This is a weird one...

[dbeardslee]

Bob - The first thing we did after changing the mechanical advance for a plain rotor was to sync that puppy, which is where I noticed the somewhat low vacuum readings. I got them all closer than 2cm of vacuum, so the sync should be good.

the boost sensor's job is to RETARD the timing during high load / low vacuum conditions. One more variable for you !

AAAAAARRRRRRGGGGGGG! .

I agree with you that just advancing the timing wouldn't cause all these woes. I'm thinking that, whatever is advancing the timing, may be causing other problems too. Where's the boost sensor located on an '81 SH? I only saw one vacuum line coming off #2 and going to the vacuum advance. The octopus has been removed, so the carb boot taps are all plugged. I think Don wants to get back into the carbs anyway as he evidently didn't get into the tops on the last go around.

Part of the problem is that we only get our hands on this machine intermittently, and when Varnae brings it over here he has to trailer it all the way from Indianoplace - a little over 100 miles each way. I'm trying to get all the ducks in a row 'cause I'm hoping the next time he brings it over will be the last time. I certainly respect your opinion on carbs, but I'd still like to have a TCI handy - just in case.

One other thing that bears mentioning - it appears someone has had the carbs off the rack at some point. I say this because the ball bearings that hold the choke open are missing. I don't know how it was running before it knocked the head off a valve and trashed the first engine - have to defer to Varnae on that. He said it was still running with a 2" hole in the top of the #3 cylinder afterwards, whatever that tells us . Anybody know what size those ball bearings are?

Looks like the next time we get our hands on the 'demon spawn' is going to be October 3rd. I should probably say the skydiver's prayer prior to touching it - "Oh God, please don't let me f*** this up."

[foreda]

Bearings

Parts from bikebandit.com

10: BALL 1/8 ((PH/R)) [BALL 1/8] 360992-001 Enter 0-99 $0.48
11: SPRING 293949-001 Enter 0-99 $5.70

[XJOK2PLAY]

Doug,

My bike is an XJ... w/ electronic setup instead of mechanical, so it won't have this boost sendor mentioned. Mine is located under the gas tank, right next to the Reg/Rec, and has a vac hose going down to the vac port on the #2 carb.

Sorry for the confusion, Randy & I have been discussing my dilemna, and he got the threads confused when I offered what we had found about pilot screw adjustment and synching having a direct affect on how much vacuum it will show it's drawing.

Understand about the term "demon spawn" well...
I've had a few choice terms for mine as of late... but got in a nice 150 mile ride on her yesterday... so there is hope still!

Ohhh... I can certainly relate to that prayer as well!!!
Hang in there, if anybody can figure it out, I'm bettin' you guys can!
What would life be w/o it's challenges??? (EASY!!! And who in the world would want that?)

ME ME ME!!!!!!!


Kat suggested to me this A.M. maybe I should change my bike's name from "Playmate" to "Typical Female"...
Actually, thoughts of another name starting with a capital "B" crossed my mind...
Has a nice ring to it, don't you guys think?

[dbeardslee]

Foreda - thanks for the heads-up on the parts.

maybe I should change my bike's name from "Playmate" to "Typical Female"

I love it! I just hope this one gets over its 'headache' soon .

[Ivan]

The 81s don't ahve a boost sensor. They use the vacuum pod, like the 79-80. The only difference is the mechanical advance is gone and programmed into the TCI. On the XJ, the pod is gone as well, and replaced with a boost sensor, which retards the timing under load just like the vacuum pod on the earlier models. So, the timing should advance with vacuum applied to the boost sensor, just like applying vacuum to the pod on other models.

At this point, I am kinda confused as to which setup were talking about...

[randy]

Ivan, that's exactly right. I don't know how I got the two threads mixed up, but I think I added to the confusion cause the two threads seemed to be describing the same issues.

[Larrym]

Following orders...

Randy,

"I still don't see how just advancing the timing could cause such a dramatic rise in idle speed."

I owned a Mercury 125 HP outboard motor: 6 cylinder/2-stroke. As part of the tune-up "Sync-and-link" the timing had to be set. What I found out was that for the first half of the throttle the carb butterflies didn't even open. All the power and rpm increase came from the linkage advancing the timing. At half throttle the butterflies opened and the timing/butterflies tracked all the way to WOT. That's my basis for saying that the timing "advance" would increase idle/engine speed.

And if the engine were running at 4500 RPM with full advance due to some transducer malfunction, then if the engine were put under load the timing would not retard to give it the power needed to overcome that load and climb to the higher RPMs.

I'm still unsure exactly what components from what bike/year are currently in place.

My working theory is that the TCI is just fine but is only doing what it would do with the inputs it is currently getting.

[Larrym]

Elimination Process.

If you're gonna have to wait until Oct. 3'rd then mebbe we have an opportunity here.

I've got a test carb bank boxed up and ready to ship. If you swapped out the carbs with the test bank then you'd know it wasn't carb related. My bank is set up for a stock 78-79 bike: airbox and 4 into 2 exhaust.

I'll pay for the shipping to.... someone on the other end pays for the shipping back.

[XJOK2PLAY]

On the XJ, the pod is gone as well, and replaced with a boost sensor, which retards the timing under load just like the vacuum pod on the earlier models. So, the timing should advance with vacuum applied to the boost sensor, just like applying vacuum to the pod on other models.

At this point, I am kinda confused as to which setup were talking about...

So, if a guy runs w/o the boost sendor hooked up to a vacuum source... no timing retard will take place... (it'll stay advanced), and the result would possibly either be ping (detonation,) and/or maybe a loss of top end power?

So far, I haven't noticed any side effects. But it was under 70 degrees last night... and not a 100 degree day. Seems to run better than it ever has.
Just curious. I'm learning something... This is cool...

[XJOK2PLAY]

Bob - The first thing we did after changing the mechanical advance for a plain rotor was to sync that puppy, which is where I noticed the somewhat low vacuum readings. I got them all closer than 2cm of vacuum, so the sync should be good.


One other thing that bears mentioning - it appears someone has had the carbs off the rack at some point. I say this because the ball bearings that hold the choke open are missing. I don't know how it was running before it knocked the head off a valve and trashed the first engine - have to defer to Varnae on that. He said it was still running with a 2" hole in the top of the #3 cylinder afterwards, whatever that tells us . Anybody know what size those ball bearings are?

That was what was wild that we experienced yesterday... we could get the 3 other carbs to synch 'pretty close' to #3... but not perfectly. Thought we had it nailed ok. Vacuum readings were around 200 mm.

But it was when we started tuning the pilot jet air screws
while the bike was running by ear, listening for the sweet spot on each cylinder... we noticed a huge jump in vacuum... 300mm! Then we noticed a BIG difference in synch... once we corrected that, we were able to get all 4 synched great. And wow... what a difference it made. All around.
Just thought I would share that as a suggestion as to why your vac readings could be low. We thought we had mine synched good too.
I had read Ken Talbots thread on tuning by ear vs. colortuning...


Yeah... I believe I remember reading his thread about creeping the bike home... wasn't that the thread where the valve came out of the muffler, yet he still rode it home w/ #3 DOA? IIRC, that was another true testament to the greatness of the mighty 11!

Good luck, Doug. Hopefully it'll all be healed soon & Varnae will have a big smile on his face again, as only an 11 can do.

[dbeardslee]

wasn't that the thread where the valve came out of the muffler, yet he still rode it home

Yup, that's the one. We told him not to hit the self-destruct button, but It was pretty impressive . I've still got what's left of the head out in the mancave. When I get through stripping it I'm going to find out what the scrap value is .

Larry - I appreciate the offer on the carbs. My inclination is to just pull the ones that are on it and do what needs to be done, unless DGXSER or Varnae want to try them. If you've got a 4R0 TCI laying around, however.... It's actually kind of funny when he brings it over here - He takes it off the trailer and we jump on it like monkeys on a cupcake.

[DGXSER]

Larry,

You are very kind to offer the carbs. To save you the cost of shipping, Doug and I both have carbs on our bikes to try in it. The carbs look pretty good to me. I just am maticulous enough to need to see everything for myself down to the needle jets, springs, washers and such to feel certain they are 100% together correctly. Carl is a good guy and certainly did clean them well from what I saw, I just feel the urge to be from Missouri on this one.

[foreda]

Show Me State

Larry,

You are very kind to offer the carbs. To save you the cost of shipping, Doug and I both have carbs on our bikes to try in it. The carbs look pretty good to me. I just am maticulous enough to need to see everything for myself down to the needle jets, springs, washers and such to feel certain they are 100% together correctly. Carl is a good guy and certainly did clean them well from what I saw, I just feel the urge to be from Missouri on this one.

Even this ole dumb coonass caught that one!!

[Larrym]

Extra Frosting, please.

Cool. If I were there with my bike I wouldn't hesitate to pull off my bike's carbs as a "rule out carburetion" tactic.

If you do R&R your carbs then be sure to re-sync them afterwards. I read somewhere on a forum here that even the act of removing and replacing a carb bank can change the sync.

"like monkeys on a cupcake."....Hmmm. Now that sounds like a good name for the bike. What has Varnae been calling this problem child?

[DGXSER]

Thanks for the heads up Larry. I can assure you that no carb will go unsynched around Dbeardslee. He just got a carbtune and he likes his toys. Honestly, he is very good with these old machines and kind enough to help others, so I am sure we will synch them either way.

As to the name, Varnae is going with "Zombie Goose", my effectionate name to date is "Demon Spawn", but I have a few others that won't make it past the forum sensorship requirements.