Carb problems? on Honda Helix

[Lurkin]

Ok boy and girls (and all the rest of you ), I'm having a problem with my Honda Helix.  Yes, I know this is a Magna board and the Helix is a scooter, but many of you have experience tuning/troubleshooting with other bikes, so I thought I would ask some advice.

The Helix is a 250cc single jug scooter with a CV carb, an auto-choke (more on this a bit later), and a CVT tranny.  Bought this as a wife-mobile, but I think I ride it more.

A few weeks ago I took it out to run it a bit, since it hadn't been run for about 2 months.  Normally I take it out every month at least, but Ike tasks pushed back the importance of that some.  When I tried to start it, it will turn over just fine, but it would not catch at all, nothing, nadda.  At that point I checked:

• Gas flow (has a pump) - flow was fine
• Spark - removed and cleaned plug, showed spark when grounded to head and cranking

Since it always started hard, I thought that the auto-choke had gone bad.  Note that the auto-choke is a dumb-system whereby a heater element in the autochoke heats up a wax insert (over about 10 minutes) that extends a needle into an extra fuel/air port.  Essentially the auto-choke is supposed to cut off the extra port as it warms up and the needle extends.  I bought a new autochoke and awaited it's arrival.

When the auto-choke arrived, it still would not start.  It would catch a bit, but would not stay running.  At this point I started going through the manual, and past knowledge, to see if I could figure out what was up.  I did the following:

• Removed and cleaned the carb, reset the pilot screw (was at 2.75 turns, set to manual recommended 2.5 turns)
• Per manual, checked the resistance of the coil, spark plug cable, stator, pulse generator (all were within specs
• Drained gas tank and float bowl (gas was only 2 months old, and it had Seafoam in it, usually keep Seafoam in it since it doesn't get ridden much), replaced with known good gas
• Put it all back together, and still the same results, will turn over fine, will catch some, but will not catch fully
• Removed and cleaned the carb again, just to be sure, but this time completely tore it apart and cleaned all jets, needles, and orfices with carb cleaner and air (note that the carb was very clean the first time).
• Checked battery voltage at rest, idle (as I could get it close to anyway), and at 3000 rpm (all checked within specs 12.6, 12.9, and 13.9)
• Exchanged battery's with my Magna (again, just to be sure)

After doing all this, it would still not remain running.  It would catch, and if I kept trying, it would start, but would not idle on it's own and it was backfiring on throttle let off.  I drove it a bit to see if it would clean itself up after a full warm-up, but it ran the same.

I'm not sure what to do next.  Note that it was running just fine the last time I ran it, it always took 2-3 tries before it would start and idle on it's own when cold.  Now it just does not want to run, and is a bear to get running at all.

Any advice on what to try next?

Apologize for the long post, but I have tried many things in my spare time over the last few weeks, and I wanted to be complete.

Thanks, Rod.

[hootmon]

I know you said you checked the Pulse Generator, but have you verified the timing?
Sounds like you should have spark and fuel.. Assuming you have air flowing in and exhaust flowing our unrestricted, that leaves the timing of the spark.. Just a thought...

[Lurkin]

Hoot, yes I've thought of it, but not sure how to verify it.  It has an ignition control module, like the Magna, but since the ICM is $170+shipping I'd like to know if there is some way to test/check before "investing" in that part.

Rod.

[hootmon]

On the Magna, you can open the big nut on the Clutch cover to observe the timing marks and use a timing light.. There must be such a place on the Scooter engine as well...

[Greg Cothern]

SO lets back track a bit..  If has sat for 2 months or so without any love??....  Any other changes?  Ran fine before the sit?
If the answere is: No other changes made prior, and yes it ran fine before.
Then it hates you for letting it sit too long without taking it out for a spin around town!  The idle circuit is clogged somewhere and not getting fuel to idle.  Then when you open it up and get it pulling fuel on the mid-range circuit it floods it out some etc.
I would use compressed air (be careful not to hurt a diaphragm or such) and make sure all the passages are patent.  Then give it a whirl!

[roboto65]

Put some Seafoam in it and try again like Greg said after 2 months she is hating you right now LOL

[dgc67]

In his defense, he did say he always uses Seafoam and has rebuilt the carb, using compressed air to clean it out as well.

Drained gas tank and float bowl (gas was only 2 months old, and it had Seafoam in it, usually keep Seafoam in it since it doesn't get ridden much)

Removed and cleaned the carb again, just to be sure, but this time completely tore it apart and cleaned all jets, needles, and orfices with carb cleaner and air (note that the carb was very clean the first time).

Now in others defense, Lurkin, you post was WAY too long.  Guys on here just don't have that kind of attention span!!   

[roboto65]

Ok sorry Seafoam is the cure all mostly  anyhow if it ran fine before you put it up albeit having to start it 2 or 3 times there has to be a plugged idle circut in the carb I know you cleaned it and all but thats just how it sounds in your description.
I had a set of carbs on the orange Magna I have now that would not Idle or run right I pretty much had to get a new to me set of carbs from Ebay they were clogged up good after I changed them out she ran fine!!!!!!!!!!!  Greg and I cleaned them and no amount of cleaning helped so I replaced them...

[Lurkin]

All, thanks for the input.  In answer to the questions posed above:

Hoot, nothing in the manual, nor through my looking all over, points to any externally visible timing mark.  I'll check further, but not hopeful.  The Helix is built simpler then the Magna, except for the CVT that is...

Greg, right, no changes during the 2 months, ran fine before.  I thought about running it quite a few times, but other things kept coming up (including making sure the Magna stayed running), I'm sorry!!! 

From the symptoms it shows I figured fuel or timing.  First time I opened the carb up was a quick-n-dirty to see if it looked dirty, or to find something amiss.  Second time was a complete tear down and clean.  I guess I need to do it again....

DG, I know, but when I do write something up, y'awl be gettin' all the gory details !

Allen, thanks for the past experience.  I hate throwing parts at an unknown problem, but it's about where I am, unless the next carb clean gets it.

There are some carbs on Ebay, but I'm torn between trying a new carb, or the ICM.

Any other ideas gents?  Appreciate all the help so far.

Rod...

[Greg Cothern]

Lets think about the timing, how would it change from just sitting 2 months with non use?  I highly suspect its OK.

Now the carbs, we all know they will clog from non use.  As Allen mentioned you can clean em but still have a passageway that is not patent.  THIS IS where I put my money.

[Lurkin]

Just to be clear, when I said timing, what I meant was the entire spark path from the pulse generator to the actual spark.  While the actual timing may be good, the spark itself may be weak.  I've verified that I have spark and the resistance levels in the pulse generator, coil, and spark wire are good, but does this mean I have a strong enough spark??  Not sure.

I am going to tear apart the carb one more time though.  One question, when you refer to the idle circuit, is it the low speed jet, the pilot needle, or both?

Anyone know of a used/junk parts dealer that may have scooter/Helix parts?

Rod...

[hootmon]

New Carb on E-bay for a 250
http://cgi.ebay.com/ebaymotors/HONDA-CARBURETOR-HELIX-CN-250-CN250-CARB-VE43AA-NEW_W0QQcmdZViewItemQQ_trkparmsZ72Q3a1207Q7c39Q3a1Q7c66Q3a2Q7c65Q3a12Q7c240Q3a1318QQ_trksidZp3286Q2ec0Q2em14QQhashZitem390005741877QQitemZ390005741877

[roboto65]

Rod here is a link to carb theory this will show how a idle circuit works. Not much to it but very small orifices and they clog very easy!!!!

ftp://thepit.shacknet.nu:1001/carb/carbs101.pdf

[Lurkin]

Hoot, thanks for the link.  I have seen that carb, and it's actually from the same person I bought the new auto-choke from.  Downside is the new carb comes with a new auto-choke too,,, another $40 lost if I go that way, oh well.

Allen, thanks for the document, but that leaves me with a couple more questions.  In the doc they refer to the pilot air screw and the pilot jet as affecting idle/low throttle operation.  How does the pilot screw and the slow jet on the Helix/Magna map into this?

I am assuming the screw is regulating fuel flow given that opening it richens the mixture, but how does the pilot screw and slow jet interact?  The pilot screw can't be metering fuel to the slow jet can it?  Or are they actually separate fuel circuits?  If so, at what throttle openings does the slow jet come into play.

Note that the Magna carb and Helix carb are close to the same functionality except for the auto-choke circuit.  Jets and needles are basically the same, per the parts fiches.

Rod.

[roboto65]

On the Magna the pilot screw regulates fuel flow to the carb throat so it comes thru the jet which provides a given amount of Fuel depending on size then up the passage to the pilot screw so the more you open the screw the richer the mixture now if your pilot screw is on the other side of the passage say closer to the airfilter then it would be opposite the more you open the screw the leaner it would get.

I hope I have not lost ya LOL but lets just say the the screw is a fine adjustment for the JET.
Take a look at the theory again on figure 7 that should give a a better idea on where each one comes into play..