81std no top end - ignition unit??

[RS Thornton]

These bikes should take off at 5k, mine bogs out and will not go over 7k rpm. Feels like a 78e with centrigul advance issues, but the 81 does that in the magical black box. Tried a spare unit and same thing, so either both are bad or it is something else. Any other way the advance might not work besides bad igniter? Bike is new to me so do not know when this started, spare igniter is off a bike I bought but never ran so could be two bad units. But want to double check everything before I spend money on another one.
Going to check timing but doubt that is it, bike runs just fine in 1500 to 3500 rpm. Then is ok 3500 to 4500 but does not accelerate as fast as it should.

[BA80]

I'm having a similar issue.......... http://www.xs11.com/forum/showthread.php?t=44707

[TopCatGr58]

Hey RS,

New to you bike, but you didn't tell us much about the bike. Does it have OEM airbox/pipes or aftermarket and PODS? IF pods, are they the inexpensive cone shaped ones...EMGO brand? They are know to cause problems with upper rpms due to restriction of air flow due to the large mounting lip on the filter that interferes with air flow for the jet ports as well as the vac. slide port! A quick test can be to just take them off and do a quick test run, and if you can get past your 7K wall, then you've confirmed the bad filters.

IF OEM airbox, then aside from clogged filter, or crimped air box snorkel, then it is possible to be the TCI. Yep, it's programmed in for the Cent. Adv. curves, which are the POWER curves. The vac. advance curves are NOT needed to reach redline rpms, so the vac. adv. pot can actually be disconnected, and you would still have the same POWER, just not the fuel economy that the vac. adv. provides. So....you can test the timing with a simple timing light on the #1 cylinder, and only need to take it up to ~5k rpm which is where it's supposed to attain the max cent. adv. of total ~35 degrees.

Finally, have you done any work on the carbs, are they in good working order? Same for the ignition coils, plugs, wires, caps.

T.C.

[motoman]

These bikes should take off at 5k, mine bogs out and will not go over 7k rpm. Feels like a 78e with centrigul advance issues, but the 81 does that in the magical black box. Tried a spare unit and same thing, so either both are bad or it is something else. Any other way the advance might not work besides bad igniter? Bike is new to me so do not know when this started, spare igniter is off a bike I bought but never ran so could be two bad units. But want to double check everything before I spend money on another one.
Going to check timing but doubt that is it, bike runs just fine in 1500 to 3500 rpm. Then is ok 3500 to 4500 but does not accelerate as fast as it should.

An easy way to check the 4RO TCI that the centrifical advance is working: Remove the vacuum advance unit. Hook a timing lite up, plug eng going to #1 plug wire, Start bike and lightly rev motor. Should see advance advanceing. If it does, mechanical advance in TCI unit is working fine.

[dbeardslee]

These bikes should take off at 5k, mine bogs out and will not go over 7k rpm. Feels like a 78e with centrigul advance issues, but the 81 does that in the magical black box. Tried a spare unit and same thing, so either both are bad or it is something else. Any other way the advance might not work besides bad igniter? Bike is new to me so do not know when this started, spare igniter is off a bike I bought but never ran so could be two bad units. But want to double check everything before I spend money on another one.
Going to check timing but doubt that is it, bike runs just fine in 1500 to 3500 rpm. Then is ok 3500 to 4500 but does not accelerate as fast as it should.

What do your plugs look like?

[RS Thornton]

Bought this one http://www.xs11.com/forum/showthread.php?t=43722

Here is Richards project thread. http://www.xs11.com/forum/showthread.php?t=25608
Lots of good work done, here is excerpt
Replaced cylinders / pistons, New rings, valve job/seals, had to replace rusted rear shocks, fork seals, rebuilt all calipers and master cylinders, installed stainless brake lines, had to replace almost every connector as it sat out in the sun since 1988 without the seat, replaced the seat and airbox as they were lost in the hurricane along with the PO's house. Tank has been sealed, just need to have it repainted some day. All the other paint rubbed out just fine.

When I picked it up he told me carbs needed final check as there was a miss at idle. . I pulled them and only found two things, one of the pilot jets was blocked, and 2 0f the floats were sticking. Everything else looked good. Texted Richard to see if he had seen this at all and if he knew status of the spare igniter he gave me. Plan is to check timing and carb sync, but not expecting those are the issue. Then will try remaining spare ignition unit. After that going to be a whole lot of head scratching.

[TopCatGr58]

Hey again,

Okay, read Roger's thread, in your syopsis, you forget to mention that "that" engine had a catastrophic head/valve failure...rammed a stuck valve out thru the side of the head , broke valve springs. SO...the head was replaced, but the thread ended there. No mention of any perceptable damage to the involved piston top? This history may have nothing to do with the current problem, though!

Okay, has the OEM airbox....but again will ask about the condition of the air filter, as well as the Snorkel...the bike had a new/different seat put on it. Are you sure nothing crawled into the snorkel and made a nest in there??

T.C.

[mro]

Okay, has the OEM airbox....but again will ask about the condition of the air filter, as well as the Snorkel...the bike had a new/different seat put on it. Are you sure nothing crawled into the snorkel and made a nest in there??

Did you know that a deep socket can fit in there?

[TopCatGr58]

Did you know that a deep socket can fit in there?

It's been awhile, but I finally remembered that reference you are making...to explain to others...YOU lost a deep socket into the snorkel, it got lodged sideways and severely restricted airflow!!!

Welcome back MRO!

T.C.

[BA80]

Did you install the head yourself?

Wondering if maybe the cam timing might be off a tooth somewhere. If it's retarded or advanced 1 tooth it would cause what you're talking about.

[RS Thornton]

Nuts!!!

So shop is now a mess and I am no able to find timing light. Either I lent it out or it got displaced during the move. Not sure it matters though, according to the 81 supplement in the clymer manual you cannot adjust timing. Thought (and still do) that I finally had a turnkey xs, but will go through all the checks in chapter 3 of the clymer through the week. Really hoping it is bad ignition box.
Does not have carb problem feel, nor the bad pickup stutter/power loss. It feels a bit like when I had a 78e cent advance on an 80 special, no giddy up at higher rpm. Not sputter or popping just no oomph. Happens in all 5 gears so bike will get up to speed, but in a most boring fashion.
Wondering about the pickups, might swap over the set from the other 81 std and see what happens.
On positive side, it passed the TX safety yesterday.

[RS Thornton]

Did you install the head yourself?

No. All I have done is pull carbs, clean, inspect and reinstall. The PO in this case has some bike experience so I would be surprised if that was the case. Bike started and stayed running and no fluid leaks. So better shape than any I bought before.

[RS Thornton]

No airbox restrictions

[BA80]

So shop is now a mess and I am no able to find timing light. Either I lent it out or it got displaced during the move. Not sure it matters though, according to the 81 supplement in the clymer manual you cannot adjust timing. Thought (and still do) that I finally had a turnkey xs, but will go through all the checks in chapter 3 of the clymer through the week. Really hoping it is bad ignition box.
Does not have carb problem feel, nor the bad pickup stutter/power loss. It feels a bit like when I had a 78e cent advance on an 80 special, no giddy up at higher rpm. Not sputter or popping just no oomph. Happens in all 5 gears so bike will get up to speed, but in a most boring fashion.
Wondering about the pickups, might swap over the set from the other 81 std and see what happens.
On positive side, it passed the TX safety yesterday.

Did you install the head yourself?

No. All I have done is pull carbs, clean, inspect and reinstall. The PO in this case has some bike experience so I would be surprised if that was the case. Bike started and stayed running and no fluid leaks. So better shape than any I bought before.

I'm talking about the cam timing. Be sure the timing marks on the cams are aligned right when the crankshaft is at TDC.

Do you have a manual?

[RS Thornton]

Greg,

Have Clymer, and i think shop manual in pdf.
will pull cam cover and check cam shaft timing. And about a dozen other things.