SOLVED! 650 w/750 juggs. Runs on choke only.

trianglelaguna wrote:

i had cleaned my 29 smoothbores with spray and air,because of dirty running and changing idles...and somehow clogged the idle circuits,,,while cleaning em!!!!!....and was sure i had em nailed...but my symptoms were as you describe to a word....i posted and was told what t.b said and others......i re-did em once more with fine wires to pass through all removable parts in a dish of carb cleaner,, and was extra, extra picky, and looking for missed fittings or holes/passages,of which a found an area that i had missed beofre,tiny passage ports....the guys were right!!! and it now idled perfect once set...pulled clean like never before...and did not pop and crackle as before under a load in downshifts.....so to repeat...you'll get to em i bet....and be soooooooo happy when you do...imo...

You're right. I did not go through it to this level of detail. I'll have them off again tonight and start back on it. I'm sure if this isn't THE cause it's still going to need to be cleaned better. I know that just soaking them didn't get them THAT clean. Here I go one more time!



mark1122 wrote:

I have had to drill out the brass bead that plugs the OEM hole before. I can’t remember if that is necessary on that model, but it is an easy fix. Just plug the hole back up when done. This can be done with a small round lead fishing sinker weight, or whatever u have on hand.

Mark I'm a little confused on this. I'm positive that my carbs have air jets in them which I'll have to deal with carefully. I don't know of any closed off passages that would deal with the pilot circuit. These are the carb model I'm using.

By the way THANKS everyone for the great advice! Glad I came here!

Just a stupid question but are the carbs filling with gas.(petcock working properly).

maybe some folks who remember can link you to a past thread on idle circuit locations...i suck at searching the archives for even my old topics....patton always post great photos with arrows in red to specific areas ..try a p.m to him or wait for someone with a brain to chime in before digging into them again... i had to ask a specific idle circuit question finaly to get my head wrapped around the area i missed...as i was on my third cleaning when i was shown where to look and have now forgotton on the carbs body area.....great pic you posted...folks will chime in...

note: i used strands of copper elec braids...and it required different guages...ie...woven speaker wire....woven lamp cord..in single sepereated strands/thickness....be super careful to go slow and not pinch/break a wire in the brass holes....i lnow it is self evident but still...it makes a whole new problem...i used a ceramic bowl and strands of copper and carb cleaner....but the idle circuits are cast into the carb bodies and require repeated soaks/sprays/and blowing out....i think was where i got er done in the end...good luck

You might want to look into getting the electronic ignition for a 750-4.

JMKZHI wrote:

You might want to look into getting the electronic ignition for a 750-4.

Oh that will be a given. I love old bikes and I know a lot of folks are sentimental about them but personally I can't stand points. I have electronic ignitions on some ancient RD400 yamaha 2-strokes that I havn't removed the cover from in 6 years and they start first kick.

kwak650 wrote:

Just a stupid question but are the carbs filling with gas.(petcock working properly).

Not a stupid question at all. It's often that kind of overlooked thng that kills you. Been there done that. I pulled the bowls last night and they were gettig a good flow.

Hoping carbs were bench-synched with thumb screw idle adjuster in mid-position.

With functional choke circuit, starting fluid shouldn't be needed. Initial cold-starting engine should be done without even touching the throttle grip. The enrichment circuit is designed to operate with the throttle slides all the way down in idle position. Don't "crack" the throttle; and don't work it back and forth. Just leave it alone. Might need to adjust thumb screw to set slightly higher idle position.

It's of course possible that a passage in the choke circuit is blocked or clogged, which is its own circuit, separate and apart from the pilot circuit.

These earlier threads may be of interest with some more info about the pilot circuit, cleaning, etc.

Pilot Circuit

More pilot circuit

New pilot jets are relatively inexpensive, and may help even though the existing pilot jets look perfectly okay.

Good Luck!

PLEASE WEAR EYE PROTECTION WHILE SPRAYING CARB CLEANER.

[Click on image to enhance view]

Patton that's fantastic! Thank you very much for that. Should make my Saturday a lot less frustrating. I'm also going to go through the ignition system I'm not exactly thrilled at the mild spark I'm getting. I'll probably find the problem spread out between the two.

Thanks again!

If your 650 carbs are known good, you might put those on temporarily to troubleshoot any other issues before attempting to tune the 900 carbs. All your carb tuning should be done last, after ignition and cam adjustments etc etc. This will save you from chasing your tail some. Good luck!

one other tip that i can pass on to you is always use a rubber tipped blow gun it conforms to the passage ways better and creates a good seal around the pilot jets as well air pressure can do amazing things. by the way that picture from Patton is one of the best i have seen showing the important passages to concentrate on. i have printed this off for my student's to use it is that good. thank's Patton

Well I sorted out the ignition. Brand new points and condenser. Really nice spark. Iggy seems dead on. The carbs are as clean as I can get them. Every passage is flowing.

The bike still will not fire off anything but a full battery charge, fast turnover on full choak with a squirt of fuel in the bellmouths to get her going and then will die off of choke. Also the bike won't run at all on my known good KZ650 carbs.

Here's what I'm thinking:
Is it possible that I set my cam chain incorrectly on the rebuild? If I'm off one tooth could this account for the behavior? Would she just barely run like this with the advance (or retard) that I would get from this error. Would the valves clear with a one link skip?

I have 20 and 22.5 pilots on the way but I'm at a loss here that I'm getting squat as far as this engine firing off at all.

I freaking stumped...

EDIT: I just remembered something relating to the possible cam chain issue. At one point while trying to start the engine, I put my hand over the carbs to check the vacuum. There is an outward blow before the vacuum cycle. I'm normally riding 2-strokes so cut me some slack on this stupid question but Is this normal?