very VERY hard starting -- out of ideas

Sounds like you are on your way to fixing this bike but after reading all the messages, I would add two things to the discussion.

First, make certain that you don't have a vacuum leak around the carb holders. Another person suggested using WD-40 to check for leaks but I would recheck using a carb/choke cleaner spray. I find it much more effective in locating leaks. Use the thin spray hose that attaches to the nozzle and use short shots of the cleaner around the carb holders and vacuum lines while the engine is running. Any small leak will cause the idle to go higher and in some cases go lower. My guess is you have an issue here not yet located.

Secondly, no mention has been made to spark quality at the plugs. Old plug wires and/or weak coils may be asked to work beyind there ability during cold-start. This is the time when an engine needs it's hottest spark to ignite the fuel. Coil voltage is very low at start-up especially if using the electric starter. A new set of mettalic core wires may be a simple solution to what you thought was a fuel problem.

Just a thought....born from experience. Good luck,

Duane

One other thing....you did put fresh gas in the tank, yes?

dnpurdy wrote:

Adjusting the idle mixture on two of the carbs caused the idle RPM to up significantly. I guess two weren't firing, or wren't firing well at idle. For the rest of the night, it fired up nicely with minimal starter. My adjustments were rather coarse though. I have a colortune on the way to make it more precise and a carb sync is totally in order.

Thank you so much for suggesting enriching the idle mixture. I'm really, REALLY hoping this puts an end to the push-start workout.

Not sure the procedure for your carbs, but I'd suggest getting a service manual for your bike. Comes in very handy. On my old carbs you adjust the air screw until the idle increases as far as it will, then I think it was turn the screws out something like 1/4 turn each. You may want to find out exactly how it's supposed to be done on your bike. Once the screws are all set a carb sync would be a good idea.
When you send your carbs out there is only so much that can be done without having the bike. I found mine don't work anywhere near where the factory says those air screws should be set. Mine are like 3/4 of a turn out, instead of 1.5 turns out. Would not idle for anything at factory spec.

**dknoel

There was very fresh gas, so I'm sure that's not it.

I had replaced the plugs (fresh B8ES), wires (Brand new copper core), can plug caps (NGK 5k caps), checked spec resistances on both primary and secondary windings of the coils. I suspected the coils too, but they seem to check out.

I've run a few vacuum tests with both WD40 and carb cleaner with no noticable effects. However, the idle is so rough and roaming anyways, until I can properly tune the air mixture and resync the carbs, I don't trust the vac leak test. The tubes look very old, so I'm considering replacing them anyways.

Welcome back, dnpurdy. . .

Been four days since we last chatted. How's the bike seem to be starting now?

If you haven't done it yet, now that you have maxed out the mixture screws, and ostensiby left them where I suggested last time. . .

With the bike warmed up and running at idle, turn one fuel supply screw in until idle quality roughens, then back it out to 1/2 the distance to where it was.

Repeat for other carbs.

Well, unfortunately, I've got a case of propagating errors.

Went out today to start it up, and the start would barely turn. Thought it might be a bad new battery, as wiredgeorge seems apt to suggest. Took it to autozone and had it load tested for it's capacity of 200 CCA. The tester heated the battery up something fierce, but it came out clean on the test.

Brought it back and put it back in. Tried to started it up and the starter would make three revolution sounds, and then pause. Repeat this over and over. Immediate thoughts were, since it's a 4 cylinder bike and a 4 brush starter, one of the 4 of these was a problem. Since I had just done the valve clearances about 2 weeks ago, I assumed it a bad brush. Took the starter off, hot as hell (never good), and opened it up. Carbon dust everywhere and one brush gone, and another nearly gone.

This is the second new brush plate I've had on this starter. At this point, better to replace the brush plate again or buy a whole new starter? Opinions?

The starter motor is wearing through brushes too quickly? I know with a starter you might find on a Car or truck; When replacing the brushes you need to check the surface of the commutator for any unevenness or lack of smoothness between the pole contacts. The irregular surface can causes brushes to wear very quickly.

--Dave

Have You done a compression test on this engine yet?
What about ignition timing AND cam timing...any of that been looked into?:whistle:

Has the top end ever had any work done to it,that You know of?

Do a compression test and post the results,and We can go from there.This has to be narrowed down some...

Whoops...just read the original post again(I'm tired,sorry)...You HAVE checked compression,and it looks good.
Look into the cam timing maybe...You could be off by a tooth,or the chain is stretched beyond the serviceable limit?

Post edited by: Sandy, at: 2007/05/14 01:53

I did a valve clearance shim swap fun a week or two ago now. When I did, I had to remove the camshafts, which made me quintuple check the timing chain. Although it is possible the chain is stretched beyond limit, I doubt it and I am sure I installed it correctly.

About the starter, I got too impatient to try to rebuilt the starter myself, so I ordered a replacement this morning. When it comes, hopefully that will help smooth out the engine starting rotation.

I pulled the jugs on mine this spring to put a new base gasket on to stop an oil leak, have had the cams out many times over the years and never had a problem untill this time. To cut to the chase, the manual cam chain tensioner was sticky and didn't tension properly and the intake cam jumped two teeth while going down the road. As soon as I slowed because it was running so poorly, it died and would not refire. Luckly the exaust cam stayed put or I'd have a bunch of bent valves now :pinch: . If it were mine I'd have a look at those cams one more time, just so I could sleep nights! good luck!

Ok, so here is an update -- closer to good, but still not great.

I bought a rebuilt starter...guess what, that grinding noise I was used to with the old starter isn't there anymore, whaddya know!

The bike starts much MUCH easier now that the starter has been replaced and the fuel mixture screws generously backed out.

I synced the carbs up with an oil menometer and it is very very well balanced now.

I started to color tune to the cylinders to get a better idea of the idle mixtures. Starting with number 1, it turns out it was only very very intermittantly firing, say every 4th stroke or so. That explains the strange "helicopter" noise at idle. The "beats" of the helicopter turned out to be when #1 would fire, causing a slight surge in the the engine. Occuring only every 4th compression cycle, it made a nice helicopter beat.

With the colortune, when I back the mixture screw out to the point that it is about to fall out, I get a more consistent blue color, firing about 85-90% of the time. When I open the throttle I see it firing more, as is expected.

However, I know this can't be right. I removed the carbs and blast half a can of carb cleaner through the idle circuit starting at the air intake side hole and watching it come out the idle mixture port.

Such a lean condition I thought would suggest an air leak. I removed the "clean air" hoses from #1 and #4 and put vacuum caps on those carbs to eliminate that as the issue. Extra tightened the manifold clamp. I will use the WD40 trick, but when I did it a week or so ago, I noticed no difference, but doing with a colortune in the cylinder might make it easier to see.

Any other suggestions as to why I'd have to back out the mixture screw all the way just to barely get a blue color. I never could get a "rich" orange without choke, and with choke is only only flickering into the orange. I have very good reason to believe the carbs are clean, but any more tests I can do to eliminate that or other causes of this leanness?

If the float bowl was even a tiny bit low, would that cause such conditions as described?

Post edited by: dnpurdy, at: 2007/05/24 11:39