Poor Acceleration after 12k Service/Wilbers install

[rehester]

My '01 LTC, nearing 48,000 on the odo badly needed replacement shocks, so I ordered Wilbers from the Pirate's Lair, and did the install in March, in conjunction with the 12K service (including replacing three shim buckets).

None of this would have been possible without the collective wisdom and experience of this list (I've been doing my own maintenance since the "sticker shock" of the first dealer-administered 12K--many of you know the feeling).

Here's the problem:

The bike started and idled normally. I took it out for the "test spin," and discovered that under hard acceleration at about 3000 rpm the engine bogs/stumbles badly, then recovers and continues to accelerate, although the hesitation/miss occurs at higher rpm, just not as pronounced. Back in the shop, I can replicate the "miss" on the center stand. I can roll the throttle on and hold various rpm above 3000 approaching the redline, and the rpm will drop 300-500 r's then pick back up.

A serach of the posts led me to suspect a displaced vacuum connection, but the subsequent strip-down revealed nothing amiss at the throttle bodies, or elsewhere. During the "event," I hear what sounds like small popping sounds, or backfiring.

Where should further diagnosis lead me? Any and all help greatly appreciated. I enjoy tinkering with my LT, but riding season is awasting, and the Reunion lies over the horizon.

TIA

Bob Hester

[stefan]

During the "event," I hear what sounds like small popping sounds, or backfiring.

Is this during steady throttle, acceleration, deceleration, a specific rpm range or all the time?

Stefan

[jazzbass]

Since you replaced 3 buckets. Did you recheck clearances?

Based on what you did versus the symptom your experiencing,
it must be valve lash, valve timing, or as simple as one of the plug
wires switched or not fully seated.

Let us know how it turns out.

[rehester]

Stefan: The sounds occur during hard acceleration between 3000 and 5000 rpm, when the engine is boggin down and losing power. The duration is three-to-five seconds, and then the rpm begins to climb again.

Larry: I rechecked the lobe-bucket clearances, after reassembling the sprockets/cams/etc--all within specs.

[JATownsend]

Heh Bob, just a thought, but, have you checked your gas filter? Or have you replaced it recently? It might be clogged or split? Or...

My bike bucked a bit like you are talking about just before the in-tank fuel line came completely OFF the filter output side. It was missing a BMW hose clamp. :(

But it sure does sound like a possible spark plug or wire issue also. :confused:

[motorhead]

Pay your local BMW shop for a mo-di-tec dignostic test .... that should point out whats not right, otherwise your only guessing :(

[rehester]

Thanks--I thought I might have installed the new filter backwards or something, but, when I stripped her down again, I pulled the fuel pump assembly out of the tank and all is well in there.

I'm an EMS helicopter pilot pulling seven-day hitches, so it'll be the middle of next week before I can get home to work on it again. I'll be looking closely at the plug wires for chafing, etc.

Bob

[rehester]

Pay your local BMW shop for a mo-di-tec dignostic test .... that should point out whats not right, otherwise your only guessing :(
Absent something very obvious, when I get to it again, I'll load the naked old girl into the pickup and make the ignominious two-plus hour drive to the dealer in Savoy, IL.

[hp1bmw]

It is probably a long shot, but did you check the sprockets alignment on the cams to be sure you did not miss one by a tooth. It happens.

[rehester]

Thanks, Jim. I double cable-tied the chain to the sprockets as per the Gunsmoke valve adjustment article, so I'm pretty sure the timing did not change in that regard.

[zaphod]

... double cable-tied the chain to the sprockets as per the Gunsmoke valve adjustment article, ...

I don't mean to hijack this thread but, I'm getting ready to do my valves and haven't heard of the "Gunsmoke valve adjustment article" you speak of. Should I read it, where do I find it??

[JATownsend]

This guide is an invaluble tool for a newcomer doing a K bike's valves.

http://www.gunsmoke.com/motorcycling/k1200rs/valves/index.html

Also check out the Hall of Wisdom link on our homepage. Very helpful posts outlining the procedure there as well.

[jazzbass]

http://www.gunsmoke.com/motorcycling/k1200rs/valves/index.html

Not bad job. A little tip. Wash around the valve cover with soapy
water and a brush. The valve cover gasket has grooves on the topside
which held some grit that ended up on my engine parts when removing
the cover.

[Dean_BMW]

If your valve clearance is correct after the re-assemble, it is safe to say you did not bend a valve on the re-assembly. So my best guess is that you have something out of time. It happens.

[zaphod]

Thanks