Tuneup Troubles

[Erik the Red]

I went to tune the bike up this weekend and ran into some issues.

1. Intake valve clearances all ~.005 in. Range is .006-.008. Is .001 going to make that much difference? Should I get the adjuster tool and swap shims?

2. Bike will NOT idle unless on 1/2 choke, and the idle adjuster knob doesn't change a dang thing when I turn it. This indicates pilot circuit needing tweaking, right? Assuming this is true, which thing needs a twist? Pilot jet (under the slotted screw in the tower next to the main jet), pilot screw (thought this was set at the factory and shouldn't be messed with), or air pilot jet?

(Compressions all between 143 and 152 psi.)

Pulled plugs, they're black. ....but that's after having idled w/ the choke on while I was tinkering with the timing. I think I need to take her out for a run on the road and see what the plug condition is then. In the mean time, is there anything I can/should do to get her running top-notch? Thanks.

-Erik

[DiverRay]

The intake may be a little tight, but if you don't run it in HOT air temp, you should be OK.
The carbs sound as if you have a vacum leak. Check the "Tech Tips" on the left side, and check for a vacum leak. You may want to check the clamps that hold the carbs on the intake manifolds, to insure they are tight. If you have "black" spark plugs, it will be hard to tune properly. Look at a manual, and read the order you need to do things to properly tune the bike. IIRC, it's:
1. Check valve lash
2. Adjust cam chain
3. Balance carbs
4. check timing.
Ray

[Erik the Red]

According to the Clymer manual the order is:

1. Tighten cylinder head nuts to spec
2. Adjust valve clearances
3. Run a compression test
4. Check and adj. ignition timing
5. Synch carbs and set idle speed

Except for the adjusting part (don't have a tool yet, and they're only a little out of spec), I set the timing okay (choke was 1/2 on), but in the factory manual it says to check the vacuum advance next by revving the engine to 5200 rpm and checking the mark to be 36 deg.

The problem came in when I tried revving it up to there. It was backfiring (I think it was comig from the muffler) and just sounded bad, so I figured I'd try to get the carbs close to okay so I could proceed with the timing.

Are the boots the only place that a vacuum leak will be? Or is there any way for it to be internal or from a different part of the system? (i.e. am I going to have to pull the carbs again to check something inside?)

[DiverRay]

The backfire may be unburned fuel. If you have a carb sync tool, put that on and see what it looks like. If one or two carbs are way out, you could have a backfire situation. To check for the vacum leaks, use carb cleaner or WD40 with the spray tube on the can. with the bike idling, spray around each intake manifold. If the idle goes up as you spray, that should be the leaking area. I would also put a timing light on the #1 plug lead, and watch for the flashes as you idle. IF the #1&4 leads flash part time, and not every time, you may have pickup coil problems.
Just a couple of quick options.
Ray

[TopCatGr58]

Hey Erik,

Another member recently posted a phantom missing problem that eluded him for quite some time, turned out to be the rubber carb manifold/intake vacuum port plug caps had hardened and even though they would fit on the port, they didn't seal, replaced with NEW flexible caps, and problem went away!

If the bike and carbs have sat for a while, then it would behoove you to remove the carbs leaving them on the mounting bracket, but remove all of the fuel jets, PILOT SCREWS....if they are still capped off you'll need to drill the caps to get them out, do a search for removing them, I've posted the technique before, this way you'll be able to verify that the pilot circuit is clear and clean. Also, you'll want to test the vacuum slides to make sure they are working properly, that there are no holes in the rubber diaphragms. The Pilot screws are adjustable, ignore that factory setting crap, it was for emissions standards!!

Having to run on choke definitely sounds like lack of fuel flow thru the pilot circuit! Good Luck!
T.C.

[Erik the Red]

Last night I sprayed down the intake boots w/ carb cleaner, and there was no noticible change in engine speed, so that checked out okay. I pulled off the carb bank and took it home (bike lives in a friend's garage 25 mi. away right now).

Tonight I'll start disassembling. I'm hoping to get through everything in an evening, so I can throw them back in this weekend. I'll double check the vacuum port plugs too, and search for your drilling process TC. I want to make sure this is the last thing I have to do to the carbs. *crossing fingers*

Thanks for the tips guys; there's no way I'd be near to where I am if it weren't for the help here. Thanks again.

-Erik

[TopCatGr58]

Erik,

Drilling them out is just using a small bit, marking the bit so that you don't drill much deeper than about 1/8" to 3/16", being able to stop the drill from going further once it breaks thru the cap. A drill press would be good! Then just screw a sheet metal screw into the hole, then use a plier of your choice to wiggle the cap or slide hammer it out! The pilot screw sits just below it, that's why you want to be careful drilling so as not to damage the head of the screw!

Don't soak the bodies in a bucket of cleaner, use spray carb cleaner to clean the passages, wear your eye protection, pay close attention to the little jet in the float bowl itself, it can get clogged, makes starting difficult, it meters fuel thru the choke circuit, if clogged, no fuel, no start!

Hopefully you've read the tech tips regarding presynching them, either using the breadstick tie, or visually using the 3 little ports/holes in the top of the engine side of the throat, just below the pilot screw position, it's actually one of those holes.
T.C.

[Erik the Red]

scratchin' my head...

Okay, I've got my #1 carb pretty much all apart right now on my coffee table. I'm still uncertain as to where to drill. I thought it was the brass cap that looks like it's going into the base of the pilot screw (the one that had the plastic cap on it), but upon removing that screw, it looks like that cap is there to ensure vacuum or something and the hole opposite the brass cap seems like it goes to those three holes at the edge of the butterfly valve.

So is that in fact where I should drill, or is it the cap next to the choke (for lack of a better term) orrifice, which is under the diaphragm after you take the top off??

I don't see any other brass caps that are on top of the carbs, next to where they fit into the intake boots. Can anyone direct me to a picture or give a more detailed description for this poor lost soul?

[TopCatGr58]

DON'T DRILL ANYTHING!

Hey Erik,

I'm sorry I got you (AND ME) confused. You've got the 78E, which has the external pilot screws sticking out the top center of the carb throat next to the engine. The caps you may be describing are the plastic caps that keep the screws from turning once they are set! You don't need to be doing any drilling!!!

The brass caps are only on the 80-81 carbs, their pilot screws are smaller and recessed in the pilot screw tower. Your's are large and sit atop the tower and just the end screws into the tower!

Pilot jet (under the slotted screw in the tower next to the main jet), pilot screw (thought this was set at the factory and shouldn't be messed with),

It was apparently a little late when I read this line in your first post, and was thinking about the pilot screws on the later carbs that are sealed to preserve their FACTORY SETTING!!
T.C.

[Erik the Red]

T.C.- Thanks for the quick reply to my question last night. I don't have a computer at home, so if I'm not at work, I have to go to the library to get on the internet. So, as I was typing up a reply, the library's server went down.

Okay, so no drilling on the '78 carbs. Now all that's left is to go through each carb and make sure each channel is open, clear and clean, correct? I'll take the pilot screws out (remembering how many turns it takes) and make sure the passageway to those three little holes on top of the butterfly valves is good.

After everything is clean though, will I be messing with those factory set pilot screws at all when I'm trying to get her to run well, or are those left alone under all circumstances?

[mro]

(remembering how many turns it takes)

After cleaning and reassembled, "LIGHTLY" screw pilot screw all the way down until it just bottoms out. Then back it out 1 1/4 turns as a starting point. (too much force screwing it in is where you can get the needle part stuck in carb body and it may brake off) (if bike won't idle right and pilot screw in less than 1 or out more than two/three something else wrong)

Outa curiosity, are fuel/petcock/vac advance/ hoses attached in all the right places?


mro

[Erik the Red]

I finished cleaning them this weekend. The tower that holds the main and pilot jet -that hole between the two was clogged on one carb. It was the #2 carb. Don't know if that made the difference or not. I still took all the pieces out, and made sure I sprayed cleaner through all the holes I could find. The pilot screws I just set back to 1 1/4 turns out from a light seat. Also pre-synched them (breadtie). Now

I believe everything is hooked up to the right stuff. IIRC, the fuel T's are the lowers, and the upper T's are vented to the airbox. The vac. advance hose is on the copper/brass tube on the #2 carb.

[Erik the Red]

Success!! ...short lived

I got the main nozzle in the mail Friday, and had the bike back together Saturday. It must've been the pilot circuit not being totally clean, 'cause now it idles fine. Sunday I finished tuning her up, and rode. Man, that felt good! Put on about 250 miles. She was pulling through all the gears for 200 of those miles.

Now here comes the problem(s?)...

About 50 miles from home I was in 5th gear, tried again to goose it, only this time at about 5500 rpm (~70 mph) it did something. The best way I can describe it is that when I hit about 5500 rpm, the tach jumps about 1000 rpm, it gets noisier, and just sounds ragged. I got it to do this in 2nd through 5th gears- it went up to 7.5k fine in first.

My guess would be the clutch since there's the rpm jump, but what does the noisy ragged sound mean? Another detail is that I think it's running rich since there's a lot of popping in the muffler when I let off the throttle and am just coasting. -didn't pull the plugs yet to verify, though. (This would just be turning the idle/mixture/pilot screws in a little, right?)

Can anyone shed some light on this? It was a fantastic experience going for that first long ride, except for those couple minor (hopefully minor) annoyances. Thanks for the help before, fellas. I'm hoping this one is a simple fix rather than an case-cracking fix.

[skids]

In those high rpms, the pilot screws do little to no difference. If it jumps 1000 rpms, the clutch might be slipping. If it runs ragged while opening the throttle all the way in top gear, maybe the fuel supply is the problem. It could also have something to do with the pick-up wires because of maximum rotation of the plate.

[TopCatGr58]

Erik,

In the tech tips you should find info on how to adjust the clutch at the engine case. After some use, the plates can wear just a bit, and then the throwout rod is pushing too much against the throwout bearing pushing the plates a little apart, so under high stress it doesn't hold. You'll want to do this soon, otherwise, constant slipping can glaze/burn the friction discs.

If after adjusting it, it still slips, then you may want to read up on the adding an extra steel plate into the clutch pack, along with new springs and new frictions!
T.C.