for a bit like I told you when we were PMing back and forth can't hurt to open the carbs and clean them checking that air will flow through all the circuits pilot, mid , main. Could pull the top covers off too and have a quick look at the rubber diaphrams that lift the slides.

I have a buddy coming over tonight that is good with carbs so I may pull them off. Just swap the plug wires?

no, you could swap the wires if you also swap the wire that powers them up. These engines are 270 deg. fire so they are not top dead at the same time. I was talking about removing them both and swapping sides but you could just swap both sets of wires and see if the problem switches sides. To be clear when I say both sets I mean the 2 sparkplug wires on the one end of the coils and the wires on the other end of the coils that power them up to maintain proper fire.

ok I think I understand that....off to the garage

Air filter is good to go.
Swapped coils and problem remained on left side.
Is there a bushing of some sort that the plunger for the choke runs through-compression type fitting that I can tighten? I am about to pull the carbs off in about 30 mins. when my buddy gets here.

And the exhaust pipe is clear as well? Then I'm back to a vacuum leak in the AI path if the carb float isn't gummed up.

Quote:

---

Then I'm back to a vacuum leak in the AI path

---

stevieh

I know you checked the condoms.
but did you remove the AI vacume line and plug that vacume
port also.
this would eliminate the possibility that the AI has
a vacume leak somewhere.
I think most bikes have the AI attached to the left side.

Yes i pulled the AI air line and put a condom from my SM onto the port. No change.

Just pulled the carbs and pulled each bowl and top also.... CLEAN as a whistle. I need a small open end wrench (who knows where mine went) to try to tighten the nut around where the choke plunger goes into the carb.....some fuel coming from this area indicates it could be a problem. I also have the new clamps coming tomorrow and will tighten those down good and put it all back together.

When at idle is seems fine....
Backfires (small-more than a decel pop) but no flame from backfire-that issue was resolved with the new boots.
With Choke pulled it hiccups....in other words the carbs kinda shake and make a pffffffft sound.

Tell you all more later.........An ideas or suggestions will gladly be taken

How far out are the air mix screws? The left carb's not missing it's air mix screw is it?

no. TOR pipes on the bike. 3 1/2 turns out.

Are you positive the air screws have all their bits? I'd pull the screws (put a towel under the carbs!) and check the placement of all parts and the condition of the O-rings.

Well since it was running fine since it was ridden to my house 3 months ago and no one has removed them I would assume they are all in there. I still have the carbs removed so its easy enough to check.....

They may be in there but you may have a dry rotted O ring that let go. Be very careful with the screws to readjust them turn in until seated very lightly thats important since it is very easy to damage them then turn back out to the adjustment you want.

Will check that tomorrow prior re-install of the carbs.

Thanks for the advice guys