This is a weird one...

[gk45241]

now now

Now Now remember to save one of those nice curse word ones for my beautiful PIA POS that always wants to throw up issue after issue.
Gary

[dbeardslee]

Gary - speaking of syncs.... Did you finish getting your mufflers installed?

[gk45241]

yes finally

Mufflers are on. I will need to change, or do some fab work on the brake pedal.

Ready for Synch when you are, owe master of the flow....lol


Gary

[dbeardslee]

After action report

OK, so all of you who said it was carbs.......you were right. We tried Varnae's TCI in DGXSER's machine, and it worked fine. We pulled the carbs and the floats were a good 3-4mm too high (running orientation). Close inspection revealed that these carbs have an orifice between the pilot jet and main jet towers. Unfortunately they didn't have the corresponding plugs in the pilot jet towers. It was loading up so bad that it was pumping raw gas into the header pipes! We set the floats to 23mm, but that still left the plugless pilot jet towers.

I went to the local Ace Hardware/Motorcycle Parts armed with a caliper set to the size of the ID of the tower hoping to find a rubber plug of the proper size. Unfortunately they didn't have anything that small. What they did have was some rubber thread protectors of the correct size. Not a good long-term fix, but good enough to see if that was the problem - it was.

After the fixes she pulled strong all the way to red line. It smoked like crazy, but after several trips around the block it burned the gas out of the mufflers and ran pretty good. Still have some minor issues below 3k, but it was getting late and we saved that tweak for another day. The advanced timing is still a mystery - couldn't figure out what's doing that. Varnae was pretty happy, and he finally got to take that ride that didn't end in "What now?!!!"

[Larrym]

CupCake Crew

Congrats on the find. For history's sake you might wanna look at this thread:

http://www.xs11.com/forum/showthread.php?t=24812

Seems that we've got a new standard fix for a new standard "reported problem": high rpm miss along with not being able to get into the upper RPMs.

Ride and tweak. Repeat as needed with pauses in between for doing the "Snoopy Dance."

[thewiz]

not surprised ... good find !! It sounded intially like a fuel starvation issue, but turned out to be the opposite, eh? Excellent

[dbeardslee]

Larry - What was interesting was that DGXSER's 81 doesn't have the orifices between the tunnels, nor the plugs. IIRC there was one year that actually had two different carb 'types'. After what we saw this afternoon I'm guessing it was the 81's .

On jets, one manufacturers #120 jet isn't necessarily the same as another manufacturer's #120. Varnae's got all miks in his. We still have to make sure he's jetted right for his setup, as we couldn't really do much with that 'till we figured out why it wouldn't go past 4.5k. He's going to run it around a bit and see what it does to the plugs - after putting the proper tower plugs in place - and we'll go from there on jetting.

Wiz - it was kind of an 'aha' moment when I looked down in the pilot jet tunnel and saw the orifice between the tunnels. Combined with the float setting, you wouldn't believe the way that thing was pumping gas through it. It was mixing with the carbon inside the exhaust, and leaking out as a black, oily-looking liquid. It took three trips around the block to burn it all out of the exhaust, and these are pretty big blocks.

Varnae was pretty pleased - I'll bet he's still grinning ear-to-ear. I'd still like to know what's causing the timing to advance, though. Another thing that may have a bearing on the timing, is the readings I was getting at the battery. It should be putting out 14.2V at 2200 rpms, and it wasn't - it was only putting out around 13V. At 4k rpms it was up around 14.5V. Varnae told me today that some of the parts in the alternator had been replaced. He thinks it was the stator. After seeing some of his former mechanic's work up close, it's hard to say what we'll find when we pull that cover off .

[DGXSER]

Hey Doug, I do nto know for sure what we have there. I think it is 80 model carbs that were bastardized between models. I think the early ones still had the crossover, but I had no idea they switched the bodies completely over as to misture down in the tower and no external vents, but still had the crossover.

With the crossover I am thinking he wants the lower/larger spacing float bowl setting of 25mm and the 137.5 mains.

I am also thinking we need to set his timing back to where it runs best instead of looking at the marks. Just my thoughts.

[Larrym]

Mpg?

Similarity was that both Chad's carbs (in his thread...) were missing the screws which plugged the idle tower circuit and Varnae's were missing the plugs. Both were only accessible after removing the float bowl.

Symptoms were that both bikes would not go above 4.5 to 5K rpms when the idle circuit was missing parts.


I suspect that in both cases the carbs were not done "One-by-one" but instead were all dissassembled into their component parts at the same time.

Keep chasing that timing anomaly. Did the timing act the same when you tested the TCI in DGXSER's bike?

Now that Varnae has a running bike he'll want to get the most gas mileage. Send him out with a full tank and get some data. Then have him do it again...and again.

[randy]

One more thought on the timing....I have seen (here) instances where the locating pin for the rotor was either lost or sheared...might be worth a look? That would knock the timing out.

[scalded dog]

Had an issue that was somewhat simlar, for 2 yrs, I road my bike '79 standard, with this issue, when I would put it under heavy load, it cut out, and black smoke billowed out of the pipes. As long as I road it normal, with normal acceleration, it ran fine. I have sprayed other riders with gas when I would go wot. Well it steadily was getting worse, then last summer, friend of mine was on his Harley, (with Mikuni carbs) It is one of the faster Harleys I've ridden with. Well he got me in the quarter and on top-end. we had ridden a lot, but he never beat me either way. Started checking the advance, pick-ups have been fixed and are working well. the vacuum canister that hooks to the pick-ups didn't seem to work right. I changed it out, and took the pick=ups off the plate. the plate was hitting rough spots, as it swiveled, and made a little metal on metal, screeching sound, I had another pick-up coil, off another bike, it would swivel smooth, with no sound. changed that out, cutting out, black smoke is gone. I road with my friend yesterday. He had no chance. LOL. Saw 125mph, before I backed off. (no BS). Later 'Dog

[thewiz]

Trouble with using the marks is ... how the hell do you know EXACTLY where the static mark should be without using a degree wheel or some other fairly accurate way of determining TDC?

I aways end up settin' the timing where it runs best as well ... FWIW

[dbeardslee]

Don - Below is the schematic from the fiche for an '81 SH carbs. Note parts #50 and 51. 50 is the pilot jet and 51 is labeled "plug, screw", yamaha part #3F7-14991-00-00. A search at Bikebandit for this part number shows it for 80 and 81 carbs. A search at Z1 yielded this image of the part -
The bowls are also identical to the ones in the picture. The other '80 model bowls I've seen don't include part #75 - just the bottom drain plug. I have to disagree on the main jet size and float height setting. The only ones that had the 137.5's were the 78's and 79's, and these carbs are definitely a later model. I think I have a set of 42.5 pilots out in the mancave that might be worth a try. He's also not heavily modified - just the Mac 4/2. I'd like to see what the condition of the plugs are and put the colortune on it before making any changes to jetting though - especially with the stock airbox. I've gotten spoiled with the ease of carb removal with pods .



Larry - Where were you when we needed you yesterday ? That would have been a great idea to check the timing while the TCI was on Don's bike, but that synapse didn't fire for anyone . The next time we've got those two bikes together, I'd love to give that a try. Great idea.

Randy - The pin is still in place, but the rotor doesn't fit as tight as the mechanical advance did. I'm pretty sure it's in there correctly, but it's easy enough to check and make sure. Any thoughts on the voltage readings at the battery?

Wiz - good point.

[dbeardslee]

Forgot to mention

We did check for TDC using a long screwdriver in the #1 plug hole. Granted, that was a crude measurement, but it should have been accurate enough for our purposes. The timing plate looked to be pretty darn close. Good thought, though.

[randy]

It should be putting out 14.2V at 2200 rpms, and it wasn't - it was only putting out around 13V. At 4k rpms it was up around 14.5V.

Haven't seen one yet that puts out 14.2v @ 2200 rpm. Specs say max output is 14.5 @ 5000 rpm. Your 14.5 @ 4000 is better than most.