project r90/6 wont start -- help needed

[pleather717]

duane, thanks for insight. i have your page bookmarked but conveniently skipped the part about the condenser. still have old parts. we shall see. i have feeling its a blocked carb passage.

thanks all

[Porge]

I might be simplifying the issue here, and have just been through a similar experience. I was guided by the mantra "spark;fuel;compression" when awakening an old bike.

If you're getting some spark, and running with aerostart, check your plugs. Any wetness? There should be if you're leaning towards spark or compression issues.

I'd suggest going through the carbs again. The enrichener circuit is displayed incorrectly in the Haynes manual, btw. Anyhow, get them apart and clean with the spray carb cleaner, and compressed are. For me, the pilot jets are worth double checking, as the aperture in question is tiny. Be sure to wear goggles when using the cleaner, too. The fluid can surprise you from time to time. Be methodical, and do it one carb at a time. If nothing else, it's worthwhile maintenance.

Good luck. You'll get there.

[Ken in Oklahoma]

I might be simplifying the issue here, and have just been through a similar experience. I was guided by the mantra "spark;fuel;compression" when awakening an old bike. . . .

That has been my mantra for years, Porge, though with a little different phrasing. Mine goes:
"If it has fuel, compression, and spark at the right time--it has to run."

The mantra serves me well at those times when I'm inclined to jump to a fix. By jump I mean spend significant money, time, or effort.

Ken

[pleather717]

update -- so it appears my idle jets are clogged, had one sitting in carb cleaner overnight and still cannot get the crud out of it. will hit it with some compressed air but even with a tiny needle i cannot get the jet cleared...

any tips/tricks/suggestions??


thanks

[barryh]

...only that if you do have to poke it with something make sure it's smaller than the jet orifice. I know that sounds kinda obvious but I though it might be useful to know what size of thing to poke it with. A 45 idle jet is not as you might think exactly 0.45mm in diameter but a little smaller at 0.435mm. I wouldn't poke it with anything bigger than O.4mm

[tsa]

For poking through small orifices - as Airbear recommended in the 2nd reply in this thread - nylon fishing line. Or similar pulled out of e.g. toothbrushes; because this is softer than the alu carb bodies and won't damage them.

Even with this, you may not reach to where the crud is. Then get the carb bodies (minus everything that can be removed from them) ultrasonically cleaned. My carbs needed two such sessions, the last for 30 minutes, completely submerged) before I could adjust them properly.

[grant81rs]

Paul, with your static timing procedure, did you rotate the engine a couple of times to check that the S mark appears in the central position for both sides? The cam nose can be slightly bent and it takes very little deflection to have wildly different sparking for each cylinder. This occurred with mine and there was almost 30 degrees difference. One cylinder was correctly timed and the other was grossly advanced (or retarded - I don't remember which). When it did run (badly) I attempted to check dynamic timing with a strobe. Only a single image in the little window but shining the strobe on the advance mechanism showed this:



It's worth checking. With a weak spark and one cylinder badly timed, starting will be very difficult.

Gidday,

Charlie, I need to talk to you one day soon about this static timing, this is something I must learn.. will be in touch

And btw this is an Interesting thread rolling along here about the carbies, best of luck with it, you can never read enough about them.

[Duane Ausherman]

Too many have depended on soaking in bad stuff and compressed air. I can tell you that neither may be good enough. It was our standard procedure to gently shove a tiny wire through the orifice.

Sometimes one can see light through the hole easily, but it can be 20% blocked and not seen without a magnifying glass.

One must be very careful when screwing the idle jet back in. Eventually, I made up a screwdriver just for that job. It was round and I rounded off the end where it was flattened out. I also ground the tip to exactly fit the slot in the jet.

I learned all of this one time when I cleared the jet and it still had the same symptom. I checked again and it had clogged again, instantly. It did this 7 times and it was being blocked by the gray matter that was a result of water damage and stuck to the sides of the cavity. My screwdriver had accidentally scrapped off a tiny bit when I was installing the jet.

Had they been ultrasonically cleaned, this wouldn't have happened over and over.

Make a dedicated screwdriver just for this job.

Learn from my mistakes, don't reinvent the wheel.

[Ken in Oklahoma]

Too many have depended on soaking in bad stuff and compressed air. I can tell you that neither may be good enough. It was our standard procedure to gently shove a tiny wire through the orifice. . . .

This may sound frightening to some, but my favorite wire to use for unclogging orifices is a (steel) guitar string, say the 1'st string (e) or second string (b). What I like about the guitar string is that it is strong, stiff, and straight. What I do not do is to clip the wire and use it. That would leave sharp edges which could do some damage, especially to orifices of precise diameter. What I do do is to take that wire to the fine wheel on my bench grinder and very gingerly create a rounded end to the wire. A very light touch is required. There would be other alternatives for rounding the end of the wire. Whet stones come to mind. Most everybody, I reckon, will have knife sharpening stones. Another possibility would be wet or dry sandpaper, used wet or dry. The silicon carbide on wet or dry sandpaper is pretty hard stuff. But other abrasives such as aluminum oxide would surely work as well.

I like to spray carb cleaner into one end of the orifice and watch for the spray to come out where it's supposed to. (Wear some kind of glasses of course.) As I've also already posted you can figure out a lot about where an passageway goes to or comes from by examining the carb casting and plugs at the ends of drillings. The drillings will be straight lines and where they need to turn a corner there will be a plug where another drilling intersects the first.

When you succeed you will wear a wide grin for quite a while.

Ken

[George Ryals]

Wire and guitar strings can be made to work, but the Cadillac of carb jet cleaning is a set of Carb jet reamers: google it.