Help with carb issues please

[chipthedonkey]

Trying to resurrect my dad's Evo Dyna.  He passed about 15 years ago and the bike wasn't rode for about 4 years before that.  Now my brother's son wants to start out on his granddad's bike.  So it's important to get it going.  Carb issues are beating me and are the last thing to get right before it goes to my nephew.

Original carb was off the bike and gone.  No idea what dad did with it and couldn't find it.  Had a few other cores around so tried to make one up.  It's a original CV were messing with.

Had a damaged body from a early Twin Cam era Dyna and took all the needles and jets from that.  Carb was never opened before so it's all a matched set of pieces.  Used them and a good kit in a well cleaned other carb body and put one together from the collection of parts.

Some of the details might not matter but I don't know for sure what's importnat and what isn't so will probably list more than I need to.

Bike starts good hot or cold.

For hot idle to be good right at 1000 cold idle is just a tick slow at maybe 1200.

Idles really good.  Nice and smooth and no raggedy vibration. 

Cracking the throttle at an idel sounds just fine.

Parking lot driving manners is good.  No issues at all under very light load like that.

Under heavier load like pulling hard away from a stop sign or climbing a highway onramp or just cruising on the highway it runs fine.  Have put a couple hundred miles on it now running 60-80 and it's a good riding bike on the highway.

Problem is in between.  Like medium load and RPMS of maybe 1500 to 3000 and loads like you'd do riding in town.  Both accel and decel it coughs and spits.  It's not like you think the engine is going to stop running.  But you can feel it chug a little and it's a sound and feel you definitely notice.  It's not right.

Also, idle mixture screw seems to have almost no impact.  Take it in all the way and you just barely hear the slightest difference.  Have tried running the bike with the screw almost all the way in and about almost two turns out and it makes no difference to that middle range popping and coughing that's going on.

Did a I think good job cleaning it out.  First 100 miles it had a dose of SeeFoam in the fuel too so that should have helped even more. 

It's got new plugs and wires.  I don't think it's an ignition problem but I'm willing to consider any ideas someone might make.  Have had the carb off half dozen times now tweaking and cleaning and checking and nothing changes that bad running problem in the cruise range that you'd do around town.

Gas mileage on the test runs so far is about 38.  So not great for a stock Evo and it should do better but cruising on the highway it's really well behaved and feels great.  Oh yeah, stock exhaust too.

Got everything else done, new tires, bearings, seals, tank flushed, etc etc etc that should be done since it sat so long.  Looking forward to my nephew getting his granddad's bike if could just get the carb issue better.  Any ideas please. 

[JW113]

Hello Chip.

So in my experience, one of the weaknesses of the CV carb is it's susceptibility to plugging up the transfer ports. This causes bad performance between idle, and full power. The transfer ports are those array of holes at the bottom of the bore, just in front of the throttle plate. There are usually about 4 of them, sometimes 5. Backfiring and such tends to plug them up with carbon. After that, you lose that off idle to main jet fuel metering.

Running Seafoam through the carb will do nothing to clean these out, if they are plugged. You need to take the carb completely apart, and using Brake Kleaner(tm) or some other such solvent, blast the crap out of the carb body. Then, you need to use some fine round files, such as those used to clean oxy-acetylend torches with, to poke through the transfer ports to make sure they are not blocked. Using the throttle to slightly crack open and position the place just past the transfer ports, blast the  out of them with the Brake Kleaner(tm) to wash them clear.

Put all back together, and give it a go. One thing many of use have is a small ultrasonic cleaner from places like Harbor Freight, which filled with Pine Sol(tm), does a great job of cleaning things like carburetors.

If all else, you can find a reasonably good CV carb on ebay, a cheap knock off Chinese made version that from what I've found, works pretty damn good. Not my first choice, but if money is a concern, a great second choice.

Good luck,
JW

[barny7655]

one starts at the beginning
1/ motor size and cam used and pistons
2/ pipes and air cleaner
3/ what carb being used
4/ go back to the drawing board as the the original jets etc
5/ a tear down and rebuild, neddle in right slot ? vacumme slide rubber check,vacumme line hole check,
6/ inlet manifold and gaskets check
7/linkages used, and adjusted to specs
8/ air cleaner fitment
9/ fuel delivery , tank ? petcock? delivery line ,
10/ vos  module check if it has one
11/ timing , plugs leads coil etc
12/ basic tunning , mixture out one and a half turns , throttle stop screw adjustment  around 1000 revs
heres a few tips i use to eliminate issues,once you have it going , the bike  manual helps, in needle slot ? idle jet,and main jet etc ,
hope this helps a bit ,its a back to basics method that ive never had a problem with , cheers Barny

[Evo160K]

If I understand correctly, the jets and such are from an early era twin-cam.  If so, I suspect the low speed jet (at least) is too large.  38 mpg seems to suggest the same.  chugging of the engine and failure to respond to changes to the idle mixture screw also suggest the same.

Well tuned evo CV's do fine with a 42 slow speed jet.  You might start there and post some feedback.

[koko3052]

Check for air leak at intake seals.

[chipthedonkey]

This has all been helpful.  The motor is a completely stock Evo.  The jets in it now are 180 and 45.  The intake seals and carb seal are all new and show no signs of leaking when you spray at them.  Plugs and wires are new along with a lot of other work all over the old bike.  It's just this middle power range surging and coughing and spitting.

The message above about a more thorough cleaning being maybe a problem sounded like a good description of the behavior of this bike.  Thanks to everyone and especially thanks to that one.  I will work on it again and pay even closer attention there.  I even have a little sound cleaner like you mentioned and just never thought about it for the carb parts. 

I also just looked at the rest of my spare parts and found a 40 and a 42 and a 170 and a 175 jet.  What would be a better pair for this bike?  Just a little Dyna with stock motor and stock pipes.  Even back in the day I never messed with bike carbs enough to learn what worked best.  So thanks again.

[chipthedonkey]

Just read all the stuff above once more time.  The voes switch and petcock are both new.  Old ones hadn't survived setting for so long time.  Vacume line and fuel line are all new too.

[Hossamania]

For a stock Evo, use the 170 main, and the 42 pilot jet.

[Panzer]

All good advise above.
As JW113 suggested above, try the torch tip cleaners or a piece of wire from a bread wrapper, strip the plastic and run it through the holes.
Any dirt that a carb picks up is from the outside, so use air or carb cleaner blown from the inside of the carb out.
Blowing air or carb cleaner from outside/in could lodge any dirt or crud tighter into the orifices.
Just my .02
Good luck, will be waiting your feed back.

[chipthedonkey]

Thanks again to everybody.  Have found on line pics showing exactly the places your telling me need cleaned.  Now know what I'm looking for.   It will be one evening this week before I get to be back where the bike is but will brag or cry about how good it went as soon as I know.

[jmorton10]

I remember on coughing spitting evo and shovel motors I Used to drill out the mid range jet that was hidden under a soft plug on the old CV carbs. I bet I did 50 of them.

I would carefully drill through the plug, use a #drill to open up the hidden jet then cover the drilled hole with epoxy. Worked wonders.

~John

[chipthedonkey]

I remember on coughing spitting evo and shovel motors I Used to drill out the mid range jet that was hidden under a soft plug on the old CV carbs. I bet I did 50 of them.

I would carefully drill through the plug, use a #drill to open up the hidden jet then cover the drilled hole with epoxy. Worked wonders.

~John

Now you've gone farther than what I know.  I have removed plugs to get at the mixture screw many times but don't know anything about a jet other than the main and the slow jets that can be unscrewed and replaced.

[smoserx1]

I will second JW113's response 100%.  Anything that has ever had gas run through it and then put into long term storage will likely have varnish buildup and those tiny off-idle orifices being plugged will likely cause exactly the problem you describe because that is what is used most in that RPM range.  Pine Sol in the ultrasonic cleaner should do the trick and not damage the carburetor body.  That is what I would be doing for sure.

[chipthedonkey]

Another question. Carb is apart again this morning.  Has been soaking in the little ultrsonic cleaner and pinesol for a half hour.  Rinsed it off and blew it all out and it definitely looks even better than it did after the prior time it'd been cleaned up.  How do I know if the holes are actually clean all the way threw though?

The little single hole that goes to the mixture screw you can tell.  It's open all the way through. The five in a group though how do you tell?  I can take a bread wire and put it down each hole just s little bit.  It's about the same on all of them but it goes only a little bit.  I'm guessing the holes turn a corner there but I dont know.  Can't see light threw to anyplace at the other end but if they turn a corner I wouldn't.  So how do you know they got cleaned out?

[smoserx1]

Read this article:
https://cv-performance.com/harley-cv-carburetor-tuning-issues

Cover the mixture screw hole and the pilot jet (slow) jet hole and with both holes covered apply compressed air to the slow air jet (bottom left hole at the front of the carburetor).  That will force the air through those tiny ports you are trying to clean.  You have to cover the mixture and pilot jet holes or your compressed air will come out these instead.  Or I guess you could cover any two and blow through the third.  Google a diagram of the carburetor circuits and you will see.  You can get a can of compressed air at an office store.

[chipthedonkey]

Thank you again for all the assistances and advice.  Got back an hour and a half ago from riding the bike for a couple hours.  It's better.  It didn't get blown out exactly as described by the last person but it did get blown out a lot.  It's better.  It's not perfect but it's at least ride able.

The near constant midrange spitting and sputtering is gone.  In hour and a half riding I heard slight decel pop twice and it spit very light in that mid range twice.  Of that 90 minutes almost half was riding around town.  So it would have shown up more if it was bad.  It's still not completely right though.

The choke cable barely bumps up a fast idle and the mixture screw still doesn't actually change anything.  Can run the mixture screw all the way in or way out and it never changes anything.  The bike runs good though.  Really well behaved low speed like parking lots and running around town it was ok.  On the highway it doesn't miss a lick.  Juts installed now are 42 and 170.

Can take it apart again and try blowing it out even more as described from the last person above.  If it starts ok cold in the morning and proves it will stay running I'll know more about the choke.  It was a warm afternoon when it didn't seem to do much earlier today.  I wish the mixure screw actually did something but if the bike runs good and the mileage is ok I could live with that too.  Could live with it until maybe doing a new carb over the winter or something. 

Wish it was all good. But it is a lot better than it was and its ride able now.

[bump]

If the idle mixture screw doesn't seem to do anything you need to lower the idle speed setting
then adjust mixture again.

[smoserx1]

You don't need to take it back off.  Get a can of compressed stuff and blow back through the slow air jet.  The mixture screw will be in place so it won't come out there and the slow jet will be submerged in gasoline so most of the air will go through those small ports.  Actually those cans of "air" are actually compressed liquids.  if you spray with the can upside down that will dispense liquid and that mat be even more effective.  You could even try WD-40.  If you have it running decent I would try several tanks of gas with extra detergent, like maybe Techron or similar and that will probably finish the cleaning  If you still get an occasional carburetor "sneeze" then you can probably solve it by shimming the needle with tine washers and/or going up one size on the slow jet.  Always tune the carburetor one step at a time.

[koko3052]

If the idle mixture screw doesn't seem to do anything you need to lower the idle speed setting
then adjust mixture again.

When the idle mix screw does nothing it means the slow jet is too big.

[JW113]

In my dealings, a 42 pilot jet is quite small. Never have been able to use anything smaller than a 45.

Idle jet screw not having any effect often means the throttle plate is open past the transfer ports, and pulling fuel from them. Unclear why this would be the case for a stock bike, though. I realize that pulling the carb off is a pain, but I think if you did, and looked at the back side of the throttle plate, you might see an exposed transfer port or two.

What is your idle speed?

-JW

[capn]

Get you an S&S e. Problem solved.

[JW113]

You might try this.

Put the 45 pilot jet back in.
Ride the bike until it's warm, then shut it off.
Turn the idle mixture jet in until it lightly touches the seat.
Back it out two turns.
Turn the idle speed adjust screw out until it is no longer touching the throttle lever.
Turn the idle speed adjust screw in until it just touches the throttle lever.
Turn the idle speed in one more turn.
Fire up the bike, using the throttle grip to keep it from stalling.
Adjust the idle speed screw to get an idle 900-1000 rpm.
Now see if turning the idle mixture jet in, then out, causes the rpms to increase and decrease. The correct adjustment is to turn in until the rpms start to drop, then counting # of turns, back it out until rpms come back up then start to drop again. Correct adjustment is 1/2 way between those two points.

-JW

[chipthedonkey]

Will look at all this again.  And thanks once again.  Even more detail to pay attention to.  Fortunately it's got to the point where I can get the carburator off the bike in about 5 minutes!

[chipthedonkey]

Home from work early today.  Took it back apart again and found something maybe.  Haven't had a chance to put the carb back on the bike yet but it is put back together.

The butterfly was opened past a couple of the little holes that it should not have been.  That's where the idle screw was holding it to have it idle at 1000 rpm.  Idle screw now backed off.  The throat is clean and polished as is the side of the butterfly.  Changed from 42 to 45.  Will see if that combination of things makes a diffeence.

Can't say if all the holes were completely clear before.  They are now though.  With better idea of where all the passages went and what to took for and do was covering different places and either blowing by mouth or with the compressor.  Blowing by mouth I could hear and feel air coming through every where it should be. 

Maybe later tonight will get the carb back on the bike and run it.  If not it may be Thursday before there is a chance to try it.

[chipthedonkey]

Chip is now officially frustrated with this motorcycle.  Did get look at it again tonight.  Initially it fired just a little then it died and wouldn't run again.  It would once in a while barely kick but wouldn't run.  This was new.

Started from scratch chasing it like I would a new problem.  Cam senser was melty.  Soft and goop that had begun to run off of it.  Actually hoped it had been in the process of dieing for awhile and might account for some of my other issues.  Did not get that lucky.

Just beofre closing got to a local indie shop and got what I could.  He had an Ultima Single Fire kit.  The one with everything in the nose.  Got it all changed and timed and the bike starts better than it ever did. 

Rest of the problems not so much.

The carb is really very very clean now.  Can blow through everything and air comes out everywhere.  It starts and idles wonderful.  It will idle all the way down to about 550 and still be smooth.  Below that it'll die.  I only kept it that low to see if I could ever adjust the mixture screw.  Even at an idle setting that low still get no response from the mixture screw.  There is no vac leak at any of the three seals on the intake.  Triple checked that with WD40 and with starting fluid.  No vac leak inside the voes switch either.  Checked that more than once also.  But it'll idle just as smooth as any Evo I've ever had.

It will won't run well in that mid range either.  A little spitting back and light spitting and bucking.  On power like on the highway no problem.  Really light power like parking lot no problem.  In between like running around town and it just isn't right. 

Even the bike starts good the choke cable has no affect on idle speed also.  Either hot or cold pulling the cable out or pushing it back in doesn't change the idle.  It for sure is a Harley plunger and spring on the end of the cable.  The cable itself could be anything since it was just an old one thrown in a box.  But if Harley parts are on the end I dind't think it made any difference if it was a Harley or a Mikuni cable.  If that is wrong please let me know.

I'm about ready to just give up on this old carb.  It's really clean and looks brand new but looks isn't all there cracked up to be.  Someone before mentioned some aftermarket carbs before.  Cheaper than Harley I assume so how good do they work.  On Amazon I saw stuff anywhere from $85 to about $200 but they all look the same.  Same stuff with different sellers just trying to make more or si there actually a difference?

Someone also mentioned doing an S&S.  The bike already has a Ness Sucker air cleaner and would like to get to keep that and the stock outer cover.  I think that leaves only the CV and the Mikuni as options.  Unless someone has any other thing I might try on this carb it's maybe time to shift gears and recommendations on the carbs.